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Linux/mm/memcontrol.c

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  1 /* memcontrol.c - Memory Controller
  2  *
  3  * Copyright IBM Corporation, 2007
  4  * Author Balbir Singh <balbir@linux.vnet.ibm.com>
  5  *
  6  * Copyright 2007 OpenVZ SWsoft Inc
  7  * Author: Pavel Emelianov <xemul@openvz.org>
  8  *
  9  * Memory thresholds
 10  * Copyright (C) 2009 Nokia Corporation
 11  * Author: Kirill A. Shutemov
 12  *
 13  * Kernel Memory Controller
 14  * Copyright (C) 2012 Parallels Inc. and Google Inc.
 15  * Authors: Glauber Costa and Suleiman Souhlal
 16  *
 17  * This program is free software; you can redistribute it and/or modify
 18  * it under the terms of the GNU General Public License as published by
 19  * the Free Software Foundation; either version 2 of the License, or
 20  * (at your option) any later version.
 21  *
 22  * This program is distributed in the hope that it will be useful,
 23  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 24  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 25  * GNU General Public License for more details.
 26  */
 27 
 28 #include <linux/res_counter.h>
 29 #include <linux/memcontrol.h>
 30 #include <linux/cgroup.h>
 31 #include <linux/mm.h>
 32 #include <linux/hugetlb.h>
 33 #include <linux/pagemap.h>
 34 #include <linux/smp.h>
 35 #include <linux/page-flags.h>
 36 #include <linux/backing-dev.h>
 37 #include <linux/bit_spinlock.h>
 38 #include <linux/rcupdate.h>
 39 #include <linux/limits.h>
 40 #include <linux/export.h>
 41 #include <linux/mutex.h>
 42 #include <linux/rbtree.h>
 43 #include <linux/slab.h>
 44 #include <linux/swap.h>
 45 #include <linux/swapops.h>
 46 #include <linux/spinlock.h>
 47 #include <linux/eventfd.h>
 48 #include <linux/sort.h>
 49 #include <linux/fs.h>
 50 #include <linux/seq_file.h>
 51 #include <linux/vmalloc.h>
 52 #include <linux/vmpressure.h>
 53 #include <linux/mm_inline.h>
 54 #include <linux/page_cgroup.h>
 55 #include <linux/cpu.h>
 56 #include <linux/oom.h>
 57 #include "internal.h"
 58 #include <net/sock.h>
 59 #include <net/ip.h>
 60 #include <net/tcp_memcontrol.h>
 61 
 62 #include <asm/uaccess.h>
 63 
 64 #include <trace/events/vmscan.h>
 65 
 66 struct cgroup_subsys mem_cgroup_subsys __read_mostly;
 67 EXPORT_SYMBOL(mem_cgroup_subsys);
 68 
 69 #define MEM_CGROUP_RECLAIM_RETRIES      5
 70 static struct mem_cgroup *root_mem_cgroup __read_mostly;
 71 
 72 #ifdef CONFIG_MEMCG_SWAP
 73 /* Turned on only when memory cgroup is enabled && really_do_swap_account = 1 */
 74 int do_swap_account __read_mostly;
 75 
 76 /* for remember boot option*/
 77 #ifdef CONFIG_MEMCG_SWAP_ENABLED
 78 static int really_do_swap_account __initdata = 1;
 79 #else
 80 static int really_do_swap_account __initdata = 0;
 81 #endif
 82 
 83 #else
 84 #define do_swap_account         0
 85 #endif
 86 
 87 
 88 /*
 89  * Statistics for memory cgroup.
 90  */
 91 enum mem_cgroup_stat_index {
 92         /*
 93          * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
 94          */
 95         MEM_CGROUP_STAT_CACHE,          /* # of pages charged as cache */
 96         MEM_CGROUP_STAT_RSS,            /* # of pages charged as anon rss */
 97         MEM_CGROUP_STAT_RSS_HUGE,       /* # of pages charged as anon huge */
 98         MEM_CGROUP_STAT_FILE_MAPPED,    /* # of pages charged as file rss */
 99         MEM_CGROUP_STAT_SWAP,           /* # of pages, swapped out */
100         MEM_CGROUP_STAT_NSTATS,
101 };
102 
103 static const char * const mem_cgroup_stat_names[] = {
104         "cache",
105         "rss",
106         "rss_huge",
107         "mapped_file",
108         "swap",
109 };
110 
111 enum mem_cgroup_events_index {
112         MEM_CGROUP_EVENTS_PGPGIN,       /* # of pages paged in */
113         MEM_CGROUP_EVENTS_PGPGOUT,      /* # of pages paged out */
114         MEM_CGROUP_EVENTS_PGFAULT,      /* # of page-faults */
115         MEM_CGROUP_EVENTS_PGMAJFAULT,   /* # of major page-faults */
116         MEM_CGROUP_EVENTS_NSTATS,
117 };
118 
119 static const char * const mem_cgroup_events_names[] = {
120         "pgpgin",
121         "pgpgout",
122         "pgfault",
123         "pgmajfault",
124 };
125 
126 static const char * const mem_cgroup_lru_names[] = {
127         "inactive_anon",
128         "active_anon",
129         "inactive_file",
130         "active_file",
131         "unevictable",
132 };
133 
134 /*
135  * Per memcg event counter is incremented at every pagein/pageout. With THP,
136  * it will be incremated by the number of pages. This counter is used for
137  * for trigger some periodic events. This is straightforward and better
138  * than using jiffies etc. to handle periodic memcg event.
139  */
140 enum mem_cgroup_events_target {
141         MEM_CGROUP_TARGET_THRESH,
142         MEM_CGROUP_TARGET_SOFTLIMIT,
143         MEM_CGROUP_TARGET_NUMAINFO,
144         MEM_CGROUP_NTARGETS,
145 };
146 #define THRESHOLDS_EVENTS_TARGET 128
147 #define SOFTLIMIT_EVENTS_TARGET 1024
148 #define NUMAINFO_EVENTS_TARGET  1024
149 
150 struct mem_cgroup_stat_cpu {
151         long count[MEM_CGROUP_STAT_NSTATS];
152         unsigned long events[MEM_CGROUP_EVENTS_NSTATS];
153         unsigned long nr_page_events;
154         unsigned long targets[MEM_CGROUP_NTARGETS];
155 };
156 
157 struct mem_cgroup_reclaim_iter {
158         /*
159          * last scanned hierarchy member. Valid only if last_dead_count
160          * matches memcg->dead_count of the hierarchy root group.
161          */
162         struct mem_cgroup *last_visited;
163         unsigned long last_dead_count;
164 
165         /* scan generation, increased every round-trip */
166         unsigned int generation;
167 };
168 
169 /*
170  * per-zone information in memory controller.
171  */
172 struct mem_cgroup_per_zone {
173         struct lruvec           lruvec;
174         unsigned long           lru_size[NR_LRU_LISTS];
175 
176         struct mem_cgroup_reclaim_iter reclaim_iter[DEF_PRIORITY + 1];
177 
178         struct rb_node          tree_node;      /* RB tree node */
179         unsigned long long      usage_in_excess;/* Set to the value by which */
180                                                 /* the soft limit is exceeded*/
181         bool                    on_tree;
182         struct mem_cgroup       *memcg;         /* Back pointer, we cannot */
183                                                 /* use container_of        */
184 };
185 
186 struct mem_cgroup_per_node {
187         struct mem_cgroup_per_zone zoneinfo[MAX_NR_ZONES];
188 };
189 
190 /*
191  * Cgroups above their limits are maintained in a RB-Tree, independent of
192  * their hierarchy representation
193  */
194 
195 struct mem_cgroup_tree_per_zone {
196         struct rb_root rb_root;
197         spinlock_t lock;
198 };
199 
200 struct mem_cgroup_tree_per_node {
201         struct mem_cgroup_tree_per_zone rb_tree_per_zone[MAX_NR_ZONES];
202 };
203 
204 struct mem_cgroup_tree {
205         struct mem_cgroup_tree_per_node *rb_tree_per_node[MAX_NUMNODES];
206 };
207 
208 static struct mem_cgroup_tree soft_limit_tree __read_mostly;
209 
210 struct mem_cgroup_threshold {
211         struct eventfd_ctx *eventfd;
212         u64 threshold;
213 };
214 
215 /* For threshold */
216 struct mem_cgroup_threshold_ary {
217         /* An array index points to threshold just below or equal to usage. */
218         int current_threshold;
219         /* Size of entries[] */
220         unsigned int size;
221         /* Array of thresholds */
222         struct mem_cgroup_threshold entries[0];
223 };
224 
225 struct mem_cgroup_thresholds {
226         /* Primary thresholds array */
227         struct mem_cgroup_threshold_ary *primary;
228         /*
229          * Spare threshold array.
230          * This is needed to make mem_cgroup_unregister_event() "never fail".
231          * It must be able to store at least primary->size - 1 entries.
232          */
233         struct mem_cgroup_threshold_ary *spare;
234 };
235 
236 /* for OOM */
237 struct mem_cgroup_eventfd_list {
238         struct list_head list;
239         struct eventfd_ctx *eventfd;
240 };
241 
242 static void mem_cgroup_threshold(struct mem_cgroup *memcg);
243 static void mem_cgroup_oom_notify(struct mem_cgroup *memcg);
244 
245 /*
246  * The memory controller data structure. The memory controller controls both
247  * page cache and RSS per cgroup. We would eventually like to provide
248  * statistics based on the statistics developed by Rik Van Riel for clock-pro,
249  * to help the administrator determine what knobs to tune.
250  *
251  * TODO: Add a water mark for the memory controller. Reclaim will begin when
252  * we hit the water mark. May be even add a low water mark, such that
253  * no reclaim occurs from a cgroup at it's low water mark, this is
254  * a feature that will be implemented much later in the future.
255  */
256 struct mem_cgroup {
257         struct cgroup_subsys_state css;
258         /*
259          * the counter to account for memory usage
260          */
261         struct res_counter res;
262 
263         /* vmpressure notifications */
264         struct vmpressure vmpressure;
265 
266         /*
267          * the counter to account for mem+swap usage.
268          */
269         struct res_counter memsw;
270 
271         /*
272          * the counter to account for kernel memory usage.
273          */
274         struct res_counter kmem;
275         /*
276          * Should the accounting and control be hierarchical, per subtree?
277          */
278         bool use_hierarchy;
279         unsigned long kmem_account_flags; /* See KMEM_ACCOUNTED_*, below */
280 
281         bool            oom_lock;
282         atomic_t        under_oom;
283 
284         int     swappiness;
285         /* OOM-Killer disable */
286         int             oom_kill_disable;
287 
288         /* set when res.limit == memsw.limit */
289         bool            memsw_is_minimum;
290 
291         /* protect arrays of thresholds */
292         struct mutex thresholds_lock;
293 
294         /* thresholds for memory usage. RCU-protected */
295         struct mem_cgroup_thresholds thresholds;
296 
297         /* thresholds for mem+swap usage. RCU-protected */
298         struct mem_cgroup_thresholds memsw_thresholds;
299 
300         /* For oom notifier event fd */
301         struct list_head oom_notify;
302 
303         /*
304          * Should we move charges of a task when a task is moved into this
305          * mem_cgroup ? And what type of charges should we move ?
306          */
307         unsigned long   move_charge_at_immigrate;
308         /*
309          * set > 0 if pages under this cgroup are moving to other cgroup.
310          */
311         atomic_t        moving_account;
312         /* taken only while moving_account > 0 */
313         spinlock_t      move_lock;
314         /*
315          * percpu counter.
316          */
317         struct mem_cgroup_stat_cpu __percpu *stat;
318         /*
319          * used when a cpu is offlined or other synchronizations
320          * See mem_cgroup_read_stat().
321          */
322         struct mem_cgroup_stat_cpu nocpu_base;
323         spinlock_t pcp_counter_lock;
324 
325         atomic_t        dead_count;
326 #if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_INET)
327         struct tcp_memcontrol tcp_mem;
328 #endif
329 #if defined(CONFIG_MEMCG_KMEM)
330         /* analogous to slab_common's slab_caches list. per-memcg */
331         struct list_head memcg_slab_caches;
332         /* Not a spinlock, we can take a lot of time walking the list */
333         struct mutex slab_caches_mutex;
334         /* Index in the kmem_cache->memcg_params->memcg_caches array */
335         int kmemcg_id;
336 #endif
337 
338         int last_scanned_node;
339 #if MAX_NUMNODES > 1
340         nodemask_t      scan_nodes;
341         atomic_t        numainfo_events;
342         atomic_t        numainfo_updating;
343 #endif
344 
345         struct mem_cgroup_per_node *nodeinfo[0];
346         /* WARNING: nodeinfo must be the last member here */
347 };
348 
349 static size_t memcg_size(void)
350 {
351         return sizeof(struct mem_cgroup) +
352                 nr_node_ids * sizeof(struct mem_cgroup_per_node);
353 }
354 
355 /* internal only representation about the status of kmem accounting. */
356 enum {
357         KMEM_ACCOUNTED_ACTIVE = 0, /* accounted by this cgroup itself */
358         KMEM_ACCOUNTED_ACTIVATED, /* static key enabled. */
359         KMEM_ACCOUNTED_DEAD, /* dead memcg with pending kmem charges */
360 };
361 
362 /* We account when limit is on, but only after call sites are patched */
363 #define KMEM_ACCOUNTED_MASK \
364                 ((1 << KMEM_ACCOUNTED_ACTIVE) | (1 << KMEM_ACCOUNTED_ACTIVATED))
365 
366 #ifdef CONFIG_MEMCG_KMEM
367 static inline void memcg_kmem_set_active(struct mem_cgroup *memcg)
368 {
369         set_bit(KMEM_ACCOUNTED_ACTIVE, &memcg->kmem_account_flags);
370 }
371 
372 static bool memcg_kmem_is_active(struct mem_cgroup *memcg)
373 {
374         return test_bit(KMEM_ACCOUNTED_ACTIVE, &memcg->kmem_account_flags);
375 }
376 
377 static void memcg_kmem_set_activated(struct mem_cgroup *memcg)
378 {
379         set_bit(KMEM_ACCOUNTED_ACTIVATED, &memcg->kmem_account_flags);
380 }
381 
382 static void memcg_kmem_clear_activated(struct mem_cgroup *memcg)
383 {
384         clear_bit(KMEM_ACCOUNTED_ACTIVATED, &memcg->kmem_account_flags);
385 }
386 
387 static void memcg_kmem_mark_dead(struct mem_cgroup *memcg)
388 {
389         /*
390          * Our caller must use css_get() first, because memcg_uncharge_kmem()
391          * will call css_put() if it sees the memcg is dead.
392          */
393         smp_wmb();
394         if (test_bit(KMEM_ACCOUNTED_ACTIVE, &memcg->kmem_account_flags))
395                 set_bit(KMEM_ACCOUNTED_DEAD, &memcg->kmem_account_flags);
396 }
397 
398 static bool memcg_kmem_test_and_clear_dead(struct mem_cgroup *memcg)
399 {
400         return test_and_clear_bit(KMEM_ACCOUNTED_DEAD,
401                                   &memcg->kmem_account_flags);
402 }
403 #endif
404 
405 /* Stuffs for move charges at task migration. */
406 /*
407  * Types of charges to be moved. "move_charge_at_immitgrate" and
408  * "immigrate_flags" are treated as a left-shifted bitmap of these types.
409  */
410 enum move_type {
411         MOVE_CHARGE_TYPE_ANON,  /* private anonymous page and swap of it */
412         MOVE_CHARGE_TYPE_FILE,  /* file page(including tmpfs) and swap of it */
413         NR_MOVE_TYPE,
414 };
415 
416 /* "mc" and its members are protected by cgroup_mutex */
417 static struct move_charge_struct {
418         spinlock_t        lock; /* for from, to */
419         struct mem_cgroup *from;
420         struct mem_cgroup *to;
421         unsigned long immigrate_flags;
422         unsigned long precharge;
423         unsigned long moved_charge;
424         unsigned long moved_swap;
425         struct task_struct *moving_task;        /* a task moving charges */
426         wait_queue_head_t waitq;                /* a waitq for other context */
427 } mc = {
428         .lock = __SPIN_LOCK_UNLOCKED(mc.lock),
429         .waitq = __WAIT_QUEUE_HEAD_INITIALIZER(mc.waitq),
430 };
431 
432 static bool move_anon(void)
433 {
434         return test_bit(MOVE_CHARGE_TYPE_ANON, &mc.immigrate_flags);
435 }
436 
437 static bool move_file(void)
438 {
439         return test_bit(MOVE_CHARGE_TYPE_FILE, &mc.immigrate_flags);
440 }
441 
442 /*
443  * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft
444  * limit reclaim to prevent infinite loops, if they ever occur.
445  */
446 #define MEM_CGROUP_MAX_RECLAIM_LOOPS            100
447 #define MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS 2
448 
449 enum charge_type {
450         MEM_CGROUP_CHARGE_TYPE_CACHE = 0,
451         MEM_CGROUP_CHARGE_TYPE_ANON,
452         MEM_CGROUP_CHARGE_TYPE_SWAPOUT, /* for accounting swapcache */
453         MEM_CGROUP_CHARGE_TYPE_DROP,    /* a page was unused swap cache */
454         NR_CHARGE_TYPE,
455 };
456 
457 /* for encoding cft->private value on file */
458 enum res_type {
459         _MEM,
460         _MEMSWAP,
461         _OOM_TYPE,
462         _KMEM,
463 };
464 
465 #define MEMFILE_PRIVATE(x, val) ((x) << 16 | (val))
466 #define MEMFILE_TYPE(val)       ((val) >> 16 & 0xffff)
467 #define MEMFILE_ATTR(val)       ((val) & 0xffff)
468 /* Used for OOM nofiier */
469 #define OOM_CONTROL             (0)
470 
471 /*
472  * Reclaim flags for mem_cgroup_hierarchical_reclaim
473  */
474 #define MEM_CGROUP_RECLAIM_NOSWAP_BIT   0x0
475 #define MEM_CGROUP_RECLAIM_NOSWAP       (1 << MEM_CGROUP_RECLAIM_NOSWAP_BIT)
476 #define MEM_CGROUP_RECLAIM_SHRINK_BIT   0x1
477 #define MEM_CGROUP_RECLAIM_SHRINK       (1 << MEM_CGROUP_RECLAIM_SHRINK_BIT)
478 
479 /*
480  * The memcg_create_mutex will be held whenever a new cgroup is created.
481  * As a consequence, any change that needs to protect against new child cgroups
482  * appearing has to hold it as well.
483  */
484 static DEFINE_MUTEX(memcg_create_mutex);
485 
486 static inline
487 struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *s)
488 {
489         return container_of(s, struct mem_cgroup, css);
490 }
491 
492 /* Some nice accessors for the vmpressure. */
493 struct vmpressure *memcg_to_vmpressure(struct mem_cgroup *memcg)
494 {
495         if (!memcg)
496                 memcg = root_mem_cgroup;
497         return &memcg->vmpressure;
498 }
499 
500 struct cgroup_subsys_state *vmpressure_to_css(struct vmpressure *vmpr)
501 {
502         return &container_of(vmpr, struct mem_cgroup, vmpressure)->css;
503 }
504 
505 struct vmpressure *css_to_vmpressure(struct cgroup_subsys_state *css)
506 {
507         return &mem_cgroup_from_css(css)->vmpressure;
508 }
509 
510 static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
511 {
512         return (memcg == root_mem_cgroup);
513 }
514 
515 /* Writing them here to avoid exposing memcg's inner layout */
516 #if defined(CONFIG_INET) && defined(CONFIG_MEMCG_KMEM)
517 
518 void sock_update_memcg(struct sock *sk)
519 {
520         if (mem_cgroup_sockets_enabled) {
521                 struct mem_cgroup *memcg;
522                 struct cg_proto *cg_proto;
523 
524                 BUG_ON(!sk->sk_prot->proto_cgroup);
525 
526                 /* Socket cloning can throw us here with sk_cgrp already
527                  * filled. It won't however, necessarily happen from
528                  * process context. So the test for root memcg given
529                  * the current task's memcg won't help us in this case.
530                  *
531                  * Respecting the original socket's memcg is a better
532                  * decision in this case.
533                  */
534                 if (sk->sk_cgrp) {
535                         BUG_ON(mem_cgroup_is_root(sk->sk_cgrp->memcg));
536                         css_get(&sk->sk_cgrp->memcg->css);
537                         return;
538                 }
539 
540                 rcu_read_lock();
541                 memcg = mem_cgroup_from_task(current);
542                 cg_proto = sk->sk_prot->proto_cgroup(memcg);
543                 if (!mem_cgroup_is_root(memcg) &&
544                     memcg_proto_active(cg_proto) && css_tryget(&memcg->css)) {
545                         sk->sk_cgrp = cg_proto;
546                 }
547                 rcu_read_unlock();
548         }
549 }
550 EXPORT_SYMBOL(sock_update_memcg);
551 
552 void sock_release_memcg(struct sock *sk)
553 {
554         if (mem_cgroup_sockets_enabled && sk->sk_cgrp) {
555                 struct mem_cgroup *memcg;
556                 WARN_ON(!sk->sk_cgrp->memcg);
557                 memcg = sk->sk_cgrp->memcg;
558                 css_put(&sk->sk_cgrp->memcg->css);
559         }
560 }
561 
562 struct cg_proto *tcp_proto_cgroup(struct mem_cgroup *memcg)
563 {
564         if (!memcg || mem_cgroup_is_root(memcg))
565                 return NULL;
566 
567         return &memcg->tcp_mem.cg_proto;
568 }
569 EXPORT_SYMBOL(tcp_proto_cgroup);
570 
571 static void disarm_sock_keys(struct mem_cgroup *memcg)
572 {
573         if (!memcg_proto_activated(&memcg->tcp_mem.cg_proto))
574                 return;
575         static_key_slow_dec(&memcg_socket_limit_enabled);
576 }
577 #else
578 static void disarm_sock_keys(struct mem_cgroup *memcg)
579 {
580 }
581 #endif
582 
583 #ifdef CONFIG_MEMCG_KMEM
584 /*
585  * This will be the memcg's index in each cache's ->memcg_params->memcg_caches.
586  * There are two main reasons for not using the css_id for this:
587  *  1) this works better in sparse environments, where we have a lot of memcgs,
588  *     but only a few kmem-limited. Or also, if we have, for instance, 200
589  *     memcgs, and none but the 200th is kmem-limited, we'd have to have a
590  *     200 entry array for that.
591  *
592  *  2) In order not to violate the cgroup API, we would like to do all memory
593  *     allocation in ->create(). At that point, we haven't yet allocated the
594  *     css_id. Having a separate index prevents us from messing with the cgroup
595  *     core for this
596  *
597  * The current size of the caches array is stored in
598  * memcg_limited_groups_array_size.  It will double each time we have to
599  * increase it.
600  */
601 static DEFINE_IDA(kmem_limited_groups);
602 int memcg_limited_groups_array_size;
603 
604 /*
605  * MIN_SIZE is different than 1, because we would like to avoid going through
606  * the alloc/free process all the time. In a small machine, 4 kmem-limited
607  * cgroups is a reasonable guess. In the future, it could be a parameter or
608  * tunable, but that is strictly not necessary.
609  *
610  * MAX_SIZE should be as large as the number of css_ids. Ideally, we could get
611  * this constant directly from cgroup, but it is understandable that this is
612  * better kept as an internal representation in cgroup.c. In any case, the
613  * css_id space is not getting any smaller, and we don't have to necessarily
614  * increase ours as well if it increases.
615  */
616 #define MEMCG_CACHES_MIN_SIZE 4
617 #define MEMCG_CACHES_MAX_SIZE 65535
618 
619 /*
620  * A lot of the calls to the cache allocation functions are expected to be
621  * inlined by the compiler. Since the calls to memcg_kmem_get_cache are
622  * conditional to this static branch, we'll have to allow modules that does
623  * kmem_cache_alloc and the such to see this symbol as well
624  */
625 struct static_key memcg_kmem_enabled_key;
626 EXPORT_SYMBOL(memcg_kmem_enabled_key);
627 
628 static void disarm_kmem_keys(struct mem_cgroup *memcg)
629 {
630         if (memcg_kmem_is_active(memcg)) {
631                 static_key_slow_dec(&memcg_kmem_enabled_key);
632                 ida_simple_remove(&kmem_limited_groups, memcg->kmemcg_id);
633         }
634         /*
635          * This check can't live in kmem destruction function,
636          * since the charges will outlive the cgroup
637          */
638         WARN_ON(res_counter_read_u64(&memcg->kmem, RES_USAGE) != 0);
639 }
640 #else
641 static void disarm_kmem_keys(struct mem_cgroup *memcg)
642 {
643 }
644 #endif /* CONFIG_MEMCG_KMEM */
645 
646 static void disarm_static_keys(struct mem_cgroup *memcg)
647 {
648         disarm_sock_keys(memcg);
649         disarm_kmem_keys(memcg);
650 }
651 
652 static void drain_all_stock_async(struct mem_cgroup *memcg);
653 
654 static struct mem_cgroup_per_zone *
655 mem_cgroup_zoneinfo(struct mem_cgroup *memcg, int nid, int zid)
656 {
657         VM_BUG_ON((unsigned)nid >= nr_node_ids);
658         return &memcg->nodeinfo[nid]->zoneinfo[zid];
659 }
660 
661 struct cgroup_subsys_state *mem_cgroup_css(struct mem_cgroup *memcg)
662 {
663         return &memcg->css;
664 }
665 
666 static struct mem_cgroup_per_zone *
667 page_cgroup_zoneinfo(struct mem_cgroup *memcg, struct page *page)
668 {
669         int nid = page_to_nid(page);
670         int zid = page_zonenum(page);
671 
672         return mem_cgroup_zoneinfo(memcg, nid, zid);
673 }
674 
675 static struct mem_cgroup_tree_per_zone *
676 soft_limit_tree_node_zone(int nid, int zid)
677 {
678         return &soft_limit_tree.rb_tree_per_node[nid]->rb_tree_per_zone[zid];
679 }
680 
681 static struct mem_cgroup_tree_per_zone *
682 soft_limit_tree_from_page(struct page *page)
683 {
684         int nid = page_to_nid(page);
685         int zid = page_zonenum(page);
686 
687         return &soft_limit_tree.rb_tree_per_node[nid]->rb_tree_per_zone[zid];
688 }
689 
690 static void
691 __mem_cgroup_insert_exceeded(struct mem_cgroup *memcg,
692                                 struct mem_cgroup_per_zone *mz,
693                                 struct mem_cgroup_tree_per_zone *mctz,
694                                 unsigned long long new_usage_in_excess)
695 {
696         struct rb_node **p = &mctz->rb_root.rb_node;
697         struct rb_node *parent = NULL;
698         struct mem_cgroup_per_zone *mz_node;
699 
700         if (mz->on_tree)
701                 return;
702 
703         mz->usage_in_excess = new_usage_in_excess;
704         if (!mz->usage_in_excess)
705                 return;
706         while (*p) {
707                 parent = *p;
708                 mz_node = rb_entry(parent, struct mem_cgroup_per_zone,
709                                         tree_node);
710                 if (mz->usage_in_excess < mz_node->usage_in_excess)
711                         p = &(*p)->rb_left;
712                 /*
713                  * We can't avoid mem cgroups that are over their soft
714                  * limit by the same amount
715                  */
716                 else if (mz->usage_in_excess >= mz_node->usage_in_excess)
717                         p = &(*p)->rb_right;
718         }
719         rb_link_node(&mz->tree_node, parent, p);
720         rb_insert_color(&mz->tree_node, &mctz->rb_root);
721         mz->on_tree = true;
722 }
723 
724 static void
725 __mem_cgroup_remove_exceeded(struct mem_cgroup *memcg,
726                                 struct mem_cgroup_per_zone *mz,
727                                 struct mem_cgroup_tree_per_zone *mctz)
728 {
729         if (!mz->on_tree)
730                 return;
731         rb_erase(&mz->tree_node, &mctz->rb_root);
732         mz->on_tree = false;
733 }
734 
735 static void
736 mem_cgroup_remove_exceeded(struct mem_cgroup *memcg,
737                                 struct mem_cgroup_per_zone *mz,
738                                 struct mem_cgroup_tree_per_zone *mctz)
739 {
740         spin_lock(&mctz->lock);
741         __mem_cgroup_remove_exceeded(memcg, mz, mctz);
742         spin_unlock(&mctz->lock);
743 }
744 
745 
746 static void mem_cgroup_update_tree(struct mem_cgroup *memcg, struct page *page)
747 {
748         unsigned long long excess;
749         struct mem_cgroup_per_zone *mz;
750         struct mem_cgroup_tree_per_zone *mctz;
751         int nid = page_to_nid(page);
752         int zid = page_zonenum(page);
753         mctz = soft_limit_tree_from_page(page);
754 
755         /*
756          * Necessary to update all ancestors when hierarchy is used.
757          * because their event counter is not touched.
758          */
759         for (; memcg; memcg = parent_mem_cgroup(memcg)) {
760                 mz = mem_cgroup_zoneinfo(memcg, nid, zid);
761                 excess = res_counter_soft_limit_excess(&memcg->res);
762                 /*
763                  * We have to update the tree if mz is on RB-tree or
764                  * mem is over its softlimit.
765                  */
766                 if (excess || mz->on_tree) {
767                         spin_lock(&mctz->lock);
768                         /* if on-tree, remove it */
769                         if (mz->on_tree)
770                                 __mem_cgroup_remove_exceeded(memcg, mz, mctz);
771                         /*
772                          * Insert again. mz->usage_in_excess will be updated.
773                          * If excess is 0, no tree ops.
774                          */
775                         __mem_cgroup_insert_exceeded(memcg, mz, mctz, excess);
776                         spin_unlock(&mctz->lock);
777                 }
778         }
779 }
780 
781 static void mem_cgroup_remove_from_trees(struct mem_cgroup *memcg)
782 {
783         int node, zone;
784         struct mem_cgroup_per_zone *mz;
785         struct mem_cgroup_tree_per_zone *mctz;
786 
787         for_each_node(node) {
788                 for (zone = 0; zone < MAX_NR_ZONES; zone++) {
789                         mz = mem_cgroup_zoneinfo(memcg, node, zone);
790                         mctz = soft_limit_tree_node_zone(node, zone);
791                         mem_cgroup_remove_exceeded(memcg, mz, mctz);
792                 }
793         }
794 }
795 
796 static struct mem_cgroup_per_zone *
797 __mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
798 {
799         struct rb_node *rightmost = NULL;
800         struct mem_cgroup_per_zone *mz;
801 
802 retry:
803         mz = NULL;
804         rightmost = rb_last(&mctz->rb_root);
805         if (!rightmost)
806                 goto done;              /* Nothing to reclaim from */
807 
808         mz = rb_entry(rightmost, struct mem_cgroup_per_zone, tree_node);
809         /*
810          * Remove the node now but someone else can add it back,
811          * we will to add it back at the end of reclaim to its correct
812          * position in the tree.
