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TOMOYO Linux Cross Reference
Linux/kernel/cgroup/cpuset.c

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  1 /*
  2  *  kernel/cpuset.c
  3  *
  4  *  Processor and Memory placement constraints for sets of tasks.
  5  *
  6  *  Copyright (C) 2003 BULL SA.
  7  *  Copyright (C) 2004-2007 Silicon Graphics, Inc.
  8  *  Copyright (C) 2006 Google, Inc
  9  *
 10  *  Portions derived from Patrick Mochel's sysfs code.
 11  *  sysfs is Copyright (c) 2001-3 Patrick Mochel
 12  *
 13  *  2003-10-10 Written by Simon Derr.
 14  *  2003-10-22 Updates by Stephen Hemminger.
 15  *  2004 May-July Rework by Paul Jackson.
 16  *  2006 Rework by Paul Menage to use generic cgroups
 17  *  2008 Rework of the scheduler domains and CPU hotplug handling
 18  *       by Max Krasnyansky
 19  *
 20  *  This file is subject to the terms and conditions of the GNU General Public
 21  *  License.  See the file COPYING in the main directory of the Linux
 22  *  distribution for more details.
 23  */
 24 
 25 #include <linux/cpu.h>
 26 #include <linux/cpumask.h>
 27 #include <linux/cpuset.h>
 28 #include <linux/err.h>
 29 #include <linux/errno.h>
 30 #include <linux/file.h>
 31 #include <linux/fs.h>
 32 #include <linux/init.h>
 33 #include <linux/interrupt.h>
 34 #include <linux/kernel.h>
 35 #include <linux/kmod.h>
 36 #include <linux/list.h>
 37 #include <linux/mempolicy.h>
 38 #include <linux/mm.h>
 39 #include <linux/memory.h>
 40 #include <linux/export.h>
 41 #include <linux/mount.h>
 42 #include <linux/fs_context.h>
 43 #include <linux/namei.h>
 44 #include <linux/pagemap.h>
 45 #include <linux/proc_fs.h>
 46 #include <linux/rcupdate.h>
 47 #include <linux/sched.h>
 48 #include <linux/sched/mm.h>
 49 #include <linux/sched/task.h>
 50 #include <linux/seq_file.h>
 51 #include <linux/security.h>
 52 #include <linux/slab.h>
 53 #include <linux/spinlock.h>
 54 #include <linux/stat.h>
 55 #include <linux/string.h>
 56 #include <linux/time.h>
 57 #include <linux/time64.h>
 58 #include <linux/backing-dev.h>
 59 #include <linux/sort.h>
 60 #include <linux/oom.h>
 61 #include <linux/sched/isolation.h>
 62 #include <linux/uaccess.h>
 63 #include <linux/atomic.h>
 64 #include <linux/mutex.h>
 65 #include <linux/cgroup.h>
 66 #include <linux/wait.h>
 67 
 68 DEFINE_STATIC_KEY_FALSE(cpusets_pre_enable_key);
 69 DEFINE_STATIC_KEY_FALSE(cpusets_enabled_key);
 70 
 71 /* See "Frequency meter" comments, below. */
 72 
 73 struct fmeter {
 74         int cnt;                /* unprocessed events count */
 75         int val;                /* most recent output value */
 76         time64_t time;          /* clock (secs) when val computed */
 77         spinlock_t lock;        /* guards read or write of above */
 78 };
 79 
 80 struct cpuset {
 81         struct cgroup_subsys_state css;
 82 
 83         unsigned long flags;            /* "unsigned long" so bitops work */
 84 
 85         /*
 86          * On default hierarchy:
 87          *
 88          * The user-configured masks can only be changed by writing to
 89          * cpuset.cpus and cpuset.mems, and won't be limited by the
 90          * parent masks.
 91          *
 92          * The effective masks is the real masks that apply to the tasks
 93          * in the cpuset. They may be changed if the configured masks are
 94          * changed or hotplug happens.
 95          *
 96          * effective_mask == configured_mask & parent's effective_mask,
 97          * and if it ends up empty, it will inherit the parent's mask.
 98          *
 99          *
100          * On legacy hierachy:
101          *
102          * The user-configured masks are always the same with effective masks.
103          */
104 
105         /* user-configured CPUs and Memory Nodes allow to tasks */
106         cpumask_var_t cpus_allowed;
107         nodemask_t mems_allowed;
108 
109         /* effective CPUs and Memory Nodes allow to tasks */
110         cpumask_var_t effective_cpus;
111         nodemask_t effective_mems;
112 
113         /*
114          * CPUs allocated to child sub-partitions (default hierarchy only)
115          * - CPUs granted by the parent = effective_cpus U subparts_cpus
116          * - effective_cpus and subparts_cpus are mutually exclusive.
117          *
118          * effective_cpus contains only onlined CPUs, but subparts_cpus
119          * may have offlined ones.
120          */
121         cpumask_var_t subparts_cpus;
122 
123         /*
124          * This is old Memory Nodes tasks took on.
125          *
126          * - top_cpuset.old_mems_allowed is initialized to mems_allowed.
127          * - A new cpuset's old_mems_allowed is initialized when some
128          *   task is moved into it.
129          * - old_mems_allowed is used in cpuset_migrate_mm() when we change
130          *   cpuset.mems_allowed and have tasks' nodemask updated, and
131          *   then old_mems_allowed is updated to mems_allowed.
132          */
133         nodemask_t old_mems_allowed;
134 
135         struct fmeter fmeter;           /* memory_pressure filter */
136 
137         /*
138          * Tasks are being attached to this cpuset.  Used to prevent
139          * zeroing cpus/mems_allowed between ->can_attach() and ->attach().
140          */
141         int attach_in_progress;
142 
143         /* partition number for rebuild_sched_domains() */
144         int pn;
145 
146         /* for custom sched domain */
147         int relax_domain_level;
148 
149         /* number of CPUs in subparts_cpus */
150         int nr_subparts_cpus;
151 
152         /* partition root state */
153         int partition_root_state;
154 
155         /*
156          * Default hierarchy only:
157          * use_parent_ecpus - set if using parent's effective_cpus
158          * child_ecpus_count - # of children with use_parent_ecpus set
159          */
160         int use_parent_ecpus;
161         int child_ecpus_count;
162 };
163 
164 /*
165  * Partition root states:
166  *
167  *   0 - not a partition root
168  *
169  *   1 - partition root
170  *
171  *  -1 - invalid partition root
172  *       None of the cpus in cpus_allowed can be put into the parent's
173  *       subparts_cpus. In this case, the cpuset is not a real partition
174  *       root anymore.  However, the CPU_EXCLUSIVE bit will still be set
175  *       and the cpuset can be restored back to a partition root if the
176  *       parent cpuset can give more CPUs back to this child cpuset.
177  */
178 #define PRS_DISABLED            0
179 #define PRS_ENABLED             1
180 #define PRS_ERROR               -1
181 
182 /*
183  * Temporary cpumasks for working with partitions that are passed among
184  * functions to avoid memory allocation in inner functions.
185  */
186 struct tmpmasks {
187         cpumask_var_t addmask, delmask; /* For partition root */
188         cpumask_var_t new_cpus;         /* For update_cpumasks_hier() */
189 };
190 
191 static inline struct cpuset *css_cs(struct cgroup_subsys_state *css)
192 {
193         return css ? container_of(css, struct cpuset, css) : NULL;
194 }
195 
196 /* Retrieve the cpuset for a task */
197 static inline struct cpuset *task_cs(struct task_struct *task)
198 {
199         return css_cs(task_css(task, cpuset_cgrp_id));
200 }
201 
202 static inline struct cpuset *parent_cs(struct cpuset *cs)
203 {
204         return css_cs(cs->css.parent);
205 }
206 
207 /* bits in struct cpuset flags field */
208 typedef enum {
209         CS_ONLINE,
210         CS_CPU_EXCLUSIVE,
211         CS_MEM_EXCLUSIVE,
212         CS_MEM_HARDWALL,
213         CS_MEMORY_MIGRATE,
214         CS_SCHED_LOAD_BALANCE,
215         CS_SPREAD_PAGE,
216         CS_SPREAD_SLAB,
217 } cpuset_flagbits_t;
218 
219 /* convenient tests for these bits */
220 static inline bool is_cpuset_online(struct cpuset *cs)
221 {
222         return test_bit(CS_ONLINE, &cs->flags) && !css_is_dying(&cs->css);
223 }
224 
225 static inline int is_cpu_exclusive(const struct cpuset *cs)
226 {
227         return test_bit(CS_CPU_EXCLUSIVE, &cs->flags);
228 }
229 
230 static inline int is_mem_exclusive(const struct cpuset *cs)
231 {
232         return test_bit(CS_MEM_EXCLUSIVE, &cs->flags);
233 }
234 
235 static inline int is_mem_hardwall(const struct cpuset *cs)
236 {
237         return test_bit(CS_MEM_HARDWALL, &cs->flags);
238 }
239 
240 static inline int is_sched_load_balance(const struct cpuset *cs)
241 {
242         return test_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
243 }
244 
245 static inline int is_memory_migrate(const struct cpuset *cs)
246 {
247         return test_bit(CS_MEMORY_MIGRATE, &cs->flags);
248 }
249 
250 static inline int is_spread_page(const struct cpuset *cs)
251 {
252         return test_bit(CS_SPREAD_PAGE, &cs->flags);
253 }
254 
255 static inline int is_spread_slab(const struct cpuset *cs)
256 {
257         return test_bit(CS_SPREAD_SLAB, &cs->flags);
258 }
259 
260 static inline int is_partition_root(const struct cpuset *cs)
261 {
262         return cs->partition_root_state > 0;
263 }
264 
265 static struct cpuset top_cpuset = {
266         .flags = ((1 << CS_ONLINE) | (1 << CS_CPU_EXCLUSIVE) |
267                   (1 << CS_MEM_EXCLUSIVE)),
268         .partition_root_state = PRS_ENABLED,
269 };
270 
271 /**
272  * cpuset_for_each_child - traverse online children of a cpuset
273  * @child_cs: loop cursor pointing to the current child
274  * @pos_css: used for iteration
275  * @parent_cs: target cpuset to walk children of
276  *
277  * Walk @child_cs through the online children of @parent_cs.  Must be used
278  * with RCU read locked.
279  */
280 #define cpuset_for_each_child(child_cs, pos_css, parent_cs)             \
281         css_for_each_child((pos_css), &(parent_cs)->css)                \
282                 if (is_cpuset_online(((child_cs) = css_cs((pos_css)))))
283 
284 /**
285  * cpuset_for_each_descendant_pre - pre-order walk of a cpuset's descendants
286  * @des_cs: loop cursor pointing to the current descendant
287  * @pos_css: used for iteration
288  * @root_cs: target cpuset to walk ancestor of
289  *
290  * Walk @des_cs through the online descendants of @root_cs.  Must be used
291  * with RCU read locked.  The caller may modify @pos_css by calling
292  * css_rightmost_descendant() to skip subtree.  @root_cs is included in the
293  * iteration and the first node to be visited.
294  */
295 #define cpuset_for_each_descendant_pre(des_cs, pos_css, root_cs)        \
296         css_for_each_descendant_pre((pos_css), &(root_cs)->css)         \
297                 if (is_cpuset_online(((des_cs) = css_cs((pos_css)))))
298 
299 /*
300  * There are two global locks guarding cpuset structures - cpuset_mutex and
301  * callback_lock. We also require taking task_lock() when dereferencing a
302  * task's cpuset pointer. See "The task_lock() exception", at the end of this
303  * comment.
304  *
305  * A task must hold both locks to modify cpusets.  If a task holds
306  * cpuset_mutex, then it blocks others wanting that mutex, ensuring that it
307  * is the only task able to also acquire callback_lock and be able to
308  * modify cpusets.  It can perform various checks on the cpuset structure
309  * first, knowing nothing will change.  It can also allocate memory while
310  * just holding cpuset_mutex.  While it is performing these checks, various
311  * callback routines can briefly acquire callback_lock to query cpusets.
312  * Once it is ready to make the changes, it takes callback_lock, blocking
313  * everyone else.