813          */
814         __mem_cgroup_remove_exceeded(mz->memcg, mz, mctz);
815         if (!res_counter_soft_limit_excess(&mz->memcg->res) ||
816                 !css_tryget(&mz->memcg->css))
817                 goto retry;
818 done:
819         return mz;
820 }
821 
822 static struct mem_cgroup_per_zone *
823 mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
824 {
825         struct mem_cgroup_per_zone *mz;
826 
827         spin_lock(&mctz->lock);
828         mz = __mem_cgroup_largest_soft_limit_node(mctz);
829         spin_unlock(&mctz->lock);
830         return mz;
831 }
832 
833 /*
834  * Implementation Note: reading percpu statistics for memcg.
835  *
836  * Both of vmstat[] and percpu_counter has threshold and do periodic
837  * synchronization to implement "quick" read. There are trade-off between
838  * reading cost and precision of value. Then, we may have a chance to implement
839  * a periodic synchronizion of counter in memcg's counter.
840  *
841  * But this _read() function is used for user interface now. The user accounts
842  * memory usage by memory cgroup and he _always_ requires exact value because
843  * he accounts memory. Even if we provide quick-and-fuzzy read, we always
844  * have to visit all online cpus and make sum. So, for now, unnecessary
845  * synchronization is not implemented. (just implemented for cpu hotplug)
846  *
847  * If there are kernel internal actions which can make use of some not-exact
848  * value, and reading all cpu value can be performance bottleneck in some
849  * common workload, threashold and synchonization as vmstat[] should be
850  * implemented.
851  */
852 static long mem_cgroup_read_stat(struct mem_cgroup *memcg,
853                                  enum mem_cgroup_stat_index idx)
854 {
855         long val = 0;
856         int cpu;
857 
858         get_online_cpus();
859         for_each_online_cpu(cpu)
860                 val += per_cpu(memcg->stat->count[idx], cpu);
861 #ifdef CONFIG_HOTPLUG_CPU
862         spin_lock(&memcg->pcp_counter_lock);
863         val += memcg->nocpu_base.count[idx];
864         spin_unlock(&memcg->pcp_counter_lock);
865 #endif
866         put_online_cpus();
867         return val;
868 }
869 
870 static void mem_cgroup_swap_statistics(struct mem_cgroup *memcg,
871                                          bool charge)
872 {
873         int val = (charge) ? 1 : -1;
874         this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_SWAP], val);
875 }
876 
877 static unsigned long mem_cgroup_read_events(struct mem_cgroup *memcg,
878                                             enum mem_cgroup_events_index idx)
879 {
880         unsigned long val = 0;
881         int cpu;
882 
883         for_each_online_cpu(cpu)
884                 val += per_cpu(memcg->stat->events[idx], cpu);
885 #ifdef CONFIG_HOTPLUG_CPU
886         spin_lock(&memcg->pcp_counter_lock);
887         val += memcg->nocpu_base.events[idx];
888         spin_unlock(&memcg->pcp_counter_lock);
889 #endif
890         return val;
891 }
892 
893 static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
894                                          struct page *page,
895                                          bool anon, int nr_pages)
896 {
897         preempt_disable();
898 
899         /*
900          * Here, RSS means 'mapped anon' and anon's SwapCache. Shmem/tmpfs is
901          * counted as CACHE even if it's on ANON LRU.
902          */
903         if (anon)
904                 __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_RSS],
905                                 nr_pages);
906         else
907                 __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_CACHE],
908                                 nr_pages);
909 
910         if (PageTransHuge(page))
911                 __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_RSS_HUGE],
912                                 nr_pages);
913 
914         /* pagein of a big page is an event. So, ignore page size */
915         if (nr_pages > 0)
916                 __this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PGPGIN]);
917         else {
918                 __this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PGPGOUT]);
919                 nr_pages = -nr_pages; /* for event */
920         }
921 
922         __this_cpu_add(memcg->stat->nr_page_events, nr_pages);
923 
924         preempt_enable();
925 }
926 
927 unsigned long
928 mem_cgroup_get_lru_size(struct lruvec *lruvec, enum lru_list lru)
929 {
930         struct mem_cgroup_per_zone *mz;
931 
932         mz = container_of(lruvec, struct mem_cgroup_per_zone, lruvec);
933         return mz->lru_size[lru];
934 }
935 
936 static unsigned long
937 mem_cgroup_zone_nr_lru_pages(struct mem_cgroup *memcg, int nid, int zid,
938                         unsigned int lru_mask)
939 {
940         struct mem_cgroup_per_zone *mz;
941         enum lru_list lru;
942         unsigned long ret = 0;
943 
944         mz = mem_cgroup_zoneinfo(memcg, nid, zid);
945 
946         for_each_lru(lru) {
947                 if (BIT(lru) & lru_mask)
948                         ret += mz->lru_size[lru];
949         }
950         return ret;
951 }
952 
953 static unsigned long
954 mem_cgroup_node_nr_lru_pages(struct mem_cgroup *memcg,
955                         int nid, unsigned int lru_mask)
956 {
957         u64 total = 0;
958         int zid;
959 
960         for (zid = 0; zid < MAX_NR_ZONES; zid++)
961                 total += mem_cgroup_zone_nr_lru_pages(memcg,
962                                                 nid, zid, lru_mask);
963 
964         return total;
965 }
966 
967 static unsigned long mem_cgroup_nr_lru_pages(struct mem_cgroup *memcg,
968                         unsigned int lru_mask)
969 {
970         int nid;
971         u64 total = 0;
972 
973         for_each_node_state(nid, N_MEMORY)
974                 total += mem_cgroup_node_nr_lru_pages(memcg, nid, lru_mask);
975         return total;
976 }
977 
978 static bool mem_cgroup_event_ratelimit(struct mem_cgroup *memcg,
979                                        enum mem_cgroup_events_target target)
980 {
981         unsigned long val, next;
982 
983         val = __this_cpu_read(memcg->stat->nr_page_events);
984         next = __this_cpu_read(memcg->stat->targets[target]);
985         /* from time_after() in jiffies.h */
986         if ((long)next - (long)val < 0) {
987                 switch (target) {
988                 case MEM_CGROUP_TARGET_THRESH:
989                         next = val + THRESHOLDS_EVENTS_TARGET;
990                         break;
991                 case MEM_CGROUP_TARGET_SOFTLIMIT:
992                         next = val + SOFTLIMIT_EVENTS_TARGET;
993                         break;
994                 case MEM_CGROUP_TARGET_NUMAINFO:
995                         next = val + NUMAINFO_EVENTS_TARGET;
996                         break;
997                 default:
998                         break;
999                 }
1000                 __this_cpu_write(memcg->stat->targets[target], next);
1001                 return true;
1002         }
1003         return false;
1004 }
1005 
1006 /*
1007  * Check events in order.
1008  *
1009  */
1010 static void memcg_check_events(struct mem_cgroup *memcg, struct page *page)
1011 {
1012         preempt_disable();
1013         /* threshold event is triggered in finer grain than soft limit */
1014         if (unlikely(mem_cgroup_event_ratelimit(memcg,
1015                                                 MEM_CGROUP_TARGET_THRESH))) {
1016                 bool do_softlimit;
1017                 bool do_numainfo __maybe_unused;
1018 
1019                 do_softlimit = mem_cgroup_event_ratelimit(memcg,
1020                                                 MEM_CGROUP_TARGET_SOFTLIMIT);
1021 #if MAX_NUMNODES > 1
1022                 do_numainfo = mem_cgroup_event_ratelimit(memcg,
1023                                                 MEM_CGROUP_TARGET_NUMAINFO);
1024 #endif
1025                 preempt_enable();
1026 
1027                 mem_cgroup_threshold(memcg);
1028                 if (unlikely(do_softlimit))
1029                         mem_cgroup_update_tree(memcg, page);
1030 #if MAX_NUMNODES > 1
1031                 if (unlikely(do_numainfo))
1032                         atomic_inc(&memcg->numainfo_events);
1033 #endif
1034         } else
1035                 preempt_enable();
1036 }
1037 
1038 struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont)
1039 {
1040         return mem_cgroup_from_css(
1041                 cgroup_subsys_state(cont, mem_cgroup_subsys_id));
1042 }
1043 
1044 struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
1045 {
1046         /*
1047          * mm_update_next_owner() may clear mm->owner to NULL
1048          * if it races with swapoff, page migration, etc.
1049          * So this can be called with p == NULL.
1050          */
1051         if (unlikely(!p))
1052                 return NULL;
1053 
1054         return mem_cgroup_from_css(task_subsys_state(p, mem_cgroup_subsys_id));
1055 }
1056 
1057 struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
1058 {
1059         struct mem_cgroup *memcg = NULL;
1060 
1061         if (!mm)
1062                 return NULL;
1063         /*
1064          * Because we have no locks, mm->owner's may be being moved to other
1065          * cgroup. We use css_tryget() here even if this looks
1066          * pessimistic (rather than adding locks here).
1067          */
1068         rcu_read_lock();
1069         do {
1070                 memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
1071                 if (unlikely(!memcg))
1072                         break;
1073         } while (!css_tryget(&memcg->css));
1074         rcu_read_unlock();
1075         return memcg;
1076 }
1077 
1078 /*
1079  * Returns a next (in a pre-order walk) alive memcg (with elevated css
1080  * ref. count) or NULL if the whole root's subtree has been visited.
1081  *
1082  * helper function to be used by mem_cgroup_iter
1083  */
1084 static struct mem_cgroup *__mem_cgroup_iter_next(struct mem_cgroup *root,
1085                 struct mem_cgroup *last_visited)
1086 {
1087         struct cgroup *prev_cgroup, *next_cgroup;
1088 
1089         /*
1090          * Root is not visited by cgroup iterators so it needs an
1091          * explicit visit.
1092          */
1093         if (!last_visited)
1094                 return root;
1095 
1096         prev_cgroup = (last_visited == root) ? NULL
1097                 : last_visited->css.cgroup;
1098 skip_node:
1099         next_cgroup = cgroup_next_descendant_pre(
1100                         prev_cgroup, root->css.cgroup);
1101 
1102         /*
1103          * Even if we found a group we have to make sure it is
1104          * alive. css && !memcg means that the groups should be
1105          * skipped and we should continue the tree walk.
1106          * last_visited css is safe to use because it is
1107          * protected by css_get and the tree walk is rcu safe.
1108          */
1109         if (next_cgroup) {
1110                 struct mem_cgroup *mem = mem_cgroup_from_cont(
1111                                 next_cgroup);
1112                 if (css_tryget(&mem->css))
1113                         return mem;
1114                 else {
1115                         prev_cgroup = next_cgroup;
1116                         goto skip_node;
1117                 }
1118         }
1119 
1120         return NULL;
1121 }
1122 
1123 static void mem_cgroup_iter_invalidate(struct mem_cgroup *root)
1124 {
1125         /*
1126          * When a group in the hierarchy below root is destroyed, the
1127          * hierarchy iterator can no longer be trusted since it might
1128          * have pointed to the destroyed group.  Invalidate it.
1129          */
1130         atomic_inc(&root->dead_count);
1131 }
1132 
1133 static struct mem_cgroup *
1134 mem_cgroup_iter_load(struct mem_cgroup_reclaim_iter *iter,
1135                      struct mem_cgroup *root,
1136                      int *sequence)
1137 {
1138         struct mem_cgroup *position = NULL;
1139         /*
1140          * A cgroup destruction happens in two stages: offlining and
1141          * release.  They are separated by a RCU grace period.
1142          *
1143          * If the iterator is valid, we may still race with an
1144          * offlining.  The RCU lock ensures the object won't be
1145          * released, tryget will fail if we lost the race.
1146          */
1147         *sequence = atomic_read(&root->dead_count);
1148         if (iter->last_dead_count == *sequence) {
1149                 smp_rmb();
1150                 position = iter->last_visited;
1151                 if (position && !css_tryget(&position->css))
1152                         position = NULL;
1153         }
1154         return position;
1155 }
1156 
1157 static void mem_cgroup_iter_update(struct mem_cgroup_reclaim_iter *iter,
1158                                    struct mem_cgroup *last_visited,
1159                                    struct mem_cgroup *new_position,
1160                                    int sequence)
1161 {
1162         if (last_visited)
1163                 css_put(&last_visited->css);
1164         /*
1165          * We store the sequence count from the time @last_visited was
1166          * loaded successfully instead of rereading it here so that we
1167          * don't lose destruction events in between.  We could have
1168          * raced with the destruction of @new_position after all.
1169          */
1170         iter->last_visited = new_position;
1171         smp_wmb();
1172         iter->last_dead_count = sequence;
1173 }
1174 
1175 /**
1176  * mem_cgroup_iter - iterate over memory cgroup hierarchy
1177  * @root: hierarchy root
1178  * @prev: previously returned memcg, NULL on first invocation
1179  * @reclaim: cookie for shared reclaim walks, NULL for full walks
1180  *
1181  * Returns references to children of the hierarchy below @root, or
1182  * @root itself, or %NULL after a full round-trip.
1183  *
1184  * Caller must pass the return value in @prev on subsequent
1185  * invocations for reference counting, or use mem_cgroup_iter_break()
1186  * to cancel a hierarchy walk before the round-trip is complete.
1187  *
1188  * Reclaimers can specify a zone and a priority level in @reclaim to
1189  * divide up the memcgs in the hierarchy among all concurrent
1190  * reclaimers operating on the same zone and priority.
1191  */
1192 struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
1193                                    struct mem_cgroup *prev,
1194                                    struct mem_cgroup_reclaim_cookie *reclaim)
1195 {
1196         struct mem_cgroup *memcg = NULL;
1197         struct mem_cgroup *last_visited = NULL;
1198 
1199         if (mem_cgroup_disabled())
1200                 return NULL;
1201 
1202         if (!root)
1203                 root = root_mem_cgroup;
1204 
1205         if (prev && !reclaim)
1206                 last_visited = prev;
1207 
1208         if (!root->use_hierarchy && root != root_mem_cgroup) {
1209                 if (prev)
1210                         goto out_css_put;
1211                 return root;
1212         }
1213 
1214         rcu_read_lock();
1215         while (!memcg) {
1216                 struct mem_cgroup_reclaim_iter *uninitialized_var(iter);
1217                 int uninitialized_var(seq);
1218 
1219                 if (reclaim) {
1220                         int nid = zone_to_nid(reclaim->zone);
1221                         int zid = zone_idx(reclaim->zone);
1222                         struct mem_cgroup_per_zone *mz;
1223 
1224                         mz = mem_cgroup_zoneinfo(root, nid, zid);
1225                         iter = &mz->reclaim_iter[reclaim->priority];
1226                         if (prev && reclaim->generation != iter->generation) {
1227                                 iter->last_visited = NULL;
1228                                 goto out_unlock;
1229                         }
1230 
1231                         last_visited = mem_cgroup_iter_load(iter, root, &seq);
1232                 }
1233 
1234                 memcg = __mem_cgroup_iter_next(root, last_visited);
1235 
1236                 if (reclaim) {
1237                         mem_cgroup_iter_update(iter, last_visited, memcg, seq);
1238 
1239                         if (!memcg)
1240                                 iter->generation++;
1241                         else if (!prev && memcg)
1242                                 reclaim->generation = iter->generation;
1243                 }
1244 
1245                 if (prev && !memcg)
1246                         goto out_unlock;
1247         }
1248 out_unlock:
1249         rcu_read_unlock();
1250 out_css_put:
1251         if (prev && prev != root)
1252                 css_put(&prev->css);
1253 
1254         return memcg;
1255 }
1256 
1257 /**
1258  * mem_cgroup_iter_break - abort a hierarchy walk prematurely
1259  * @root: hierarchy root
1260  * @prev: last visited hierarchy member as returned by mem_cgroup_iter()
1261  */
1262 void mem_cgroup_iter_break(struct mem_cgroup *root,
1263                            struct mem_cgroup *prev)
1264 {
1265         if (!root)
1266                 root = root_mem_cgroup;
1267         if (prev && prev != root)
1268                 css_put(&prev->css);
1269 }
1270 
1271 /*
1272  * Iteration constructs for visiting all cgroups (under a tree).  If
1273  * loops are exited prematurely (break), mem_cgroup_iter_break() must
1274  * be used for reference counting.
1275  */
1276 #define for_each_mem_cgroup_tree(iter, root)            \
1277         for (iter = mem_cgroup_iter(root, NULL, NULL);  \
1278              iter != NULL;                              \
1279              iter = mem_cgroup_iter(root, iter, NULL))
1280 
1281 #define for_each_mem_cgroup(iter)                       \
1282         for (iter = mem_cgroup_iter(NULL, NULL, NULL);  \
1283              iter != NULL;                              \
1284              iter = mem_cgroup_iter(NULL, iter, NULL))
1285 
1286 void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
1287 {
1288         struct mem_cgroup *memcg;
1289 
1290         rcu_read_lock();
1291         memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
1292         if (unlikely(!memcg))
1293                 goto out;
1294 
1295         switch (idx) {
1296         case PGFAULT:
1297                 this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PGFAULT]);
1298                 break;
1299         case PGMAJFAULT:
1300                 this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PGMAJFAULT]);
1301                 break;
1302         default:
1303                 BUG();
1304         }
1305 out:
1306         rcu_read_unlock();
1307 }
1308 EXPORT_SYMBOL(__mem_cgroup_count_vm_event);
1309 
1310 /**
1311  * mem_cgroup_zone_lruvec - get the lru list vector for a zone and memcg
1312  * @zone: zone of the wanted lruvec
1313  * @memcg: memcg of the wanted lruvec
1314  *
1315  * Returns the lru list vector holding pages for the given @zone and
1316  * @mem.  This can be the global zone lruvec, if the memory controller
1317  * is disabled.
1318  */
1319 struct lruvec *mem_cgroup_zone_lruvec(struct zone *zone,
1320                                       struct mem_cgroup *memcg)
1321 {
1322         struct mem_cgroup_per_zone *mz;
1323         struct lruvec *lruvec;
1324 
1325         if (mem_cgroup_disabled()) {
1326                 lruvec = &zone->lruvec;
1327                 goto out;
1328         }
1329 
1330         mz = mem_cgroup_zoneinfo(memcg, zone_to_nid(zone), zone_idx(zone));
1331         lruvec = &mz->lruvec;
1332 out:
1333         /*
1334          * Since a node can be onlined after the mem_cgroup was created,
1335          * we have to be prepared to initialize lruvec->zone here;
1336          * and if offlined then reonlined, we need to reinitialize it.
1337          */
1338         if (unlikely(lruvec->zone != zone))
1339                 lruvec->zone = zone;
1340         return lruvec;
1341 }
1342 
1343 /*
1344  * Following LRU functions are allowed to be used without PCG_LOCK.
1345  * Operations are called by routine of global LRU independently from memcg.
1346  * What we have to take care of here is validness of pc->mem_cgroup.
1347  *
1348  * Changes to pc->mem_cgroup happens when
1349  * 1. charge
1350  * 2. moving account
1351  * In typical case, "charge" is done before add-to-lru. Exception is SwapCache.
1352  * It is added to LRU before charge.
1353  * If PCG_USED bit is not set, page_cgroup is not added to this private LRU.
1354  * When moving account, the page is not on LRU. It's isolated.
1355  */
1356 
1357 /**
1358  * mem_cgroup_page_lruvec - return lruvec for adding an lru page
1359  * @page: the page
1360  * @zone: zone of the page
1361  */
1362 struct lruvec *mem_cgroup_page_lruvec(struct page *page, struct zone *zone)
1363 {
1364         struct mem_cgroup_per_zone *mz;
1365         struct mem_cgroup *memcg;
1366         struct page_cgroup *pc;
1367         struct lruvec *lruvec;
1368 
1369         if (mem_cgroup_disabled()) {
1370                 lruvec = &zone->lruvec;
1371                 goto out;
1372         }
1373 
1374         pc = lookup_page_cgroup(page);
1375         memcg = pc->mem_cgroup;
1376 
1377         /*
1378          * Surreptitiously switch any uncharged offlist page to root:
1379          * an uncharged page off lru does nothing to secure
1380          * its former mem_cgroup from sudden removal.
1381          *
1382          * Our caller holds lru_lock, and PageCgroupUsed is updated
1383          * under page_cgroup lock: between them, they make all uses
1384          * of pc->mem_cgroup safe.
1385          */
1386         if (!PageLRU(page) && !PageCgroupUsed(pc) && memcg != root_mem_cgroup)
1387                 pc->mem_cgroup = memcg = root_mem_cgroup;
1388 
1389         mz = page_cgroup_zoneinfo(memcg, page);
1390         lruvec = &mz->lruvec;
1391 out:
1392         /*
1393          * Since a node can be onlined after the mem_cgroup was created,
1394          * we have to be prepared to initialize lruvec->zone here;
1395          * and if offlined then reonlined, we need to reinitialize it.
1396          */
1397         if (unlikely(lruvec->zone != zone))
1398                 lruvec->zone = zone;
1399         return lruvec;
1400 }
1401 
1402 /**
1403  * mem_cgroup_update_lru_size - account for adding or removing an lru page
1404  * @lruvec: mem_cgroup per zone lru vector
1405  * @lru: index of lru list the page is sitting on
1406  * @nr_pages: positive when adding or negative when removing
1407  *
1408  * This function must be called when a page is added to or removed from an
1409  * lru list.
1410  */
1411 void mem_cgroup_update_lru_size(struct lruvec *lruvec, enum lru_list lru,
1412                                 int nr_pages)
1413 {
1414         struct mem_cgroup_per_zone *mz;
1415         unsigned long *lru_size;
1416 
1417         if (mem_cgroup_disabled())
1418                 return;
1419 
1420         mz = container_of(lruvec, struct mem_cgroup_per_zone, lruvec);
1421         lru_size = mz->lru_size + lru;
1422         *lru_size += nr_pages;
1423         VM_BUG_ON((long)(*lru_size) < 0);
1424 }
1425 
1426 /*
1427  * Checks whether given mem is same or in the root_mem_cgroup's
1428  * hierarchy subtree
1429  */
1430 bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
1431                                   struct mem_cgroup *memcg)
1432 {
1433         if (root_memcg == memcg)
1434                 return true;
1435         if (!root_memcg->use_hierarchy || !memcg)
1436                 return false;
1437         return css_is_ancestor(&memcg->css, &root_memcg->css);
1438 }
1439 
1440 static bool mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
1441                                        struct mem_cgroup *memcg)
1442 {
1443         bool ret;
1444 
1445         rcu_read_lock();
1446         ret = __mem_cgroup_same_or_subtree(root_memcg, memcg);
1447         rcu_read_unlock();
1448         return ret;
1449 }
1450 
1451 bool task_in_mem_cgroup(struct task_struct *task,
1452                         const struct mem_cgroup *memcg)
1453 {
1454         struct mem_cgroup *curr = NULL;
1455         struct task_struct *p;
1456         bool ret;
1457 
1458         p = find_lock_task_mm(task);
1459         if (p) {
1460                 curr = try_get_mem_cgroup_from_mm(p->mm);
1461                 task_unlock(p);
1462         } else {
1463                 /*
1464                  * All threads may have already detached their mm's, but the oom
1465                  * killer still needs to detect if they have already been oom
1466                  * killed to prevent needlessly killing additional tasks.
1467                  */
1468                 rcu_read_lock();
1469                 curr = mem_cgroup_from_task(task);
1470                 if (curr)
1471                         css_get(&curr->css);
1472                 rcu_read_unlock();
1473         }
1474         if (!curr)
1475                 return false;
1476         /*
1477          * We should check use_hierarchy of "memcg" not "curr". Because checking
1478          * use_hierarchy of "curr" here make this function true if hierarchy is
1479          * enabled in "curr" and "curr" is a child of "memcg" in *cgroup*
1480          * hierarchy(even if use_hierarchy is disabled in "memcg").
1481          */
1482         ret = mem_cgroup_same_or_subtree(memcg, curr);
1483         css_put(&curr->css);
1484         return ret;
1485 }
1486 
1487 int mem_cgroup_inactive_anon_is_low(struct lruvec *lruvec)
1488 {
1489         unsigned long inactive_ratio;
1490         unsigned long inactive;
1491         unsigned long active;
1492         unsigned long gb;
1493 
1494         inactive = mem_cgroup_get_lru_size(lruvec, LRU_INACTIVE_ANON);
1495         active = mem_cgroup_get_lru_size(lruvec, LRU_ACTIVE_ANON);
1496 
1497         gb = (inactive + active) >> (30 - PAGE_SHIFT);
1498         if (gb)
1499                 inactive_ratio = int_sqrt(10 * gb);
1500         else
1501                 inactive_ratio = 1;
1502 
1503         return inactive * inactive_ratio < active;
1504 }
1505 
1506 #define mem_cgroup_from_res_counter(counter, member)    \
1507         container_of(counter, struct mem_cgroup, member)
1508 
1509 /**
1510  * mem_cgroup_margin - calculate chargeable space of a memory cgroup
1511  * @memcg: the memory cgroup
1512  *
1513  * Returns the maximum amount of memory @mem can be charged with, in
1514  * pages.
1515  */
1516 static unsigned long mem_cgroup_margin(struct mem_cgroup *memcg)
1517 {
1518         unsigned long long margin;
1519 
1520         margin = res_counter_margin(&memcg->res);
1521         if (do_swap_account)
1522                 margin = min(margin, res_counter_margin(&memcg->memsw));
1523         return margin >> PAGE_SHIFT;
1524 }
1525 
1526 int mem_cgroup_swappiness(struct mem_cgroup *memcg)
1527 {
1528         struct cgroup *cgrp = memcg->css.cgroup;
1529 
1530         /* root ? */
1531         if (cgrp->parent == NULL)
1532                 return vm_swappiness;
1533 
1534         return memcg->swappiness;
1535 }
1536 
1537 /*
1538  * memcg->moving_account is used for checking possibility that some thread is
1539  * calling move_account(). When a thread on CPU-A starts moving pages under
1540  * a memcg, other threads should check memcg->moving_account under
1541  * rcu_read_lock(), like this:
1542  *
1543  *         CPU-A                                    CPU-B
1544  *                                              rcu_read_lock()
1545  *         memcg->moving_account+1              if (memcg->mocing_account)
1546  *                                                   take heavy locks.
1547  *         synchronize_rcu()                    update something.
1548  *                                              rcu_read_unlock()
1549  *         start move here.
1550  */
1551 
1552 /* for quick checking without looking up memcg */
1553 atomic_t memcg_moving __read_mostly;
1554 
1555 static void mem_cgroup_start_move(struct mem_cgroup *memcg)
1556 {
1557         atomic_inc(&memcg_moving);
1558         atomic_inc(&memcg->moving_account);
1559         synchronize_rcu();
1560 }
1561 
1562 static void mem_cgroup_end_move(struct mem_cgroup *memcg)
1563 {
1564         /*
1565          * Now, mem_cgroup_clear_mc() may call this function with NULL.
1566          * We check NULL in callee rather than caller.
1567          */
1568         if (memcg) {
1569                 atomic_dec(&memcg_moving);
1570                 atomic_dec(&memcg->moving_account);
1571         }
1572 }
1573 
1574 /*
1575  * 2 routines for checking "mem" is under move_account() or not.
1576  *
1577  * mem_cgroup_stolen() -  checking whether a cgroup is mc.from or not. This
1578  *                        is used for avoiding races in accounting.  If true,
1579  *                        pc->mem_cgroup may be overwritten.
1580  *
1581  * mem_cgroup_under_move() - checking a cgroup is mc.from or mc.to or
1582  *                        under hierarchy of moving cgroups. This is for
1583  *                        waiting at hith-memory prressure caused by "move".
1584  */
1585 
1586 static bool mem_cgroup_stolen(struct mem_cgroup *memcg)
1587 {
1588         VM_BUG_ON(!rcu_read_lock_held());
1589         return atomic_read(&memcg->moving_account) > 0;
1590 }
1591 
1592 static bool mem_cgroup_under_move(struct mem_cgroup *memcg)
1593 {
1594         struct mem_cgroup *from;
1595         struct mem_cgroup *to;
1596         bool ret = false;
1597         /*
1598          * Unlike task_move routines, we access mc.to, mc.from not under
1599          * mutual exclusion by cgroup_mutex. Here, we take spinlock instead.
1600          */
1601         spin_lock(&mc.lock);
1602         from = mc.from;
1603         to = mc.to;
1604         if (!from)
1605                 goto unlock;
1606 
1607         ret = mem_cgroup_same_or_subtree(memcg, from)
1608                 || mem_cgroup_same_or_subtree(memcg, to);
1609 unlock:
1610         spin_unlock(&mc.lock);
1611         return ret;
1612 }
1613 
1614 static bool mem_cgroup_wait_acct_move(struct mem_cgroup *memcg)
1615 {
1616         if (mc.moving_task && current != mc.moving_task) {
1617                 if (mem_cgroup_under_move(memcg)) {
1618                         DEFINE_WAIT(wait);
1619                         prepare_to_wait(&mc.waitq, &wait, TASK_INTERRUPTIBLE);
1620                         /* moving charge context might have finished. */
1621                         if (mc.moving_task)
1622                                 schedule();
1623                         finish_wait(&mc.waitq, &wait);
1624                         return true;
1625                 }
1626         }
1627         return false;
1628 }
1629 
1630 /*
1631  * Take this lock when
1632  * - a code tries to modify page's memcg while it's USED.
1633  * - a code tries to modify page state accounting in a memcg.
1634  * see mem_cgroup_stolen(), too.
1635  */
1636 static void move_lock_mem_cgroup(struct mem_cgroup *memcg,
1637                                   unsigned long *flags)
1638 {
1639         spin_lock_irqsave(&memcg->move_lock, *flags);
1640 }
1641 
1642 static void move_unlock_mem_cgroup(struct mem_cgroup *memcg,
1643                                 unsigned long *flags)
1644 {
1645         spin_unlock_irqrestore(&memcg->move_lock, *flags);
1646 }
1647 
1648 #define K(x) ((x) << (PAGE_SHIFT-10))
1649 /**
1650  * mem_cgroup_print_oom_info: Print OOM information relevant to memory controller.
1651  * @memcg: The memory cgroup that went over limit
1652  * @p: Task that is going to be killed
1653  *
1654  * NOTE: @memcg and @p's mem_cgroup can be different when hierarchy is
1655  * enabled
1656  */
1657 void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
1658 {
1659         struct cgroup *task_cgrp;
1660         struct cgroup *mem_cgrp;
1661         /*
1662          * Need a buffer in BSS, can't rely on allocations. The code relies
1663          * on the assumption that OOM is serialized for memory controller.
1664          * If this assumption is broken, revisit this code.
1665          */
1666         static char memcg_name[PATH_MAX];
1667         int ret;
1668         struct mem_cgroup *iter;
1669         unsigned int i;
1670 
1671         if (!p)
1672                 return;
1673 
1674         rcu_read_lock();
1675 
1676         mem_cgrp = memcg->css.cgroup;
1677         task_cgrp = task_cgroup(p, mem_cgroup_subsys_id);
1678 
1679         ret = cgroup_path(task_cgrp, memcg_name, PATH_MAX);
1680         if (ret < 0) {
1681                 /*
1682                  * Unfortunately, we are unable to convert to a useful name
1683                  * But we'll still print out the usage information
1684                  */
1685                 rcu_read_unlock();
1686                 goto done;
1687         }
1688         rcu_read_unlock();
1689 
1690         pr_info("Task in %s killed", memcg_name);
1691 
1692         rcu_read_lock();
1693         ret = cgroup_path(mem_cgrp, memcg_name, PATH_MAX);
1694         if (ret < 0) {
1695                 rcu_read_unlock();
1696                 goto done;
1697         }
1698         rcu_read_unlock();
1699 
1700         /*
1701          * Continues from above, so we don't need an KERN_ level
1702          */
1703         pr_cont(" as a result of limit of %s\n", memcg_name);
1704 done:
1705 
1706         pr_info("memory: usage %llukB, limit %llukB, failcnt %llu\n",
1707                 res_counter_read_u64(&memcg->res, RES_USAGE) >> 10,
1708                 res_counter_read_u64(&memcg->res, RES_LIMIT) >> 10,
1709                 res_counter_read_u64(&memcg->res, RES_FAILCNT));
1710         pr_info("memory+swap: usage %llukB, limit %llukB, failcnt %llu\n",
1711                 res_counter_read_u64(&memcg->memsw, RES_USAGE) >> 10,
1712                 res_counter_read_u64(&memcg->memsw, RES_LIMIT) >> 10,
1713                 res_counter_read_u64(&memcg->memsw, RES_FAILCNT));
1714         pr_info("kmem: usage %llukB, limit %llukB, failcnt %llu\n",
1715                 res_counter_read_u64(&memcg->kmem, RES_USAGE) >> 10,
1716                 res_counter_read_u64(&memcg->kmem, RES_LIMIT) >> 10,
1717                 res_counter_read_u64(&memcg->kmem, RES_FAILCNT));
1718 
1719         for_each_mem_cgroup_tree(iter, memcg) {
1720                 pr_info("Memory cgroup stats");
1721 
1722                 rcu_read_lock();
1723                 ret = cgroup_path(iter->css.cgroup, memcg_name, PATH_MAX);
1724                 if (!ret)
1725                         pr_cont(" for %s", memcg_name);
1726                 rcu_read_unlock();
1727                 pr_cont(":");
1728 
1729                 for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) {
1730                         if (i == MEM_CGROUP_STAT_SWAP && !do_swap_account)
1731                                 continue;
1732                         pr_cont(" %s:%ldKB", mem_cgroup_stat_names[i],
1733                                 K(mem_cgroup_read_stat(iter, i)));
1734                 }
1735 
1736                 for (i = 0; i < NR_LRU_LISTS; i++)
1737                         pr_cont(" %s:%luKB", mem_cgroup_lru_names[i],
1738                                 K(mem_cgroup_nr_lru_pages(iter, BIT(i))));
1739 
1740                 pr_cont("\n");
1741         }
1742 }
1743 
1744 /*
1745  * This function returns the number of memcg under hierarchy tree. Returns
1746  * 1(self count) if no children.
1747  */
1748 static int mem_cgroup_count_children(struct mem_cgroup *memcg)
1749 {
1750         int num = 0;
1751         struct mem_cgroup *iter;
1752 
1753         for_each_mem_cgroup_tree(iter, memcg)
1754                 num++;
1755         return num;
1756 }
1757 
1758 /*
1759  * Return the memory (and swap, if configured) limit for a memcg.
1760  */
1761 static u64 mem_cgroup_get_limit(struct mem_cgroup *memcg)
1762 {
1763         u64 limit;
1764 
1765         limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
1766 
1767         /*
1768          * Do not consider swap space if we cannot swap due to swappiness
1769          */
1770         if (mem_cgroup_swappiness(memcg)) {
1771                 u64 memsw;
1772 
1773                 limit += total_swap_pages << PAGE_SHIFT;
1774                 memsw = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
1775 
1776                 /*
1777                  * If memsw is finite and limits the amount of swap space
1778                  * available to this memcg, return that limit.
1779                  */
1780                 limit = min(limit, memsw);
1781         }
1782 
1783         return limit;
1784 }
1785 
1786 static void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
1787                                      int order)
1788 {
1789         struct mem_cgroup *iter;
1790         unsigned long chosen_points = 0;
1791         unsigned long totalpages;
1792         unsigned int points = 0;
1793         struct task_struct *chosen = NULL;
1794 
1795         /*
1796          * If current has a pending SIGKILL or is exiting, then automatically
1797          * select it.  The goal is to allow it to allocate so that it may
1798          * quickly exit and free its memory.
1799          */
1800         if (fatal_signal_pending(current) || current->flags & PF_EXITING) {
1801                 set_thread_flag(TIF_MEMDIE);
1802                 return;
1803         }
1804 
1805         check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, order, NULL);
1806         totalpages = mem_cgroup_get_limit(memcg) >> PAGE_SHIFT ? : 1;
1807         for_each_mem_cgroup_tree(iter, memcg) {
1808                 struct cgroup *cgroup = iter->css.cgroup;
1809                 struct cgroup_iter it;
1810                 struct task_struct *task;
1811 
1812                 cgroup_iter_start(cgroup, &it);
1813                 while ((task = cgroup_iter_next(cgroup, &it))) {
1814                         switch (oom_scan_process_thread(task, totalpages, NULL,
1815                                                         false)) {
1816                         case OOM_SCAN_SELECT:
1817                                 if (chosen)
1818                                         put_task_struct(chosen);
1819                                 chosen = task;
1820                                 chosen_points = ULONG_MAX;
1821                                 get_task_struct(chosen);
1822                                 /* fall through */
1823                         case OOM_SCAN_CONTINUE:
1824                                 continue;
1825                         case OOM_SCAN_ABORT:
1826                                 cgroup_iter_end(cgroup, &it);
1827                                 mem_cgroup_iter_break(memcg, iter);
1828                                 if (chosen)
1829                                         put_task_struct(chosen);
1830                                 return;
1831                         case OOM_SCAN_OK:
1832                                 break;
1833                         };
1834                         points = oom_badness(task, memcg, NULL, totalpages);
1835                         if (points > chosen_points) {
1836                                 if (chosen)
1837                                         put_task_struct(chosen);
1838                                 chosen = task;
1839                                 chosen_points = points;
1840                                 get_task_struct(chosen);
1841                         }
1842                 }
1843                 cgroup_iter_end(cgroup, &it);
1844         }
1845 
1846         if (!chosen)
1847                 return;
1848         points = chosen_points * 1000 / totalpages;
1849         oom_kill_process(chosen, gfp_mask, order, points, totalpages, memcg,
1850                          NULL, "Memory cgroup out of memory");
1851 }
1852 
1853 static unsigned long mem_cgroup_reclaim(struct mem_cgroup *memcg,
1854                                         gfp_t gfp_mask,
1855                                         unsigned long flags)
1856 {
1857         unsigned long total = 0;
1858         bool noswap = false;
1859         int loop;
1860 
1861         if (flags & MEM_CGROUP_RECLAIM_NOSWAP)
1862                 noswap = true;
1863         if (!(flags & MEM_CGROUP_RECLAIM_SHRINK) && memcg->memsw_is_minimum)
1864                 noswap = true;
1865 
1866         for (loop = 0; loop < MEM_CGROUP_MAX_RECLAIM_LOOPS; loop++) {
1867                 if (loop)
1868                         drain_all_stock_async(memcg);
1869                 total += try_to_free_mem_cgroup_pages(memcg, gfp_mask, noswap);
1870                 /*
1871                  * Allow limit shrinkers, which are triggered directly
1872                  * by userspace, to catch signals and stop reclaim
1873                  * after minimal progress, regardless of the margin.
1874                  */
1875                 if (total && (flags & MEM_CGROUP_RECLAIM_SHRINK))
1876                         break;
1877                 if (mem_cgroup_margin(memcg))
1878                         break;
1879                 /*
1880                  * If nothing was reclaimed after two attempts, there
1881                  * may be no reclaimable pages in this hierarchy.
1882                  */
1883                 if (loop && !total)
1884                         break;
1885         }
1886         return total;
1887 }
1888 
1889 /**
1890  * test_mem_cgroup_node_reclaimable
1891  * @memcg: the target memcg
1892  * @nid: the node ID to be checked.
1893  * @noswap : specify true here if the user wants flle only information.
1894  *
1895  * This function returns whether the specified memcg contains any
1896  * reclaimable pages on a node. Returns true if there are any reclaimable
1897  * pages in the node.
1898  */
1899 static bool test_mem_cgroup_node_reclaimable(struct mem_cgroup *memcg,
1900                 int nid, bool noswap)
1901 {
1902         if (mem_cgroup_node_nr_lru_pages(memcg, nid, LRU_ALL_FILE))
1903                 return true;
1904         if (noswap || !total_swap_pages)
1905                 return false;
1906         if (mem_cgroup_node_nr_lru_pages(memcg, nid, LRU_ALL_ANON))
1907                 return true;
1908         return false;
1909 
1910 }
1911 #if MAX_NUMNODES > 1
1912 
1913 /*
1914  * Always updating the nodemask is not very good - even if we have an empty
1915  * list or the wrong list here, we can start from some node and traverse all
1916  * nodes based on the zonelist. So update the list loosely once per 10 secs.
1917  *
1918  */
1919 static void mem_cgroup_may_update_nodemask(struct mem_cgroup *memcg)
1920 {
1921         int nid;
1922         /*
1923          * numainfo_events > 0 means there was at least NUMAINFO_EVENTS_TARGET
1924          * pagein/pageout changes since the last update.
1925          */
1926         if (!atomic_read(&memcg->numainfo_events))
1927                 return;
1928         if (atomic_inc_return(&memcg->numainfo_updating) > 1)
1929                 return;
1930 
1931         /* make a nodemask where this memcg uses memory from */
1932         memcg->scan_nodes = node_states[N_MEMORY];
1933 
1934         for_each_node_mask(nid, node_states[N_MEMORY]) {
1935 
1936                 if (!test_mem_cgroup_node_reclaimable(memcg, nid, false))
1937                         node_clear(nid, memcg->scan_nodes);
1938         }
1939 
1940         atomic_set(&memcg->numainfo_events, 0);
1941         atomic_set(&memcg->numainfo_updating, 0);
1942 }
1943 
1944 /*
1945  * Selecting a node where we start reclaim from. Because what we need is just
1946  * reducing usage counter, start from anywhere is O,K. Considering
1947  * memory reclaim from current node, there are pros. and cons.
1948  *
1949  * Freeing memory from current node means freeing memory from a node which
1950  * we'll use or we've used. So, it may make LRU bad. And if several threads
1951  * hit limits, it will see a contention on a node. But freeing from remote
1952  * node means more costs for memory reclaim because of memory latency.
1953  *
1954  * Now, we use round-robin. Better algorithm is welcomed.
1955  */
1956 int mem_cgroup_select_victim_node(struct mem_cgroup *memcg)
1957 {
1958         int node;
1959 
1960         mem_cgroup_may_update_nodemask(memcg);
1961         node = memcg->last_scanned_node;
1962 
1963         node = next_node(node, memcg->scan_nodes);
1964         if (node == MAX_NUMNODES)
1965                 node = first_node(memcg->scan_nodes);
1966         /*
1967          * We call this when we hit limit, not when pages are added to LRU.
1968          * No LRU may hold pages because all pages are UNEVICTABLE or
1969          * memcg is too small and all pages are not on LRU. In that case,
1970          * we use curret node.
1971          */
1972         if (unlikely(node == MAX_NUMNODES))
1973                 node = numa_node_id();
1974 
1975         memcg->last_scanned_node = node;
1976         return node;
1977 }
1978 
1979 /*
1980  * Check all nodes whether it contains reclaimable pages or not.
1981  * For quick scan, we make use of scan_nodes. This will allow us to skip
1982  * unused nodes. But scan_nodes is lazily updated and may not cotain
1983  * enough new information. We need to do double check.
1984  */
1985 static bool mem_cgroup_reclaimable(struct mem_cgroup *memcg, bool noswap)
1986 {
1987         int nid;
1988 
1989         /*
1990          * quick check...making use of scan_node.
1991          * We can skip unused nodes.
1992          */
1993         if (!nodes_empty(memcg->scan_nodes)) {
1994                 for (nid = first_node(memcg->scan_nodes);
1995                      nid < MAX_NUMNODES;
1996                      nid = next_node(nid, memcg->scan_nodes)) {
1997 
1998                         if (test_mem_cgroup_node_reclaimable(memcg, nid, noswap))
1999                                 return true;
2000                 }
2001         }
2002         /*
2003          * Check rest of nodes.
2004          */
2005         for_each_node_state(nid, N_MEMORY) {
2006                 if (node_isset(nid, memcg->scan_nodes))
2007                         continue;
2008                 if (test_mem_cgroup_node_reclaimable(memcg, nid, noswap))
2009                         return true;
2010         }
2011         return false;
2012 }
2013 
2014 #else
2015 int mem_cgroup_select_victim_node(struct mem_cgroup *memcg)
2016 {
2017         return 0;
2018 }
2019 
2020 static bool mem_cgroup_reclaimable(struct mem_cgroup *memcg, bool noswap)
2021 {
2022         return test_mem_cgroup_node_reclaimable(memcg, 0, noswap);
2023 }
2024 #endif
2025 
2026 static int mem_cgroup_soft_reclaim(struct mem_cgroup *root_memcg,
2027                                    struct zone *zone,
2028                                    gfp_t gfp_mask,
2029                                    unsigned long *total_scanned)
2030 {
2031         struct mem_cgroup *victim = NULL;
2032         int total = 0;
2033         int loop = 0;
2034         unsigned long excess;
2035         unsigned long nr_scanned;
2036         struct mem_cgroup_reclaim_cookie reclaim = {
2037                 .zone = zone,
2038                 .priority = 0,
2039         };
2040 
2041         excess = res_counter_soft_limit_excess(&root_memcg->res) >> PAGE_SHIFT;
2042 
2043         while (1) {
2044                 victim = mem_cgroup_iter(root_memcg, victim, &reclaim);
2045                 if (!victim) {
2046                         loop++;
2047                         if (loop >= 2) {
2048                                 /*
2049                                  * If we have not been able to reclaim
2050                                  * anything, it might because there are
2051                                  * no reclaimable pages under this hierarchy
2052                                  */
2053                                 if (!total)
2054                                         break;
2055                                 /*
2056                                  * We want to do more targeted reclaim.
2057                                  * excess >> 2 is not to excessive so as to
2058                                  * reclaim too much, nor too less that we keep
2059                                  * coming back to reclaim from this cgroup
2060                                  */
2061                                 if (total >= (excess >> 2) ||
2062                                         (loop > MEM_CGROUP_MAX_RECLAIM_LOOPS))
2063                                         break;
2064                         }
2065                         continue;
2066                 }
2067                 if (!mem_cgroup_reclaimable(victim, false))
2068                         continue;
2069                 total += mem_cgroup_shrink_node_zone(victim, gfp_mask, false,
2070                                                      zone, &nr_scanned);
2071                 *total_scanned += nr_scanned;
2072                 if (!res_counter_soft_limit_excess(&root_memcg->res))
2073                         break;
2074         }
2075         mem_cgroup_iter_break(root_memcg, victim);
2076         return total;
2077 }
2078 
2079 /*
2080  * Check OOM-Killer is already running under our hierarchy.
2081  * If someone is running, return false.
2082  * Has to be called with memcg_oom_lock
2083  */
2084 static bool mem_cgroup_oom_lock(struct mem_cgroup *memcg)
2085 {
2086         struct mem_cgroup *iter, *failed = NULL;
2087 
2088         for_each_mem_cgroup_tree(iter, memcg) {
2089                 if (iter->oom_lock) {
2090                         /*
2091                          * this subtree of our hierarchy is already locked
2092                          * so we cannot give a lock.
2093                          */
2094                         failed = iter;
2095                         mem_cgroup_iter_break(memcg, iter);
2096                         break;
2097                 } else
2098                         iter->oom_lock = true;
2099         }
2100 
2101         if (!failed)
2102                 return true;
2103 
2104         /*
2105          * OK, we failed to lock the whole subtree so we have to clean up
2106          * what we set up to the failing subtree
2107          */
2108         for_each_mem_cgroup_tree(iter, memcg) {
2109                 if (iter == failed) {
2110                         mem_cgroup_iter_break(memcg, iter);
2111                         break;
2112                 }
2113                 iter->oom_lock = false;
2114         }
2115         return false;
2116 }
2117 
2118 /*
2119  * Has to be called with memcg_oom_lock
2120  */
2121 static int mem_cgroup_oom_unlock(struct mem_cgroup *memcg)
2122 {
2123         struct mem_cgroup *iter;
2124 
2125         for_each_mem_cgroup_tree(iter, memcg)
2126                 iter->oom_lock = false;
2127         return 0;
2128 }
2129 
2130 static void mem_cgroup_mark_under_oom(struct mem_cgroup *memcg)
2131 {
2132         struct mem_cgroup *iter;
2133 
2134         for_each_mem_cgroup_tree(iter, memcg)
2135                 atomic_inc(&iter->under_oom);
2136 }
2137 
2138 static void mem_cgroup_unmark_under_oom(struct mem_cgroup *memcg)
2139 {
2140         struct mem_cgroup *iter;
2141 
2142         /*
2143          * When a new child is created while the hierarchy is under oom,
2144          * mem_cgroup_oom_lock() may not be called. We have to use
2145          * atomic_add_unless() here.
2146          */
2147         for_each_mem_cgroup_tree(iter, memcg)
2148                 atomic_add_unless(&iter->under_oom, -1, 0);
2149 }
2150 
2151 static DEFINE_SPINLOCK(memcg_oom_lock);
2152 static DECLARE_WAIT_QUEUE_HEAD(memcg_oom_waitq);
2153 
2154 struct oom_wait_info {
2155         struct mem_cgroup *memcg;
2156         wait_queue_t    wait;
2157 };
2158 
2159 static int memcg_oom_wake_function(wait_queue_t *wait,
2160         unsigned mode, int sync, void *arg)
2161 {
2162         struct mem_cgroup *wake_memcg = (struct mem_cgroup *)arg;
2163         struct mem_cgroup *oom_wait_memcg;
2164         struct oom_wait_info *oom_wait_info;
2165 
2166         oom_wait_info = container_of(wait, struct oom_wait_info, wait);
2167         oom_wait_memcg = oom_wait_info->memcg;
2168 
2169         /*
2170          * Both of oom_wait_info->memcg and wake_memcg are stable under us.
2171          * Then we can use css_is_ancestor without taking care of RCU.
2172          */
2173         if (!mem_cgroup_same_or_subtree(oom_wait_memcg, wake_memcg)
2174                 && !mem_cgroup_same_or_subtree(wake_memcg, oom_wait_memcg))
2175                 return 0;
2176         return autoremove_wake_function(wait, mode, sync, arg);
2177 }
2178 
2179 static void memcg_wakeup_oom(struct mem_cgroup *memcg)
2180 {
2181         /* for filtering, pass "memcg" as argument. */
2182         __wake_up(&memcg_oom_waitq, TASK_NORMAL, 0, memcg);
2183 }
2184 
2185 static void memcg_oom_recover(struct mem_cgroup *memcg)
2186 {
2187         if (memcg && atomic_read(&memcg->under_oom))
2188                 memcg_wakeup_oom(memcg);
2189 }
2190 
2191 /*
2192  * try to call OOM killer. returns false if we should exit memory-reclaim loop.
2193  */
2194 static bool mem_cgroup_handle_oom(struct mem_cgroup *memcg, gfp_t mask,
2195                                   int order)
2196 {
2197         struct oom_wait_info owait;
2198         bool locked, need_to_kill;
2199 
2200         owait.memcg = memcg;
2201         owait.wait.flags = 0;
2202         owait.wait.func = memcg_oom_wake_function;
2203         owait.wait.private = current;
2204         INIT_LIST_HEAD(&owait.wait.task_list);
2205         need_to_kill = true;
2206         mem_cgroup_mark_under_oom(memcg);
2207 
2208         /* At first, try to OOM lock hierarchy under memcg.*/
2209         spin_lock(&memcg_oom_lock);
2210         locked = mem_cgroup_oom_lock(memcg);
2211         /*
2212          * Even if signal_pending(), we can't quit charge() loop without
2213          * accounting. So, UNINTERRUPTIBLE is appropriate. But SIGKILL
2214          * under OOM is always welcomed, use TASK_KILLABLE here.
2215          */
2216         prepare_to_wait(&memcg_oom_waitq, &owait.wait, TASK_KILLABLE);
2217         if (!locked || memcg->oom_kill_disable)
2218                 need_to_kill = false;
2219         if (locked)
2220                 mem_cgroup_oom_notify(memcg);
2221         spin_unlock(&memcg_oom_lock);
2222 
2223         if (need_to_kill) {
2224                 finish_wait(&memcg_oom_waitq, &owait.wait);
2225                 mem_cgroup_out_of_memory(memcg, mask, order);
2226         } else {
2227                 schedule();
2228                 finish_wait(&memcg_oom_waitq, &owait.wait);
2229         }
2230         spin_lock(&memcg_oom_lock);
2231         if (locked)
2232                 mem_cgroup_oom_unlock(memcg);
2233         memcg_wakeup_oom(memcg);
2234         spin_unlock(&memcg_oom_lock);
2235 
2236         mem_cgroup_unmark_under_oom(memcg);
2237 
2238         if (test_thread_flag(TIF_MEMDIE) || fatal_signal_pending(current))
2239                 return false;
2240         /* Give chance to dying process */
2241         schedule_timeout_uninterruptible(1);
2242         return true;
2243 }
2244 
2245 /*
2246  * Currently used to update mapped file statistics, but the routine can be
2247  * generalized to update other statistics as well.
2248  *
2249  * Notes: Race condition
2250  *
2251  * We usually use page_cgroup_lock() for accessing page_cgroup member but
2252  * it tends to be costly. But considering some conditions, we doesn't need
2253  * to do so _always_.
2254  *
2255  * Considering "charge", lock_page_cgroup() is not required because all
2256  * file-stat operations happen after a page is attached to radix-tree. There
2257  * are no race with "charge".
2258  *
2259  * Considering "uncharge", we know that memcg doesn't clear pc->mem_cgroup
2260  * at "uncharge" intentionally. So, we always see valid pc->mem_cgroup even
2261  * if there are race with "uncharge". Statistics itself is properly handled
2262  * by flags.
2263  *
2264  * Considering "move", this is an only case we see a race. To make the race
2265  * small, we check mm->moving_account and detect there are possibility of race
2266  * If there is, we take a lock.
2267  */
2268 
2269 void __mem_cgroup_begin_update_page_stat(struct page *page,
2270                                 bool *locked, unsigned long *flags)
2271 {
2272         struct mem_cgroup *memcg;
2273         struct page_cgroup *pc;
2274 
2275         pc = lookup_page_cgroup(page);
2276 again:
2277         memcg = pc->mem_cgroup;
2278         if (unlikely(!memcg || !PageCgroupUsed(pc)))
2279                 return;
2280         /*
2281          * If this memory cgroup is not under account moving, we don't
2282          * need to take move_lock_mem_cgroup(). Because we already hold
2283          * rcu_read_lock(), any calls to move_account will be delayed until
2284          * rcu_read_unlock() if mem_cgroup_stolen() == true.
2285          */
2286         if (!mem_cgroup_stolen(memcg))
2287                 return;
2288 
2289         move_lock_mem_cgroup(memcg, flags);
2290         if (memcg != pc->mem_cgroup || !PageCgroupUsed(pc)) {
2291                 move_unlock_mem_cgroup(memcg, flags);
2292                 goto again;
2293         }
2294         *locked = true;
2295 }
2296 
2297 void __mem_cgroup_end_update_page_stat(struct page *page, unsigned long *flags)
2298 {
2299         struct page_cgroup *pc = lookup_page_cgroup(page);
2300 
2301         /*
2302          * It's guaranteed that pc->mem_cgroup never changes while
2303          * lock is held because a routine modifies pc->mem_cgroup
2304          * should take move_lock_mem_cgroup().
2305          */
2306         move_unlock_mem_cgroup(pc->mem_cgroup, flags);
2307 }
2308 
2309 void mem_cgroup_update_page_stat(struct page *page,
2310                                  enum mem_cgroup_page_stat_item idx, int val)
2311 {
2312         struct mem_cgroup *memcg;
2313         struct page_cgroup *pc = lookup_page_cgroup(page);
2314         unsigned long uninitialized_var(flags);
2315 
2316         if (mem_cgroup_disabled())
2317                 return;
2318 
2319         memcg = pc->mem_cgroup;
2320         if (unlikely(!memcg || !PageCgroupUsed(pc)))
2321                 return;
2322 
2323         switch (idx) {
2324         case MEMCG_NR_FILE_MAPPED:
2325                 idx = MEM_CGROUP_STAT_FILE_MAPPED;
2326                 break;
2327         default:
2328                 BUG();
2329         }
2330 
2331         this_cpu_add(memcg->stat->count[idx], val);
2332 }
2333 
2334 /*
2335  * size of first charge trial. "32" comes from vmscan.c's magic value.
2336  * TODO: maybe necessary to use big numbers in big irons.
2337  */
2338 #define CHARGE_BATCH    32U
2339 struct memcg_stock_pcp {
2340         struct mem_cgroup *cached; /* this never be root cgroup */
2341         unsigned int nr_pages;
2342         struct work_struct work;
2343         unsigned long flags;
2344 #define FLUSHING_CACHED_CHARGE  0
2345 };
2346 static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock);
2347 static DEFINE_MUTEX(percpu_charge_mutex);
2348 
2349 /**
2350  * consume_stock: Try to consume stocked charge on this cpu.
2351  * @memcg: memcg to consume from.
2352  * @nr_pages: how many pages to charge.
2353  *
2354  * The charges will only happen if @memcg matches the current cpu's memcg
2355  * stock, and at least @nr_pages are available in that stock.  Failure to
2356  * service an allocation will refill the stock.
2357  *
2358  * returns true if successful, false otherwise.
2359  */
2360 static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
2361 {
2362         struct memcg_stock_pcp *stock;
2363         bool ret = true;
2364 
2365         if (nr_pages > CHARGE_BATCH)
2366                 return false;
2367 
2368         stock = &get_cpu_var(memcg_stock);
2369         if (memcg == stock->cached && stock->nr_pages >= nr_pages)
2370                 stock->nr_pages -= nr_pages;
2371         else /* need to call res_counter_charge */
2372                 ret = false;
2373         put_cpu_var(memcg_stock);
2374         return ret;
2375 }
2376 
2377 /*
2378  * Returns stocks cached in percpu to res_counter and reset cached information.
2379  */
2380 static void drain_stock(struct memcg_stock_pcp *stock)
2381 {
2382         struct mem_cgroup *old = stock->cached;
2383 
2384         if (stock->nr_pages) {
2385                 unsigned long bytes = stock->nr_pages * PAGE_SIZE;
2386 
2387                 res_counter_uncharge(&old->res, bytes);
2388                 if (do_swap_account)
2389                         res_counter_uncharge(&old->memsw, bytes);
2390                 stock->nr_pages = 0;
2391         }
2392         stock->cached = NULL;
2393 }
2394 
2395 /*
2396  * This must be called under preempt disabled or must be called by
2397  * a thread which is pinned to local cpu.
2398  */
2399 static void drain_local_stock(struct work_struct *dummy)
2400 {
2401         struct memcg_stock_pcp *stock = &__get_cpu_var(memcg_stock);
2402         drain_stock(stock);
2403         clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags);
2404 }
2405 
2406 static void __init memcg_stock_init(void)
2407 {
2408         int cpu;
2409 
2410         for_each_possible_cpu(cpu) {
2411                 struct memcg_stock_pcp *stock =
2412                                         &per_cpu(memcg_stock, cpu);
2413                 INIT_WORK(&stock->work, drain_local_stock);
2414         }
2415 }
2416 
2417 /*
2418  * Cache charges(val) which is from res_counter, to local per_cpu area.
2419  * This will be consumed by consume_stock() function, later.
2420  */
2421 static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
2422 {
2423         struct memcg_stock_pcp *stock = &get_cpu_var(memcg_stock);
2424 
2425         if (stock->cached != memcg) { /* reset if necessary */
2426                 drain_stock(stock);
2427                 stock->cached = memcg;
2428         }
2429         stock->nr_pages += nr_pages;
2430         put_cpu_var(memcg_stock);
2431 }
2432 
2433 /*
2434  * Drains all per-CPU charge caches for given root_memcg resp. subtree
2435  * of the hierarchy under it. sync flag says whether we should block
2436  * until the work is done.
2437  */
2438 static void drain_all_stock(struct mem_cgroup *root_memcg, bool sync)
2439 {
2440         int cpu, curcpu;
2441 
2442         /* Notify other cpus that system-wide "drain" is running */
2443         get_online_cpus();
2444         curcpu = get_cpu();
2445         for_each_online_cpu(cpu) {
2446                 struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu);
2447                 struct mem_cgroup *memcg;
2448 
2449                 memcg = stock->cached;
2450                 if (!memcg || !stock->nr_pages)
2451                         continue;
2452                 if (!mem_cgroup_same_or_subtree(root_memcg, memcg))
2453                         continue;
2454                 if (!test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags)) {
2455                         if (cpu == curcpu)
2456                                 drain_local_stock(&stock->work);
2457                         else
2458                                 schedule_work_on(cpu, &stock->work);
2459                 }
2460         }
2461         put_cpu();
2462 
2463         if (!sync)
2464                 goto out;
2465 
2466         for_each_online_cpu(cpu) {
2467                 struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu);
2468                 if (test_bit(FLUSHING_CACHED_CHARGE, &stock->flags))
2469                         flush_work(&stock->work);
2470         }
2471 out:
2472         put_online_cpus();
2473 }
2474 
2475 /*
2476  * Tries to drain stocked charges in other cpus. This function is asynchronous
2477  * and just put a work per cpu for draining localy on each cpu. Caller can
2478  * expects some charges will be back to res_counter later but cannot wait for
2479  * it.