314  *
315  * Calls to the kernel memory allocator can not be made while holding
316  * callback_lock, as that would risk double tripping on callback_lock
317  * from one of the callbacks into the cpuset code from within
318  * __alloc_pages().
319  *
320  * If a task is only holding callback_lock, then it has read-only
321  * access to cpusets.
322  *
323  * Now, the task_struct fields mems_allowed and mempolicy may be changed
324  * by other task, we use alloc_lock in the task_struct fields to protect
325  * them.
326  *
327  * The cpuset_common_file_read() handlers only hold callback_lock across
328  * small pieces of code, such as when reading out possibly multi-word
329  * cpumasks and nodemasks.
330  *
331  * Accessing a task's cpuset should be done in accordance with the
332  * guidelines for accessing subsystem state in kernel/cgroup.c
333  */
334 
335 static DEFINE_MUTEX(cpuset_mutex);
336 static DEFINE_SPINLOCK(callback_lock);
337 
338 static struct workqueue_struct *cpuset_migrate_mm_wq;
339 
340 /*
341  * CPU / memory hotplug is handled asynchronously.
342  */
343 static void cpuset_hotplug_workfn(struct work_struct *work);
344 static DECLARE_WORK(cpuset_hotplug_work, cpuset_hotplug_workfn);
345 
346 static DECLARE_WAIT_QUEUE_HEAD(cpuset_attach_wq);
347 
348 /*
349  * Cgroup v2 behavior is used when on default hierarchy or the
350  * cgroup_v2_mode flag is set.
351  */
352 static inline bool is_in_v2_mode(void)
353 {
354         return cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||
355               (cpuset_cgrp_subsys.root->flags & CGRP_ROOT_CPUSET_V2_MODE);
356 }
357 
358 /*
359  * This is ugly, but preserves the userspace API for existing cpuset
360  * users. If someone tries to mount the "cpuset" filesystem, we
361  * silently switch it to mount "cgroup" instead
362  */
363 static int cpuset_get_tree(struct fs_context *fc)
364 {
365         struct file_system_type *cgroup_fs;
366         struct fs_context *new_fc;
367         int ret;
368 
369         cgroup_fs = get_fs_type("cgroup");
370         if (!cgroup_fs)
371                 return -ENODEV;
372 
373         new_fc = fs_context_for_mount(cgroup_fs, fc->sb_flags);
374         if (IS_ERR(new_fc)) {
375                 ret = PTR_ERR(new_fc);
376         } else {
377                 static const char agent_path[] = "/sbin/cpuset_release_agent";
378                 ret = vfs_parse_fs_string(new_fc, "cpuset", NULL, 0);
379                 if (!ret)
380                         ret = vfs_parse_fs_string(new_fc, "noprefix", NULL, 0);
381                 if (!ret)
382                         ret = vfs_parse_fs_string(new_fc, "release_agent",
383                                         agent_path, sizeof(agent_path) - 1);
384                 if (!ret)
385                         ret = vfs_get_tree(new_fc);
386                 if (!ret) {     /* steal the result */
387                         fc->root = new_fc->root;
388                         new_fc->root = NULL;
389                 }
390                 put_fs_context(new_fc);
391         }
392         put_filesystem(cgroup_fs);
393         return ret;
394 }
395 
396 static const struct fs_context_operations cpuset_fs_context_ops = {
397         .get_tree       = cpuset_get_tree,
398 };
399 
400 static int cpuset_init_fs_context(struct fs_context *fc)
401 {
402         fc->ops = &cpuset_fs_context_ops;
403         return 0;
404 }
405 
406 static struct file_system_type cpuset_fs_type = {
407         .name                   = "cpuset",
408         .init_fs_context        = cpuset_init_fs_context,
409 };
410 
411 /*
412  * Return in pmask the portion of a cpusets's cpus_allowed that
413  * are online.  If none are online, walk up the cpuset hierarchy
414  * until we find one that does have some online cpus.
415  *
416  * One way or another, we guarantee to return some non-empty subset
417  * of cpu_online_mask.
418  *
419  * Call with callback_lock or cpuset_mutex held.
420  */
421 static void guarantee_online_cpus(struct cpuset *cs, struct cpumask *pmask)
422 {
423         while (!cpumask_intersects(cs->effective_cpus, cpu_online_mask)) {
424                 cs = parent_cs(cs);
425                 if (unlikely(!cs)) {
426                         /*
427                          * The top cpuset doesn't have any online cpu as a
428                          * consequence of a race between cpuset_hotplug_work
429                          * and cpu hotplug notifier.  But we know the top
430                          * cpuset's effective_cpus is on its way to to be
431                          * identical to cpu_online_mask.
432                          */
433                         cpumask_copy(pmask, cpu_online_mask);
434                         return;
435                 }
436         }
437         cpumask_and(pmask, cs->effective_cpus, cpu_online_mask);
438 }
439 
440 /*
441  * Return in *pmask the portion of a cpusets's mems_allowed that
442  * are online, with memory.  If none are online with memory, walk
443  * up the cpuset hierarchy until we find one that does have some
444  * online mems.  The top cpuset always has some mems online.
445  *
446  * One way or another, we guarantee to return some non-empty subset
447  * of node_states[N_MEMORY].
448  *
449  * Call with callback_lock or cpuset_mutex held.
450  */
451 static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask)
452 {
453         while (!nodes_intersects(cs->effective_mems, node_states[N_MEMORY]))
454                 cs = parent_cs(cs);
455         nodes_and(*pmask, cs->effective_mems, node_states[N_MEMORY]);
456 }
457 
458 /*
459  * update task's spread flag if cpuset's page/slab spread flag is set
460  *
461  * Call with callback_lock or cpuset_mutex held.
462  */
463 static void cpuset_update_task_spread_flag(struct cpuset *cs,
464                                         struct task_struct *tsk)
465 {
466         if (is_spread_page(cs))
467                 task_set_spread_page(tsk);
468         else
469                 task_clear_spread_page(tsk);
470 
471         if (is_spread_slab(cs))
472                 task_set_spread_slab(tsk);
473         else
474                 task_clear_spread_slab(tsk);
475 }
476 
477 /*
478  * is_cpuset_subset(p, q) - Is cpuset p a subset of cpuset q?
479  *
480  * One cpuset is a subset of another if all its allowed CPUs and
481  * Memory Nodes are a subset of the other, and its exclusive flags
482  * are only set if the other's are set.  Call holding cpuset_mutex.
483  */
484 
485 static int is_cpuset_subset(const struct cpuset *p, const struct cpuset *q)
486 {
487         return  cpumask_subset(p->cpus_allowed, q->cpus_allowed) &&
488                 nodes_subset(p->mems_allowed, q->mems_allowed) &&
489                 is_cpu_exclusive(p) <= is_cpu_exclusive(q) &&
490                 is_mem_exclusive(p) <= is_mem_exclusive(q);
491 }
492 
493 /**
494  * alloc_cpumasks - allocate three cpumasks for cpuset
495  * @cs:  the cpuset that have cpumasks to be allocated.
496  * @tmp: the tmpmasks structure pointer
497  * Return: 0 if successful, -ENOMEM otherwise.
498  *
499  * Only one of the two input arguments should be non-NULL.
500  */
501 static inline int alloc_cpumasks(struct cpuset *cs, struct tmpmasks *tmp)
502 {
503         cpumask_var_t *pmask1, *pmask2, *pmask3;
504 
505         if (cs) {
506                 pmask1 = &cs->cpus_allowed;
507                 pmask2 = &cs->effective_cpus;
508                 pmask3 = &cs->subparts_cpus;
509         } else {
510                 pmask1 = &tmp->new_cpus;
511                 pmask2 = &tmp->addmask;
512                 pmask3 = &tmp->delmask;
513         }
514 
515         if (!zalloc_cpumask_var(pmask1, GFP_KERNEL))
516                 return -ENOMEM;
517 
518         if (!zalloc_cpumask_var(pmask2, GFP_KERNEL))
519                 goto free_one;
520 
521         if (!zalloc_cpumask_var(pmask3, GFP_KERNEL))
522                 goto free_two;
523 
524         return 0;
525 
526 free_two:
527         free_cpumask_var(*pmask2);
528 free_one:
529         free_cpumask_var(*pmask1);
530         return -ENOMEM;
531 }
532 
533 /**
534  * free_cpumasks - free cpumasks in a tmpmasks structure
535  * @cs:  the cpuset that have cpumasks to be free.
536  * @tmp: the tmpmasks structure pointer
537  */
538 static inline void free_cpumasks(struct cpuset *cs, struct tmpmasks *tmp)
539 {
540         if (cs) {
541                 free_cpumask_var(cs->cpus_allowed);
542                 free_cpumask_var(cs->effective_cpus);
543                 free_cpumask_var(cs->subparts_cpus);
544         }
545         if (tmp) {
546                 free_cpumask_var(tmp->new_cpus);
547                 free_cpumask_var(tmp->addmask);
548                 free_cpumask_var(tmp->delmask);
549         }
550 }
551 
552 /**
553  * alloc_trial_cpuset - allocate a trial cpuset
554  * @cs: the cpuset that the trial cpuset duplicates
555  */
556 static struct cpuset *alloc_trial_cpuset(struct cpuset *cs)
557 {
558         struct cpuset *trial;
559 
560         trial = kmemdup(cs, sizeof(*cs), GFP_KERNEL);
561         if (!trial)
562                 return NULL;
563 
564         if (alloc_cpumasks(trial, NULL)) {
565                 kfree(trial);
566                 return NULL;
567         }
568 
569         cpumask_copy(trial->cpus_allowed, cs->cpus_allowed);
570         cpumask_copy(trial->effective_cpus, cs->effective_cpus);
571         return trial;
572 }
573 
574 /**
575  * free_cpuset - free the cpuset
576  * @cs: the cpuset to be freed
577  */
578 static inline void free_cpuset(struct cpuset *cs)
579 {
580         free_cpumasks(cs, NULL);
581         kfree(cs);
582 }
583 
584 /*
585  * validate_change() - Used to validate that any proposed cpuset change
586  *                     follows the structural rules for cpusets.
587  *
588  * If we replaced the flag and mask values of the current cpuset
589  * (cur) with those values in the trial cpuset (trial), would
590  * our various subset and exclusive rules still be valid?  Presumes
591  * cpuset_mutex held.
592  *
593  * 'cur' is the address of an actual, in-use cpuset.  Operations
594  * such as list traversal that depend on the actual address of the
595  * cpuset in the list must use cur below, not trial.
596  *
597  * 'trial' is the address of bulk structure copy of cur, with
598  * perhaps one or more of the fields cpus_allowed, mems_allowed,
599  * or flags changed to new, trial values.
600  *
601  * Return 0 if valid, -errno if not.
602  */
603 
604 static int validate_change(struct cpuset *cur, struct cpuset *trial)
605 {
606         struct cgroup_subsys_state *css;
607         struct cpuset *c, *par;
608         int ret;
609 
610         rcu_read_lock();
611 
612         /* Each of our child cpusets must be a subset of us */
613         ret = -EBUSY;
614         cpuset_for_each_child(c, css, cur)
615                 if (!is_cpuset_subset(c, trial))
616                         goto out;
617 
618         /* Remaining checks don't apply to root cpuset */
619         ret = 0;
620         if (cur == &top_cpuset)
621                 goto out;
622 
623         par = parent_cs(cur);
624 
625         /* On legacy hiearchy, we must be a subset of our parent cpuset. */
626         ret = -EACCES;
627         if (!is_in_v2_mode() && !is_cpuset_subset(trial, par))
628                 goto out;
629 
630         /*
631          * If either I or some sibling (!= me) is exclusive, we can't
632          * overlap
633          */
634         ret = -EINVAL;
635         cpuset_for_each_child(c, css, par) {
636                 if ((is_cpu_exclusive(trial) || is_cpu_exclusive(c)) &&
637                     c != cur &&
638                     cpumask_intersects(trial->cpus_allowed, c->cpus_allowed))
639                         goto out;
640                 if ((is_mem_exclusive(trial) || is_mem_exclusive(c)) &&
641                     c != cur &&
642                     nodes_intersects(trial->mems_allowed, c->mems_allowed))
643                         goto out;
644         }
645 
646         /*
647          * Cpusets with tasks - existing or newly being attached - can't
648          * be changed to have empty cpus_allowed or mems_allowed.