2480  */
2481 static void drain_all_stock_async(struct mem_cgroup *root_memcg)
2482 {
2483         /*
2484          * If someone calls draining, avoid adding more kworker runs.
2485          */
2486         if (!mutex_trylock(&percpu_charge_mutex))
2487                 return;
2488         drain_all_stock(root_memcg, false);
2489         mutex_unlock(&percpu_charge_mutex);
2490 }
2491 
2492 /* This is a synchronous drain interface. */
2493 static void drain_all_stock_sync(struct mem_cgroup *root_memcg)
2494 {
2495         /* called when force_empty is called */
2496         mutex_lock(&percpu_charge_mutex);
2497         drain_all_stock(root_memcg, true);
2498         mutex_unlock(&percpu_charge_mutex);
2499 }
2500 
2501 /*
2502  * This function drains percpu counter value from DEAD cpu and
2503  * move it to local cpu. Note that this function can be preempted.
2504  */
2505 static void mem_cgroup_drain_pcp_counter(struct mem_cgroup *memcg, int cpu)
2506 {
2507         int i;
2508 
2509         spin_lock(&memcg->pcp_counter_lock);
2510         for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) {
2511                 long x = per_cpu(memcg->stat->count[i], cpu);
2512 
2513                 per_cpu(memcg->stat->count[i], cpu) = 0;
2514                 memcg->nocpu_base.count[i] += x;
2515         }
2516         for (i = 0; i < MEM_CGROUP_EVENTS_NSTATS; i++) {
2517                 unsigned long x = per_cpu(memcg->stat->events[i], cpu);
2518 
2519                 per_cpu(memcg->stat->events[i], cpu) = 0;
2520                 memcg->nocpu_base.events[i] += x;
2521         }
2522         spin_unlock(&memcg->pcp_counter_lock);
2523 }
2524 
2525 static int memcg_cpu_hotplug_callback(struct notifier_block *nb,
2526                                         unsigned long action,
2527                                         void *hcpu)
2528 {
2529         int cpu = (unsigned long)hcpu;
2530         struct memcg_stock_pcp *stock;
2531         struct mem_cgroup *iter;
2532 
2533         if (action == CPU_ONLINE)
2534                 return NOTIFY_OK;
2535 
2536         if (action != CPU_DEAD && action != CPU_DEAD_FROZEN)
2537                 return NOTIFY_OK;
2538 
2539         for_each_mem_cgroup(iter)
2540                 mem_cgroup_drain_pcp_counter(iter, cpu);
2541 
2542         stock = &per_cpu(memcg_stock, cpu);
2543         drain_stock(stock);
2544         return NOTIFY_OK;
2545 }
2546 
2547 
2548 /* See __mem_cgroup_try_charge() for details */
2549 enum {
2550         CHARGE_OK,              /* success */
2551         CHARGE_RETRY,           /* need to retry but retry is not bad */
2552         CHARGE_NOMEM,           /* we can't do more. return -ENOMEM */
2553         CHARGE_WOULDBLOCK,      /* GFP_WAIT wasn't set and no enough res. */
2554         CHARGE_OOM_DIE,         /* the current is killed because of OOM */
2555 };
2556 
2557 static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
2558                                 unsigned int nr_pages, unsigned int min_pages,
2559                                 bool oom_check)
2560 {
2561         unsigned long csize = nr_pages * PAGE_SIZE;
2562         struct mem_cgroup *mem_over_limit;
2563         struct res_counter *fail_res;
2564         unsigned long flags = 0;
2565         int ret;
2566 
2567         ret = res_counter_charge(&memcg->res, csize, &fail_res);
2568 
2569         if (likely(!ret)) {
2570                 if (!do_swap_account)
2571                         return CHARGE_OK;
2572                 ret = res_counter_charge(&memcg->memsw, csize, &fail_res);
2573                 if (likely(!ret))
2574                         return CHARGE_OK;
2575 
2576                 res_counter_uncharge(&memcg->res, csize);
2577                 mem_over_limit = mem_cgroup_from_res_counter(fail_res, memsw);
2578                 flags |= MEM_CGROUP_RECLAIM_NOSWAP;
2579         } else
2580                 mem_over_limit = mem_cgroup_from_res_counter(fail_res, res);
2581         /*
2582          * Never reclaim on behalf of optional batching, retry with a
2583          * single page instead.
2584          */
2585         if (nr_pages > min_pages)
2586                 return CHARGE_RETRY;
2587 
2588         if (!(gfp_mask & __GFP_WAIT))
2589                 return CHARGE_WOULDBLOCK;
2590 
2591         if (gfp_mask & __GFP_NORETRY)
2592                 return CHARGE_NOMEM;
2593 
2594         ret = mem_cgroup_reclaim(mem_over_limit, gfp_mask, flags);
2595         if (mem_cgroup_margin(mem_over_limit) >= nr_pages)
2596                 return CHARGE_RETRY;
2597         /*
2598          * Even though the limit is exceeded at this point, reclaim
2599          * may have been able to free some pages.  Retry the charge
2600          * before killing the task.
2601          *
2602          * Only for regular pages, though: huge pages are rather
2603          * unlikely to succeed so close to the limit, and we fall back
2604          * to regular pages anyway in case of failure.
2605          */
2606         if (nr_pages <= (1 << PAGE_ALLOC_COSTLY_ORDER) && ret)
2607                 return CHARGE_RETRY;
2608 
2609         /*
2610          * At task move, charge accounts can be doubly counted. So, it's
2611          * better to wait until the end of task_move if something is going on.
2612          */
2613         if (mem_cgroup_wait_acct_move(mem_over_limit))
2614                 return CHARGE_RETRY;
2615 
2616         /* If we don't need to call oom-killer at el, return immediately */
2617         if (!oom_check)
2618                 return CHARGE_NOMEM;
2619         /* check OOM */
2620         if (!mem_cgroup_handle_oom(mem_over_limit, gfp_mask, get_order(csize)))
2621                 return CHARGE_OOM_DIE;
2622 
2623         return CHARGE_RETRY;
2624 }
2625 
2626 /*
2627  * __mem_cgroup_try_charge() does
2628  * 1. detect memcg to be charged against from passed *mm and *ptr,
2629  * 2. update res_counter
2630  * 3. call memory reclaim if necessary.
2631  *
2632  * In some special case, if the task is fatal, fatal_signal_pending() or
2633  * has TIF_MEMDIE, this function returns -EINTR while writing root_mem_cgroup
2634  * to *ptr. There are two reasons for this. 1: fatal threads should quit as soon
2635  * as possible without any hazards. 2: all pages should have a valid
2636  * pc->mem_cgroup. If mm is NULL and the caller doesn't pass a valid memcg
2637  * pointer, that is treated as a charge to root_mem_cgroup.
2638  *
2639  * So __mem_cgroup_try_charge() will return
2640  *  0       ...  on success, filling *ptr with a valid memcg pointer.
2641  *  -ENOMEM ...  charge failure because of resource limits.
2642  *  -EINTR  ...  if thread is fatal. *ptr is filled with root_mem_cgroup.
2643  *
2644  * Unlike the exported interface, an "oom" parameter is added. if oom==true,
2645  * the oom-killer can be invoked.
2646  */
2647 static int __mem_cgroup_try_charge(struct mm_struct *mm,
2648                                    gfp_t gfp_mask,
2649                                    unsigned int nr_pages,
2650                                    struct mem_cgroup **ptr,
2651                                    bool oom)
2652 {
2653         unsigned int batch = max(CHARGE_BATCH, nr_pages);
2654         int nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
2655         struct mem_cgroup *memcg = NULL;
2656         int ret;
2657 
2658         /*
2659          * Unlike gloval-vm's OOM-kill, we're not in memory shortage
2660          * in system level. So, allow to go ahead dying process in addition to
2661          * MEMDIE process.
2662          */
2663         if (unlikely(test_thread_flag(TIF_MEMDIE)
2664                      || fatal_signal_pending(current)))
2665                 goto bypass;
2666 
2667         /*
2668          * We always charge the cgroup the mm_struct belongs to.
2669          * The mm_struct's mem_cgroup changes on task migration if the
2670          * thread group leader migrates. It's possible that mm is not
2671          * set, if so charge the root memcg (happens for pagecache usage).
2672          */
2673         if (!*ptr && !mm)
2674                 *ptr = root_mem_cgroup;
2675 again:
2676         if (*ptr) { /* css should be a valid one */
2677                 memcg = *ptr;
2678                 if (mem_cgroup_is_root(memcg))
2679                         goto done;
2680                 if (consume_stock(memcg, nr_pages))
2681                         goto done;
2682                 css_get(&memcg->css);
2683         } else {
2684                 struct task_struct *p;
2685 
2686                 rcu_read_lock();
2687                 p = rcu_dereference(mm->owner);
2688                 /*
2689                  * Because we don't have task_lock(), "p" can exit.
2690                  * In that case, "memcg" can point to root or p can be NULL with
2691                  * race with swapoff. Then, we have small risk of mis-accouning.
2692                  * But such kind of mis-account by race always happens because
2693                  * we don't have cgroup_mutex(). It's overkill and we allo that
2694                  * small race, here.
2695                  * (*) swapoff at el will charge against mm-struct not against
2696                  * task-struct. So, mm->owner can be NULL.
2697                  */
2698                 memcg = mem_cgroup_from_task(p);
2699                 if (!memcg)
2700                         memcg = root_mem_cgroup;
2701                 if (mem_cgroup_is_root(memcg)) {
2702                         rcu_read_unlock();
2703                         goto done;
2704                 }
2705                 if (consume_stock(memcg, nr_pages)) {
2706                         /*
2707                          * It seems dagerous to access memcg without css_get().
2708                          * But considering how consume_stok works, it's not
2709                          * necessary. If consume_stock success, some charges
2710                          * from this memcg are cached on this cpu. So, we
2711                          * don't need to call css_get()/css_tryget() before
2712                          * calling consume_stock().
2713                          */
2714                         rcu_read_unlock();
2715                         goto done;
2716                 }
2717                 /* after here, we may be blocked. we need to get refcnt */
2718                 if (!css_tryget(&memcg->css)) {
2719                         rcu_read_unlock();
2720                         goto again;
2721                 }
2722                 rcu_read_unlock();
2723         }
2724 
2725         do {
2726                 bool oom_check;
2727 
2728                 /* If killed, bypass charge */
2729                 if (fatal_signal_pending(current)) {
2730                         css_put(&memcg->css);
2731                         goto bypass;
2732                 }
2733 
2734                 oom_check = false;
2735                 if (oom && !nr_oom_retries) {
2736                         oom_check = true;
2737                         nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
2738                 }
2739 
2740                 ret = mem_cgroup_do_charge(memcg, gfp_mask, batch, nr_pages,
2741                     oom_check);
2742                 switch (ret) {
2743                 case CHARGE_OK:
2744                         break;
2745                 case CHARGE_RETRY: /* not in OOM situation but retry */
2746                         batch = nr_pages;
2747                         css_put(&memcg->css);
2748                         memcg = NULL;
2749                         goto again;
2750                 case CHARGE_WOULDBLOCK: /* !__GFP_WAIT */
2751                         css_put(&memcg->css);
2752                         goto nomem;
2753                 case CHARGE_NOMEM: /* OOM routine works */
2754                         if (!oom) {
2755                                 css_put(&memcg->css);
2756                                 goto nomem;
2757                         }
2758                         /* If oom, we never return -ENOMEM */
2759                         nr_oom_retries--;
2760                         break;
2761                 case CHARGE_OOM_DIE: /* Killed by OOM Killer */
2762                         css_put(&memcg->css);
2763                         goto bypass;
2764                 }
2765         } while (ret != CHARGE_OK);
2766 
2767         if (batch > nr_pages)
2768                 refill_stock(memcg, batch - nr_pages);
2769         css_put(&memcg->css);
2770 done:
2771         *ptr = memcg;
2772         return 0;
2773 nomem:
2774         *ptr = NULL;
2775         return -ENOMEM;
2776 bypass:
2777         *ptr = root_mem_cgroup;
2778         return -EINTR;
2779 }
2780 
2781 /*
2782  * Somemtimes we have to undo a charge we got by try_charge().
2783  * This function is for that and do uncharge, put css's refcnt.
2784  * gotten by try_charge().
2785  */
2786 static void __mem_cgroup_cancel_charge(struct mem_cgroup *memcg,
2787                                        unsigned int nr_pages)
2788 {
2789         if (!mem_cgroup_is_root(memcg)) {
2790                 unsigned long bytes = nr_pages * PAGE_SIZE;
2791 
2792                 res_counter_uncharge(&memcg->res, bytes);
2793                 if (do_swap_account)
2794                         res_counter_uncharge(&memcg->memsw, bytes);
2795         }
2796 }
2797 
2798 /*
2799  * Cancel chrages in this cgroup....doesn't propagate to parent cgroup.
2800  * This is useful when moving usage to parent cgroup.
2801  */
2802 static void __mem_cgroup_cancel_local_charge(struct mem_cgroup *memcg,
2803                                         unsigned int nr_pages)
2804 {
2805         unsigned long bytes = nr_pages * PAGE_SIZE;
2806 
2807         if (mem_cgroup_is_root(memcg))
2808                 return;
2809 
2810         res_counter_uncharge_until(&memcg->res, memcg->res.parent, bytes);
2811         if (do_swap_account)
2812                 res_counter_uncharge_until(&memcg->memsw,
2813                                                 memcg->memsw.parent, bytes);
2814 }
2815 
2816 /*
2817  * A helper function to get mem_cgroup from ID. must be called under
2818  * rcu_read_lock().  The caller is responsible for calling css_tryget if
2819  * the mem_cgroup is used for charging. (dropping refcnt from swap can be
2820  * called against removed memcg.)
2821  */
2822 static struct mem_cgroup *mem_cgroup_lookup(unsigned short id)
2823 {
2824         struct cgroup_subsys_state *css;
2825 
2826         /* ID 0 is unused ID */
2827         if (!id)
2828                 return NULL;
2829         css = css_lookup(&mem_cgroup_subsys, id);
2830         if (!css)
2831                 return NULL;
2832         return mem_cgroup_from_css(css);
2833 }
2834 
2835 struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
2836 {
2837         struct mem_cgroup *memcg = NULL;
2838         struct page_cgroup *pc;
2839         unsigned short id;
2840         swp_entry_t ent;
2841 
2842         VM_BUG_ON(!PageLocked(page));
2843 
2844         pc = lookup_page_cgroup(page);
2845         lock_page_cgroup(pc);
2846         if (PageCgroupUsed(pc)) {
2847                 memcg = pc->mem_cgroup;
2848                 if (memcg && !css_tryget(&memcg->css))
2849                         memcg = NULL;
2850         } else if (PageSwapCache(page)) {
2851                 ent.val = page_private(page);
2852                 id = lookup_swap_cgroup_id(ent);
2853                 rcu_read_lock();
2854                 memcg = mem_cgroup_lookup(id);
2855                 if (memcg && !css_tryget(&memcg->css))
2856                         memcg = NULL;
2857                 rcu_read_unlock();
2858         }
2859         unlock_page_cgroup(pc);
2860         return memcg;
2861 }
2862 
2863 static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
2864                                        struct page *page,
2865                                        unsigned int nr_pages,
2866                                        enum charge_type ctype,
2867                                        bool lrucare)
2868 {
2869         struct page_cgroup *pc = lookup_page_cgroup(page);
2870         struct zone *uninitialized_var(zone);
2871         struct lruvec *lruvec;
2872         bool was_on_lru = false;
2873         bool anon;
2874 
2875         lock_page_cgroup(pc);
2876         VM_BUG_ON(PageCgroupUsed(pc));
2877         /*
2878          * we don't need page_cgroup_lock about tail pages, becase they are not
2879          * accessed by any other context at this point.
2880          */
2881 
2882         /*
2883          * In some cases, SwapCache and FUSE(splice_buf->radixtree), the page
2884          * may already be on some other mem_cgroup's LRU.  Take care of it.
2885          */
2886         if (lrucare) {
2887                 zone = page_zone(page);
2888                 spin_lock_irq(&zone->lru_lock);
2889                 if (PageLRU(page)) {
2890                         lruvec = mem_cgroup_zone_lruvec(zone, pc->mem_cgroup);
2891                         ClearPageLRU(page);
2892                         del_page_from_lru_list(page, lruvec, page_lru(page));
2893                         was_on_lru = true;
2894                 }
2895         }
2896 
2897         pc->mem_cgroup = memcg;
2898         /*
2899          * We access a page_cgroup asynchronously without lock_page_cgroup().
2900          * Especially when a page_cgroup is taken from a page, pc->mem_cgroup
2901          * is accessed after testing USED bit. To make pc->mem_cgroup visible
2902          * before USED bit, we need memory barrier here.
2903          * See mem_cgroup_add_lru_list(), etc.
2904          */
2905         smp_wmb();
2906         SetPageCgroupUsed(pc);
2907 
2908         if (lrucare) {
2909                 if (was_on_lru) {
2910                         lruvec = mem_cgroup_zone_lruvec(zone, pc->mem_cgroup);
2911                         VM_BUG_ON(PageLRU(page));
2912                         SetPageLRU(page);
2913                         add_page_to_lru_list(page, lruvec, page_lru(page));
2914                 }
2915                 spin_unlock_irq(&zone->lru_lock);
2916         }
2917 
2918         if (ctype == MEM_CGROUP_CHARGE_TYPE_ANON)
2919                 anon = true;
2920         else
2921                 anon = false;
2922 
2923         mem_cgroup_charge_statistics(memcg, page, anon, nr_pages);
2924         unlock_page_cgroup(pc);
2925 
2926         /*
2927          * "charge_statistics" updated event counter. Then, check it.
2928          * Insert ancestor (and ancestor's ancestors), to softlimit RB-tree.
2929          * if they exceeds softlimit.
2930          */
2931         memcg_check_events(memcg, page);
2932 }
2933 
2934 static DEFINE_MUTEX(set_limit_mutex);
2935 
2936 #ifdef CONFIG_MEMCG_KMEM
2937 static inline bool memcg_can_account_kmem(struct mem_cgroup *memcg)
2938 {
2939         return !mem_cgroup_disabled() && !mem_cgroup_is_root(memcg) &&
2940                 (memcg->kmem_account_flags & KMEM_ACCOUNTED_MASK);
2941 }
2942 
2943 /*
2944  * This is a bit cumbersome, but it is rarely used and avoids a backpointer
2945  * in the memcg_cache_params struct.
2946  */
2947 static struct kmem_cache *memcg_params_to_cache(struct memcg_cache_params *p)
2948 {
2949         struct kmem_cache *cachep;
2950 
2951         VM_BUG_ON(p->is_root_cache);
2952         cachep = p->root_cache;
2953         return cachep->memcg_params->memcg_caches[memcg_cache_id(p->memcg)];
2954 }
2955 
2956 #ifdef CONFIG_SLABINFO
2957 static int mem_cgroup_slabinfo_read(struct cgroup *cont, struct cftype *cft,
2958                                         struct seq_file *m)
2959 {
2960         struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
2961         struct memcg_cache_params *params;
2962 
2963         if (!memcg_can_account_kmem(memcg))
2964                 return -EIO;
2965 
2966         print_slabinfo_header(m);
2967 
2968         mutex_lock(&memcg->slab_caches_mutex);
2969         list_for_each_entry(params, &memcg->memcg_slab_caches, list)
2970                 cache_show(memcg_params_to_cache(params), m);
2971         mutex_unlock(&memcg->slab_caches_mutex);
2972 
2973         return 0;
2974 }
2975 #endif
2976 
2977 static int memcg_charge_kmem(struct mem_cgroup *memcg, gfp_t gfp, u64 size)
2978 {
2979         struct res_counter *fail_res;
2980         struct mem_cgroup *_memcg;
2981         int ret = 0;
2982         bool may_oom;
2983 
2984         ret = res_counter_charge(&memcg->kmem, size, &fail_res);
2985         if (ret)
2986                 return ret;
2987 
2988         /*
2989          * Conditions under which we can wait for the oom_killer. Those are
2990          * the same conditions tested by the core page allocator
2991          */
2992         may_oom = (gfp & __GFP_FS) && !(gfp & __GFP_NORETRY);
2993 
2994         _memcg = memcg;
2995         ret = __mem_cgroup_try_charge(NULL, gfp, size >> PAGE_SHIFT,
2996                                       &_memcg, may_oom);
2997 
2998         if (ret == -EINTR)  {
2999                 /*
3000                  * __mem_cgroup_try_charge() chosed to bypass to root due to
3001                  * OOM kill or fatal signal.  Since our only options are to
3002                  * either fail the allocation or charge it to this cgroup, do
3003                  * it as a temporary condition. But we can't fail. From a
3004                  * kmem/slab perspective, the cache has already been selected,
3005                  * by mem_cgroup_kmem_get_cache(), so it is too late to change
3006                  * our minds.
3007                  *
3008                  * This condition will only trigger if the task entered
3009                  * memcg_charge_kmem in a sane state, but was OOM-killed during
3010                  * __mem_cgroup_try_charge() above. Tasks that were already
3011                  * dying when the allocation triggers should have been already
3012                  * directed to the root cgroup in memcontrol.h
3013                  */
3014                 res_counter_charge_nofail(&memcg->res, size, &fail_res);
3015                 if (do_swap_account)
3016                         res_counter_charge_nofail(&memcg->memsw, size,
3017                                                   &fail_res);
3018                 ret = 0;
3019         } else if (ret)
3020                 res_counter_uncharge(&memcg->kmem, size);
3021 
3022         return ret;
3023 }
3024 
3025 static void memcg_uncharge_kmem(struct mem_cgroup *memcg, u64 size)
3026 {
3027         res_counter_uncharge(&memcg->res, size);
3028         if (do_swap_account)
3029                 res_counter_uncharge(&memcg->memsw, size);
3030 
3031         /* Not down to 0 */
3032         if (res_counter_uncharge(&memcg->kmem, size))
3033                 return;
3034 
3035         /*
3036          * Releases a reference taken in kmem_cgroup_css_offline in case
3037          * this last uncharge is racing with the offlining code or it is
3038          * outliving the memcg existence.
3039          *
3040          * The memory barrier imposed by test&clear is paired with the
3041          * explicit one in memcg_kmem_mark_dead().
3042          */
3043         if (memcg_kmem_test_and_clear_dead(memcg))
3044                 css_put(&memcg->css);
3045 }
3046 
3047 void memcg_cache_list_add(struct mem_cgroup *memcg, struct kmem_cache *cachep)
3048 {
3049         if (!memcg)
3050                 return;
3051 
3052         mutex_lock(&memcg->slab_caches_mutex);
3053         list_add(&cachep->memcg_params->list, &memcg->memcg_slab_caches);
3054         mutex_unlock(&memcg->slab_caches_mutex);
3055 }
3056 
3057 /*
3058  * helper for acessing a memcg's index. It will be used as an index in the
3059  * child cache array in kmem_cache, and also to derive its name. This function
3060  * will return -1 when this is not a kmem-limited memcg.
3061  */
3062 int memcg_cache_id(struct mem_cgroup *memcg)
3063 {
3064         return memcg ? memcg->kmemcg_id : -1;
3065 }
3066 
3067 /*
3068  * This ends up being protected by the set_limit mutex, during normal
3069  * operation, because that is its main call site.
3070  *
3071  * But when we create a new cache, we can call this as well if its parent
3072  * is kmem-limited. That will have to hold set_limit_mutex as well.
3073  */
3074 int memcg_update_cache_sizes(struct mem_cgroup *memcg)
3075 {
3076         int num, ret;
3077 
3078         num = ida_simple_get(&kmem_limited_groups,
3079                                 0, MEMCG_CACHES_MAX_SIZE, GFP_KERNEL);
3080         if (num < 0)
3081                 return num;
3082         /*
3083          * After this point, kmem_accounted (that we test atomically in
3084          * the beginning of this conditional), is no longer 0. This
3085          * guarantees only one process will set the following boolean
3086          * to true. We don't need test_and_set because we're protected
3087          * by the set_limit_mutex anyway.
3088          */
3089         memcg_kmem_set_activated(memcg);
3090 
3091         ret = memcg_update_all_caches(num+1);
3092         if (ret) {
3093                 ida_simple_remove(&kmem_limited_groups, num);
3094                 memcg_kmem_clear_activated(memcg);
3095                 return ret;
3096         }
3097 
3098         memcg->kmemcg_id = num;
3099         INIT_LIST_HEAD(&memcg->memcg_slab_caches);
3100         mutex_init(&memcg->slab_caches_mutex);
3101         return 0;
3102 }
3103 
3104 static size_t memcg_caches_array_size(int num_groups)
3105 {
3106         ssize_t size;
3107         if (num_groups <= 0)
3108                 return 0;
3109 
3110         size = 2 * num_groups;
3111         if (size < MEMCG_CACHES_MIN_SIZE)
3112                 size = MEMCG_CACHES_MIN_SIZE;
3113         else if (size > MEMCG_CACHES_MAX_SIZE)
3114                 size = MEMCG_CACHES_MAX_SIZE;
3115 
3116         return size;
3117 }
3118 
3119 /*
3120  * We should update the current array size iff all caches updates succeed. This
3121  * can only be done from the slab side. The slab mutex needs to be held when
3122  * calling this.
3123  */
3124 void memcg_update_array_size(int num)
3125 {
3126         if (num > memcg_limited_groups_array_size)
3127                 memcg_limited_groups_array_size = memcg_caches_array_size(num);
3128 }
3129 
3130 static void kmem_cache_destroy_work_func(struct work_struct *w);
3131 
3132 int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
3133 {
3134         struct memcg_cache_params *cur_params = s->memcg_params;
3135 
3136         VM_BUG_ON(s->memcg_params && !s->memcg_params->is_root_cache);
3137 
3138         if (num_groups > memcg_limited_groups_array_size) {
3139                 int i;
3140                 ssize_t size = memcg_caches_array_size(num_groups);
3141 
3142                 size *= sizeof(void *);
3143                 size += sizeof(struct memcg_cache_params);
3144 
3145                 s->memcg_params = kzalloc(size, GFP_KERNEL);
3146                 if (!s->memcg_params) {
3147                         s->memcg_params = cur_params;
3148                         return -ENOMEM;
3149                 }
3150 
3151                 s->memcg_params->is_root_cache = true;
3152 
3153                 /*
3154                  * There is the chance it will be bigger than
3155                  * memcg_limited_groups_array_size, if we failed an allocation
3156                  * in a cache, in which case all caches updated before it, will
3157                  * have a bigger array.
3158                  *
3159                  * But if that is the case, the data after
3160                  * memcg_limited_groups_array_size is certainly unused
3161                  */
3162                 for (i = 0; i < memcg_limited_groups_array_size; i++) {
3163                         if (!cur_params->memcg_caches[i])
3164                                 continue;
3165                         s->memcg_params->memcg_caches[i] =
3166                                                 cur_params->memcg_caches[i];
3167                 }
3168 
3169                 /*
3170                  * Ideally, we would wait until all caches succeed, and only
3171                  * then free the old one. But this is not worth the extra
3172                  * pointer per-cache we'd have to have for this.
3173                  *
3174                  * It is not a big deal if some caches are left with a size
3175                  * bigger than the others. And all updates will reset this
3176                  * anyway.
3177                  */
3178                 kfree(cur_params);
3179         }
3180         return 0;
3181 }
3182 
3183 int memcg_register_cache(struct mem_cgroup *memcg, struct kmem_cache *s,
3184                          struct kmem_cache *root_cache)
3185 {
3186         size_t size = sizeof(struct memcg_cache_params);
3187 
3188         if (!memcg_kmem_enabled())
3189                 return 0;
3190 
3191         if (!memcg)
3192                 size += memcg_limited_groups_array_size * sizeof(void *);
3193 
3194         s->memcg_params = kzalloc(size, GFP_KERNEL);
3195         if (!s->memcg_params)
3196                 return -ENOMEM;
3197 
3198         if (memcg) {
3199                 s->memcg_params->memcg = memcg;
3200                 s->memcg_params->root_cache = root_cache;
3201                 INIT_WORK(&s->memcg_params->destroy,
3202                                 kmem_cache_destroy_work_func);
3203         } else
3204                 s->memcg_params->is_root_cache = true;
3205 
3206         return 0;
3207 }
3208 
3209 void memcg_release_cache(struct kmem_cache *s)
3210 {
3211         struct kmem_cache *root;
3212         struct mem_cgroup *memcg;
3213         int id;
3214 
3215         /*
3216          * This happens, for instance, when a root cache goes away before we
3217          * add any memcg.
3218          */
3219         if (!s->memcg_params)
3220                 return;
3221 
3222         if (s->memcg_params->is_root_cache)
3223                 goto out;
3224 
3225         memcg = s->memcg_params->memcg;
3226         id  = memcg_cache_id(memcg);
3227 
3228         root = s->memcg_params->root_cache;
3229         root->memcg_params->memcg_caches[id] = NULL;
3230 
3231         mutex_lock(&memcg->slab_caches_mutex);
3232         list_del(&s->memcg_params->list);
3233         mutex_unlock(&memcg->slab_caches_mutex);
3234 
3235         css_put(&memcg->css);
3236 out:
3237         kfree(s->memcg_params);
3238 }
3239 
3240 /*
3241  * During the creation a new cache, we need to disable our accounting mechanism
3242  * altogether. This is true even if we are not creating, but rather just
3243  * enqueing new caches to be created.
3244  *
3245  * This is because that process will trigger allocations; some visible, like
3246  * explicit kmallocs to auxiliary data structures, name strings and internal
3247  * cache structures; some well concealed, like INIT_WORK() that can allocate
3248  * objects during debug.
3249  *
3250  * If any allocation happens during memcg_kmem_get_cache, we will recurse back
3251  * to it. This may not be a bounded recursion: since the first cache creation
3252  * failed to complete (waiting on the allocation), we'll just try to create the
3253  * cache again, failing at the same point.
3254  *
3255  * memcg_kmem_get_cache is prepared to abort after seeing a positive count of
3256  * memcg_kmem_skip_account. So we enclose anything that might allocate memory
3257  * inside the following two functions.
3258  */
3259 static inline void memcg_stop_kmem_account(void)
3260 {
3261         VM_BUG_ON(!current->mm);
3262         current->memcg_kmem_skip_account++;
3263 }
3264 
3265 static inline void memcg_resume_kmem_account(void)
3266 {
3267         VM_BUG_ON(!current->mm);
3268         current->memcg_kmem_skip_account--;
3269 }
3270 
3271 static void kmem_cache_destroy_work_func(struct work_struct *w)
3272 {
3273         struct kmem_cache *cachep;
3274         struct memcg_cache_params *p;
3275 
3276         p = container_of(w, struct memcg_cache_params, destroy);
3277 
3278         cachep = memcg_params_to_cache(p);
3279 
3280         /*
3281          * If we get down to 0 after shrink, we could delete right away.
3282          * However, memcg_release_pages() already puts us back in the workqueue
3283          * in that case. If we proceed deleting, we'll get a dangling
3284          * reference, and removing the object from the workqueue in that case
3285          * is unnecessary complication. We are not a fast path.
3286          *
3287          * Note that this case is fundamentally different from racing with
3288          * shrink_slab(): if memcg_cgroup_destroy_cache() is called in
3289          * kmem_cache_shrink, not only we would be reinserting a dead cache
3290          * into the queue, but doing so from inside the worker racing to
3291          * destroy it.
3292          *
3293          * So if we aren't down to zero, we'll just schedule a worker and try
3294          * again
3295          */
3296         if (atomic_read(&cachep->memcg_params->nr_pages) != 0) {
3297                 kmem_cache_shrink(cachep);
3298                 if (atomic_read(&cachep->memcg_params->nr_pages) == 0)
3299                         return;
3300         } else
3301                 kmem_cache_destroy(cachep);
3302 }
3303 
3304 void mem_cgroup_destroy_cache(struct kmem_cache *cachep)
3305 {
3306         if (!cachep->memcg_params->dead)
3307                 return;
3308 
3309         /*
3310          * There are many ways in which we can get here.
3311          *
3312          * We can get to a memory-pressure situation while the delayed work is
3313          * still pending to run. The vmscan shrinkers can then release all
3314          * cache memory and get us to destruction. If this is the case, we'll
3315          * be executed twice, which is a bug (the second time will execute over
3316          * bogus data). In this case, cancelling the work should be fine.
3317          *
3318          * But we can also get here from the worker itself, if
3319          * kmem_cache_shrink is enough to shake all the remaining objects and
3320          * get the page count to 0. In this case, we'll deadlock if we try to
3321          * cancel the work (the worker runs with an internal lock held, which
3322          * is the same lock we would hold for cancel_work_sync().)
3323          *
3324          * Since we can't possibly know who got us here, just refrain from
3325          * running if there is already work pending
3326          */
3327         if (work_pending(&cachep->memcg_params->destroy))
3328                 return;
3329         /*
3330          * We have to defer the actual destroying to a workqueue, because
3331          * we might currently be in a context that cannot sleep.
3332          */
3333         schedule_work(&cachep->memcg_params->destroy);
3334 }
3335 
3336 /*
3337  * This lock protects updaters, not readers. We want readers to be as fast as
3338  * they can, and they will either see NULL or a valid cache value. Our model
3339  * allow them to see NULL, in which case the root memcg will be selected.
3340  *
3341  * We need this lock because multiple allocations to the same cache from a non
3342  * will span more than one worker. Only one of them can create the cache.
3343  */
3344 static DEFINE_MUTEX(memcg_cache_mutex);
3345 
3346 /*
3347  * Called with memcg_cache_mutex held
3348  */
3349 static struct kmem_cache *kmem_cache_dup(struct mem_cgroup *memcg,
3350                                          struct kmem_cache *s)
3351 {
3352         struct kmem_cache *new;
3353         static char *tmp_name = NULL;
3354 
3355         lockdep_assert_held(&memcg_cache_mutex);
3356 
3357         /*
3358          * kmem_cache_create_memcg duplicates the given name and
3359          * cgroup_name for this name requires RCU context.
3360          * This static temporary buffer is used to prevent from
3361          * pointless shortliving allocation.
3362          */
3363         if (!tmp_name) {
3364                 tmp_name = kmalloc(PATH_MAX, GFP_KERNEL);
3365                 if (!tmp_name)
3366                         return NULL;
3367         }
3368 
3369         rcu_read_lock();
3370         snprintf(tmp_name, PATH_MAX, "%s(%d:%s)", s->name,
3371                          memcg_cache_id(memcg), cgroup_name(memcg->css.cgroup));
3372         rcu_read_unlock();
3373 
3374         new = kmem_cache_create_memcg(memcg, tmp_name, s->object_size, s->align,
3375                                       (s->flags & ~SLAB_PANIC), s->ctor, s);
3376 
3377         if (new)
3378                 new->allocflags |= __GFP_KMEMCG;
3379 
3380         return new;
3381 }
3382 
3383 static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
3384                                                   struct kmem_cache *cachep)
3385 {
3386         struct kmem_cache *new_cachep;
3387         int idx;
3388 
3389         BUG_ON(!memcg_can_account_kmem(memcg));
3390 
3391         idx = memcg_cache_id(memcg);
3392 
3393         mutex_lock(&memcg_cache_mutex);
3394         new_cachep = cachep->memcg_params->memcg_caches[idx];
3395         if (new_cachep) {
3396                 css_put(&memcg->css);
3397                 goto out;
3398         }
3399 
3400         new_cachep = kmem_cache_dup(memcg, cachep);
3401         if (new_cachep == NULL) {
3402                 new_cachep = cachep;
3403                 css_put(&memcg->css);
3404                 goto out;
3405         }
3406 
3407         atomic_set(&new_cachep->memcg_params->nr_pages , 0);
3408 
3409         cachep->memcg_params->memcg_caches[idx] = new_cachep;
3410         /*
3411          * the readers won't lock, make sure everybody sees the updated value,
3412          * so they won't put stuff in the queue again for no reason
3413          */
3414         wmb();
3415 out:
3416         mutex_unlock(&memcg_cache_mutex);
3417         return new_cachep;
3418 }
3419 
3420 void kmem_cache_destroy_memcg_children(struct kmem_cache *s)
3421 {
3422         struct kmem_cache *c;
3423         int i;
3424 
3425         if (!s->memcg_params)
3426                 return;
3427         if (!s->memcg_params->is_root_cache)
3428                 return;
3429 
3430         /*
3431          * If the cache is being destroyed, we trust that there is no one else
3432          * requesting objects from it. Even if there are, the sanity checks in
3433          * kmem_cache_destroy should caught this ill-case.
3434          *
3435          * Still, we don't want anyone else freeing memcg_caches under our
3436          * noses, which can happen if a new memcg comes to life. As usual,
3437          * we'll take the set_limit_mutex to protect ourselves against this.
3438          */
3439         mutex_lock(&set_limit_mutex);
3440         for (i = 0; i < memcg_limited_groups_array_size; i++) {
3441                 c = s->memcg_params->memcg_caches[i];
3442                 if (!c)
3443                         continue;
3444 
3445                 /*
3446                  * We will now manually delete the caches, so to avoid races
3447                  * we need to cancel all pending destruction workers and
3448                  * proceed with destruction ourselves.
3449                  *
3450                  * kmem_cache_destroy() will call kmem_cache_shrink internally,
3451                  * and that could spawn the workers again: it is likely that
3452                  * the cache still have active pages until this very moment.
3453                  * This would lead us back to mem_cgroup_destroy_cache.
3454                  *
3455                  * But that will not execute at all if the "dead" flag is not
3456                  * set, so flip it down to guarantee we are in control.
3457                  */
3458                 c->memcg_params->dead = false;
3459                 cancel_work_sync(&c->memcg_params->destroy);
3460                 kmem_cache_destroy(c);
3461         }
3462         mutex_unlock(&set_limit_mutex);
3463 }
3464 
3465 struct create_work {
3466         struct mem_cgroup *memcg;
3467         struct kmem_cache *cachep;
3468         struct work_struct work;
3469 };
3470 
3471 static void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
3472 {
3473         struct kmem_cache *cachep;
3474         struct memcg_cache_params *params;
3475 
3476         if (!memcg_kmem_is_active(memcg))
3477                 return;
3478 
3479         mutex_lock(&memcg->slab_caches_mutex);
3480         list_for_each_entry(params, &memcg->memcg_slab_caches, list) {
3481                 cachep = memcg_params_to_cache(params);
3482                 cachep->memcg_params->dead = true;
3483                 schedule_work(&cachep->memcg_params->destroy);
3484         }
3485         mutex_unlock(&memcg->slab_caches_mutex);
3486 }
3487 
3488 static void memcg_create_cache_work_func(struct work_struct *w)
3489 {
3490         struct create_work *cw;
3491 
3492         cw = container_of(w, struct create_work, work);
3493         memcg_create_kmem_cache(cw->memcg, cw->cachep);
3494         kfree(cw);
3495 }
3496 
3497 /*
3498  * Enqueue the creation of a per-memcg kmem_cache.
3499  */
3500 static void __memcg_create_cache_enqueue(struct mem_cgroup *memcg,
3501                                          struct kmem_cache *cachep)
3502 {
3503         struct create_work *cw;
3504 
3505         cw = kmalloc(sizeof(struct create_work), GFP_NOWAIT);
3506         if (cw == NULL) {
3507                 css_put(&memcg->css);
3508                 return;
3509         }
3510 
3511         cw->memcg = memcg;
3512         cw->cachep = cachep;
3513 
3514         INIT_WORK(&cw->work, memcg_create_cache_work_func);
3515         schedule_work(&cw->work);
3516 }
3517 
3518 static void memcg_create_cache_enqueue(struct mem_cgroup *memcg,
3519                                        struct kmem_cache *cachep)
3520 {
3521         /*
3522          * We need to stop accounting when we kmalloc, because if the
3523          * corresponding kmalloc cache is not yet created, the first allocation
3524          * in __memcg_create_cache_enqueue will recurse.
3525          *
3526          * However, it is better to enclose the whole function. Depending on
3527          * the debugging options enabled, INIT_WORK(), for instance, can
3528          * trigger an allocation. This too, will make us recurse. Because at
3529          * this point we can't allow ourselves back into memcg_kmem_get_cache,
3530          * the safest choice is to do it like this, wrapping the whole function.
3531          */
3532         memcg_stop_kmem_account();
3533         __memcg_create_cache_enqueue(memcg, cachep);
3534         memcg_resume_kmem_account();
3535 }
3536 /*
3537  * Return the kmem_cache we're supposed to use for a slab allocation.
3538  * We try to use the current memcg's version of the cache.
3539  *
3540  * If the cache does not exist yet, if we are the first user of it,
3541  * we either create it immediately, if possible, or create it asynchronously
3542  * in a workqueue.
3543  * In the latter case, we will let the current allocation go through with
3544  * the original cache.
3545  *
3546  * Can't be called in interrupt context or from kernel threads.
3547  * This function needs to be called with rcu_read_lock() held.
3548  */
3549 struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep,
3550                                           gfp_t gfp)
3551 {
3552         struct mem_cgroup *memcg;
3553         int idx;
3554 
3555         VM_BUG_ON(!cachep->memcg_params);
3556         VM_BUG_ON(!cachep->memcg_params->is_root_cache);
3557 
3558         if (!current->mm || current->memcg_kmem_skip_account)
3559                 return cachep;
3560 
3561         rcu_read_lock();
3562         memcg = mem_cgroup_from_task(rcu_dereference(current->mm->owner));
3563 
3564         if (!memcg_can_account_kmem(memcg))
3565                 goto out;
3566 
3567         idx = memcg_cache_id(memcg);
3568 
3569         /*
3570          * barrier to mare sure we're always seeing the up to date value.  The
3571          * code updating memcg_caches will issue a write barrier to match this.
3572          */
3573         read_barrier_depends();
3574         if (likely(cachep->memcg_params->memcg_caches[idx])) {
3575                 cachep = cachep->memcg_params->memcg_caches[idx];
3576                 goto out;
3577         }
3578 
3579         /* The corresponding put will be done in the workqueue. */
3580         if (!css_tryget(&memcg->css))
3581                 goto out;
3582         rcu_read_unlock();
3583 
3584         /*
3585          * If we are in a safe context (can wait, and not in interrupt
3586          * context), we could be be predictable and return right away.
3587          * This would guarantee that the allocation being performed
3588          * already belongs in the new cache.
3589          *
3590          * However, there are some clashes that can arrive from locking.
3591          * For instance, because we acquire the slab_mutex while doing
3592          * kmem_cache_dup, this means no further allocation could happen
3593          * with the slab_mutex held.
3594          *
3595          * Also, because cache creation issue get_online_cpus(), this
3596          * creates a lock chain: memcg_slab_mutex -> cpu_hotplug_mutex,
3597          * that ends up reversed during cpu hotplug. (cpuset allocates
3598          * a bunch of GFP_KERNEL memory during cpuup). Due to all that,
3599          * better to defer everything.
3600          */
3601         memcg_create_cache_enqueue(memcg, cachep);
3602         return cachep;
3603 out:
3604         rcu_read_unlock();
3605         return cachep;
3606 }
3607 EXPORT_SYMBOL(__memcg_kmem_get_cache);
3608 
3609 /*
3610  * We need to verify if the allocation against current->mm->owner's memcg is
3611  * possible for the given order. But the page is not allocated yet, so we'll
3612  * need a further commit step to do the final arrangements.
3613  *
3614  * It is possible for the task to switch cgroups in this mean time, so at
3615  * commit time, we can't rely on task conversion any longer.  We'll then use
3616  * the handle argument to return to the caller which cgroup we should commit
3617  * against. We could also return the memcg directly and avoid the pointer
3618  * passing, but a boolean return value gives better semantics considering
3619  * the compiled-out case as well.
3620  *
3621  * Returning true means the allocation is possible.
3622  */
3623 bool
3624 __memcg_kmem_newpage_charge(gfp_t gfp, struct mem_cgroup **_memcg, int order)
3625 {
3626         struct mem_cgroup *memcg;
3627         int ret;
3628 
3629         *_memcg = NULL;
3630 
3631         /*
3632          * Disabling accounting is only relevant for some specific memcg
3633          * internal allocations. Therefore we would initially not have such
3634          * check here, since direct calls to the page allocator that are marked
3635          * with GFP_KMEMCG only happen outside memcg core. We are mostly
3636          * concerned with cache allocations, and by having this test at
3637          * memcg_kmem_get_cache, we are already able to relay the allocation to
3638          * the root cache and bypass the memcg cache altogether.
3639          *
3640          * There is one exception, though: the SLUB allocator does not create
3641          * large order caches, but rather service large kmallocs directly from
3642          * the page allocator. Therefore, the following sequence when backed by
3643          * the SLUB allocator:
3644          *
3645          *      memcg_stop_kmem_account();
3646          *      kmalloc(<large_number>)
3647          *      memcg_resume_kmem_account();
3648          *
3649          * would effectively ignore the fact that we should skip accounting,
3650          * since it will drive us directly to this function without passing
3651          * through the cache selector memcg_kmem_get_cache. Such large
3652          * allocations are extremely rare but can happen, for instance, for the
3653          * cache arrays. We bring this test here.
3654          */
3655         if (!current->mm || current->memcg_kmem_skip_account)
3656                 return true;
3657 
3658         memcg = try_get_mem_cgroup_from_mm(current->mm);
3659 
3660         /*
3661          * very rare case described in mem_cgroup_from_task. Unfortunately there
3662          * isn't much we can do without complicating this too much, and it would
3663          * be gfp-dependent anyway. Just let it go
3664          */
3665         if (unlikely(!memcg))
3666                 return true;
3667 
3668         if (!memcg_can_account_kmem(memcg)) {
3669                 css_put(&memcg->css);
3670                 return true;
3671         }
3672 
3673         ret = memcg_charge_kmem(memcg, gfp, PAGE_SIZE << order);
3674         if (!ret)
3675                 *_memcg = memcg;
3676 
3677         css_put(&memcg->css);
3678         return (ret == 0);
3679 }
3680 
3681 void __memcg_kmem_commit_charge(struct page *page, struct mem_cgroup *memcg,
3682                               int order)
3683 {
3684         struct page_cgroup *pc;
3685 
3686         VM_BUG_ON(mem_cgroup_is_root(memcg));
3687 
3688         /* The page allocation failed. Revert */
3689         if (!page) {
3690                 memcg_uncharge_kmem(memcg, PAGE_SIZE << order);
3691                 return;
3692         }
3693 
3694         pc = lookup_page_cgroup(page);
3695         lock_page_cgroup(pc);
3696         pc->mem_cgroup = memcg;
3697         SetPageCgroupUsed(pc);
3698         unlock_page_cgroup(pc);
3699 }
3700 
3701 void __memcg_kmem_uncharge_pages(struct page *page, int order)
3702 {
3703         struct mem_cgroup *memcg = NULL;
3704         struct page_cgroup *pc;
3705 
3706 
3707         pc = lookup_page_cgroup(page);
3708         /*
3709          * Fast unlocked return. Theoretically might have changed, have to
3710          * check again after locking.
3711          */
3712         if (!PageCgroupUsed(pc))
3713                 return;
3714 
3715         lock_page_cgroup(pc);
3716         if (PageCgroupUsed(pc)) {
3717                 memcg = pc->mem_cgroup;
3718                 ClearPageCgroupUsed(pc);
3719         }
3720         unlock_page_cgroup(pc);
3721 
3722         /*
3723          * We trust that only if there is a memcg associated with the page, it
3724          * is a valid allocation
3725          */
3726         if (!memcg)
3727                 return;
3728 
3729         VM_BUG_ON(mem_cgroup_is_root(memcg));
3730         memcg_uncharge_kmem(memcg, PAGE_SIZE << order);
3731 }
3732 #else
3733 static inline void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
3734 {
3735 }
3736 #endif /* CONFIG_MEMCG_KMEM */
3737 
3738 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
3739 
3740 #define PCGF_NOCOPY_AT_SPLIT (1 << PCG_LOCK | 1 << PCG_MIGRATION)
3741 /*
3742  * Because tail pages are not marked as "used", set it. We're under
3743  * zone->lru_lock, 'splitting on pmd' and compound_lock.
3744  * charge/uncharge will be never happen and move_account() is done under
3745  * compound_lock(), so we don't have to take care of races.
3746  */
3747 void mem_cgroup_split_huge_fixup(struct page *head)
3748 {
3749         struct page_cgroup *head_pc = lookup_page_cgroup(head);
3750         struct page_cgroup *pc;
3751         struct mem_cgroup *memcg;
3752         int i;
3753 
3754         if (mem_cgroup_disabled())
3755                 return;
3756 
3757         memcg = head_pc->mem_cgroup;
3758         for (i = 1; i < HPAGE_PMD_NR; i++) {
3759                 pc = head_pc + i;
3760                 pc->mem_cgroup = memcg;
3761                 smp_wmb();/* see __commit_charge() */
3762                 pc->flags = head_pc->flags & ~PCGF_NOCOPY_AT_SPLIT;
3763         }
3764         __this_cpu_sub(memcg->stat->count[MEM_CGROUP_STAT_RSS_HUGE],
3765                        HPAGE_PMD_NR);
3766 }
3767 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
3768 
3769 /**
3770  * mem_cgroup_move_account - move account of the page
3771  * @page: the page
3772  * @nr_pages: number of regular pages (>1 for huge pages)
3773  * @pc: page_cgroup of the page.
3774  * @from: mem_cgroup which the page is moved from.
3775  * @to: mem_cgroup which the page is moved to. @from != @to.
3776  *
3777  * The caller must confirm following.
3778  * - page is not on LRU (isolate_page() is useful.)
3779  * - compound_lock is held when nr_pages > 1
3780  *
3781  * This function doesn't do "charge" to new cgroup and doesn't do "uncharge"
3782  * from old cgroup.
3783  */
3784 static int mem_cgroup_move_account(struct page *page,
3785                                    unsigned int nr_pages,
3786                                    struct page_cgroup *pc,
3787                                    struct mem_cgroup *from,
3788                                    struct mem_cgroup *to)
3789 {
3790         unsigned long flags;
3791         int ret;
3792         bool anon = PageAnon(page);
3793 
3794         VM_BUG_ON(from == to);
3795         VM_BUG_ON(PageLRU(page));
3796         /*
3797          * The page is isolated from LRU. So, collapse function
3798          * will not handle this page. But page splitting can happen.
3799          * Do this check under compound_page_lock(). The caller should
3800          * hold it.
3801          */
3802         ret = -EBUSY;
3803         if (nr_pages > 1 && !PageTransHuge(page))
3804                 goto out;
3805 
3806         lock_page_cgroup(pc);
3807 
3808         ret = -EINVAL;
3809         if (!PageCgroupUsed(pc) || pc->mem_cgroup != from)
3810                 goto unlock;
3811 
3812         move_lock_mem_cgroup(from, &flags);
3813 
3814         if (!anon && page_mapped(page)) {
3815                 /* Update mapped_file data for mem_cgroup */
3816                 preempt_disable();
3817                 __this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
3818                 __this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
3819                 preempt_enable();
3820         }
3821         mem_cgroup_charge_statistics(from, page, anon, -nr_pages);
3822 
3823         /* caller should have done css_get */
3824         pc->mem_cgroup = to;
3825         mem_cgroup_charge_statistics(to, page, anon, nr_pages);
3826         move_unlock_mem_cgroup(from, &flags);
3827         ret = 0;
3828 unlock:
3829         unlock_page_cgroup(pc);
3830         /*
3831          * check events
3832          */
3833         memcg_check_events(to, page);
3834         memcg_check_events(from, page);
3835 out:
3836         return ret;
3837 }
3838 
3839 /**
3840  * mem_cgroup_move_parent - moves page to the parent group
3841  * @page: the page to move
3842  * @pc: page_cgroup of the page
3843  * @child: page's cgroup
3844  *
3845  * move charges to its parent or the root cgroup if the group has no
3846  * parent (aka use_hierarchy==0).
3847  * Although this might fail (get_page_unless_zero, isolate_lru_page or
3848  * mem_cgroup_move_account fails) the failure is always temporary and
3849  * it signals a race with a page removal/uncharge or migration. In the
3850  * first case the page is on the way out and it will vanish from the LRU
3851  * on the next attempt and the call should be retried later.
3852  * Isolation from the LRU fails only if page has been isolated from
3853  * the LRU since we looked at it and that usually means either global
3854  * reclaim or migration going on. The page will either get back to the
3855  * LRU or vanish.
3856  * Finaly mem_cgroup_move_account fails only if the page got uncharged
3857  * (!PageCgroupUsed) or moved to a different group. The page will
3858  * disappear in the next attempt.
3859  */
3860 static int mem_cgroup_move_parent(struct page *page,
3861                                   struct page_cgroup *pc,
3862                                   struct mem_cgroup *child)
3863 {
3864         struct mem_cgroup *parent;
3865         unsigned int nr_pages;
3866         unsigned long uninitialized_var(flags);
3867         int ret;
3868 
3869         VM_BUG_ON(mem_cgroup_is_root(child));
3870 
3871         ret = -EBUSY;
3872         if (!get_page_unless_zero(page))
3873                 goto out;
3874         if (isolate_lru_page(page))
3875                 goto put;
3876 
3877         nr_pages = hpage_nr_pages(page);
3878 
3879         parent = parent_mem_cgroup(child);
3880         /*
3881          * If no parent, move charges to root cgroup.
3882          */
3883         if (!parent)
3884                 parent = root_mem_cgroup;
3885 
3886         if (nr_pages > 1) {
3887                 VM_BUG_ON(!PageTransHuge(page));
3888                 flags = compound_lock_irqsave(page);
3889         }
3890 
3891         ret = mem_cgroup_move_account(page, nr_pages,
3892                                 pc, child, parent);
3893         if (!ret)
3894                 __mem_cgroup_cancel_local_charge(child, nr_pages);
3895 
3896         if (nr_pages > 1)
3897                 compound_unlock_irqrestore(page, flags);
3898         putback_lru_page(page);
3899 put:
3900         put_page(page);
3901 out:
3902         return ret;
3903 }
3904 
3905 /*
3906  * Charge the memory controller for page usage.
3907  * Return
3908  * 0 if the charge was successful
3909  * < 0 if the cgroup is over its limit
3910  */
3911 static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
3912                                 gfp_t gfp_mask, enum charge_type ctype)
3913 {
3914         struct mem_cgroup *memcg = NULL;
3915         unsigned int nr_pages = 1;
3916         bool oom = true;
3917         int ret;
3918 
3919         if (PageTransHuge(page)) {
3920                 nr_pages <<= compound_order(page);
3921                 VM_BUG_ON(!PageTransHuge(page));
3922                 /*
3923                  * Never OOM-kill a process for a huge page.  The
3924                  * fault handler will fall back to regular pages.
3925                  */
3926                 oom = false;
3927         }
3928 
3929         ret = __mem_cgroup_try_charge(mm, gfp_mask, nr_pages, &memcg, oom);
3930         if (ret == -ENOMEM)
3931                 return ret;
3932         __mem_cgroup_commit_charge(memcg, page, nr_pages, ctype, false);
3933         return 0;
3934 }
3935 
3936 int mem_cgroup_newpage_charge(struct page *page,
3937                               struct mm_struct *mm, gfp_t gfp_mask)
3938 {
3939         if (mem_cgroup_disabled())
3940                 return 0;
3941         VM_BUG_ON(page_mapped(page));
3942         VM_BUG_ON(page->mapping && !PageAnon(page));
3943         VM_BUG_ON(!mm);
3944         return mem_cgroup_charge_common(page, mm, gfp_mask,
3945                                         MEM_CGROUP_CHARGE_TYPE_ANON);
3946 }
3947 
3948 /*
3949  * While swap-in, try_charge -> commit or cancel, the page is locked.
3950  * And when try_charge() successfully returns, one refcnt to memcg without
3951  * struct page_cgroup is acquired. This refcnt will be consumed by
3952  * "commit()" or removed by "cancel()"
3953  */
3954 static int __mem_cgroup_try_charge_swapin(struct mm_struct *mm,
3955                                           struct page *page,
3956                                           gfp_t mask,
3957                                           struct mem_cgroup **memcgp)
3958 {
3959         struct mem_cgroup *memcg;
3960         struct page_cgroup *pc;
3961         int ret;
3962 
3963         pc = lookup_page_cgroup(page);
3964         /*
3965          * Every swap fault against a single page tries to charge the
3966          * page, bail as early as possible.  shmem_unuse() encounters
3967          * already charged pages, too.  The USED bit is protected by
3968          * the page lock, which serializes swap cache removal, which
3969          * in turn serializes uncharging.
3970          */
3971         if (PageCgroupUsed(pc))
3972                 return 0;
3973         if (!do_swap_account)
3974                 goto charge_cur_mm;
3975         memcg = try_get_mem_cgroup_from_page(page);
3976         if (!memcg)
3977                 goto charge_cur_mm;
3978         *memcgp = memcg;
3979         ret = __mem_cgroup_try_charge(NULL, mask, 1, memcgp, true);
3980         css_put(&memcg->css);
3981         if (ret == -EINTR)
3982                 ret = 0;
3983         return ret;
3984 charge_cur_mm:
3985         ret = __mem_cgroup_try_charge(mm, mask, 1, memcgp, true);
3986         if (ret == -EINTR)
3987                 ret = 0;
3988         return ret;
3989 }
3990 
3991 int mem_cgroup_try_charge_swapin(struct mm_struct *mm, struct page *page,
3992                                  gfp_t gfp_mask, struct mem_cgroup **memcgp)
3993 {
3994         *memcgp = NULL;
3995         if (mem_cgroup_disabled())
3996                 return 0;
3997         /*
3998          * A racing thread's fault, or swapoff, may have already
3999          * updated the pte, and even removed page from swap cache: in
4000          * those cases unuse_pte()'s pte_same() test will fail; but
4001          * there's also a KSM case which does need to charge the page.
4002          */
4003         if (!PageSwapCache(page)) {
4004                 int ret;
4005 
4006                 ret = __mem_cgroup_try_charge(mm, gfp_mask, 1, memcgp, true);
4007                 if (ret == -EINTR)
4008                         ret = 0;
4009                 return ret;
4010         }
4011         return __mem_cgroup_try_charge_swapin(mm, page, gfp_mask, memcgp);
4012 }
4013 
4014 void mem_cgroup_cancel_charge_swapin(struct mem_cgroup *memcg)
4015 {
4016         if (mem_cgroup_disabled())
4017                 return;
4018         if (!memcg)
4019                 return;
4020         __mem_cgroup_cancel_charge(memcg, 1);
4021 }
4022 
4023 static void
4024 __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *memcg,
4025                                         enum charge_type ctype)
4026 {
4027         if (mem_cgroup_disabled())
4028                 return;
4029         if (!memcg)
4030                 return;
4031 
4032         __mem_cgroup_commit_charge(memcg, page, 1, ctype, true);
4033         /*
4034          * Now swap is on-memory. This means this page may be
4035          * counted both as mem and swap....double count.
4036          * Fix it by uncharging from memsw. Basically, this SwapCache is stable
4037          * under lock_page(). But in do_swap_page()::memory.c, reuse_swap_page()
4038          * may call delete_from_swap_cache() before reach here.
4039          */
4040         if (do_swap_account && PageSwapCache(page)) {
4041                 swp_entry_t ent = {.val = page_private(page)};
4042                 mem_cgroup_uncharge_swap(ent);
4043         }
4044 }
4045 
4046 void mem_cgroup_commit_charge_swapin(struct page *page,
4047                                      struct mem_cgroup *memcg)
4048 {
4049         __mem_cgroup_commit_charge_swapin(page, memcg,
4050                                           MEM_CGROUP_CHARGE_TYPE_ANON);
4051 }
4052 
4053 int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
4054                                 gfp_t gfp_mask)
4055 {
4056         struct mem_cgroup *memcg = NULL;
4057         enum charge_type type = MEM_CGROUP_CHARGE_TYPE_CACHE;
4058         int ret;
4059 
4060         if (mem_cgroup_disabled())
4061                 return 0;
4062         if (PageCompound(page))
4063                 return 0;
4064 
4065         if (!PageSwapCache(page))
4066                 ret = mem_cgroup_charge_common(page, mm, gfp_mask, type);
4067         else { /* page is swapcache/shmem */
4068                 ret = __mem_cgroup_try_charge_swapin(mm, page,
4069                                                      gfp_mask, &memcg);
4070                 if (!ret)
4071                         __mem_cgroup_commit_charge_swapin(page, memcg, type);
4072         }
4073         return ret;
4074 }
4075 
4076 static void mem_cgroup_do_uncharge(struct mem_cgroup *memcg,
4077                                    unsigned int nr_pages,
4078                                    const enum charge_type ctype)
4079 {
4080         struct memcg_batch_info *batch = NULL;
4081         bool uncharge_memsw = true;
4082 
4083         /* If swapout, usage of swap doesn't decrease */
4084         if (!do_swap_account || ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT)
4085                 uncharge_memsw = false;
4086 
4087         batch = &current->memcg_batch;
4088         /*
4089          * In usual, we do css_get() when we remember memcg pointer.