649          */
650         ret = -ENOSPC;
651         if ((cgroup_is_populated(cur->css.cgroup) || cur->attach_in_progress)) {
652                 if (!cpumask_empty(cur->cpus_allowed) &&
653                     cpumask_empty(trial->cpus_allowed))
654                         goto out;
655                 if (!nodes_empty(cur->mems_allowed) &&
656                     nodes_empty(trial->mems_allowed))
657                         goto out;
658         }
659 
660         /*
661          * We can't shrink if we won't have enough room for SCHED_DEADLINE
662          * tasks.
663          */
664         ret = -EBUSY;
665         if (is_cpu_exclusive(cur) &&
666             !cpuset_cpumask_can_shrink(cur->cpus_allowed,
667                                        trial->cpus_allowed))
668                 goto out;
669 
670         ret = 0;
671 out:
672         rcu_read_unlock();
673         return ret;
674 }
675 
676 #ifdef CONFIG_SMP
677 /*
678  * Helper routine for generate_sched_domains().
679  * Do cpusets a, b have overlapping effective cpus_allowed masks?
680  */
681 static int cpusets_overlap(struct cpuset *a, struct cpuset *b)
682 {
683         return cpumask_intersects(a->effective_cpus, b->effective_cpus);
684 }
685 
686 static void
687 update_domain_attr(struct sched_domain_attr *dattr, struct cpuset *c)
688 {
689         if (dattr->relax_domain_level < c->relax_domain_level)
690                 dattr->relax_domain_level = c->relax_domain_level;
691         return;
692 }
693 
694 static void update_domain_attr_tree(struct sched_domain_attr *dattr,
695                                     struct cpuset *root_cs)
696 {
697         struct cpuset *cp;
698         struct cgroup_subsys_state *pos_css;
699 
700         rcu_read_lock();
701         cpuset_for_each_descendant_pre(cp, pos_css, root_cs) {
702                 /* skip the whole subtree if @cp doesn't have any CPU */
703                 if (cpumask_empty(cp->cpus_allowed)) {
704                         pos_css = css_rightmost_descendant(pos_css);
705                         continue;
706                 }
707 
708                 if (is_sched_load_balance(cp))
709                         update_domain_attr(dattr, cp);
710         }
711         rcu_read_unlock();
712 }
713 
714 /* Must be called with cpuset_mutex held.  */
715 static inline int nr_cpusets(void)
716 {
717         /* jump label reference count + the top-level cpuset */
718         return static_key_count(&cpusets_enabled_key.key) + 1;
719 }
720 
721 /*
722  * generate_sched_domains()
723  *
724  * This function builds a partial partition of the systems CPUs
725  * A 'partial partition' is a set of non-overlapping subsets whose
726  * union is a subset of that set.
727  * The output of this function needs to be passed to kernel/sched/core.c
728  * partition_sched_domains() routine, which will rebuild the scheduler's
729  * load balancing domains (sched domains) as specified by that partial
730  * partition.
731  *
732  * See "What is sched_load_balance" in Documentation/cgroup-v1/cpusets.txt
733  * for a background explanation of this.
734  *
735  * Does not return errors, on the theory that the callers of this
736  * routine would rather not worry about failures to rebuild sched
737  * domains when operating in the severe memory shortage situations
738  * that could cause allocation failures below.
739  *
740  * Must be called with cpuset_mutex held.
741  *
742  * The three key local variables below are:
743  *    q  - a linked-list queue of cpuset pointers, used to implement a
744  *         top-down scan of all cpusets.  This scan loads a pointer
745  *         to each cpuset marked is_sched_load_balance into the
746  *         array 'csa'.  For our purposes, rebuilding the schedulers
747  *         sched domains, we can ignore !is_sched_load_balance cpusets.
748  *  csa  - (for CpuSet Array) Array of pointers to all the cpusets
749  *         that need to be load balanced, for convenient iterative
750  *         access by the subsequent code that finds the best partition,
751  *         i.e the set of domains (subsets) of CPUs such that the
752  *         cpus_allowed of every cpuset marked is_sched_load_balance
753  *         is a subset of one of these domains, while there are as
754  *         many such domains as possible, each as small as possible.
755  * doms  - Conversion of 'csa' to an array of cpumasks, for passing to
756  *         the kernel/sched/core.c routine partition_sched_domains() in a
757  *         convenient format, that can be easily compared to the prior
758  *         value to determine what partition elements (sched domains)
759  *         were changed (added or removed.)
760  *
761  * Finding the best partition (set of domains):
762  *      The triple nested loops below over i, j, k scan over the
763  *      load balanced cpusets (using the array of cpuset pointers in
764  *      csa[]) looking for pairs of cpusets that have overlapping
765  *      cpus_allowed, but which don't have the same 'pn' partition
766  *      number and gives them in the same partition number.  It keeps
767  *      looping on the 'restart' label until it can no longer find
768  *      any such pairs.
769  *
770  *      The union of the cpus_allowed masks from the set of
771  *      all cpusets having the same 'pn' value then form the one
772  *      element of the partition (one sched domain) to be passed to
773  *      partition_sched_domains().
774  */
775 static int generate_sched_domains(cpumask_var_t **domains,
776                         struct sched_domain_attr **attributes)
777 {
778         struct cpuset *cp;      /* scans q */
779         struct cpuset **csa;    /* array of all cpuset ptrs */
780         int csn;                /* how many cpuset ptrs in csa so far */
781         int i, j, k;            /* indices for partition finding loops */
782         cpumask_var_t *doms;    /* resulting partition; i.e. sched domains */
783         struct sched_domain_attr *dattr;  /* attributes for custom domains */
784         int ndoms = 0;          /* number of sched domains in result */
785         int nslot;              /* next empty doms[] struct cpumask slot */
786         struct cgroup_subsys_state *pos_css;
787         bool root_load_balance = is_sched_load_balance(&top_cpuset);
788 
789         doms = NULL;
790         dattr = NULL;
791         csa = NULL;
792 
793         /* Special case for the 99% of systems with one, full, sched domain */
794         if (root_load_balance && !top_cpuset.nr_subparts_cpus) {
795                 ndoms = 1;
796                 doms = alloc_sched_domains(ndoms);
797                 if (!doms)
798                         goto done;
799 
800                 dattr = kmalloc(sizeof(struct sched_domain_attr), GFP_KERNEL);
801                 if (dattr) {
802                         *dattr = SD_ATTR_INIT;
803                         update_domain_attr_tree(dattr, &top_cpuset);
804                 }
805                 cpumask_and(doms[0], top_cpuset.effective_cpus,
806                             housekeeping_cpumask(HK_FLAG_DOMAIN));
807 
808                 goto done;
809         }
810 
811         csa = kmalloc_array(nr_cpusets(), sizeof(cp), GFP_KERNEL);
812         if (!csa)
813                 goto done;
814         csn = 0;
815 
816         rcu_read_lock();
817         if (root_load_balance)
818                 csa[csn++] = &top_cpuset;
819         cpuset_for_each_descendant_pre(cp, pos_css, &top_cpuset) {
820                 if (cp == &top_cpuset)
821                         continue;
822                 /*
823                  * Continue traversing beyond @cp iff @cp has some CPUs and
824                  * isn't load balancing.  The former is obvious.  The
825                  * latter: All child cpusets contain a subset of the
826                  * parent's cpus, so just skip them, and then we call
827                  * update_domain_attr_tree() to calc relax_domain_level of
828                  * the corresponding sched domain.
829                  *
830                  * If root is load-balancing, we can skip @cp if it
831                  * is a subset of the root's effective_cpus.
832                  */
833                 if (!cpumask_empty(cp->cpus_allowed) &&
834                     !(is_sched_load_balance(cp) &&
835                       cpumask_intersects(cp->cpus_allowed,
836                                          housekeeping_cpumask(HK_FLAG_DOMAIN))))
837                         continue;
838 
839                 if (root_load_balance &&
840                     cpumask_subset(cp->cpus_allowed, top_cpuset.effective_cpus))
841                         continue;
842 
843                 if (is_sched_load_balance(cp))
844                         csa[csn++] = cp;
845 
846                 /* skip @cp's subtree if not a partition root */
847                 if (!is_partition_root(cp))
848                         pos_css = css_rightmost_descendant(pos_css);
849         }
850         rcu_read_unlock();
851 
852         for (i = 0; i < csn; i++)
853                 csa[i]->pn = i;
854         ndoms = csn;
855 
856 restart:
857         /* Find the best partition (set of sched domains) */
858         for (i = 0; i < csn; i++) {
859                 struct cpuset *a = csa[i];
860                 int apn = a->pn;
861 
862                 for (j = 0; j < csn; j++) {
863                         struct cpuset *b = csa[j];
864                         int bpn = b->pn;
865 
866                         if (apn != bpn && cpusets_overlap(a, b)) {
867                                 for (k = 0; k < csn; k++) {
868                                         struct cpuset *c = csa[k];
869 
870                                         if (c->pn == bpn)
871                                                 c->pn = apn;
872                                 }
873                                 ndoms--;        /* one less element */
874                                 goto restart;
875                         }
876                 }
877         }
878 
879         /*
880          * Now we know how many domains to create.
881          * Convert <csn, csa> to <ndoms, doms> and populate cpu masks.
882          */
883         doms = alloc_sched_domains(ndoms);
884         if (!doms)
885                 goto done;
886 
887         /*
888          * The rest of the code, including the scheduler, can deal with
889          * dattr==NULL case. No need to abort if alloc fails.
890          */
891         dattr = kmalloc_array(ndoms, sizeof(struct sched_domain_attr),
892                               GFP_KERNEL);
893 
894         for (nslot = 0, i = 0; i < csn; i++) {
895                 struct cpuset *a = csa[i];
896                 struct cpumask *dp;
897                 int apn = a->pn;
898 
899                 if (apn < 0) {
900                         /* Skip completed partitions */
901                         continue;
902                 }
903 
904                 dp = doms[nslot];
905 
906                 if (nslot == ndoms) {
907                         static int warnings = 10;
908                         if (warnings) {
909                                 pr_warn("rebuild_sched_domains confused: nslot %d, ndoms %d, csn %d, i %d, apn %d\n",
910                                         nslot, ndoms, csn, i, apn);
911                                 warnings--;
912                         }
913                         continue;
914                 }
915 
916                 cpumask_clear(dp);
917                 if (dattr)
918                         *(dattr + nslot) = SD_ATTR_INIT;
919                 for (j = i; j < csn; j++) {
920                         struct cpuset *b = csa[j];
921 
922                         if (apn == b->pn) {
923                                 cpumask_or(dp, dp, b->effective_cpus);
924                                 cpumask_and(dp, dp, housekeeping_cpumask(HK_FLAG_DOMAIN));
925                                 if (dattr)
926                                         update_domain_attr_tree(dattr + nslot, b);
927 
928                                 /* Done with this partition */
929                                 b->pn = -1;
930                         }
931                 }
932                 nslot++;
933         }
934         BUG_ON(nslot != ndoms);
935 
936 done:
937         kfree(csa);
938 
939         /*
940          * Fallback to the default domain if kmalloc() failed.
941          * See comments in partition_sched_domains().
942          */
943         if (doms == NULL)
944                 ndoms = 1;
945 
946         *domains    = doms;
947         *attributes = dattr;
948         return ndoms;
949 }
950 
951 /*
952  * Rebuild scheduler domains.
953  *
954  * If the flag 'sched_load_balance' of any cpuset with non-empty
955  * 'cpus' changes, or if the 'cpus' allowed changes in any cpuset
956  * which has that flag enabled, or if any cpuset with a non-empty
957  * 'cpus' is removed, then call this routine to rebuild the
958  * scheduler's dynamic sched domains.
959  *
960  * Call with cpuset_mutex held.  Takes get_online_cpus().
961  */
962 static void rebuild_sched_domains_locked(void)
963 {
964         struct sched_domain_attr *attr;
965         cpumask_var_t *doms;
966         int ndoms;
967 
968         lockdep_assert_held(&cpuset_mutex);
969         get_online_cpus();
970 
971         /*
972          * We have raced with CPU hotplug. Don't do anything to avoid
973          * passing doms with offlined cpu to partition_sched_domains().