4090          * But in this case, we keep res->usage until end of a series of
4091          * uncharges. Then, it's ok to ignore memcg's refcnt.
4092          */
4093         if (!batch->memcg)
4094                 batch->memcg = memcg;
4095         /*
4096          * do_batch > 0 when unmapping pages or inode invalidate/truncate.
4097          * In those cases, all pages freed continuously can be expected to be in
4098          * the same cgroup and we have chance to coalesce uncharges.
4099          * But we do uncharge one by one if this is killed by OOM(TIF_MEMDIE)
4100          * because we want to do uncharge as soon as possible.
4101          */
4102 
4103         if (!batch->do_batch || test_thread_flag(TIF_MEMDIE))
4104                 goto direct_uncharge;
4105 
4106         if (nr_pages > 1)
4107                 goto direct_uncharge;
4108 
4109         /*
4110          * In typical case, batch->memcg == mem. This means we can
4111          * merge a series of uncharges to an uncharge of res_counter.
4112          * If not, we uncharge res_counter ony by one.
4113          */
4114         if (batch->memcg != memcg)
4115                 goto direct_uncharge;
4116         /* remember freed charge and uncharge it later */
4117         batch->nr_pages++;
4118         if (uncharge_memsw)
4119                 batch->memsw_nr_pages++;
4120         return;
4121 direct_uncharge:
4122         res_counter_uncharge(&memcg->res, nr_pages * PAGE_SIZE);
4123         if (uncharge_memsw)
4124                 res_counter_uncharge(&memcg->memsw, nr_pages * PAGE_SIZE);
4125         if (unlikely(batch->memcg != memcg))
4126                 memcg_oom_recover(memcg);
4127 }
4128 
4129 /*
4130  * uncharge if !page_mapped(page)
4131  */
4132 static struct mem_cgroup *
4133 __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype,
4134                              bool end_migration)
4135 {
4136         struct mem_cgroup *memcg = NULL;
4137         unsigned int nr_pages = 1;
4138         struct page_cgroup *pc;
4139         bool anon;
4140 
4141         if (mem_cgroup_disabled())
4142                 return NULL;
4143 
4144         if (PageTransHuge(page)) {
4145                 nr_pages <<= compound_order(page);
4146                 VM_BUG_ON(!PageTransHuge(page));
4147         }
4148         /*
4149          * Check if our page_cgroup is valid
4150          */
4151         pc = lookup_page_cgroup(page);
4152         if (unlikely(!PageCgroupUsed(pc)))
4153                 return NULL;
4154 
4155         lock_page_cgroup(pc);
4156 
4157         memcg = pc->mem_cgroup;
4158 
4159         if (!PageCgroupUsed(pc))
4160                 goto unlock_out;
4161 
4162         anon = PageAnon(page);
4163 
4164         switch (ctype) {
4165         case MEM_CGROUP_CHARGE_TYPE_ANON:
4166                 /*
4167                  * Generally PageAnon tells if it's the anon statistics to be
4168                  * updated; but sometimes e.g. mem_cgroup_uncharge_page() is
4169                  * used before page reached the stage of being marked PageAnon.
4170                  */
4171                 anon = true;
4172                 /* fallthrough */
4173         case MEM_CGROUP_CHARGE_TYPE_DROP:
4174                 /* See mem_cgroup_prepare_migration() */
4175                 if (page_mapped(page))
4176                         goto unlock_out;
4177                 /*
4178                  * Pages under migration may not be uncharged.  But
4179                  * end_migration() /must/ be the one uncharging the
4180                  * unused post-migration page and so it has to call
4181                  * here with the migration bit still set.  See the
4182                  * res_counter handling below.
4183                  */
4184                 if (!end_migration && PageCgroupMigration(pc))
4185                         goto unlock_out;
4186                 break;
4187         case MEM_CGROUP_CHARGE_TYPE_SWAPOUT:
4188                 if (!PageAnon(page)) {  /* Shared memory */
4189                         if (page->mapping && !page_is_file_cache(page))
4190                                 goto unlock_out;
4191                 } else if (page_mapped(page)) /* Anon */
4192                                 goto unlock_out;
4193                 break;
4194         default:
4195                 break;
4196         }
4197 
4198         mem_cgroup_charge_statistics(memcg, page, anon, -nr_pages);
4199 
4200         ClearPageCgroupUsed(pc);
4201         /*
4202          * pc->mem_cgroup is not cleared here. It will be accessed when it's
4203          * freed from LRU. This is safe because uncharged page is expected not
4204          * to be reused (freed soon). Exception is SwapCache, it's handled by
4205          * special functions.
4206          */
4207 
4208         unlock_page_cgroup(pc);
4209         /*
4210          * even after unlock, we have memcg->res.usage here and this memcg
4211          * will never be freed, so it's safe to call css_get().
4212          */
4213         memcg_check_events(memcg, page);
4214         if (do_swap_account && ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT) {
4215                 mem_cgroup_swap_statistics(memcg, true);
4216                 css_get(&memcg->css);
4217         }
4218         /*
4219          * Migration does not charge the res_counter for the
4220          * replacement page, so leave it alone when phasing out the
4221          * page that is unused after the migration.
4222          */
4223         if (!end_migration && !mem_cgroup_is_root(memcg))
4224                 mem_cgroup_do_uncharge(memcg, nr_pages, ctype);
4225 
4226         return memcg;
4227 
4228 unlock_out:
4229         unlock_page_cgroup(pc);
4230         return NULL;
4231 }
4232 
4233 void mem_cgroup_uncharge_page(struct page *page)
4234 {
4235         /* early check. */
4236         if (page_mapped(page))
4237                 return;
4238         VM_BUG_ON(page->mapping && !PageAnon(page));
4239         /*
4240          * If the page is in swap cache, uncharge should be deferred
4241          * to the swap path, which also properly accounts swap usage
4242          * and handles memcg lifetime.
4243          *
4244          * Note that this check is not stable and reclaim may add the
4245          * page to swap cache at any time after this.  However, if the
4246          * page is not in swap cache by the time page->mapcount hits
4247          * 0, there won't be any page table references to the swap
4248          * slot, and reclaim will free it and not actually write the
4249          * page to disk.
4250          */
4251         if (PageSwapCache(page))
4252                 return;
4253         __mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_ANON, false);
4254 }
4255 
4256 void mem_cgroup_uncharge_cache_page(struct page *page)
4257 {
4258         VM_BUG_ON(page_mapped(page));
4259         VM_BUG_ON(page->mapping);
4260         __mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_CACHE, false);
4261 }
4262 
4263 /*
4264  * Batch_start/batch_end is called in unmap_page_range/invlidate/trucate.
4265  * In that cases, pages are freed continuously and we can expect pages
4266  * are in the same memcg. All these calls itself limits the number of
4267  * pages freed at once, then uncharge_start/end() is called properly.
4268  * This may be called prural(2) times in a context,
4269  */
4270 
4271 void mem_cgroup_uncharge_start(void)
4272 {
4273         current->memcg_batch.do_batch++;
4274         /* We can do nest. */
4275         if (current->memcg_batch.do_batch == 1) {
4276                 current->memcg_batch.memcg = NULL;
4277                 current->memcg_batch.nr_pages = 0;
4278                 current->memcg_batch.memsw_nr_pages = 0;
4279         }
4280 }
4281 
4282 void mem_cgroup_uncharge_end(void)
4283 {
4284         struct memcg_batch_info *batch = &current->memcg_batch;
4285 
4286         if (!batch->do_batch)
4287                 return;
4288 
4289         batch->do_batch--;
4290         if (batch->do_batch) /* If stacked, do nothing. */
4291                 return;
4292 
4293         if (!batch->memcg)
4294                 return;
4295         /*
4296          * This "batch->memcg" is valid without any css_get/put etc...
4297          * bacause we hide charges behind us.
4298          */
4299         if (batch->nr_pages)
4300                 res_counter_uncharge(&batch->memcg->res,
4301                                      batch->nr_pages * PAGE_SIZE);
4302         if (batch->memsw_nr_pages)
4303                 res_counter_uncharge(&batch->memcg->memsw,
4304                                      batch->memsw_nr_pages * PAGE_SIZE);
4305         memcg_oom_recover(batch->memcg);
4306         /* forget this pointer (for sanity check) */
4307         batch->memcg = NULL;
4308 }
4309 
4310 #ifdef CONFIG_SWAP
4311 /*
4312  * called after __delete_from_swap_cache() and drop "page" account.
4313  * memcg information is recorded to swap_cgroup of "ent"
4314  */
4315 void
4316 mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)
4317 {
4318         struct mem_cgroup *memcg;
4319         int ctype = MEM_CGROUP_CHARGE_TYPE_SWAPOUT;
4320 
4321         if (!swapout) /* this was a swap cache but the swap is unused ! */
4322                 ctype = MEM_CGROUP_CHARGE_TYPE_DROP;
4323 
4324         memcg = __mem_cgroup_uncharge_common(page, ctype, false);
4325 
4326         /*
4327          * record memcg information,  if swapout && memcg != NULL,
4328          * css_get() was called in uncharge().
4329          */
4330         if (do_swap_account && swapout && memcg)
4331                 swap_cgroup_record(ent, css_id(&memcg->css));
4332 }
4333 #endif
4334 
4335 #ifdef CONFIG_MEMCG_SWAP
4336 /*
4337  * called from swap_entry_free(). remove record in swap_cgroup and
4338  * uncharge "memsw" account.
4339  */
4340 void mem_cgroup_uncharge_swap(swp_entry_t ent)
4341 {
4342         struct mem_cgroup *memcg;
4343         unsigned short id;
4344 
4345         if (!do_swap_account)
4346                 return;
4347 
4348         id = swap_cgroup_record(ent, 0);
4349         rcu_read_lock();
4350         memcg = mem_cgroup_lookup(id);
4351         if (memcg) {
4352                 /*
4353                  * We uncharge this because swap is freed.
4354                  * This memcg can be obsolete one. We avoid calling css_tryget
4355                  */
4356                 if (!mem_cgroup_is_root(memcg))
4357                         res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
4358                 mem_cgroup_swap_statistics(memcg, false);
4359                 css_put(&memcg->css);
4360         }
4361         rcu_read_unlock();
4362 }
4363 
4364 /**
4365  * mem_cgroup_move_swap_account - move swap charge and swap_cgroup's record.
4366  * @entry: swap entry to be moved
4367  * @from:  mem_cgroup which the entry is moved from
4368  * @to:  mem_cgroup which the entry is moved to
4369  *
4370  * It succeeds only when the swap_cgroup's record for this entry is the same
4371  * as the mem_cgroup's id of @from.
4372  *
4373  * Returns 0 on success, -EINVAL on failure.
4374  *
4375  * The caller must have charged to @to, IOW, called res_counter_charge() about
4376  * both res and memsw, and called css_get().
4377  */
4378 static int mem_cgroup_move_swap_account(swp_entry_t entry,
4379                                 struct mem_cgroup *from, struct mem_cgroup *to)
4380 {
4381         unsigned short old_id, new_id;
4382 
4383         old_id = css_id(&from->css);
4384         new_id = css_id(&to->css);
4385 
4386         if (swap_cgroup_cmpxchg(entry, old_id, new_id) == old_id) {
4387                 mem_cgroup_swap_statistics(from, false);
4388                 mem_cgroup_swap_statistics(to, true);
4389                 /*
4390                  * This function is only called from task migration context now.
4391                  * It postpones res_counter and refcount handling till the end
4392                  * of task migration(mem_cgroup_clear_mc()) for performance
4393                  * improvement. But we cannot postpone css_get(to)  because if
4394                  * the process that has been moved to @to does swap-in, the
4395                  * refcount of @to might be decreased to 0.
4396                  *
4397                  * We are in attach() phase, so the cgroup is guaranteed to be
4398                  * alive, so we can just call css_get().
4399                  */
4400                 css_get(&to->css);
4401                 return 0;
4402         }
4403         return -EINVAL;
4404 }
4405 #else
4406 static inline int mem_cgroup_move_swap_account(swp_entry_t entry,
4407                                 struct mem_cgroup *from, struct mem_cgroup *to)
4408 {
4409         return -EINVAL;
4410 }
4411 #endif
4412 
4413 /*
4414  * Before starting migration, account PAGE_SIZE to mem_cgroup that the old
4415  * page belongs to.
4416  */
4417 void mem_cgroup_prepare_migration(struct page *page, struct page *newpage,
4418                                   struct mem_cgroup **memcgp)
4419 {
4420         struct mem_cgroup *memcg = NULL;
4421         unsigned int nr_pages = 1;
4422         struct page_cgroup *pc;
4423         enum charge_type ctype;
4424 
4425         *memcgp = NULL;
4426 
4427         if (mem_cgroup_disabled())
4428                 return;
4429 
4430         if (PageTransHuge(page))
4431                 nr_pages <<= compound_order(page);
4432 
4433         pc = lookup_page_cgroup(page);
4434         lock_page_cgroup(pc);
4435         if (PageCgroupUsed(pc)) {
4436                 memcg = pc->mem_cgroup;
4437                 css_get(&memcg->css);
4438                 /*
4439                  * At migrating an anonymous page, its mapcount goes down
4440                  * to 0 and uncharge() will be called. But, even if it's fully
4441                  * unmapped, migration may fail and this page has to be
4442                  * charged again. We set MIGRATION flag here and delay uncharge
4443                  * until end_migration() is called
4444                  *
4445                  * Corner Case Thinking
4446                  * A)
4447                  * When the old page was mapped as Anon and it's unmap-and-freed
4448                  * while migration was ongoing.
4449                  * If unmap finds the old page, uncharge() of it will be delayed
4450                  * until end_migration(). If unmap finds a new page, it's
4451                  * uncharged when it make mapcount to be 1->0. If unmap code
4452                  * finds swap_migration_entry, the new page will not be mapped
4453                  * and end_migration() will find it(mapcount==0).
4454                  *
4455                  * B)
4456                  * When the old page was mapped but migraion fails, the kernel
4457                  * remaps it. A charge for it is kept by MIGRATION flag even
4458                  * if mapcount goes down to 0. We can do remap successfully
4459                  * without charging it again.
4460                  *
4461                  * C)
4462                  * The "old" page is under lock_page() until the end of
4463                  * migration, so, the old page itself will not be swapped-out.
4464                  * If the new page is swapped out before end_migraton, our
4465                  * hook to usual swap-out path will catch the event.
4466                  */
4467                 if (PageAnon(page))
4468                         SetPageCgroupMigration(pc);
4469         }
4470         unlock_page_cgroup(pc);
4471         /*
4472          * If the page is not charged at this point,
4473          * we return here.
4474          */
4475         if (!memcg)
4476                 return;
4477 
4478         *memcgp = memcg;
4479         /*
4480          * We charge new page before it's used/mapped. So, even if unlock_page()
4481          * is called before end_migration, we can catch all events on this new
4482          * page. In the case new page is migrated but not remapped, new page's
4483          * mapcount will be finally 0 and we call uncharge in end_migration().
4484          */
4485         if (PageAnon(page))
4486                 ctype = MEM_CGROUP_CHARGE_TYPE_ANON;
4487         else
4488                 ctype = MEM_CGROUP_CHARGE_TYPE_CACHE;
4489         /*
4490          * The page is committed to the memcg, but it's not actually
4491          * charged to the res_counter since we plan on replacing the
4492          * old one and only one page is going to be left afterwards.
4493          */
4494         __mem_cgroup_commit_charge(memcg, newpage, nr_pages, ctype, false);
4495 }
4496 
4497 /* remove redundant charge if migration failed*/
4498 void mem_cgroup_end_migration(struct mem_cgroup *memcg,
4499         struct page *oldpage, struct page *newpage, bool migration_ok)
4500 {
4501         struct page *used, *unused;
4502         struct page_cgroup *pc;
4503         bool anon;
4504 
4505         if (!memcg)
4506                 return;
4507 
4508         if (!migration_ok) {
4509                 used = oldpage;
4510                 unused = newpage;
4511         } else {
4512                 used = newpage;
4513                 unused = oldpage;
4514         }
4515         anon = PageAnon(used);
4516         __mem_cgroup_uncharge_common(unused,
4517                                      anon ? MEM_CGROUP_CHARGE_TYPE_ANON
4518                                      : MEM_CGROUP_CHARGE_TYPE_CACHE,
4519                                      true);
4520         css_put(&memcg->css);
4521         /*
4522          * We disallowed uncharge of pages under migration because mapcount
4523          * of the page goes down to zero, temporarly.
4524          * Clear the flag and check the page should be charged.
4525          */
4526         pc = lookup_page_cgroup(oldpage);
4527         lock_page_cgroup(pc);
4528         ClearPageCgroupMigration(pc);
4529         unlock_page_cgroup(pc);
4530 
4531         /*
4532          * If a page is a file cache, radix-tree replacement is very atomic
4533          * and we can skip this check. When it was an Anon page, its mapcount
4534          * goes down to 0. But because we added MIGRATION flage, it's not
4535          * uncharged yet. There are several case but page->mapcount check
4536          * and USED bit check in mem_cgroup_uncharge_page() will do enough
4537          * check. (see prepare_charge() also)
4538          */
4539         if (anon)
4540                 mem_cgroup_uncharge_page(used);
4541 }
4542 
4543 /*
4544  * At replace page cache, newpage is not under any memcg but it's on
4545  * LRU. So, this function doesn't touch res_counter but handles LRU
4546  * in correct way. Both pages are locked so we cannot race with uncharge.
4547  */
4548 void mem_cgroup_replace_page_cache(struct page *oldpage,
4549                                   struct page *newpage)
4550 {
4551         struct mem_cgroup *memcg = NULL;
4552         struct page_cgroup *pc;
4553         enum charge_type type = MEM_CGROUP_CHARGE_TYPE_CACHE;
4554 
4555         if (mem_cgroup_disabled())
4556                 return;
4557 
4558         pc = lookup_page_cgroup(oldpage);
4559         /* fix accounting on old pages */
4560         lock_page_cgroup(pc);
4561         if (PageCgroupUsed(pc)) {
4562                 memcg = pc->mem_cgroup;
4563                 mem_cgroup_charge_statistics(memcg, oldpage, false, -1);
4564                 ClearPageCgroupUsed(pc);
4565         }
4566         unlock_page_cgroup(pc);
4567 
4568         /*
4569          * When called from shmem_replace_page(), in some cases the
4570          * oldpage has already been charged, and in some cases not.
4571          */
4572         if (!memcg)
4573                 return;
4574         /*
4575          * Even if newpage->mapping was NULL before starting replacement,
4576          * the newpage may be on LRU(or pagevec for LRU) already. We lock
4577          * LRU while we overwrite pc->mem_cgroup.
4578          */
4579         __mem_cgroup_commit_charge(memcg, newpage, 1, type, true);
4580 }
4581 
4582 #ifdef CONFIG_DEBUG_VM
4583 static struct page_cgroup *lookup_page_cgroup_used(struct page *page)
4584 {
4585         struct page_cgroup *pc;
4586 
4587         pc = lookup_page_cgroup(page);
4588         /*
4589          * Can be NULL while feeding pages into the page allocator for
4590          * the first time, i.e. during boot or memory hotplug;
4591          * or when mem_cgroup_disabled().
4592          */
4593         if (likely(pc) && PageCgroupUsed(pc))
4594                 return pc;
4595         return NULL;
4596 }
4597 
4598 bool mem_cgroup_bad_page_check(struct page *page)
4599 {
4600         if (mem_cgroup_disabled())
4601                 return false;
4602 
4603         return lookup_page_cgroup_used(page) != NULL;
4604 }
4605 
4606 void mem_cgroup_print_bad_page(struct page *page)
4607 {
4608         struct page_cgroup *pc;
4609 
4610         pc = lookup_page_cgroup_used(page);
4611         if (pc) {
4612                 pr_alert("pc:%p pc->flags:%lx pc->mem_cgroup:%p\n",
4613                          pc, pc->flags, pc->mem_cgroup);
4614         }
4615 }
4616 #endif
4617 
4618 static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
4619                                 unsigned long long val)
4620 {
4621         int retry_count;
4622         u64 memswlimit, memlimit;
4623         int ret = 0;
4624         int children = mem_cgroup_count_children(memcg);
4625         u64 curusage, oldusage;
4626         int enlarge;
4627 
4628         /*
4629          * For keeping hierarchical_reclaim simple, how long we should retry
4630          * is depends on callers. We set our retry-count to be function
4631          * of # of children which we should visit in this loop.
4632          */
4633         retry_count = MEM_CGROUP_RECLAIM_RETRIES * children;
4634 
4635         oldusage = res_counter_read_u64(&memcg->res, RES_USAGE);
4636 
4637         enlarge = 0;
4638         while (retry_count) {
4639                 if (signal_pending(current)) {
4640                         ret = -EINTR;
4641                         break;
4642                 }
4643                 /*
4644                  * Rather than hide all in some function, I do this in
4645                  * open coded manner. You see what this really does.
4646                  * We have to guarantee memcg->res.limit <= memcg->memsw.limit.
4647                  */
4648                 mutex_lock(&set_limit_mutex);
4649                 memswlimit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
4650                 if (memswlimit < val) {
4651                         ret = -EINVAL;
4652                         mutex_unlock(&set_limit_mutex);
4653                         break;
4654                 }
4655 
4656                 memlimit = res_counter_read_u64(&memcg->res, RES_LIMIT);
4657                 if (memlimit < val)
4658                         enlarge = 1;
4659 
4660                 ret = res_counter_set_limit(&memcg->res, val);
4661                 if (!ret) {
4662                         if (memswlimit == val)
4663                                 memcg->memsw_is_minimum = true;
4664                         else
4665                                 memcg->memsw_is_minimum = false;
4666                 }
4667                 mutex_unlock(&set_limit_mutex);
4668 
4669                 if (!ret)
4670                         break;
4671 
4672                 mem_cgroup_reclaim(memcg, GFP_KERNEL,
4673                                    MEM_CGROUP_RECLAIM_SHRINK);
4674                 curusage = res_counter_read_u64(&memcg->res, RES_USAGE);
4675                 /* Usage is reduced ? */
4676                 if (curusage >= oldusage)
4677                         retry_count--;
4678                 else
4679                         oldusage = curusage;
4680         }
4681         if (!ret && enlarge)
4682                 memcg_oom_recover(memcg);
4683 
4684         return ret;
4685 }
4686 
4687 static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
4688                                         unsigned long long val)
4689 {
4690         int retry_count;
4691         u64 memlimit, memswlimit, oldusage, curusage;
4692         int children = mem_cgroup_count_children(memcg);
4693         int ret = -EBUSY;
4694         int enlarge = 0;
4695 
4696         /* see mem_cgroup_resize_res_limit */
4697         retry_count = children * MEM_CGROUP_RECLAIM_RETRIES;
4698         oldusage = res_counter_read_u64(&memcg->memsw, RES_USAGE);
4699         while (retry_count) {
4700                 if (signal_pending(current)) {
4701                         ret = -EINTR;
4702                         break;
4703                 }
4704                 /*
4705                  * Rather than hide all in some function, I do this in
4706                  * open coded manner. You see what this really does.
4707                  * We have to guarantee memcg->res.limit <= memcg->memsw.limit.
4708                  */
4709                 mutex_lock(&set_limit_mutex);
4710                 memlimit = res_counter_read_u64(&memcg->res, RES_LIMIT);
4711                 if (memlimit > val) {
4712                         ret = -EINVAL;
4713                         mutex_unlock(&set_limit_mutex);
4714                         break;
4715                 }
4716                 memswlimit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
4717                 if (memswlimit < val)
4718                         enlarge = 1;
4719                 ret = res_counter_set_limit(&memcg->memsw, val);
4720                 if (!ret) {
4721                         if (memlimit == val)
4722                                 memcg->memsw_is_minimum = true;
4723                         else
4724                                 memcg->memsw_is_minimum = false;
4725                 }
4726                 mutex_unlock(&set_limit_mutex);
4727 
4728                 if (!ret)
4729                         break;
4730 
4731                 mem_cgroup_reclaim(memcg, GFP_KERNEL,
4732                                    MEM_CGROUP_RECLAIM_NOSWAP |
4733                                    MEM_CGROUP_RECLAIM_SHRINK);
4734                 curusage = res_counter_read_u64(&memcg->memsw, RES_USAGE);
4735                 /* Usage is reduced ? */
4736                 if (curusage >= oldusage)
4737                         retry_count--;
4738                 else
4739                         oldusage = curusage;
4740         }
4741         if (!ret && enlarge)
4742                 memcg_oom_recover(memcg);
4743         return ret;
4744 }
4745 
4746 unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
4747                                             gfp_t gfp_mask,
4748                                             unsigned long *total_scanned)
4749 {
4750         unsigned long nr_reclaimed = 0;
4751         struct mem_cgroup_per_zone *mz, *next_mz = NULL;
4752         unsigned long reclaimed;
4753         int loop = 0;
4754         struct mem_cgroup_tree_per_zone *mctz;
4755         unsigned long long excess;
4756         unsigned long nr_scanned;
4757 
4758         if (order > 0)
4759                 return 0;
4760 
4761         mctz = soft_limit_tree_node_zone(zone_to_nid(zone), zone_idx(zone));
4762         /*
4763          * This loop can run a while, specially if mem_cgroup's continuously
4764          * keep exceeding their soft limit and putting the system under
4765          * pressure
4766          */
4767         do {
4768                 if (next_mz)
4769                         mz = next_mz;
4770                 else
4771                         mz = mem_cgroup_largest_soft_limit_node(mctz);
4772                 if (!mz)
4773                         break;
4774 
4775                 nr_scanned = 0;
4776                 reclaimed = mem_cgroup_soft_reclaim(mz->memcg, zone,
4777                                                     gfp_mask, &nr_scanned);
4778                 nr_reclaimed += reclaimed;
4779                 *total_scanned += nr_scanned;
4780                 spin_lock(&mctz->lock);
4781 
4782                 /*
4783                  * If we failed to reclaim anything from this memory cgroup
4784                  * it is time to move on to the next cgroup
4785                  */
4786                 next_mz = NULL;
4787                 if (!reclaimed) {
4788                         do {
4789                                 /*
4790                                  * Loop until we find yet another one.
4791                                  *
4792                                  * By the time we get the soft_limit lock
4793                                  * again, someone might have aded the
4794                                  * group back on the RB tree. Iterate to
4795                                  * make sure we get a different mem.
4796                                  * mem_cgroup_largest_soft_limit_node returns
4797                                  * NULL if no other cgroup is present on
4798                                  * the tree
4799                                  */
4800                                 next_mz =
4801                                 __mem_cgroup_largest_soft_limit_node(mctz);
4802                                 if (next_mz == mz)
4803                                         css_put(&next_mz->memcg->css);
4804                                 else /* next_mz == NULL or other memcg */
4805                                         break;
4806                         } while (1);
4807                 }
4808                 __mem_cgroup_remove_exceeded(mz->memcg, mz, mctz);
4809                 excess = res_counter_soft_limit_excess(&mz->memcg->res);
4810                 /*
4811                  * One school of thought says that we should not add
4812                  * back the node to the tree if reclaim returns 0.
4813                  * But our reclaim could return 0, simply because due
4814                  * to priority we are exposing a smaller subset of
4815                  * memory to reclaim from. Consider this as a longer
4816                  * term TODO.
4817                  */
4818                 /* If excess == 0, no tree ops */
4819                 __mem_cgroup_insert_exceeded(mz->memcg, mz, mctz, excess);
4820                 spin_unlock(&mctz->lock);
4821                 css_put(&mz->memcg->css);
4822                 loop++;
4823                 /*
4824                  * Could not reclaim anything and there are no more
4825                  * mem cgroups to try or we seem to be looping without
4826                  * reclaiming anything.
4827                  */
4828                 if (!nr_reclaimed &&
4829                         (next_mz == NULL ||
4830                         loop > MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS))
4831                         break;
4832         } while (!nr_reclaimed);
4833         if (next_mz)
4834                 css_put(&next_mz->memcg->css);
4835         return nr_reclaimed;
4836 }
4837 
4838 /**
4839  * mem_cgroup_force_empty_list - clears LRU of a group
4840  * @memcg: group to clear
4841  * @node: NUMA node
4842  * @zid: zone id
4843  * @lru: lru to to clear
4844  *
4845  * Traverse a specified page_cgroup list and try to drop them all.  This doesn't
4846  * reclaim the pages page themselves - pages are moved to the parent (or root)
4847  * group.
4848  */
4849 static void mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
4850                                 int node, int zid, enum lru_list lru)
4851 {
4852         struct lruvec *lruvec;
4853         unsigned long flags;
4854         struct list_head *list;
4855         struct page *busy;
4856         struct zone *zone;
4857 
4858         zone = &NODE_DATA(node)->node_zones[zid];
4859         lruvec = mem_cgroup_zone_lruvec(zone, memcg);
4860         list = &lruvec->lists[lru];
4861 
4862         busy = NULL;
4863         do {
4864                 struct page_cgroup *pc;
4865                 struct page *page;
4866 
4867                 spin_lock_irqsave(&zone->lru_lock, flags);
4868                 if (list_empty(list)) {
4869                         spin_unlock_irqrestore(&zone->lru_lock, flags);
4870                         break;
4871                 }
4872                 page = list_entry(list->prev, struct page, lru);
4873                 if (busy == page) {
4874                         list_move(&page->lru, list);
4875                         busy = NULL;
4876                         spin_unlock_irqrestore(&zone->lru_lock, flags);
4877                         continue;
4878                 }
4879                 spin_unlock_irqrestore(&zone->lru_lock, flags);
4880 
4881                 pc = lookup_page_cgroup(page);
4882 
4883                 if (mem_cgroup_move_parent(page, pc, memcg)) {
4884                         /* found lock contention or "pc" is obsolete. */
4885                         busy = page;
4886                         cond_resched();
4887                 } else
4888                         busy = NULL;
4889         } while (!list_empty(list));
4890 }
4891 
4892 /*
4893  * make mem_cgroup's charge to be 0 if there is no task by moving
4894  * all the charges and pages to the parent.
4895  * This enables deleting this mem_cgroup.
4896  *
4897  * Caller is responsible for holding css reference on the memcg.
4898  */
4899 static void mem_cgroup_reparent_charges(struct mem_cgroup *memcg)
4900 {
4901         int node, zid;
4902         u64 usage;
4903 
4904         do {
4905                 /* This is for making all *used* pages to be on LRU. */
4906                 lru_add_drain_all();
4907                 drain_all_stock_sync(memcg);
4908                 mem_cgroup_start_move(memcg);
4909                 for_each_node_state(node, N_MEMORY) {
4910                         for (zid = 0; zid < MAX_NR_ZONES; zid++) {
4911                                 enum lru_list lru;
4912                                 for_each_lru(lru) {
4913                                         mem_cgroup_force_empty_list(memcg,
4914                                                         node, zid, lru);
4915                                 }
4916                         }
4917                 }
4918                 mem_cgroup_end_move(memcg);
4919                 memcg_oom_recover(memcg);
4920                 cond_resched();
4921 
4922                 /*
4923                  * Kernel memory may not necessarily be trackable to a specific
4924                  * process. So they are not migrated, and therefore we can't
4925                  * expect their value to drop to 0 here.
4926                  * Having res filled up with kmem only is enough.
4927                  *
4928                  * This is a safety check because mem_cgroup_force_empty_list
4929                  * could have raced with mem_cgroup_replace_page_cache callers
4930                  * so the lru seemed empty but the page could have been added
4931                  * right after the check. RES_USAGE should be safe as we always
4932                  * charge before adding to the LRU.
4933                  */
4934                 usage = res_counter_read_u64(&memcg->res, RES_USAGE) -
4935                         res_counter_read_u64(&memcg->kmem, RES_USAGE);
4936         } while (usage > 0);
4937 }
4938 
4939 /*
4940  * This mainly exists for tests during the setting of set of use_hierarchy.
4941  * Since this is the very setting we are changing, the current hierarchy value
4942  * is meaningless
4943  */
4944 static inline bool __memcg_has_children(struct mem_cgroup *memcg)
4945 {
4946         struct cgroup *pos;
4947 
4948         /* bounce at first found */
4949         cgroup_for_each_child(pos, memcg->css.cgroup)
4950                 return true;
4951         return false;
4952 }
4953 
4954 /*
4955  * Must be called with memcg_create_mutex held, unless the cgroup is guaranteed
4956  * to be already dead (as in mem_cgroup_force_empty, for instance).  This is
4957  * from mem_cgroup_count_children(), in the sense that we don't really care how
4958  * many children we have; we only need to know if we have any.  It also counts
4959  * any memcg without hierarchy as infertile.
4960  */
4961 static inline bool memcg_has_children(struct mem_cgroup *memcg)
4962 {
4963         return memcg->use_hierarchy && __memcg_has_children(memcg);
4964 }
4965 
4966 /*
4967  * Reclaims as many pages from the given memcg as possible and moves
4968  * the rest to the parent.
4969  *
4970  * Caller is responsible for holding css reference for memcg.
4971  */
4972 static int mem_cgroup_force_empty(struct mem_cgroup *memcg)
4973 {
4974         int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
4975         struct cgroup *cgrp = memcg->css.cgroup;
4976 
4977         /* returns EBUSY if there is a task or if we come here twice. */
4978         if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children))
4979                 return -EBUSY;
4980 
4981         /* we call try-to-free pages for make this cgroup empty */
4982         lru_add_drain_all();
4983         /* try to free all pages in this cgroup */
4984         while (nr_retries && res_counter_read_u64(&memcg->res, RES_USAGE) > 0) {
4985                 int progress;
4986 
4987                 if (signal_pending(current))
4988                         return -EINTR;
4989 
4990                 progress = try_to_free_mem_cgroup_pages(memcg, GFP_KERNEL,
4991                                                 false);
4992                 if (!progress) {
4993                         nr_retries--;
4994                         /* maybe some writeback is necessary */
4995                         congestion_wait(BLK_RW_ASYNC, HZ/10);
4996                 }
4997 
4998         }
4999         lru_add_drain();
5000         mem_cgroup_reparent_charges(memcg);
5001 
5002         return 0;
5003 }
5004 
5005 static int mem_cgroup_force_empty_write(struct cgroup *cont, unsigned int event)
5006 {
5007         struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
5008         int ret;
5009 
5010         if (mem_cgroup_is_root(memcg))
5011                 return -EINVAL;
5012         css_get(&memcg->css);
5013         ret = mem_cgroup_force_empty(memcg);
5014         css_put(&memcg->css);
5015 
5016         return ret;
5017 }
5018 
5019 
5020 static u64 mem_cgroup_hierarchy_read(struct cgroup *cont, struct cftype *cft)
5021 {
5022         return mem_cgroup_from_cont(cont)->use_hierarchy;
5023 }
5024 
5025 static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
5026                                         u64 val)
5027 {
5028         int retval = 0;
5029         struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
5030         struct cgroup *parent = cont->parent;
5031         struct mem_cgroup *parent_memcg = NULL;
5032 
5033         if (parent)
5034                 parent_memcg = mem_cgroup_from_cont(parent);
5035 
5036         mutex_lock(&memcg_create_mutex);
5037 
5038         if (memcg->use_hierarchy == val)
5039                 goto out;
5040 
5041         /*
5042          * If parent's use_hierarchy is set, we can't make any modifications
5043          * in the child subtrees. If it is unset, then the change can
5044          * occur, provided the current cgroup has no children.
5045          *
5046          * For the root cgroup, parent_mem is NULL, we allow value to be
5047          * set if there are no children.
5048          */
5049         if ((!parent_memcg || !parent_memcg->use_hierarchy) &&
5050                                 (val == 1 || val == 0)) {
5051                 if (!__memcg_has_children(memcg))
5052                         memcg->use_hierarchy = val;
5053                 else
5054                         retval = -EBUSY;
5055         } else
5056                 retval = -EINVAL;
5057 
5058 out:
5059         mutex_unlock(&memcg_create_mutex);
5060 
5061         return retval;
5062 }
5063 
5064 
5065 static unsigned long mem_cgroup_recursive_stat(struct mem_cgroup *memcg,
5066                                                enum mem_cgroup_stat_index idx)
5067 {
5068         struct mem_cgroup *iter;
5069         long val = 0;
5070 
5071         /* Per-cpu values can be negative, use a signed accumulator */
5072         for_each_mem_cgroup_tree(iter, memcg)
5073                 val += mem_cgroup_read_stat(iter, idx);
5074 
5075         if (val < 0) /* race ? */
5076                 val = 0;
5077         return val;
5078 }
5079 
5080 static inline u64 mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)
5081 {
5082         u64 val;
5083 
5084         if (!mem_cgroup_is_root(memcg)) {
5085                 if (!swap)
5086                         return res_counter_read_u64(&memcg->res, RES_USAGE);
5087                 else
5088                         return res_counter_read_u64(&memcg->memsw, RES_USAGE);
5089         }
5090 
5091         /*
5092          * Transparent hugepages are still accounted for in MEM_CGROUP_STAT_RSS
5093          * as well as in MEM_CGROUP_STAT_RSS_HUGE.
5094          */
5095         val = mem_cgroup_recursive_stat(memcg, MEM_CGROUP_STAT_CACHE);
5096         val += mem_cgroup_recursive_stat(memcg, MEM_CGROUP_STAT_RSS);
5097 
5098         if (swap)
5099                 val += mem_cgroup_recursive_stat(memcg, MEM_CGROUP_STAT_SWAP);
5100 
5101         return val << PAGE_SHIFT;
5102 }
5103 
5104 static ssize_t mem_cgroup_read(struct cgroup *cont, struct cftype *cft,
5105                                struct file *file, char __user *buf,
5106                                size_t nbytes, loff_t *ppos)
5107 {
5108         struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
5109         char str[64];
5110         u64 val;
5111         int name, len;
5112         enum res_type type;
5113 
5114         type = MEMFILE_TYPE(cft->private);
5115         name = MEMFILE_ATTR(cft->private);
5116 
5117         switch (type) {
5118         case _MEM:
5119                 if (name == RES_USAGE)
5120                         val = mem_cgroup_usage(memcg, false);
5121                 else
5122                         val = res_counter_read_u64(&memcg->res, name);
5123                 break;
5124         case _MEMSWAP:
5125                 if (name == RES_USAGE)
5126                         val = mem_cgroup_usage(memcg, true);
5127                 else
5128                         val = res_counter_read_u64(&memcg->memsw, name);
5129                 break;
5130         case _KMEM:
5131                 val = res_counter_read_u64(&memcg->kmem, name);
5132                 break;
5133         default:
5134                 BUG();
5135         }
5136 
5137         len = scnprintf(str, sizeof(str), "%llu\n", (unsigned long long)val);
5138         return simple_read_from_buffer(buf, nbytes, ppos, str, len);
5139 }
5140 
5141 static int memcg_update_kmem_limit(struct cgroup *cont, u64 val)
5142 {
5143         int ret = -EINVAL;
5144 #ifdef CONFIG_MEMCG_KMEM
5145         struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
5146         /*
5147          * For simplicity, we won't allow this to be disabled.  It also can't
5148          * be changed if the cgroup has children already, or if tasks had
5149          * already joined.
5150          *
5151          * If tasks join before we set the limit, a person looking at
5152          * kmem.usage_in_bytes will have no way to determine when it took
5153          * place, which makes the value quite meaningless.
5154          *
5155          * After it first became limited, changes in the value of the limit are
5156          * of course permitted.
5157          */
5158         mutex_lock(&memcg_create_mutex);
5159         mutex_lock(&set_limit_mutex);
5160         if (!memcg->kmem_account_flags && val != RESOURCE_MAX) {
5161                 if (cgroup_task_count(cont) || memcg_has_children(memcg)) {
5162                         ret = -EBUSY;
5163                         goto out;
5164                 }
5165                 ret = res_counter_set_limit(&memcg->kmem, val);
5166                 VM_BUG_ON(ret);
5167 
5168                 ret = memcg_update_cache_sizes(memcg);
5169                 if (ret) {
5170                         res_counter_set_limit(&memcg->kmem, RESOURCE_MAX);
5171                         goto out;
5172                 }
5173                 static_key_slow_inc(&memcg_kmem_enabled_key);
5174                 /*
5175                  * setting the active bit after the inc will guarantee no one
5176                  * starts accounting before all call sites are patched
5177                  */
5178                 memcg_kmem_set_active(memcg);
5179         } else
5180                 ret = res_counter_set_limit(&memcg->kmem, val);
5181 out:
5182         mutex_unlock(&set_limit_mutex);
5183         mutex_unlock(&memcg_create_mutex);
5184 #endif
5185         return ret;
5186 }
5187 
5188 #ifdef CONFIG_MEMCG_KMEM
5189 static int memcg_propagate_kmem(struct mem_cgroup *memcg)
5190 {
5191         int ret = 0;
5192         struct mem_cgroup *parent = parent_mem_cgroup(memcg);
5193         if (!parent)
5194                 goto out;
5195 
5196         memcg->kmem_account_flags = parent->kmem_account_flags;
5197         /*
5198          * When that happen, we need to disable the static branch only on those
5199          * memcgs that enabled it. To achieve this, we would be forced to
5200          * complicate the code by keeping track of which memcgs were the ones
5201          * that actually enabled limits, and which ones got it from its
5202          * parents.
5203          *
5204          * It is a lot simpler just to do static_key_slow_inc() on every child
5205          * that is accounted.
5206          */
5207         if (!memcg_kmem_is_active(memcg))
5208                 goto out;
5209 
5210         /*
5211          * __mem_cgroup_free() will issue static_key_slow_dec() because this
5212          * memcg is active already. If the later initialization fails then the
5213          * cgroup core triggers the cleanup so we do not have to do it here.
5214          */
5215         static_key_slow_inc(&memcg_kmem_enabled_key);
5216 
5217         mutex_lock(&set_limit_mutex);
5218         memcg_stop_kmem_account();
5219         ret = memcg_update_cache_sizes(memcg);
5220         memcg_resume_kmem_account();
5221         mutex_unlock(&set_limit_mutex);
5222 out:
5223         return ret;
5224 }
5225 #endif /* CONFIG_MEMCG_KMEM */
5226 
5227 /*
5228  * The user of this function is...
5229  * RES_LIMIT.
5230  */
5231 static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
5232                             const char *buffer)
5233 {
5234         struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
5235         enum res_type type;
5236         int name;
5237         unsigned long long val;
5238         int ret;
5239 
5240         type = MEMFILE_TYPE(cft->private);
5241         name = MEMFILE_ATTR(cft->private);
5242 
5243         switch (name) {
5244         case RES_LIMIT:
5245                 if (mem_cgroup_is_root(memcg)) { /* Can't set limit on root */
5246                         ret = -EINVAL;
5247                         break;
5248                 }
5249                 /* This function does all necessary parse...reuse it */
5250                 ret = res_counter_memparse_write_strategy(buffer, &val);
5251                 if (ret)
5252                         break;
5253                 if (type == _MEM)
5254                         ret = mem_cgroup_resize_limit(memcg, val);
5255                 else if (type == _MEMSWAP)
5256                         ret = mem_cgroup_resize_memsw_limit(memcg, val);
5257                 else if (type == _KMEM)
5258                         ret = memcg_update_kmem_limit(cont, val);
5259                 else
5260                         return -EINVAL;
5261                 break;
5262         case RES_SOFT_LIMIT:
5263                 ret = res_counter_memparse_write_strategy(buffer, &val);
5264                 if (ret)
5265                         break;
5266                 /*
5267                  * For memsw, soft limits are hard to implement in terms
5268                  * of semantics, for now, we support soft limits for
5269                  * control without swap
5270                  */
5271                 if (type == _MEM)
5272                         ret = res_counter_set_soft_limit(&memcg->res, val);
5273                 else
5274                         ret = -EINVAL;
5275                 break;
5276         default:
5277                 ret = -EINVAL; /* should be BUG() ? */
5278                 break;
5279         }
5280         return ret;
5281 }
5282 
5283 static void memcg_get_hierarchical_limit(struct mem_cgroup *memcg,
5284                 unsigned long long *mem_limit, unsigned long long *memsw_limit)
5285 {
5286         struct cgroup *cgroup;
5287         unsigned long long min_limit, min_memsw_limit, tmp;
5288 
5289         min_limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
5290         min_memsw_limit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
5291         cgroup = memcg->css.cgroup;
5292         if (!memcg->use_hierarchy)
5293                 goto out;
5294 
5295         while (cgroup->parent) {
5296                 cgroup = cgroup->parent;
5297                 memcg = mem_cgroup_from_cont(cgroup);
5298                 if (!memcg->use_hierarchy)
5299                         break;
5300                 tmp = res_counter_read_u64(&memcg->res, RES_LIMIT);
5301                 min_limit = min(min_limit, tmp);
5302                 tmp = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
5303                 min_memsw_limit = min(min_memsw_limit, tmp);
5304         }
5305 out:
5306         *mem_limit = min_limit;
5307         *memsw_limit = min_memsw_limit;
5308 }
5309 
5310 static int mem_cgroup_reset(struct cgroup *cont, unsigned int event)
5311 {
5312         struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
5313         int name;
5314         enum res_type type;
5315 
5316         type = MEMFILE_TYPE(event);
5317         name = MEMFILE_ATTR(event);
5318 
5319         switch (name) {
5320         case RES_MAX_USAGE:
5321                 if (type == _MEM)
5322                         res_counter_reset_max(&memcg->res);
5323                 else if (type == _MEMSWAP)
5324                         res_counter_reset_max(&memcg->memsw);
5325                 else if (type == _KMEM)
5326                         res_counter_reset_max(&memcg->kmem);
5327                 else
5328                         return -EINVAL;
5329                 break;
5330         case RES_FAILCNT:
5331                 if (type == _MEM)
5332                         res_counter_reset_failcnt(&memcg->res);
5333                 else if (type == _MEMSWAP)
5334                         res_counter_reset_failcnt(&memcg->memsw);
5335                 else if (type == _KMEM)
5336                         res_counter_reset_failcnt(&memcg->kmem);
5337                 else
5338                         return -EINVAL;
5339                 break;
5340         }
5341 
5342         return 0;
5343 }
5344 
5345 static u64 mem_cgroup_move_charge_read(struct cgroup *cgrp,
5346                                         struct cftype *cft)
5347 {
5348         return mem_cgroup_from_cont(cgrp)->move_charge_at_immigrate;
5349 }
5350 
5351 #ifdef CONFIG_MMU
5352 static int mem_cgroup_move_charge_write(struct cgroup *cgrp,
5353                                         struct cftype *cft, u64 val)
5354 {
5355         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
5356 
5357         if (val >= (1 << NR_MOVE_TYPE))
5358                 return -EINVAL;
5359 
5360         /*
5361          * No kind of locking is needed in here, because ->can_attach() will
5362          * check this value once in the beginning of the process, and then carry
5363          * on with stale data. This means that changes to this value will only
5364          * affect task migrations starting after the change.
5365          */
5366         memcg->move_charge_at_immigrate = val;
5367         return 0;
5368 }
5369 #else
5370 static int mem_cgroup_move_charge_write(struct cgroup *cgrp,
5371                                         struct cftype *cft, u64 val)
5372 {
5373         return -ENOSYS;
5374 }
5375 #endif
5376 
5377 #ifdef CONFIG_NUMA
5378 static int memcg_numa_stat_show(struct cgroup *cont, struct cftype *cft,
5379                                       struct seq_file *m)
5380 {
5381         int nid;
5382         unsigned long total_nr, file_nr, anon_nr, unevictable_nr;
5383         unsigned long node_nr;
5384         struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
5385 
5386         total_nr = mem_cgroup_nr_lru_pages(memcg, LRU_ALL);
5387         seq_printf(m, "total=%lu", total_nr);
5388         for_each_node_state(nid, N_MEMORY) {
5389                 node_nr = mem_cgroup_node_nr_lru_pages(memcg, nid, LRU_ALL);
5390                 seq_printf(m, " N%d=%lu", nid, node_nr);
5391         }
5392         seq_putc(m, '\n');
5393 
5394         file_nr = mem_cgroup_nr_lru_pages(memcg, LRU_ALL_FILE);
5395         seq_printf(m, "file=%lu", file_nr);
5396         for_each_node_state(nid, N_MEMORY) {
5397                 node_nr = mem_cgroup_node_nr_lru_pages(memcg, nid,
5398                                 LRU_ALL_FILE);
5399                 seq_printf(m, " N%d=%lu", nid, node_nr);
5400         }
5401         seq_putc(m, '\n');
5402 
5403         anon_nr = mem_cgroup_nr_lru_pages(memcg, LRU_ALL_ANON);
5404         seq_printf(m, "anon=%lu", anon_nr);
5405         for_each_node_state(nid, N_MEMORY) {
5406                 node_nr = mem_cgroup_node_nr_lru_pages(memcg, nid,
5407                                 LRU_ALL_ANON);
5408                 seq_printf(m, " N%d=%lu", nid, node_nr);
5409         }
5410         seq_putc(m, '\n');
5411 
5412         unevictable_nr = mem_cgroup_nr_lru_pages(memcg, BIT(LRU_UNEVICTABLE));
5413         seq_printf(m, "unevictable=%lu", unevictable_nr);
5414         for_each_node_state(nid, N_MEMORY) {
5415                 node_nr = mem_cgroup_node_nr_lru_pages(memcg, nid,
5416                                 BIT(LRU_UNEVICTABLE));
5417                 seq_printf(m, " N%d=%lu", nid, node_nr);
5418         }
5419         seq_putc(m, '\n');
5420         return 0;
5421 }
5422 #endif /* CONFIG_NUMA */
5423 
5424 static inline void mem_cgroup_lru_names_not_uptodate(void)
5425 {
5426         BUILD_BUG_ON(ARRAY_SIZE(mem_cgroup_lru_names) != NR_LRU_LISTS);
5427 }
5428 
5429 static int memcg_stat_show(struct cgroup *cont, struct cftype *cft,
5430                                  struct seq_file *m)
5431 {
5432         struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
5433         struct mem_cgroup *mi;
5434         unsigned int i;
5435 
5436         for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) {
5437                 if (i == MEM_CGROUP_STAT_SWAP && !do_swap_account)
5438                         continue;
5439                 seq_printf(m, "%s %ld\n", mem_cgroup_stat_names[i],
5440                            mem_cgroup_read_stat(memcg, i) * PAGE_SIZE);
5441         }
5442 
5443         for (i = 0; i < MEM_CGROUP_EVENTS_NSTATS; i++)
5444                 seq_printf(m, "%s %lu\n", mem_cgroup_events_names[i],
5445                            mem_cgroup_read_events(memcg, i));
5446 
5447         for (i = 0; i < NR_LRU_LISTS; i++)
5448                 seq_printf(m, "%s %lu\n", mem_cgroup_lru_names[i],
5449                            mem_cgroup_nr_lru_pages(memcg, BIT(i)) * PAGE_SIZE);
5450 
5451         /* Hierarchical information */
5452         {
5453                 unsigned long long limit, memsw_limit;
5454                 memcg_get_hierarchical_limit(memcg, &limit, &memsw_limit);
5455                 seq_printf(m, "hierarchical_memory_limit %llu\n", limit);
5456                 if (do_swap_account)
5457                         seq_printf(m, "hierarchical_memsw_limit %llu\n",
5458                                    memsw_limit);
5459         }
5460 
5461         for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) {
5462                 long long val = 0;
5463 
5464                 if (i == MEM_CGROUP_STAT_SWAP && !do_swap_account)
5465                         continue;
5466                 for_each_mem_cgroup_tree(mi, memcg)
5467                         val += mem_cgroup_read_stat(mi, i) * PAGE_SIZE;
5468                 seq_printf(m, "total_%s %lld\n", mem_cgroup_stat_names[i], val);
5469         }
5470 
5471         for (i = 0; i < MEM_CGROUP_EVENTS_NSTATS; i++) {
5472                 unsigned long long val = 0;
5473 
5474                 for_each_mem_cgroup_tree(mi, memcg)
5475                         val += mem_cgroup_read_events(mi, i);
5476                 seq_printf(m, "total_%s %llu\n",
5477                            mem_cgroup_events_names[i], val);
5478         }
5479 
5480         for (i = 0; i < NR_LRU_LISTS; i++) {
5481                 unsigned long long val = 0;
5482 
5483                 for_each_mem_cgroup_tree(mi, memcg)
5484                         val += mem_cgroup_nr_lru_pages(mi, BIT(i)) * PAGE_SIZE;
5485                 seq_printf(m, "total_%s %llu\n", mem_cgroup_lru_names[i], val);
5486         }
5487 
5488 #ifdef CONFIG_DEBUG_VM
5489         {
5490                 int nid, zid;
5491                 struct mem_cgroup_per_zone *mz;
5492                 struct zone_reclaim_stat *rstat;
5493                 unsigned long recent_rotated[2] = {0, 0};
5494                 unsigned long recent_scanned[2] = {0, 0};
5495 
5496                 for_each_online_node(nid)
5497                         for (zid = 0; zid < MAX_NR_ZONES; zid++) {
5498                                 mz = mem_cgroup_zoneinfo(memcg, nid, zid);
5499                                 rstat = &mz->lruvec.reclaim_stat;
5500 
5501                                 recent_rotated[0] += rstat->recent_rotated[0];
5502                                 recent_rotated[1] += rstat->recent_rotated[1];
5503                                 recent_scanned[0] += rstat->recent_scanned[0];
5504                                 recent_scanned[1] += rstat->recent_scanned[1];
5505                         }
5506                 seq_printf(m, "recent_rotated_anon %lu\n", recent_rotated[0]);
5507                 seq_printf(m, "recent_rotated_file %lu\n", recent_rotated[1]);
5508                 seq_printf(m, "recent_scanned_anon %lu\n", recent_scanned[0]);
5509                 seq_printf(m, "recent_scanned_file %lu\n", recent_scanned[1]);
5510         }
5511 #endif
5512 
5513         return 0;
5514 }
5515 
5516 static u64 mem_cgroup_swappiness_read(struct cgroup *cgrp, struct cftype *cft)
5517 {
5518         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
5519 
5520         return mem_cgroup_swappiness(memcg);
5521 }
5522 
5523 static int mem_cgroup_swappiness_write(struct cgroup *cgrp, struct cftype *cft,
5524                                        u64 val)
5525 {
5526         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
5527         struct mem_cgroup *parent;
5528 
5529         if (val > 100)
5530                 return -EINVAL;
5531 
5532         if (cgrp->parent == NULL)
5533                 return -EINVAL;
5534 
5535         parent = mem_cgroup_from_cont(cgrp->parent);
5536 
5537         mutex_lock(&memcg_create_mutex);
5538 
5539         /* If under hierarchy, only empty-root can set this value */
5540         if ((parent->use_hierarchy) || memcg_has_children(memcg)) {
5541                 mutex_unlock(&memcg_create_mutex);
5542                 return -EINVAL;
5543         }
5544 
5545         memcg->swappiness = val;
5546 
5547         mutex_unlock(&memcg_create_mutex);
5548 
5549         return 0;
5550 }
5551 
5552 static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap)
5553 {
5554         struct mem_cgroup_threshold_ary *t;
5555         u64 usage;
5556         int i;
5557 
5558         rcu_read_lock();
5559         if (!swap)
5560                 t = rcu_dereference(memcg->thresholds.primary);
5561         else
5562                 t = rcu_dereference(memcg->memsw_thresholds.primary);
5563 
5564         if (!t)
5565                 goto unlock;
5566 
5567         usage = mem_cgroup_usage(memcg, swap);
5568 
5569         /*
5570          * current_threshold points to threshold just below or equal to usage.
5571          * If it's not true, a threshold was crossed after last
5572          * call of __mem_cgroup_threshold().
5573          */
5574         i = t->current_threshold;
5575 
5576         /*
5577          * Iterate backward over array of thresholds starting from
5578          * current_threshold and check if a threshold is crossed.
5579          * If none of thresholds below usage is crossed, we read
5580          * only one element of the array here.
5581          */
5582         for (; i >= 0 && unlikely(t->entries[i].threshold > usage); i--)
5583                 eventfd_signal(t->entries[i].eventfd, 1);
5584 
5585         /* i = current_threshold + 1 */
5586         i++;
5587 
5588         /*
5589          * Iterate forward over array of thresholds starting from
5590          * current_threshold+1 and check if a threshold is crossed.
5591          * If none of thresholds above usage is crossed, we read
5592          * only one element of the array here.
5593          */
5594         for (; i < t->size && unlikely(t->entries[i].threshold <= usage); i++)
5595                 eventfd_signal(t->entries[i].eventfd, 1);
5596 
5597         /* Update current_threshold */
5598         t->current_threshold = i - 1;
5599 unlock:
5600         rcu_read_unlock();
5601 }
5602 
5603 static void mem_cgroup_threshold(struct mem_cgroup *memcg)
5604 {
5605         while (memcg) {
5606                 __mem_cgroup_threshold(memcg, false);
5607                 if (do_swap_account)
5608                         __mem_cgroup_threshold(memcg, true);
5609 
5610                 memcg = parent_mem_cgroup(memcg);
5611         }
5612 }
5613 
5614 static int compare_thresholds(const void *a, const void *b)
5615 {
5616         const struct mem_cgroup_threshold *_a = a;
5617         const struct mem_cgroup_threshold *_b = b;
5618 
5619         if (_a->threshold > _b->threshold)
5620                 return 1;
5621 
5622         if (_a->threshold < _b->threshold)
5623                 return -1;
5624 
5625         return 0;
5626 }
5627 
5628 static int mem_cgroup_oom_notify_cb(struct mem_cgroup *memcg)
5629 {
5630         struct mem_cgroup_eventfd_list *ev;
5631 
5632         list_for_each_entry(ev, &memcg->oom_notify, list)
5633                 eventfd_signal(ev->eventfd, 1);
5634         return 0;
5635 }
5636 
5637 static void mem_cgroup_oom_notify(struct mem_cgroup *memcg)
5638 {
5639         struct mem_cgroup *iter;
5640 
5641         for_each_mem_cgroup_tree(iter, memcg)
5642                 mem_cgroup_oom_notify_cb(iter);
5643 }
5644 
5645 static int mem_cgroup_usage_register_event(struct cgroup *cgrp,
5646         struct cftype *cft, struct eventfd_ctx *eventfd, const char *args)
5647 {
5648         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
5649         struct mem_cgroup_thresholds *thresholds;
5650         struct mem_cgroup_threshold_ary *new;
5651         enum res_type type = MEMFILE_TYPE(cft->private);
5652         u64 threshold, usage;
5653         int i, size, ret;
5654 
5655         ret = res_counter_memparse_write_strategy(args, &threshold);
5656         if (ret)
5657                 return ret;
5658 
5659         mutex_lock(&memcg->thresholds_lock);
5660 
5661         if (type == _MEM)
5662                 thresholds = &memcg->thresholds;
5663         else if (type == _MEMSWAP)
5664                 thresholds = &memcg->memsw_thresholds;
5665         else
5666                 BUG();
5667 
5668         usage = mem_cgroup_usage(memcg, type == _MEMSWAP);
5669 
5670         /* Check if a threshold crossed before adding a new one */
5671         if (thresholds->primary)
5672                 __mem_cgroup_threshold(memcg, type == _MEMSWAP);
5673 
5674         size = thresholds->primary ? thresholds->primary->size + 1 : 1;
5675 
5676         /* Allocate memory for new array of thresholds */
5677         new = kmalloc(sizeof(*new) + size * sizeof(struct mem_cgroup_threshold),
5678                         GFP_KERNEL);
5679         if (!new) {
5680                 ret = -ENOMEM;
5681                 goto unlock;
5682         }
5683         new->size = size;
5684 
5685         /* Copy thresholds (if any) to new array */
5686         if (thresholds->primary) {
5687                 memcpy(new->entries, thresholds->primary->entries, (size - 1) *
5688                                 sizeof(struct mem_cgroup_threshold));
5689         }
5690 
5691         /* Add new threshold */
5692         new->entries[size - 1].eventfd = eventfd;
5693         new->entries[size - 1].threshold = threshold;
5694 
5695         /* Sort thresholds. Registering of new threshold isn't time-critical */
5696         sort(new->entries, size, sizeof(struct mem_cgroup_threshold),
5697                         compare_thresholds, NULL);
5698 
5699         /* Find current threshold */
5700         new->current_threshold = -1;
5701         for (i = 0; i < size; i++) {
5702                 if (new->entries[i].threshold <= usage) {
5703                         /*
5704                          * new->current_threshold will not be used until
5705                          * rcu_assign_pointer(), so it's safe to increment
5706                          * it here.