974          * Anyways, hotplug work item will rebuild sched domains.
975          */
976         if (!top_cpuset.nr_subparts_cpus &&
977             !cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
978                 goto out;
979 
980         if (top_cpuset.nr_subparts_cpus &&
981            !cpumask_subset(top_cpuset.effective_cpus, cpu_active_mask))
982                 goto out;
983 
984         /* Generate domain masks and attrs */
985         ndoms = generate_sched_domains(&doms, &attr);
986 
987         /* Have scheduler rebuild the domains */
988         partition_sched_domains(ndoms, doms, attr);
989 out:
990         put_online_cpus();
991 }
992 #else /* !CONFIG_SMP */
993 static void rebuild_sched_domains_locked(void)
994 {
995 }
996 #endif /* CONFIG_SMP */
997 
998 void rebuild_sched_domains(void)
999 {
1000         mutex_lock(&cpuset_mutex);
1001         rebuild_sched_domains_locked();
1002         mutex_unlock(&cpuset_mutex);
1003 }
1004 
1005 /**
1006  * update_tasks_cpumask - Update the cpumasks of tasks in the cpuset.
1007  * @cs: the cpuset in which each task's cpus_allowed mask needs to be changed
1008  *
1009  * Iterate through each task of @cs updating its cpus_allowed to the
1010  * effective cpuset's.  As this function is called with cpuset_mutex held,
1011  * cpuset membership stays stable.
1012  */
1013 static void update_tasks_cpumask(struct cpuset *cs)
1014 {
1015         struct css_task_iter it;
1016         struct task_struct *task;
1017 
1018         css_task_iter_start(&cs->css, 0, &it);
1019         while ((task = css_task_iter_next(&it)))
1020                 set_cpus_allowed_ptr(task, cs->effective_cpus);
1021         css_task_iter_end(&it);
1022 }
1023 
1024 /**
1025  * compute_effective_cpumask - Compute the effective cpumask of the cpuset
1026  * @new_cpus: the temp variable for the new effective_cpus mask
1027  * @cs: the cpuset the need to recompute the new effective_cpus mask
1028  * @parent: the parent cpuset
1029  *
1030  * If the parent has subpartition CPUs, include them in the list of
1031  * allowable CPUs in computing the new effective_cpus mask. Since offlined
1032  * CPUs are not removed from subparts_cpus, we have to use cpu_active_mask
1033  * to mask those out.
1034  */
1035 static void compute_effective_cpumask(struct cpumask *new_cpus,
1036                                       struct cpuset *cs, struct cpuset *parent)
1037 {
1038         if (parent->nr_subparts_cpus) {
1039                 cpumask_or(new_cpus, parent->effective_cpus,
1040                            parent->subparts_cpus);
1041                 cpumask_and(new_cpus, new_cpus, cs->cpus_allowed);
1042                 cpumask_and(new_cpus, new_cpus, cpu_active_mask);
1043         } else {
1044                 cpumask_and(new_cpus, cs->cpus_allowed, parent->effective_cpus);
1045         }
1046 }
1047 
1048 /*
1049  * Commands for update_parent_subparts_cpumask
1050  */
1051 enum subparts_cmd {
1052         partcmd_enable,         /* Enable partition root         */
1053         partcmd_disable,        /* Disable partition root        */
1054         partcmd_update,         /* Update parent's subparts_cpus */
1055 };
1056 
1057 /**
1058  * update_parent_subparts_cpumask - update subparts_cpus mask of parent cpuset
1059  * @cpuset:  The cpuset that requests change in partition root state
1060  * @cmd:     Partition root state change command
1061  * @newmask: Optional new cpumask for partcmd_update
1062  * @tmp:     Temporary addmask and delmask
1063  * Return:   0, 1 or an error code
1064  *
1065  * For partcmd_enable, the cpuset is being transformed from a non-partition
1066  * root to a partition root. The cpus_allowed mask of the given cpuset will
1067  * be put into parent's subparts_cpus and taken away from parent's
1068  * effective_cpus. The function will return 0 if all the CPUs listed in
1069  * cpus_allowed can be granted or an error code will be returned.
1070  *
1071  * For partcmd_disable, the cpuset is being transofrmed from a partition
1072  * root back to a non-partition root. any CPUs in cpus_allowed that are in
1073  * parent's subparts_cpus will be taken away from that cpumask and put back
1074  * into parent's effective_cpus. 0 should always be returned.
1075  *
1076  * For partcmd_update, if the optional newmask is specified, the cpu
1077  * list is to be changed from cpus_allowed to newmask. Otherwise,
1078  * cpus_allowed is assumed to remain the same. The cpuset should either
1079  * be a partition root or an invalid partition root. The partition root
1080  * state may change if newmask is NULL and none of the requested CPUs can
1081  * be granted by the parent. The function will return 1 if changes to
1082  * parent's subparts_cpus and effective_cpus happen or 0 otherwise.
1083  * Error code should only be returned when newmask is non-NULL.
1084  *
1085  * The partcmd_enable and partcmd_disable commands are used by
1086  * update_prstate(). The partcmd_update command is used by
1087  * update_cpumasks_hier() with newmask NULL and update_cpumask() with
1088  * newmask set.
1089  *
1090  * The checking is more strict when enabling partition root than the
1091  * other two commands.
1092  *
1093  * Because of the implicit cpu exclusive nature of a partition root,
1094  * cpumask changes that violates the cpu exclusivity rule will not be
1095  * permitted when checked by validate_change(). The validate_change()
1096  * function will also prevent any changes to the cpu list if it is not
1097  * a superset of children's cpu lists.
1098  */
1099 static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
1100                                           struct cpumask *newmask,
1101                                           struct tmpmasks *tmp)
1102 {
1103         struct cpuset *parent = parent_cs(cpuset);
1104         int adding;     /* Moving cpus from effective_cpus to subparts_cpus */
1105         int deleting;   /* Moving cpus from subparts_cpus to effective_cpus */
1106         bool part_error = false;        /* Partition error? */
1107 
1108         lockdep_assert_held(&cpuset_mutex);
1109 
1110         /*
1111          * The parent must be a partition root.
1112          * The new cpumask, if present, or the current cpus_allowed must
1113          * not be empty.
1114          */
1115         if (!is_partition_root(parent) ||
1116            (newmask && cpumask_empty(newmask)) ||
1117            (!newmask && cpumask_empty(cpuset->cpus_allowed)))
1118                 return -EINVAL;
1119 
1120         /*
1121          * Enabling/disabling partition root is not allowed if there are
1122          * online children.
1123          */
1124         if ((cmd != partcmd_update) && css_has_online_children(&cpuset->css))
1125                 return -EBUSY;
1126 
1127         /*
1128          * Enabling partition root is not allowed if not all the CPUs
1129          * can be granted from parent's effective_cpus or at least one
1130          * CPU will be left after that.
1131          */
1132         if ((cmd == partcmd_enable) &&
1133            (!cpumask_subset(cpuset->cpus_allowed, parent->effective_cpus) ||
1134              cpumask_equal(cpuset->cpus_allowed, parent->effective_cpus)))
1135                 return -EINVAL;
1136 
1137         /*
1138          * A cpumask update cannot make parent's effective_cpus become empty.
1139          */
1140         adding = deleting = false;
1141         if (cmd == partcmd_enable) {
1142                 cpumask_copy(tmp->addmask, cpuset->cpus_allowed);
1143                 adding = true;
1144         } else if (cmd == partcmd_disable) {
1145                 deleting = cpumask_and(tmp->delmask, cpuset->cpus_allowed,
1146                                        parent->subparts_cpus);
1147         } else if (newmask) {
1148                 /*
1149                  * partcmd_update with newmask:
1150                  *
1151                  * delmask = cpus_allowed & ~newmask & parent->subparts_cpus
1152                  * addmask = newmask & parent->effective_cpus
1153                  *                   & ~parent->subparts_cpus
1154                  */
1155                 cpumask_andnot(tmp->delmask, cpuset->cpus_allowed, newmask);
1156                 deleting = cpumask_and(tmp->delmask, tmp->delmask,
1157                                        parent->subparts_cpus);
1158 
1159                 cpumask_and(tmp->addmask, newmask, parent->effective_cpus);
1160                 adding = cpumask_andnot(tmp->addmask, tmp->addmask,
1161                                         parent->subparts_cpus);
1162                 /*
1163                  * Return error if the new effective_cpus could become empty.
1164                  */
1165                 if (adding &&
1166                     cpumask_equal(parent->effective_cpus, tmp->addmask)) {
1167                         if (!deleting)
1168                                 return -EINVAL;
1169                         /*
1170                          * As some of the CPUs in subparts_cpus might have
1171                          * been offlined, we need to compute the real delmask
1172                          * to confirm that.
1173                          */
1174                         if (!cpumask_and(tmp->addmask, tmp->delmask,
1175                                          cpu_active_mask))
1176                                 return -EINVAL;
1177                         cpumask_copy(tmp->addmask, parent->effective_cpus);
1178                 }
1179         } else {
1180                 /*
1181                  * partcmd_update w/o newmask:
1182                  *
1183                  * addmask = cpus_allowed & parent->effectiveb_cpus
1184                  *
1185                  * Note that parent's subparts_cpus may have been
1186                  * pre-shrunk in case there is a change in the cpu list.
1187                  * So no deletion is needed.
1188                  */
1189                 adding = cpumask_and(tmp->addmask, cpuset->cpus_allowed,
1190                                      parent->effective_cpus);
1191                 part_error = cpumask_equal(tmp->addmask,
1192                                            parent->effective_cpus);
1193         }
1194 
1195         if (cmd == partcmd_update) {
1196                 int prev_prs = cpuset->partition_root_state;
1197 
1198                 /*
1199                  * Check for possible transition between PRS_ENABLED
1200                  * and PRS_ERROR.
1201                  */
1202                 switch (cpuset->partition_root_state) {
1203                 case PRS_ENABLED:
1204                         if (part_error)
1205                                 cpuset->partition_root_state = PRS_ERROR;
1206                         break;
1207                 case PRS_ERROR:
1208                         if (!part_error)
1209                                 cpuset->partition_root_state = PRS_ENABLED;
1210                         break;
1211                 }
1212                 /*
1213                  * Set part_error if previously in invalid state.
1214                  */
1215                 part_error = (prev_prs == PRS_ERROR);
1216         }
1217 
1218         if (!part_error && (cpuset->partition_root_state == PRS_ERROR))
1219                 return 0;       /* Nothing need to be done */
1220 
1221         if (cpuset->partition_root_state == PRS_ERROR) {
1222                 /*
1223                  * Remove all its cpus from parent's subparts_cpus.
1224                  */
1225                 adding = false;
1226                 deleting = cpumask_and(tmp->delmask, cpuset->cpus_allowed,
1227                                        parent->subparts_cpus);
1228         }
1229 
1230         if (!adding && !deleting)
1231                 return 0;
1232 
1233         /*
1234          * Change the parent's subparts_cpus.
1235          * Newly added CPUs will be removed from effective_cpus and
1236          * newly deleted ones will be added back to effective_cpus.
1237          */
1238         spin_lock_irq(&callback_lock);
1239         if (adding) {
1240                 cpumask_or(parent->subparts_cpus,
1241                            parent->subparts_cpus, tmp->addmask);
1242                 cpumask_andnot(parent->effective_cpus,
1243                                parent->effective_cpus, tmp->addmask);
1244         }
1245         if (deleting) {
1246                 cpumask_andnot(parent->subparts_cpus,
1247                                parent->subparts_cpus, tmp->delmask);
1248                 /*
1249                  * Some of the CPUs in subparts_cpus might have been offlined.
1250                  */
1251                 cpumask_and(tmp->delmask, tmp->delmask, cpu_active_mask);
1252                 cpumask_or(parent->effective_cpus,
1253                            parent->effective_cpus, tmp->delmask);
1254         }
1255 
1256         parent->nr_subparts_cpus = cpumask_weight(parent->subparts_cpus);
1257         spin_unlock_irq(&callback_lock);
1258 
1259         return cmd == partcmd_update;
1260 }
1261 
1262 /*
1263  * update_cpumasks_hier - Update effective cpumasks and tasks in the subtree
1264  * @cs:  the cpuset to consider
1265  * @tmp: temp variables for calculating effective_cpus & partition setup
1266  *
1267  * When congifured cpumask is changed, the effective cpumasks of this cpuset
1268  * and all its descendants need to be updated.
1269  *
1270  * On legacy hierachy, effective_cpus will be the same with cpu_allowed.
1271  *
1272  * Called with cpuset_mutex held
1273  */
1274 static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
1275 {
1276         struct cpuset *cp;
1277         struct cgroup_subsys_state *pos_css;
1278         bool need_rebuild_sched_domains = false;
1279 
1280         rcu_read_lock();
1281         cpuset_for_each_descendant_pre(cp, pos_css, cs) {
1282                 struct cpuset *parent = parent_cs(cp);
1283 
1284                 compute_effective_cpumask(tmp->new_cpus, cp, parent);
1285 
1286                 /*
1287                  * If it becomes empty, inherit the effective mask of the
1288                  * parent, which is guaranteed to have some CPUs.
1289                  */
1290                 if (is_in_v2_mode() && cpumask_empty(tmp->new_cpus)) {
1291                         cpumask_copy(tmp->new_cpus, parent->effective_cpus);
1292                         if (!cp->use_parent_ecpus) {
1293                                 cp->use_parent_ecpus = true;
1294                                 parent->child_ecpus_count++;
1295                         }
1296                 } else if (cp->use_parent_ecpus) {
1297                         cp->use_parent_ecpus = false;
1298                         WARN_ON_ONCE(!parent->child_ecpus_count);
1299                         parent->child_ecpus_count--;
1300                 }
1301 
1302                 /*
1303                  * Skip the whole subtree if the cpumask remains the same
1304                  * and has no partition root state.
1305                  */
1306                 if (!cp->partition_root_state &&
1307                     cpumask_equal(tmp->new_cpus, cp->effective_cpus)) {
1308                         pos_css = css_rightmost_descendant(pos_css);
1309                         continue;
1310                 }
1311 
1312                 /*
1313                  * update_parent_subparts_cpumask() should have been called
1314                  * for cs already in update_cpumask(). We should also call
1315                  * update_tasks_cpumask() again for tasks in the parent
1316                  * cpuset if the parent's subparts_cpus changes.
1317                  */
1318                 if ((cp != cs) && cp->partition_root_state) {
1319                         switch (parent->partition_root_state) {
1320                         case PRS_DISABLED:
1321                                 /*
1322                                  * If parent is not a partition root or an
1323                                  * invalid partition root, clear the state
1324                                  * state and the CS_CPU_EXCLUSIVE flag.
1325                                  */
1326                                 WARN_ON_ONCE(cp->partition_root_state
1327                                              != PRS_ERROR);
1328                                 cp->partition_root_state = 0;
1329 
1330                                 /*
1331                                  * clear_bit() is an atomic operation and
1332                                  * readers aren't interested in the state
1333                                  * of CS_CPU_EXCLUSIVE anyway. So we can
1334                                  * just update the flag without holding
1335                                  * the callback_lock.
1336                                  */
1337                                 clear_bit(CS_CPU_EXCLUSIVE, &cp->flags);
1338                                 break;
1339 
1340                         case PRS_ENABLED:
1341                                 if (update_parent_subparts_cpumask(cp, partcmd_update, NULL, tmp))
1342                                         update_tasks_cpumask(parent);
1343                                 break;
1344 
1345                         case PRS_ERROR:
1346                                 /*
1347                                  * When parent is invalid, it has to be too.
1348                                  */
1349                                 cp->partition_root_state = PRS_ERROR;
1350                                 if (cp->nr_subparts_cpus) {
1351                                         cp->nr_subparts_cpus = 0;
1352                                         cpumask_clear(cp->subparts_cpus);
1353                                 }
1354                                 break;
1355                         }
1356                 }
1357 
1358                 if (!css_tryget_online(&cp->css))
1359                         continue;
1360                 rcu_read_unlock();
1361 
1362                 spin_lock_irq(&callback_lock);
1363 
1364                 cpumask_copy(cp->effective_cpus, tmp->new_cpus);
1365                 if (cp->nr_subparts_cpus &&
1366                    (cp->partition_root_state != PRS_ENABLED)) {
1367                         cp->nr_subparts_cpus = 0;
1368                         cpumask_clear(cp->subparts_cpus);
1369                 } else if (cp->nr_subparts_cpus) {
1370                         /*
1371                          * Make sure that effective_cpus & subparts_cpus
1372                          * are mutually exclusive.
1373                          *
1374                          * In the unlikely event that effective_cpus
1375                          * becomes empty. we clear cp->nr_subparts_cpus and
1376                          * let its child partition roots to compete for
1377                          * CPUs again.
1378                          */
1379                         cpumask_andnot(cp->effective_cpus, cp->effective_cpus,
1380                                        cp->subparts_cpus);
1381                         if (cpumask_empty(cp->effective_cpus)) {
1382                                 cpumask_copy(cp->effective_cpus, tmp->new_cpus);
1383                                 cpumask_clear(cp->subparts_cpus);
1384                                 cp->nr_subparts_cpus = 0;
1385                         } else if (!cpumask_subset(cp->subparts_cpus,
1386                                                    tmp->new_cpus)) {
1387                                 cpumask_andnot(cp->subparts_cpus,
1388                                         cp->subparts_cpus, tmp->new_cpus);
1389                                 cp->nr_subparts_cpus
1390                                         = cpumask_weight(cp->subparts_cpus);
1391                         }
1392                 }
1393                 spin_unlock_irq(&callback_lock);
1394 
1395                 WARN_ON(!is_in_v2_mode() &&
1396                         !cpumask_equal(cp->cpus_allowed, cp->effective_cpus));
1397 
1398                 update_tasks_cpumask(cp);
1399 
1400                 /*
1401                  * On legacy hierarchy, if the effective cpumask of any non-
1402                  * empty cpuset is changed, we need to rebuild sched domains.
1403                  * On default hierarchy, the cpuset needs to be a partition
1404                  * root as well.
1405                  */
1406                 if (!cpumask_empty(cp->cpus_allowed) &&
1407                     is_sched_load_balance(cp) &&
1408                    (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||
1409                     is_partition_root(cp)))
1410                         need_rebuild_sched_domains = true;
1411 
1412                 rcu_read_lock();
1413                 css_put(&cp->css);
1414         }
1415         rcu_read_unlock();
1416 
1417         if (need_rebuild_sched_domains)
1418                 rebuild_sched_domains_locked();
1419 }
1420 
1421 /**
1422  * update_sibling_cpumasks - Update siblings cpumasks
1423  * @parent:  Parent cpuset
1424  * @cs:      Current cpuset
1425  * @tmp:     Temp variables
1426  */
1427 static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
1428                                     struct tmpmasks *tmp)
1429 {
1430         struct cpuset *sibling;
1431         struct cgroup_subsys_state *pos_css;
1432 
1433         /*
1434          * Check all its siblings and call update_cpumasks_hier()
1435          * if their use_parent_ecpus flag is set in order for them
1436          * to use the right effective_cpus value.
1437          */
1438         rcu_read_lock();
1439         cpuset_for_each_child(sibling, pos_css, parent) {
1440                 if (sibling == cs)
1441                         continue;
1442                 if (!sibling->use_parent_ecpus)
1443                         continue;
1444 
1445                 update_cpumasks_hier(sibling, tmp);
1446         }
1447         rcu_read_unlock();
1448 }
1449 
1450 /**
1451  * update_cpumask - update the cpus_allowed mask of a cpuset and all tasks in it
1452  * @cs: the cpuset to consider
1453  * @trialcs: trial cpuset
1454  * @buf: buffer of cpu numbers written to this cpuset
1455  */
1456 static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
1457                           const char *buf)
1458 {
1459         int retval;
1460         struct tmpmasks tmp;
1461 
1462         /* top_cpuset.cpus_allowed tracks cpu_online_mask; it's read-only */
1463         if (cs == &top_cpuset)
1464                 return -EACCES;
1465 
1466         /*
1467          * An empty cpus_allowed is ok only if the cpuset has no tasks.
1468          * Since cpulist_parse() fails on an empty mask, we special case
1469          * that parsing.  The validate_change() call ensures that cpusets
1470          * with tasks have cpus.
1471          */
1472         if (!*buf) {
1473                 cpumask_clear(trialcs->cpus_allowed);
1474         } else {
1475                 retval = cpulist_parse(buf, trialcs->cpus_allowed);
1476                 if (retval < 0)
1477                         return retval;
1478 
1479                 if (!cpumask_subset(trialcs->cpus_allowed,
1480                                     top_cpuset.cpus_allowed))
1481                         return -EINVAL;
1482         }
1483 
1484         /* Nothing to do if the cpus didn't change */
1485         if (cpumask_equal(cs->cpus_allowed, trialcs->cpus_allowed))
1486                 return 0;
1487 
1488         retval = validate_change(cs, trialcs);
1489         if (retval < 0)
1490                 return retval;
1491 
1492 #ifdef CONFIG_CPUMASK_OFFSTACK
1493         /*
1494          * Use the cpumasks in trialcs for tmpmasks when they are pointers
1495          * to allocated cpumasks.
1496          */
1497         tmp.addmask  = trialcs->subparts_cpus;
1498         tmp.delmask  = trialcs->effective_cpus;
1499         tmp.new_cpus = trialcs->cpus_allowed;
1500 #endif
1501 
1502         if (cs->partition_root_state) {
1503                 /* Cpumask of a partition root cannot be empty */
1504                 if (cpumask_empty(trialcs->cpus_allowed))
1505                         return -EINVAL;
1506                 if (update_parent_subparts_cpumask(cs, partcmd_update,
1507                                         trialcs->cpus_allowed, &tmp) < 0)
1508                         return -EINVAL;
1509         }
1510 
1511         spin_lock_irq(&callback_lock);
1512         cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
1513 
1514         /*
1515          * Make sure that subparts_cpus is a subset of cpus_allowed.
1516          */
1517         if (cs->nr_subparts_cpus) {
1518                 cpumask_andnot(cs->subparts_cpus, cs->subparts_cpus,
1519                                cs->cpus_allowed);
1520                 cs->nr_subparts_cpus = cpumask_weight(cs->subparts_cpus);
1521         }
1522         spin_unlock_irq(&callback_lock);
1523 
1524         update_cpumasks_hier(cs, &tmp);
1525 
1526         if (cs->partition_root_state) {
1527                 struct cpuset *parent = parent_cs(cs);
1528 
1529                 /*
1530                  * For partition root, update the cpumasks of sibling
1531                  * cpusets if they use parent's effective_cpus.
1532                  */
1533                 if (parent->child_ecpus_count)
1534                         update_sibling_cpumasks(parent, cs, &tmp);
1535         }
1536         return 0;
1537 }
1538 
1539 /*
1540  * Migrate memory region from one set of nodes to another.  This is
1541  * performed asynchronously as it can be called from process migration path
1542  * holding locks involved in process management.  All mm migrations are
1543  * performed in the queued order and can be waited for by flushing
1544  * cpuset_migrate_mm_wq.
1545  */
1546 
1547 struct cpuset_migrate_mm_work {
1548         struct work_struct      work;
1549         struct mm_struct        *mm;
1550         nodemask_t              from;
1551         nodemask_t              to;
1552 };
1553 
1554 static void cpuset_migrate_mm_workfn(struct work_struct *work)
1555 {
1556         struct cpuset_migrate_mm_work *mwork =
1557                 container_of(work, struct cpuset_migrate_mm_work, work);
1558 
1559         /* on a wq worker, no need to worry about %current's mems_allowed */
1560         do_migrate_pages(mwork->mm, &mwork->from, &mwork->to, MPOL_MF_MOVE_ALL);
1561         mmput(mwork->mm);
1562         kfree(mwork);
1563 }
1564 
1565 static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
1566                                                         const nodemask_t *to)
1567 {
1568         struct cpuset_migrate_mm_work *mwork;
1569 
1570         mwork = kzalloc(sizeof(*mwork), GFP_KERNEL);
1571         if (mwork) {
1572                 mwork->mm = mm;
1573                 mwork->from = *from;
1574                 mwork->to = *to;
1575                 INIT_WORK(&mwork->work, cpuset_migrate_mm_workfn);
1576                 queue_work(cpuset_migrate_mm_wq, &mwork->work);
1577         } else {
1578                 mmput(mm);
1579         }
1580 }
1581 
1582 static void cpuset_post_attach(void)
1583 {
1584         flush_workqueue(cpuset_migrate_mm_wq);
1585 }
1586 
1587 /*
1588  * cpuset_change_task_nodemask - change task's mems_allowed and mempolicy
1589  * @tsk: the task to change
1590  * @newmems: new nodes that the task will be set
1591  *
1592  * We use the mems_allowed_seq seqlock to safely update both tsk->mems_allowed
1593  * and rebind an eventual tasks' mempolicy. If the task is allocating in
1594  * parallel, it might temporarily see an empty intersection, which results in
1595  * a seqlock check and retry before OOM or allocation failure.