5707                          */
5708                         ++new->current_threshold;
5709                 } else
5710                         break;
5711         }
5712 
5713         /* Free old spare buffer and save old primary buffer as spare */
5714         kfree(thresholds->spare);
5715         thresholds->spare = thresholds->primary;
5716 
5717         rcu_assign_pointer(thresholds->primary, new);
5718 
5719         /* To be sure that nobody uses thresholds */
5720         synchronize_rcu();
5721 
5722 unlock:
5723         mutex_unlock(&memcg->thresholds_lock);
5724 
5725         return ret;
5726 }
5727 
5728 static void mem_cgroup_usage_unregister_event(struct cgroup *cgrp,
5729         struct cftype *cft, struct eventfd_ctx *eventfd)
5730 {
5731         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
5732         struct mem_cgroup_thresholds *thresholds;
5733         struct mem_cgroup_threshold_ary *new;
5734         enum res_type type = MEMFILE_TYPE(cft->private);
5735         u64 usage;
5736         int i, j, size;
5737 
5738         mutex_lock(&memcg->thresholds_lock);
5739         if (type == _MEM)
5740                 thresholds = &memcg->thresholds;
5741         else if (type == _MEMSWAP)
5742                 thresholds = &memcg->memsw_thresholds;
5743         else
5744                 BUG();
5745 
5746         if (!thresholds->primary)
5747                 goto unlock;
5748 
5749         usage = mem_cgroup_usage(memcg, type == _MEMSWAP);
5750 
5751         /* Check if a threshold crossed before removing */
5752         __mem_cgroup_threshold(memcg, type == _MEMSWAP);
5753 
5754         /* Calculate new number of threshold */
5755         size = 0;
5756         for (i = 0; i < thresholds->primary->size; i++) {
5757                 if (thresholds->primary->entries[i].eventfd != eventfd)
5758                         size++;
5759         }
5760 
5761         new = thresholds->spare;
5762 
5763         /* Set thresholds array to NULL if we don't have thresholds */
5764         if (!size) {
5765                 kfree(new);
5766                 new = NULL;
5767                 goto swap_buffers;
5768         }
5769 
5770         new->size = size;
5771 
5772         /* Copy thresholds and find current threshold */
5773         new->current_threshold = -1;
5774         for (i = 0, j = 0; i < thresholds->primary->size; i++) {
5775                 if (thresholds->primary->entries[i].eventfd == eventfd)
5776                         continue;
5777 
5778                 new->entries[j] = thresholds->primary->entries[i];
5779                 if (new->entries[j].threshold <= usage) {
5780                         /*
5781                          * new->current_threshold will not be used
5782                          * until rcu_assign_pointer(), so it's safe to increment
5783                          * it here.
5784                          */
5785                         ++new->current_threshold;
5786                 }
5787                 j++;
5788         }
5789 
5790 swap_buffers:
5791         /* Swap primary and spare array */
5792         thresholds->spare = thresholds->primary;
5793         /* If all events are unregistered, free the spare array */
5794         if (!new) {
5795                 kfree(thresholds->spare);
5796                 thresholds->spare = NULL;
5797         }
5798 
5799         rcu_assign_pointer(thresholds->primary, new);
5800 
5801         /* To be sure that nobody uses thresholds */
5802         synchronize_rcu();
5803 unlock:
5804         mutex_unlock(&memcg->thresholds_lock);
5805 }
5806 
5807 static int mem_cgroup_oom_register_event(struct cgroup *cgrp,
5808         struct cftype *cft, struct eventfd_ctx *eventfd, const char *args)
5809 {
5810         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
5811         struct mem_cgroup_eventfd_list *event;
5812         enum res_type type = MEMFILE_TYPE(cft->private);
5813 
5814         BUG_ON(type != _OOM_TYPE);
5815         event = kmalloc(sizeof(*event), GFP_KERNEL);
5816         if (!event)
5817                 return -ENOMEM;
5818 
5819         spin_lock(&memcg_oom_lock);
5820 
5821         event->eventfd = eventfd;
5822         list_add(&event->list, &memcg->oom_notify);
5823 
5824         /* already in OOM ? */
5825         if (atomic_read(&memcg->under_oom))
5826                 eventfd_signal(eventfd, 1);
5827         spin_unlock(&memcg_oom_lock);
5828 
5829         return 0;
5830 }
5831 
5832 static void mem_cgroup_oom_unregister_event(struct cgroup *cgrp,
5833         struct cftype *cft, struct eventfd_ctx *eventfd)
5834 {
5835         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
5836         struct mem_cgroup_eventfd_list *ev, *tmp;
5837         enum res_type type = MEMFILE_TYPE(cft->private);
5838 
5839         BUG_ON(type != _OOM_TYPE);
5840 
5841         spin_lock(&memcg_oom_lock);
5842 
5843         list_for_each_entry_safe(ev, tmp, &memcg->oom_notify, list) {
5844                 if (ev->eventfd == eventfd) {
5845                         list_del(&ev->list);
5846                         kfree(ev);
5847                 }
5848         }
5849 
5850         spin_unlock(&memcg_oom_lock);
5851 }
5852 
5853 static int mem_cgroup_oom_control_read(struct cgroup *cgrp,
5854         struct cftype *cft,  struct cgroup_map_cb *cb)
5855 {
5856         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
5857 
5858         cb->fill(cb, "oom_kill_disable", memcg->oom_kill_disable);
5859 
5860         if (atomic_read(&memcg->under_oom))
5861                 cb->fill(cb, "under_oom", 1);
5862         else
5863                 cb->fill(cb, "under_oom", 0);
5864         return 0;
5865 }
5866 
5867 static int mem_cgroup_oom_control_write(struct cgroup *cgrp,
5868         struct cftype *cft, u64 val)
5869 {
5870         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
5871         struct mem_cgroup *parent;
5872 
5873         /* cannot set to root cgroup and only 0 and 1 are allowed */
5874         if (!cgrp->parent || !((val == 0) || (val == 1)))
5875                 return -EINVAL;
5876 
5877         parent = mem_cgroup_from_cont(cgrp->parent);
5878 
5879         mutex_lock(&memcg_create_mutex);
5880         /* oom-kill-disable is a flag for subhierarchy. */
5881         if ((parent->use_hierarchy) || memcg_has_children(memcg)) {
5882                 mutex_unlock(&memcg_create_mutex);
5883                 return -EINVAL;
5884         }
5885         memcg->oom_kill_disable = val;
5886         if (!val)
5887                 memcg_oom_recover(memcg);
5888         mutex_unlock(&memcg_create_mutex);
5889         return 0;
5890 }
5891 
5892 #ifdef CONFIG_MEMCG_KMEM
5893 static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
5894 {
5895         int ret;
5896 
5897         memcg->kmemcg_id = -1;
5898         ret = memcg_propagate_kmem(memcg);
5899         if (ret)
5900                 return ret;
5901 
5902         return mem_cgroup_sockets_init(memcg, ss);
5903 }
5904 
5905 static void memcg_destroy_kmem(struct mem_cgroup *memcg)
5906 {
5907         mem_cgroup_sockets_destroy(memcg);
5908 }
5909 
5910 static void kmem_cgroup_css_offline(struct mem_cgroup *memcg)
5911 {
5912         if (!memcg_kmem_is_active(memcg))
5913                 return;
5914 
5915         /*
5916          * kmem charges can outlive the cgroup. In the case of slab
5917          * pages, for instance, a page contain objects from various
5918          * processes. As we prevent from taking a reference for every
5919          * such allocation we have to be careful when doing uncharge
5920          * (see memcg_uncharge_kmem) and here during offlining.
5921          *
5922          * The idea is that that only the _last_ uncharge which sees
5923          * the dead memcg will drop the last reference. An additional
5924          * reference is taken here before the group is marked dead
5925          * which is then paired with css_put during uncharge resp. here.
5926          *
5927          * Although this might sound strange as this path is called from
5928          * css_offline() when the referencemight have dropped down to 0
5929          * and shouldn't be incremented anymore (css_tryget would fail)
5930          * we do not have other options because of the kmem allocations
5931          * lifetime.
5932          */
5933         css_get(&memcg->css);
5934 
5935         memcg_kmem_mark_dead(memcg);
5936 
5937         if (res_counter_read_u64(&memcg->kmem, RES_USAGE) != 0)
5938                 return;
5939 
5940         if (memcg_kmem_test_and_clear_dead(memcg))
5941                 css_put(&memcg->css);
5942 }
5943 #else
5944 static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
5945 {
5946         return 0;
5947 }
5948 
5949 static void memcg_destroy_kmem(struct mem_cgroup *memcg)
5950 {
5951 }
5952 
5953 static void kmem_cgroup_css_offline(struct mem_cgroup *memcg)
5954 {
5955 }
5956 #endif
5957 
5958 static struct cftype mem_cgroup_files[] = {
5959         {
5960                 .name = "usage_in_bytes",
5961                 .private = MEMFILE_PRIVATE(_MEM, RES_USAGE),
5962                 .read = mem_cgroup_read,
5963                 .register_event = mem_cgroup_usage_register_event,
5964                 .unregister_event = mem_cgroup_usage_unregister_event,
5965         },
5966         {
5967                 .name = "max_usage_in_bytes",
5968                 .private = MEMFILE_PRIVATE(_MEM, RES_MAX_USAGE),
5969                 .trigger = mem_cgroup_reset,
5970                 .read = mem_cgroup_read,
5971         },
5972         {
5973                 .name = "limit_in_bytes",
5974                 .private = MEMFILE_PRIVATE(_MEM, RES_LIMIT),
5975                 .write_string = mem_cgroup_write,
5976                 .read = mem_cgroup_read,
5977         },
5978         {
5979                 .name = "soft_limit_in_bytes",
5980                 .private = MEMFILE_PRIVATE(_MEM, RES_SOFT_LIMIT),
5981                 .write_string = mem_cgroup_write,
5982                 .read = mem_cgroup_read,
5983         },
5984         {
5985                 .name = "failcnt",
5986                 .private = MEMFILE_PRIVATE(_MEM, RES_FAILCNT),
5987                 .trigger = mem_cgroup_reset,
5988                 .read = mem_cgroup_read,
5989         },
5990         {
5991                 .name = "stat",
5992                 .read_seq_string = memcg_stat_show,
5993         },
5994         {
5995                 .name = "force_empty",
5996                 .trigger = mem_cgroup_force_empty_write,
5997         },
5998         {
5999                 .name = "use_hierarchy",
6000                 .flags = CFTYPE_INSANE,
6001                 .write_u64 = mem_cgroup_hierarchy_write,
6002                 .read_u64 = mem_cgroup_hierarchy_read,
6003         },
6004         {
6005                 .name = "swappiness",
6006                 .read_u64 = mem_cgroup_swappiness_read,
6007                 .write_u64 = mem_cgroup_swappiness_write,
6008         },
6009         {
6010                 .name = "move_charge_at_immigrate",
6011                 .read_u64 = mem_cgroup_move_charge_read,
6012                 .write_u64 = mem_cgroup_move_charge_write,
6013         },
6014         {
6015                 .name = "oom_control",
6016                 .read_map = mem_cgroup_oom_control_read,
6017                 .write_u64 = mem_cgroup_oom_control_write,
6018                 .register_event = mem_cgroup_oom_register_event,
6019                 .unregister_event = mem_cgroup_oom_unregister_event,
6020                 .private = MEMFILE_PRIVATE(_OOM_TYPE, OOM_CONTROL),
6021         },
6022         {
6023                 .name = "pressure_level",
6024                 .register_event = vmpressure_register_event,
6025                 .unregister_event = vmpressure_unregister_event,
6026         },
6027 #ifdef CONFIG_NUMA
6028         {
6029                 .name = "numa_stat",
6030                 .read_seq_string = memcg_numa_stat_show,
6031         },
6032 #endif
6033 #ifdef CONFIG_MEMCG_KMEM
6034         {
6035                 .name = "kmem.limit_in_bytes",
6036                 .private = MEMFILE_PRIVATE(_KMEM, RES_LIMIT),
6037                 .write_string = mem_cgroup_write,
6038                 .read = mem_cgroup_read,
6039         },
6040         {
6041                 .name = "kmem.usage_in_bytes",
6042                 .private = MEMFILE_PRIVATE(_KMEM, RES_USAGE),
6043                 .read = mem_cgroup_read,
6044         },
6045         {
6046                 .name = "kmem.failcnt",
6047                 .private = MEMFILE_PRIVATE(_KMEM, RES_FAILCNT),
6048                 .trigger = mem_cgroup_reset,
6049                 .read = mem_cgroup_read,
6050         },
6051         {
6052                 .name = "kmem.max_usage_in_bytes",
6053                 .private = MEMFILE_PRIVATE(_KMEM, RES_MAX_USAGE),
6054                 .trigger = mem_cgroup_reset,
6055                 .read = mem_cgroup_read,
6056         },
6057 #ifdef CONFIG_SLABINFO
6058         {
6059                 .name = "kmem.slabinfo",
6060                 .read_seq_string = mem_cgroup_slabinfo_read,
6061         },
6062 #endif
6063 #endif
6064         { },    /* terminate */
6065 };
6066 
6067 #ifdef CONFIG_MEMCG_SWAP
6068 static struct cftype memsw_cgroup_files[] = {
6069         {
6070                 .name = "memsw.usage_in_bytes",
6071                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_USAGE),
6072                 .read = mem_cgroup_read,
6073                 .register_event = mem_cgroup_usage_register_event,
6074                 .unregister_event = mem_cgroup_usage_unregister_event,
6075         },
6076         {
6077                 .name = "memsw.max_usage_in_bytes",
6078                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_MAX_USAGE),
6079                 .trigger = mem_cgroup_reset,
6080                 .read = mem_cgroup_read,
6081         },
6082         {
6083                 .name = "memsw.limit_in_bytes",
6084                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_LIMIT),
6085                 .write_string = mem_cgroup_write,
6086                 .read = mem_cgroup_read,
6087         },
6088         {
6089                 .name = "memsw.failcnt",
6090                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_FAILCNT),
6091                 .trigger = mem_cgroup_reset,
6092                 .read = mem_cgroup_read,
6093         },
6094         { },    /* terminate */
6095 };
6096 #endif
6097 static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *memcg, int node)
6098 {
6099         struct mem_cgroup_per_node *pn;
6100         struct mem_cgroup_per_zone *mz;
6101         int zone, tmp = node;
6102         /*
6103          * This routine is called against possible nodes.
6104          * But it's BUG to call kmalloc() against offline node.
6105          *
6106          * TODO: this routine can waste much memory for nodes which will
6107          *       never be onlined. It's better to use memory hotplug callback
6108          *       function.
6109          */
6110         if (!node_state(node, N_NORMAL_MEMORY))
6111                 tmp = -1;
6112         pn = kzalloc_node(sizeof(*pn), GFP_KERNEL, tmp);
6113         if (!pn)
6114                 return 1;
6115 
6116         for (zone = 0; zone < MAX_NR_ZONES; zone++) {
6117                 mz = &pn->zoneinfo[zone];
6118                 lruvec_init(&mz->lruvec);
6119                 mz->usage_in_excess = 0;
6120                 mz->on_tree = false;
6121                 mz->memcg = memcg;
6122         }
6123         memcg->nodeinfo[node] = pn;
6124         return 0;
6125 }
6126 
6127 static void free_mem_cgroup_per_zone_info(struct mem_cgroup *memcg, int node)
6128 {
6129         kfree(memcg->nodeinfo[node]);
6130 }
6131 
6132 static struct mem_cgroup *mem_cgroup_alloc(void)
6133 {
6134         struct mem_cgroup *memcg;
6135         size_t size = memcg_size();
6136 
6137         /* Can be very big if nr_node_ids is very big */
6138         if (size < PAGE_SIZE)
6139                 memcg = kzalloc(size, GFP_KERNEL);
6140         else
6141                 memcg = vzalloc(size);
6142 
6143         if (!memcg)
6144                 return NULL;
6145 
6146         memcg->stat = alloc_percpu(struct mem_cgroup_stat_cpu);
6147         if (!memcg->stat)
6148                 goto out_free;
6149         spin_lock_init(&memcg->pcp_counter_lock);
6150         return memcg;
6151 
6152 out_free:
6153         if (size < PAGE_SIZE)
6154                 kfree(memcg);
6155         else
6156                 vfree(memcg);
6157         return NULL;
6158 }
6159 
6160 /*
6161  * At destroying mem_cgroup, references from swap_cgroup can remain.
6162  * (scanning all at force_empty is too costly...)
6163  *
6164  * Instead of clearing all references at force_empty, we remember
6165  * the number of reference from swap_cgroup and free mem_cgroup when
6166  * it goes down to 0.
6167  *
6168  * Removal of cgroup itself succeeds regardless of refs from swap.
6169  */
6170 
6171 static void __mem_cgroup_free(struct mem_cgroup *memcg)
6172 {
6173         int node;
6174         size_t size = memcg_size();
6175 
6176         mem_cgroup_remove_from_trees(memcg);
6177         free_css_id(&mem_cgroup_subsys, &memcg->css);
6178 
6179         for_each_node(node)
6180                 free_mem_cgroup_per_zone_info(memcg, node);
6181 
6182         free_percpu(memcg->stat);
6183 
6184         /*
6185          * We need to make sure that (at least for now), the jump label
6186          * destruction code runs outside of the cgroup lock. This is because
6187          * get_online_cpus(), which is called from the static_branch update,
6188          * can't be called inside the cgroup_lock. cpusets are the ones
6189          * enforcing this dependency, so if they ever change, we might as well.
6190          *
6191          * schedule_work() will guarantee this happens. Be careful if you need
6192          * to move this code around, and make sure it is outside
6193          * the cgroup_lock.
6194          */
6195         disarm_static_keys(memcg);
6196         if (size < PAGE_SIZE)
6197                 kfree(memcg);
6198         else
6199                 vfree(memcg);
6200 }
6201 
6202 /*
6203  * Returns the parent mem_cgroup in memcgroup hierarchy with hierarchy enabled.
6204  */
6205 struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg)
6206 {
6207         if (!memcg->res.parent)
6208                 return NULL;
6209         return mem_cgroup_from_res_counter(memcg->res.parent, res);
6210 }
6211 EXPORT_SYMBOL(parent_mem_cgroup);
6212 
6213 static void __init mem_cgroup_soft_limit_tree_init(void)
6214 {
6215         struct mem_cgroup_tree_per_node *rtpn;
6216         struct mem_cgroup_tree_per_zone *rtpz;
6217         int tmp, node, zone;
6218 
6219         for_each_node(node) {
6220                 tmp = node;
6221                 if (!node_state(node, N_NORMAL_MEMORY))
6222                         tmp = -1;
6223                 rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, tmp);
6224                 BUG_ON(!rtpn);
6225 
6226                 soft_limit_tree.rb_tree_per_node[node] = rtpn;
6227 
6228                 for (zone = 0; zone < MAX_NR_ZONES; zone++) {
6229                         rtpz = &rtpn->rb_tree_per_zone[zone];
6230                         rtpz->rb_root = RB_ROOT;
6231                         spin_lock_init(&rtpz->lock);
6232                 }
6233         }
6234 }
6235 
6236 static struct cgroup_subsys_state * __ref
6237 mem_cgroup_css_alloc(struct cgroup *cont)
6238 {
6239         struct mem_cgroup *memcg;
6240         long error = -ENOMEM;
6241         int node;
6242 
6243         memcg = mem_cgroup_alloc();
6244         if (!memcg)
6245                 return ERR_PTR(error);
6246 
6247         for_each_node(node)
6248                 if (alloc_mem_cgroup_per_zone_info(memcg, node))
6249                         goto free_out;
6250 
6251         /* root ? */
6252         if (cont->parent == NULL) {
6253                 root_mem_cgroup = memcg;
6254                 res_counter_init(&memcg->res, NULL);
6255                 res_counter_init(&memcg->memsw, NULL);
6256                 res_counter_init(&memcg->kmem, NULL);
6257         }
6258 
6259         memcg->last_scanned_node = MAX_NUMNODES;
6260         INIT_LIST_HEAD(&memcg->oom_notify);
6261         memcg->move_charge_at_immigrate = 0;
6262         mutex_init(&memcg->thresholds_lock);
6263         spin_lock_init(&memcg->move_lock);
6264         vmpressure_init(&memcg->vmpressure);
6265 
6266         return &memcg->css;
6267 
6268 free_out:
6269         __mem_cgroup_free(memcg);
6270         return ERR_PTR(error);
6271 }
6272 
6273 static int
6274 mem_cgroup_css_online(struct cgroup *cont)
6275 {
6276         struct mem_cgroup *memcg, *parent;
6277         int error = 0;
6278 
6279         if (!cont->parent)
6280                 return 0;
6281 
6282         mutex_lock(&memcg_create_mutex);
6283         memcg = mem_cgroup_from_cont(cont);
6284         parent = mem_cgroup_from_cont(cont->parent);
6285 
6286         memcg->use_hierarchy = parent->use_hierarchy;
6287         memcg->oom_kill_disable = parent->oom_kill_disable;
6288         memcg->swappiness = mem_cgroup_swappiness(parent);
6289 
6290         if (parent->use_hierarchy) {
6291                 res_counter_init(&memcg->res, &parent->res);
6292                 res_counter_init(&memcg->memsw, &parent->memsw);
6293                 res_counter_init(&memcg->kmem, &parent->kmem);
6294 
6295                 /*
6296                  * No need to take a reference to the parent because cgroup
6297                  * core guarantees its existence.
6298                  */
6299         } else {
6300                 res_counter_init(&memcg->res, NULL);
6301                 res_counter_init(&memcg->memsw, NULL);
6302                 res_counter_init(&memcg->kmem, NULL);
6303                 /*
6304                  * Deeper hierachy with use_hierarchy == false doesn't make
6305                  * much sense so let cgroup subsystem know about this
6306                  * unfortunate state in our controller.
6307                  */
6308                 if (parent != root_mem_cgroup)
6309                         mem_cgroup_subsys.broken_hierarchy = true;
6310         }
6311 
6312         error = memcg_init_kmem(memcg, &mem_cgroup_subsys);
6313         mutex_unlock(&memcg_create_mutex);
6314         return error;
6315 }
6316 
6317 /*
6318  * Announce all parents that a group from their hierarchy is gone.
6319  */
6320 static void mem_cgroup_invalidate_reclaim_iterators(struct mem_cgroup *memcg)
6321 {
6322         struct mem_cgroup *parent = memcg;
6323 
6324         while ((parent = parent_mem_cgroup(parent)))
6325                 mem_cgroup_iter_invalidate(parent);
6326 
6327         /*
6328          * if the root memcg is not hierarchical we have to check it
6329          * explicitely.
6330          */
6331         if (!root_mem_cgroup->use_hierarchy)
6332                 mem_cgroup_iter_invalidate(root_mem_cgroup);
6333 }
6334 
6335 static void mem_cgroup_css_offline(struct cgroup *cont)
6336 {
6337         struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
6338 
6339         kmem_cgroup_css_offline(memcg);
6340 
6341         mem_cgroup_invalidate_reclaim_iterators(memcg);
6342         mem_cgroup_reparent_charges(memcg);
6343         mem_cgroup_destroy_all_caches(memcg);
6344         vmpressure_cleanup(&memcg->vmpressure);
6345 }
6346 
6347 static void mem_cgroup_css_free(struct cgroup *cont)
6348 {
6349         struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
6350 
6351         memcg_destroy_kmem(memcg);
6352         __mem_cgroup_free(memcg);
6353 }
6354 
6355 #ifdef CONFIG_MMU
6356 /* Handlers for move charge at task migration. */
6357 #define PRECHARGE_COUNT_AT_ONCE 256
6358 static int mem_cgroup_do_precharge(unsigned long count)
6359 {
6360         int ret = 0;
6361         int batch_count = PRECHARGE_COUNT_AT_ONCE;
6362         struct mem_cgroup *memcg = mc.to;
6363 
6364         if (mem_cgroup_is_root(memcg)) {
6365                 mc.precharge += count;
6366                 /* we don't need css_get for root */
6367                 return ret;
6368         }
6369         /* try to charge at once */
6370         if (count > 1) {
6371                 struct res_counter *dummy;
6372                 /*
6373                  * "memcg" cannot be under rmdir() because we've already checked
6374                  * by cgroup_lock_live_cgroup() that it is not removed and we
6375                  * are still under the same cgroup_mutex. So we can postpone
6376                  * css_get().
6377                  */
6378                 if (res_counter_charge(&memcg->res, PAGE_SIZE * count, &dummy))
6379                         goto one_by_one;
6380                 if (do_swap_account && res_counter_charge(&memcg->memsw,
6381                                                 PAGE_SIZE * count, &dummy)) {
6382                         res_counter_uncharge(&memcg->res, PAGE_SIZE * count);
6383                         goto one_by_one;
6384                 }
6385                 mc.precharge += count;
6386                 return ret;
6387         }
6388 one_by_one:
6389         /* fall back to one by one charge */
6390         while (count--) {
6391                 if (signal_pending(current)) {
6392                         ret = -EINTR;
6393                         break;
6394                 }
6395                 if (!batch_count--) {
6396                         batch_count = PRECHARGE_COUNT_AT_ONCE;
6397                         cond_resched();
6398                 }
6399                 ret = __mem_cgroup_try_charge(NULL,
6400                                         GFP_KERNEL, 1, &memcg, false);
6401                 if (ret)
6402                         /* mem_cgroup_clear_mc() will do uncharge later */
6403                         return ret;
6404                 mc.precharge++;
6405         }
6406         return ret;
6407 }
6408 
6409 /**
6410  * get_mctgt_type - get target type of moving charge
6411  * @vma: the vma the pte to be checked belongs
6412  * @addr: the address corresponding to the pte to be checked
6413  * @ptent: the pte to be checked
6414  * @target: the pointer the target page or swap ent will be stored(can be NULL)
6415  *
6416  * Returns
6417  *   0(MC_TARGET_NONE): if the pte is not a target for move charge.
6418  *   1(MC_TARGET_PAGE): if the page corresponding to this pte is a target for
6419  *     move charge. if @target is not NULL, the page is stored in target->page
6420  *     with extra refcnt got(Callers should handle it).
6421  *   2(MC_TARGET_SWAP): if the swap entry corresponding to this pte is a
6422  *     target for charge migration. if @target is not NULL, the entry is stored
6423  *     in target->ent.
6424  *
6425  * Called with pte lock held.
6426  */
6427 union mc_target {
6428         struct page     *page;
6429         swp_entry_t     ent;
6430 };
6431 
6432 enum mc_target_type {
6433         MC_TARGET_NONE = 0,
6434         MC_TARGET_PAGE,
6435         MC_TARGET_SWAP,
6436 };
6437 
6438 static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
6439                                                 unsigned long addr, pte_t ptent)
6440 {
6441         struct page *page = vm_normal_page(vma, addr, ptent);
6442 
6443         if (!page || !page_mapped(page))
6444                 return NULL;
6445         if (PageAnon(page)) {
6446                 /* we don't move shared anon */
6447                 if (!move_anon())
6448                         return NULL;
6449         } else if (!move_file())
6450                 /* we ignore mapcount for file pages */
6451                 return NULL;
6452         if (!get_page_unless_zero(page))
6453                 return NULL;
6454 
6455         return page;
6456 }
6457 
6458 #ifdef CONFIG_SWAP
6459 static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
6460                         unsigned long addr, pte_t ptent, swp_entry_t *entry)
6461 {
6462         struct page *page = NULL;
6463         swp_entry_t ent = pte_to_swp_entry(ptent);
6464 
6465         if (!move_anon() || non_swap_entry(ent))
6466                 return NULL;
6467         /*
6468          * Because lookup_swap_cache() updates some statistics counter,
6469          * we call find_get_page() with swapper_space directly.
6470          */
6471         page = find_get_page(swap_address_space(ent), ent.val);
6472         if (do_swap_account)
6473                 entry->val = ent.val;
6474 
6475         return page;
6476 }
6477 #else
6478 static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
6479                         unsigned long addr, pte_t ptent, swp_entry_t *entry)
6480 {
6481         return NULL;
6482 }
6483 #endif
6484 
6485 static struct page *mc_handle_file_pte(struct vm_area_struct *vma,
6486                         unsigned long addr, pte_t ptent, swp_entry_t *entry)
6487 {
6488         struct page *page = NULL;
6489         struct address_space *mapping;
6490         pgoff_t pgoff;
6491 
6492         if (!vma->vm_file) /* anonymous vma */
6493                 return NULL;
6494         if (!move_file())
6495                 return NULL;
6496 
6497         mapping = vma->vm_file->f_mapping;
6498         if (pte_none(ptent))
6499                 pgoff = linear_page_index(vma, addr);
6500         else /* pte_file(ptent) is true */
6501                 pgoff = pte_to_pgoff(ptent);
6502 
6503         /* page is moved even if it's not RSS of this task(page-faulted). */
6504         page = find_get_page(mapping, pgoff);
6505 
6506 #ifdef CONFIG_SWAP
6507         /* shmem/tmpfs may report page out on swap: account for that too. */
6508         if (radix_tree_exceptional_entry(page)) {
6509                 swp_entry_t swap = radix_to_swp_entry(page);
6510                 if (do_swap_account)
6511                         *entry = swap;
6512                 page = find_get_page(swap_address_space(swap), swap.val);
6513         }
6514 #endif
6515         return page;
6516 }
6517 
6518 static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
6519                 unsigned long addr, pte_t ptent, union mc_target *target)
6520 {
6521         struct page *page = NULL;
6522         struct page_cgroup *pc;
6523         enum mc_target_type ret = MC_TARGET_NONE;
6524         swp_entry_t ent = { .val = 0 };
6525 
6526         if (pte_present(ptent))
6527                 page = mc_handle_present_pte(vma, addr, ptent);
6528         else if (is_swap_pte(ptent))
6529                 page = mc_handle_swap_pte(vma, addr, ptent, &ent);
6530         else if (pte_none(ptent) || pte_file(ptent))
6531                 page = mc_handle_file_pte(vma, addr, ptent, &ent);
6532 
6533         if (!page && !ent.val)
6534                 return ret;
6535         if (page) {
6536                 pc = lookup_page_cgroup(page);
6537                 /*
6538                  * Do only loose check w/o page_cgroup lock.
6539                  * mem_cgroup_move_account() checks the pc is valid or not under
6540                  * the lock.
6541                  */
6542                 if (PageCgroupUsed(pc) && pc->mem_cgroup == mc.from) {
6543                         ret = MC_TARGET_PAGE;
6544                         if (target)
6545                                 target->page = page;
6546                 }
6547                 if (!ret || !target)
6548                         put_page(page);
6549         }
6550         /* There is a swap entry and a page doesn't exist or isn't charged */
6551         if (ent.val && !ret &&
6552