1596  */
1597 static void cpuset_change_task_nodemask(struct task_struct *tsk,
1598                                         nodemask_t *newmems)
1599 {
1600         task_lock(tsk);
1601 
1602         local_irq_disable();
1603         write_seqcount_begin(&tsk->mems_allowed_seq);
1604 
1605         nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems);
1606         mpol_rebind_task(tsk, newmems);
1607         tsk->mems_allowed = *newmems;
1608 
1609         write_seqcount_end(&tsk->mems_allowed_seq);
1610         local_irq_enable();
1611 
1612         task_unlock(tsk);
1613 }
1614 
1615 static void *cpuset_being_rebound;
1616 
1617 /**
1618  * update_tasks_nodemask - Update the nodemasks of tasks in the cpuset.
1619  * @cs: the cpuset in which each task's mems_allowed mask needs to be changed
1620  *
1621  * Iterate through each task of @cs updating its mems_allowed to the
1622  * effective cpuset's.  As this function is called with cpuset_mutex held,
1623  * cpuset membership stays stable.
1624  */
1625 static void update_tasks_nodemask(struct cpuset *cs)
1626 {
1627         static nodemask_t newmems;      /* protected by cpuset_mutex */
1628         struct css_task_iter it;
1629         struct task_struct *task;
1630 
1631         cpuset_being_rebound = cs;              /* causes mpol_dup() rebind */
1632 
1633         guarantee_online_mems(cs, &newmems);
1634 
1635         /*
1636          * The mpol_rebind_mm() call takes mmap_sem, which we couldn't
1637          * take while holding tasklist_lock.  Forks can happen - the
1638          * mpol_dup() cpuset_being_rebound check will catch such forks,
1639          * and rebind their vma mempolicies too.  Because we still hold
1640          * the global cpuset_mutex, we know that no other rebind effort
1641          * will be contending for the global variable cpuset_being_rebound.
1642          * It's ok if we rebind the same mm twice; mpol_rebind_mm()
1643          * is idempotent.  Also migrate pages in each mm to new nodes.
1644          */
1645         css_task_iter_start(&cs->css, 0, &it);
1646         while ((task = css_task_iter_next(&it))) {
1647                 struct mm_struct *mm;
1648                 bool migrate;
1649 
1650                 cpuset_change_task_nodemask(task, &newmems);
1651 
1652                 mm = get_task_mm(task);
1653                 if (!mm)
1654                         continue;
1655 
1656                 migrate = is_memory_migrate(cs);
1657 
1658                 mpol_rebind_mm(mm, &cs->mems_allowed);
1659                 if (migrate)
1660                         cpuset_migrate_mm(mm, &cs->old_mems_allowed, &newmems);
1661                 else
1662                         mmput(mm);
1663         }
1664         css_task_iter_end(&it);
1665 
1666         /*
1667          * All the tasks' nodemasks have been updated, update
1668          * cs->old_mems_allowed.
1669          */
1670         cs->old_mems_allowed = newmems;
1671 
1672         /* We're done rebinding vmas to this cpuset's new mems_allowed. */
1673         cpuset_being_rebound = NULL;
1674 }
1675 
1676 /*
1677  * update_nodemasks_hier - Update effective nodemasks and tasks in the subtree
1678  * @cs: the cpuset to consider
1679  * @new_mems: a temp variable for calculating new effective_mems
1680  *
1681  * When configured nodemask is changed, the effective nodemasks of this cpuset
1682  * and all its descendants need to be updated.
1683  *
1684  * On legacy hiearchy, effective_mems will be the same with mems_allowed.
1685  *
1686  * Called with cpuset_mutex held
1687  */
1688 static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems)
1689 {
1690         struct cpuset *cp;
1691         struct cgroup_subsys_state *pos_css;
1692 
1693         rcu_read_lock();
1694         cpuset_for_each_descendant_pre(cp, pos_css, cs) {
1695                 struct cpuset *parent = parent_cs(cp);
1696 
1697                 nodes_and(*new_mems, cp->mems_allowed, parent->effective_mems);
1698 
1699                 /*
1700                  * If it becomes empty, inherit the effective mask of the
1701                  * parent, which is guaranteed to have some MEMs.
1702                  */
1703                 if (is_in_v2_mode() && nodes_empty(*new_mems))
1704                         *new_mems = parent->effective_mems;
1705 
1706                 /* Skip the whole subtree if the nodemask remains the same. */
1707                 if (nodes_equal(*new_mems, cp->effective_mems)) {
1708                         pos_css = css_rightmost_descendant(pos_css);
1709                         continue;
1710                 }
1711 
1712                 if (!css_tryget_online(&cp->css))
1713                         continue;
1714                 rcu_read_unlock();
1715 
1716                 spin_lock_irq(&callback_lock);
1717                 cp->effective_mems = *new_mems;
1718                 spin_unlock_irq(&callback_lock);
1719 
1720                 WARN_ON(!is_in_v2_mode() &&
1721                         !nodes_equal(cp->mems_allowed, cp->effective_mems));
1722 
1723                 update_tasks_nodemask(cp);
1724 
1725                 rcu_read_lock();
1726                 css_put(&cp->css);
1727         }
1728         rcu_read_unlock();
1729 }
1730 
1731 /*
1732  * Handle user request to change the 'mems' memory placement
1733  * of a cpuset.  Needs to validate the request, update the
1734  * cpusets mems_allowed, and for each task in the cpuset,
1735  * update mems_allowed and rebind task's mempolicy and any vma
1736  * mempolicies and if the cpuset is marked 'memory_migrate',
1737  * migrate the tasks pages to the new memory.
1738  *
1739  * Call with cpuset_mutex held. May take callback_lock during call.
1740  * Will take tasklist_lock, scan tasklist for tasks in cpuset cs,
1741  * lock each such tasks mm->mmap_sem, scan its vma's and rebind
1742  * their mempolicies to the cpusets new mems_allowed.
1743  */
1744 static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
1745                            const char *buf)
1746 {
1747         int retval;
1748 
1749         /*
1750          * top_cpuset.mems_allowed tracks node_stats[N_MEMORY];
1751          * it's read-only
1752          */
1753         if (cs == &top_cpuset) {
1754                 retval = -EACCES;
1755                 goto done;
1756         }
1757 
1758         /*
1759          * An empty mems_allowed is ok iff there are no tasks in the cpuset.
1760          * Since nodelist_parse() fails on an empty mask, we special case
1761          * that parsing.  The validate_change() call ensures that cpusets
1762          * with tasks have memory.
1763          */
1764         if (!*buf) {
1765                 nodes_clear(trialcs->mems_allowed);
1766         } else {
1767                 retval = nodelist_parse(buf, trialcs->mems_allowed);
1768                 if (retval < 0)
1769                         goto done;
1770 
1771                 if (!nodes_subset(trialcs->mems_allowed,
1772                                   top_cpuset.mems_allowed)) {
1773                         retval = -EINVAL;
1774                         goto done;
1775                 }
1776         }
1777 
1778         if (nodes_equal(cs->mems_allowed, trialcs->mems_allowed)) {
1779                 retval = 0;             /* Too easy - nothing to do */
1780                 goto done;
1781         }
1782         retval = validate_change(cs, trialcs);
1783         if (retval < 0)
1784                 goto done;
1785 
1786         spin_lock_irq(&callback_lock);
1787         cs->mems_allowed = trialcs->mems_allowed;
1788         spin_unlock_irq(&callback_lock);
1789 
1790         /* use trialcs->mems_allowed as a temp variable */
1791         update_nodemasks_hier(cs, &trialcs->mems_allowed);
1792 done:
1793         return retval;
1794 }
1795 
1796 bool current_cpuset_is_being_rebound(void)
1797 {
1798         bool ret;
1799 
1800         rcu_read_lock();
1801         ret = task_cs(current) == cpuset_being_rebound;
1802         rcu_read_unlock();
1803 
1804         return ret;
1805 }
1806 
1807 static int update_relax_domain_level(struct cpuset *cs, s64 val)
1808 {
1809 #ifdef CONFIG_SMP
1810         if (val < -1 || val >= sched_domain_level_max)
1811                 return -EINVAL;
1812 #endif
1813 
1814         if (val != cs->relax_domain_level) {
1815                 cs->relax_domain_level = val;
1816                 if (!cpumask_empty(cs->cpus_allowed) &&
1817                     is_sched_load_balance(cs))
1818                         rebuild_sched_domains_locked();
1819         }
1820 
1821         return 0;
1822 }
1823 
1824 /**
1825  * update_tasks_flags - update the spread flags of tasks in the cpuset.
1826  * @cs: the cpuset in which each task's spread flags needs to be changed
1827  *
1828  * Iterate through each task of @cs updating its spread flags.  As this
1829  * function is called with cpuset_mutex held, cpuset membership stays
1830  * stable.
1831  */
1832 static void update_tasks_flags(struct cpuset *cs)
1833 {
1834         struct css_task_iter it;
1835         struct task_struct *task;
1836 
1837         css_task_iter_start(&cs->css, 0, &it);
1838         while ((task = css_task_iter_next(&it)))
1839                 cpuset_update_task_spread_flag(cs, task);
1840         css_task_iter_end(&it);
1841 }
1842 
1843 /*
1844  * update_flag - read a 0 or a 1 in a file and update associated flag
1845  * bit:         the bit to update (see cpuset_flagbits_t)
1846  * cs:          the cpuset to update
1847  * turning_on:  whether the flag is being set or cleared
1848  *
1849  * Call with cpuset_mutex held.
1850  */
1851 
1852 static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
1853                        int turning_on)
1854 {
1855         struct cpuset *trialcs;
1856         int balance_flag_changed;
1857         int spread_flag_changed;
1858         int err;
1859 
1860         trialcs = alloc_trial_cpuset(cs);
1861         if (!trialcs)
1862                 return -ENOMEM;
1863 
1864         if (turning_on)
1865                 set_bit(bit, &trialcs->flags);
1866         else
1867                 clear_bit(bit, &trialcs->flags);
1868 
1869         err = validate_change(cs, trialcs);
1870         if (err < 0)
1871                 goto out;
1872 
1873         balance_flag_changed = (is_sched_load_balance(cs) !=
1874                                 is_sched_load_balance(trialcs));
1875 
1876         spread_flag_changed = ((is_spread_slab(cs) != is_spread_slab(trialcs))
1877                         || (is_spread_page(cs) != is_spread_page(trialcs)));
1878 
1879         spin_lock_irq(&callback_lock);
1880         cs->flags = trialcs->flags;
1881         spin_unlock_irq(&callback_lock);
1882 
1883         if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed)
1884                 rebuild_sched_domains_locked();
1885 
1886         if (spread_flag_changed)
1887                 update_tasks_flags(cs);
1888 out:
1889         free_cpuset(trialcs);
1890         return err;
1891 }
1892 
1893 /*
1894  * update_prstate - update partititon_root_state
1895  * cs:  the cpuset to update
1896  * val: 0 - disabled, 1 - enabled
1897  *
1898  * Call with cpuset_mutex held.
1899  */
1900 static int update_prstate(struct cpuset *cs, int val)
1901 {
1902         int err;
1903         struct cpuset *parent = parent_cs(cs);
1904         struct tmpmasks tmp;
1905 
1906         if ((val != 0) && (val != 1))
1907                 return -EINVAL;
1908         if (val == cs->partition_root_state)
1909                 return 0;
1910 
1911         /*
1912          * Cannot force a partial or invalid partition root to a full
1913          * partition root.
1914          */
1915         if (val && cs->partition_root_state)
1916                 return -EINVAL;
1917 
1918         if (alloc_cpumasks(NULL, &tmp))
1919                 return -ENOMEM;
1920 
1921         err = -EINVAL;
1922         if (!cs->partition_root_state) {
1923                 /*
1924                  * Turning on partition root requires setting the
1925                  * CS_CPU_EXCLUSIVE bit implicitly as well and cpus_allowed
1926                  * cannot be NULL.
1927                  */
1928                 if (cpumask_empty(cs->cpus_allowed))
1929                         goto out;
1930 
1931                 err = update_flag(CS_CPU_EXCLUSIVE, cs, 1);
1932                 if (err)
1933                         goto out;
1934 
1935                 err = update_parent_subparts_cpumask(cs, partcmd_enable,
1936                                                      NULL, &tmp);
1937                 if (err) {
1938                         update_flag(CS_CPU_EXCLUSIVE, cs, 0);
1939                         goto out;
1940                 }
1941                 cs->partition_root_state = PRS_ENABLED;
1942         } else {
1943                 /*
1944                  * Turning off partition root will clear the
1945                  * CS_CPU_EXCLUSIVE bit.
1946                  */
1947                 if (cs->partition_root_state == PRS_ERROR) {
1948                         cs->partition_root_state = 0;
1949                         update_flag(CS_CPU_EXCLUSIVE, cs, 0);
1950                         err = 0;
1951                         goto out;
1952                 }
1953 
1954                 err = update_parent_subparts_cpumask(cs, partcmd_disable,
1955                                                      NULL, &tmp);
1956                 if (err)
1957                         goto out;
1958 
1959                 cs->partition_root_state = 0;
1960 
1961                 /* Turning off CS_CPU_EXCLUSIVE will not return error */
1962                 update_flag(CS_CPU_EXCLUSIVE, cs, 0);
1963         }
1964 
1965         /*
1966          * Update cpumask of parent's tasks except when it is the top
1967          * cpuset as some system daemons cannot be mapped to other CPUs.
1968          */
1969         if (parent != &top_cpuset)
1970                 update_tasks_cpumask(parent);
1971 
1972         if (parent->child_ecpus_count)
1973                 update_sibling_cpumasks(parent, cs, &tmp);
1974 
1975         rebuild_sched_domains_locked();
1976 out:
1977         free_cpumasks(NULL, &tmp);
1978         return err;
1979 }
1980 
1981 /*
1982  * Frequency meter - How fast is some event occurring?
1983  *
1984  * These routines manage a digitally filtered, constant time based,
1985  * event frequency meter.  There are four routines:
1986  *   fmeter_init() - initialize a frequency meter.
1987  *   fmeter_markevent() - called each time the event happens.
1988  *   fmeter_getrate() - returns the recent rate of such events.
1989  *   fmeter_update() - internal routine used to update fmeter.
1990  *
1991  * A common data structure is passed to each of these routines,
1992  * which is used to keep track of the state required to manage the
1993  * frequency meter and its digital filter.
1994  *
1995  * The filter works on the number of events marked per unit time.
1996  * The filter is single-pole low-pass recursive (IIR).  The time unit
1997  * is 1 second.  Arithmetic is done using 32-bit integers scaled to
1998  * simulate 3 decimal digits of precision (multiplied by 1000).
1999  *
2000  * With an FM_COEF of 933, and a time base of 1 second, the filter
2001  * has a half-life of 10 seconds, meaning that if the events quit
2002  * happening, then the rate returned from the fmeter_getrate()
2003  * will be cut in half each 10 seconds, until it converges to zero.
2004  *
2005  * It is not worth doing a real infinitely recursive filter.  If more
2006  * than FM_MAXTICKS ticks have elapsed since the last filter event,
2007  * just compute FM_MAXTICKS ticks worth, by which point the level
2008  * will be stable.
2009  *
2010  * Limit the count of unprocessed events to FM_MAXCNT, so as to avoid
2011  * arithmetic overflow in the fmeter_update() routine.
2012  *
2013  * Given the simple 32 bit integer arithmetic used, this meter works
2014  * best for reporting rates between one per millisecond (msec) and
2015  * one per 32 (approx) seconds.  At constant rates faster than one
2016  * per msec it maxes out at values just under 1,000,000.  At constant
2017  * rates between one per msec, and one per second it will stabilize
2018  * to a value N*1000, where N is the rate of events per second.
2019  * At constant rates between one per second and one per 32 seconds,
2020  * it will be choppy, moving up on the seconds that have an event,
2021  * and then decaying until the next event.  At rates slower than
2022  * about one in 32 seconds, it decays all the way back to zero between
2023  * each event.
2024  */
2025 
2026 #define FM_COEF 933             /* coefficient for half-life of 10 secs */
2027 #define FM_MAXTICKS ((u32)99)   /* useless computing more ticks than this */
2028 #define FM_MAXCNT 1000000       /* limit cnt to avoid overflow */
2029 #define FM_SCALE 1000           /* faux fixed point scale */
2030 
2031 /* Initialize a frequency meter */
2032 static void fmeter_init(struct fmeter *fmp)
2033 {
2034         fmp->cnt = 0;
2035         fmp->val = 0;
2036         fmp->time = 0;
2037         spin_lock_init(&fmp->lock);
2038 }
2039 
2040 /* Internal meter update - process cnt events and update value */
2041 static void fmeter_update(struct fmeter *fmp)
2042 {
2043         time64_t now;
2044         u32 ticks;
2045 
2046         now = ktime_get_seconds();
2047         ticks = now - fmp->time;
2048 
2049         if (ticks == 0)
2050                 return;
2051 
2052         ticks = min(FM_MAXTICKS, ticks);
2053         while (ticks-- > 0)
2054                 fmp->val = (FM_COEF * fmp->val) / FM_SCALE;
2055         fmp->time = now;
2056 
2057         fmp->val += ((FM_SCALE - FM_COEF) * fmp->cnt) / FM_SCALE;
2058         fmp->cnt = 0;
2059 }
2060 
2061 /* Process any previous ticks, then bump cnt by one (times scale). */
2062 static void fmeter_markevent(struct fmeter *fmp)
2063 {
2064         spin_lock(&fmp->lock);
2065         fmeter_update(fmp);
2066         fmp->cnt = min(FM_MAXCNT, fmp->cnt + FM_SCALE);
2067         spin_unlock(&fmp->lock);
2068 }
2069 
2070 /* Process any previous ticks, then return current value. */
2071 static int fmeter_getrate(struct fmeter *fmp)
2072 {
2073         int val;
2074 
2075         spin_lock(&fmp->lock);
2076         fmeter_update(fmp);
2077         val = fmp->val;
2078         spin_unlock(&fmp->lock);
2079         return val;
2080 }
2081 
2082 static struct cpuset *cpuset_attach_old_cs;
2083 
2084 /* Called by cgroups to determine if a cpuset is usable; cpuset_mutex held */
2085 static int cpuset_can_attach(struct cgroup_taskset *tset)
2086 {
2087         struct cgroup_subsys_state *css;
2088         struct cpuset *cs;
2089         struct task_struct *task;
2090         int ret;
2091 
2092         /* used later by cpuset_attach() */
2093         cpuset_attach_old_cs = task_cs(cgroup_taskset_first(tset, &css));
2094         cs = css_cs(css);
2095 
2096         mutex_lock(&cpuset_mutex);
2097 
2098         /* allow moving tasks into an empty cpuset if on default hierarchy */
2099         ret = -ENOSPC;
2100         if (!is_in_v2_mode() &&
2101             (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed)))
2102                 goto out_unlock;
2103 
2104         cgroup_taskset_for_each(task, css, tset) {
2105                 ret = task_can_attach(task, cs->cpus_allowed);
2106                 if (ret)
2107                         goto out_unlock;
2108                 ret = security_task_setscheduler(task);
2109                 if (ret)
2110                         goto out_unlock;
2111         }
2112 
2113         /*
2114          * Mark attach is in progress.  This makes validate_change() fail
2115          * changes which zero cpus/mems_allowed.
2116          */
2117         cs->attach_in_progress++;
2118         ret = 0;
2119 out_unlock:
2120         mutex_unlock(&cpuset_mutex);
2121         return ret;
2122 }
2123 
2124 static void cpuset_cancel_attach(struct cgroup_taskset *tset)
2125 {
2126         struct cgroup_subsys_state *css;
2127 
2128         cgroup_taskset_first(tset, &css);
2129 
2130         mutex_lock(&cpuset_mutex);
2131         css_cs(css)->attach_in_progress--;
2132         mutex_unlock(&cpuset_mutex);
2133 }
2134 
2135 /*
2136  * Protected by cpuset_mutex.  cpus_attach is used only by cpuset_attach()
2137  * but we can't allocate it dynamically there.  Define it global and
2138  * allocate from cpuset_init().
2139  */
2140 static cpumask_var_t cpus_attach;
2141 
2142 static void cpuset_attach(struct cgroup_taskset *tset)
2143 {
2144         /* static buf protected by cpuset_mutex */
2145         static nodemask_t cpuset_attach_nodemask_to;
2146         struct task_struct *task;
2147         struct task_struct *leader;
2148         struct cgroup_subsys_state *css;
2149         struct cpuset *cs;
2150         struct cpuset *oldcs = cpuset_attach_old_cs;
2151 
2152         cgroup_taskset_first(tset, &css);
2153         cs = css_cs(css);
2154 
2155         mutex_lock(&cpuset_mutex);
2156 
2157         /* prepare for attach */
2158         if (cs == &top_cpuset)
2159                 cpumask_copy(cpus_attach, cpu_possible_mask);
2160         else
2161                 guarantee_online_cpus(cs, cpus_attach);
2162 
2163         guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
2164 
2165         cgroup_taskset_for_each(task, css, tset) {
2166                 /*
2167                  * can_attach beforehand should guarantee that this doesn't
2168                  * fail.  TODO: have a better way to handle failure here
2169                  */
2170                 WARN_ON_ONCE(set_cpus_allowed_ptr(task, cpus_attach));
2171 
2172                 cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to);
2173                 cpuset_update_task_spread_flag(cs, task);
2174         }
2175 
2176         /*
2177          * Change mm for all threadgroup leaders. This is expensive and may
2178          * sleep and should be moved outside migration path proper.
2179          */
2180         cpuset_attach_nodemask_to = cs->effective_mems;
2181         cgroup_taskset_for_each_leader(leader, css, tset) {
2182                 struct mm_struct *mm = get_task_mm(leader);
2183 
2184                 if (mm) {
2185                         mpol_rebind_mm(mm, &cpuset_attach_nodemask_to);
2186 
2187                         /*
2188                          * old_mems_allowed is the same with mems_allowed
2189                          * here, except if this task is being moved
2190                          * automatically due to hotplug.  In that case
2191                          * @mems_allowed has been updated and is empty, so
2192                          * @old_mems_allowed is the right nodesets that we
2193                          * migrate mm from.
2194                          */
2195                         if (is_memory_migrate(cs))
2196                                 cpuset_migrate_mm(mm, &oldcs->old_mems_allowed,
2197                                                   &cpuset_attach_nodemask_to);
2198                         else
2199                                 mmput(mm);
2200                 }
2201         }
2202 
2203         cs->old_mems_allowed = cpuset_attach_nodemask_to;
2204 
2205         cs->attach_in_progress--;
2206         if (!cs->attach_in_progress)
2207                 wake_up(&cpuset_attach_wq);
2208 
2209         mutex_unlock(&cpuset_mutex);
2210 }
2211 
2212 /* The various types of files and directories in a cpuset file system */
2213 
2214 typedef enum {
2215         FILE_MEMORY_MIGRATE,
2216         FILE_CPULIST,
2217         FILE_MEMLIST,
2218         FILE_EFFECTIVE_CPULIST,
2219         FILE_EFFECTIVE_MEMLIST,
2220         FILE_SUBPARTS_CPULIST,
2221         FILE_CPU_EXCLUSIVE,
2222         FILE_MEM_EXCLUSIVE,
2223         FILE_MEM_HARDWALL,
2224         FILE_SCHED_LOAD_BALANCE,
2225         FILE_PARTITION_ROOT,
2226         FILE_SCHED_RELAX_DOMAIN_LEVEL,
2227         FILE_MEMORY_PRESSURE_ENABLED,
2228         FILE_MEMORY_PRESSURE,
2229         FILE_SPREAD_PAGE,
2230         FILE_SPREAD_SLAB,
2231 } cpuset_filetype_t;
2232 
2233 static int cpuset_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
2234                             u64 val)
2235 {
2236         struct cpuset *cs = css_cs(css);
2237         cpuset_filetype_t type = cft->private;
2238         int retval = 0;
2239 
2240         mutex_lock(&cpuset_mutex);
2241         if (!is_cpuset_online(cs)) {
2242                 retval = -ENODEV;
2243                 goto out_unlock;
2244         }
2245 
2246         switch (type) {
2247         case FILE_CPU_EXCLUSIVE:
2248                 retval = update_flag(CS_CPU_EXCLUSIVE, cs, val);
2249                 break;
2250         case FILE_MEM_EXCLUSIVE:
2251                 retval = update_flag(CS_MEM_EXCLUSIVE, cs, val);
2252                 break;
2253         case FILE_MEM_HARDWALL:
2254                 retval = update_flag(CS_MEM_HARDWALL, cs, val);
2255                 break;
2256         case FILE_SCHED_LOAD_BALANCE:
2257                 retval = update_flag(CS_SCHED_LOAD_BALANCE, cs, val);
2258                 break;
2259         case FILE_MEMORY_MIGRATE:
2260                 retval = update_flag(CS_MEMORY_MIGRATE, cs, val);
2261                 break;
2262         case FILE_MEMORY_PRESSURE_ENABLED:
2263                 cpuset_memory_pressure_enabled = !!val;
2264                 break;
2265         case FILE_SPREAD_PAGE:
2266                 retval = update_flag(CS_SPREAD_PAGE, cs, val);
2267                 break;
2268         case FILE_SPREAD_SLAB:
2269                 retval = update_flag(CS_SPREAD_SLAB, cs, val);
2270                 break;
2271         default:
2272                 retval = -EINVAL;
2273                 break;
2274         }
2275 out_unlock:
2276         mutex_unlock(&cpuset_mutex);
2277         return retval;
2278 }
2279 
2280 static int cpuset_write_s64(struct cgroup_subsys_state *css, struct cftype *cft,
2281                             s64 val)
2282 {
2283         struct cpuset *cs = css_cs(css);
2284         cpuset_filetype_t type = cft->private;
2285         int retval = -ENODEV;
2286 
2287         mutex_lock(&cpuset_mutex);
2288         if (!is_cpuset_online(cs))
2289                 goto out_unlock;
2290 
2291         switch (type) {
2292         case FILE_SCHED_RELAX_DOMAIN_LEVEL:
2293                 retval = update_relax_domain_level(cs, val);
2294                 break;
2295         default:
2296                 retval = -EINVAL;
2297                 break;
2298         }
2299 out_unlock:
2300         mutex_unlock(&cpuset_mutex);
2301         return retval;
2302 }
2303 
2304 /*
2305  * Common handling for a write to a "cpus" or "mems" file.
2306  */
2307 static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
2308                                     char *buf, size_t nbytes, loff_t off)
2309 {
2310         struct cpuset *cs = css_cs(of_css(of));
2311         struct cpuset *trialcs;
2312         int retval = -ENODEV;
2313 
2314         buf = strstrip(buf);
2315 
2316         /*
2317          * CPU or memory hotunplug may leave @cs w/o any execution
2318          * resources, in which case the hotplug code asynchronously updates
2319          * configuration and transfers all tasks to the nearest ancestor
2320          * which can execute.
2321          *
2322          * As writes to "cpus" or "mems" may restore @cs's execution
2323          * resources, wait for the previously scheduled operations before
2324          * proceeding, so that we don't end up keep removing tasks added
2325          * after execution capability is restored.
2326          *
2327          * cpuset_hotplug_work calls back into cgroup core via
2328          * cgroup_transfer_tasks() and waiting for it from a cgroupfs
2329          * operation like this one can lead to a deadlock through kernfs
2330          * active_ref protection.  Let's break the protection.  Losing the
2331          * protection is okay as we check whether @cs is online after
2332          * grabbing cpuset_mutex anyway.  This only happens on the legacy
2333          * hierarchies.
2334          */
2335         css_get(&cs->css);
2336         kernfs_break_active_protection(of->kn);
2337         flush_work(&cpuset_hotplug_work);
2338 
2339         mutex_lock(&cpuset_mutex);
2340         if (!is_cpuset_online(cs))
2341                 goto out_unlock;
2342 
2343         trialcs = alloc_trial_cpuset(cs);
2344         if (!trialcs) {
2345                 retval = -ENOMEM;
2346                 goto out_unlock;
2347         }
2348 
2349         switch (of_cft(of)->private) {
2350         case FILE_CPULIST:
2351                 retval = update_cpumask(cs, trialcs, buf);
2352                 break;
2353         case FILE_MEMLIST:
2354                 retval = update_nodemask(cs, trialcs, buf);
2355                 break;
2356         default:
2357                 retval = -EINVAL;
2358                 break;
2359         }
2360 
2361         free_cpuset(trialcs);
2362 out_unlock:
2363         mutex_unlock(&cpuset_mutex);
2364         kernfs_unbreak_active_protection(of->kn);
2365         css_put(&cs->css);
2366         flush_workqueue(cpuset_migrate_mm_wq);
2367         return retval ?: nbytes;
2368 }
2369 
2370 /*
2371  * These ascii lists should be read in a single call, by using a user
2372  * buffer large enough to hold the entire map.  If read in smaller
2373  * chunks, there is no guarantee of atomicity.  Since the display format
2374  * used, list of ranges of sequential numbers, is variable length,
2375  * and since these maps can change value dynamically, one could read
2376  * gibberish by doing partial reads while a list was changing.
2377  */
2378 static int cpuset_common_seq_show(struct seq_file *sf, void *v)
2379 {
2380         struct cpuset *cs = css_cs(seq_css(sf));
2381         cpuset_filetype_t type = seq_cft(sf)->private;
2382         int ret = 0;
2383 
2384         spin_lock_irq(&callback_lock);
2385 
2386         switch (type) {
2387         case FILE_CPULIST:
2388                 seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->cpus_allowed));
2389                 break;
2390         case FILE_MEMLIST:
2391                 seq_printf(sf, "%*pbl\n", nodemask_pr_args(&cs->mems_allowed));
2392                 break;
2393         case FILE_EFFECTIVE_CPULIST:
2394                 seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->effective_cpus));
2395                 break;
2396         case FILE_EFFECTIVE_MEMLIST:
2397                 seq_printf(sf, "%*pbl\n", nodemask_pr_args(&cs->effective_mems));
2398                 break;
2399         case FILE_SUBPARTS_CPULIST:
2400                 seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->subparts_cpus));
2401                 break;
2402         default:
2403                 ret = -EINVAL;
2404         }
2405 
2406         spin_unlock_irq(&callback_lock);
2407         return ret;
2408 }
2409 
2410 static u64 cpuset_read_u64(struct cgroup_subsys_state *css, struct cftype *cft)
2411 {
2412         struct cpuset *cs = css_cs(css);
2413         cpuset_filetype_t type = cft->private;
2414         switch (type) {
2415         case FILE_CPU_EXCLUSIVE:
2416                 return is_cpu_exclusive(cs);
2417         case FILE_MEM_EXCLUSIVE:
2418                 return is_mem_exclusive(cs);
2419         case FILE_MEM_HARDWALL:
2420                 return is_mem_hardwall(cs);
2421         case FILE_SCHED_LOAD_BALANCE:
2422                 return is_sched_load_balance(cs);
2423         case FILE_MEMORY_MIGRATE:
2424                 return is_memory_migrate(cs);
2425         case FILE_MEMORY_PRESSURE_ENABLED:
2426                 return cpuset_memory_pressure_enabled;
2427         case FILE_MEMORY_PRESSURE:
2428                 return fmeter_getrate(&cs->fmeter);
2429         case FILE_SPREAD_PAGE:
2430                 return is_spread_page(cs);
2431         case FILE_SPREAD_SLAB:
2432                 return is_spread_slab(cs);
2433         default:
2434                 BUG();
2435         }
2436 
2437         /* Unreachable but makes gcc happy */
2438         return 0;
2439 }
2440 
2441 static s64 cpuset_read_s64(struct cgroup_subsys_state *css, struct cftype *cft)
2442 {
2443         struct cpuset *cs = css_cs(css);
2444         cpuset_filetype_t type = cft->private;
2445         switch (type) {
2446         case FILE_SCHED_RELAX_DOMAIN_LEVEL:
2447                 return cs->relax_domain_level;
2448         default:
2449                 BUG();
2450         }
2451 
2452         /* Unrechable but makes gcc happy */
2453         return 0;
2454 }
2455 
2456 static int sched_partition_show(struct seq_file *seq, void *v)
2457 {
2458         struct cpuset *cs = css_cs(seq_css(seq));
2459 
2460         switch (cs->partition_root_state) {
2461         case PRS_ENABLED:
2462                 seq_puts(seq, "root\n");
2463                 break;
2464         case PRS_DISABLED:
2465                 seq_puts(seq, "member\n");
2466                 break;
2467         case PRS_ERROR:
2468                 seq_puts(seq, "root invalid\n");
2469                 break;
2470         }
2471         return 0;
2472 }
2473 
2474 static ssize_t sched_partition_write(struct kernfs_open_file *of, char *buf,
2475                                      size_t nbytes, loff_t off)
2476 {
2477         struct cpuset *cs = css_cs(of_css(of));
2478         int val;
2479         int retval = -ENODEV;
2480 
2481         buf = strstrip(buf);
2482 
2483         /*
2484          * Convert "root" to ENABLED, and convert "member" to DISABLED.
2485          */
2486         if (!strcmp(buf, "root"))
2487                 val = PRS_ENABLED;
2488         else if (!strcmp(buf, "member"))
2489                 val = PRS_DISABLED;
2490         else
2491                 return -EINVAL;
2492 
2493         css_get(&cs->css);
2494         mutex_lock(&cpuset_mutex);
2495         if (!is_cpuset_online(cs))
2496                 goto out_unlock;
2497 
2498         retval = update_prstate(cs, val);
2499 out_unlock:
2500         mutex_unlock(&cpuset_mutex);
2501         css_put(&cs->css);
2502         return retval ?: nbytes;
2503 }
2504 
2505 /*
2506  * for the common functions, 'private' gives the type of file
2507  */
2508 
2509 static struct cftype legacy_files[] = {
2510         {
2511                 .name = "cpus",
2512                 .seq_show = cpuset_common_seq_show,
2513                 .write = cpuset_write_resmask,
2514                 .max_write_len = (100U + 6 * NR_CPUS),
2515                 .private = FILE_CPULIST,
2516         },
2517 
2518         {
2519                 .name = "mems",
2520                 .seq_show = cpuset_common_seq_show,
2521                 .write = cpuset_write_resmask,
2522                 .max_write_len = (100U + 6 * MAX_NUMNODES),
2523                 .private = FILE_MEMLIST,
2524         },
2525 
2526         {
2527                 .name = "effective_cpus",
2528                 .seq_show = cpuset_common_seq_show,
2529                 .private = FILE_EFFECTIVE_CPULIST,
2530         },
2531 
2532         {
2533                 .name = "effective_mems",
2534                 .seq_show = cpuset_common_seq_show,
2535                 .private = FILE_EFFECTIVE_MEMLIST,
2536         },
2537 
2538         {
2539                 .name = "cpu_exclusive",
2540                 .read_u64 = cpuset_read_u64,
2541                 .write_u64 = cpuset_write_u64,
2542                 .private = FILE_CPU_EXCLUSIVE,
2543         },
2544 
2545         {
2546                 .name = "mem_exclusive",
2547                 .read_u64 = cpuset_read_u64,
2548                 .write_u64 = cpuset_write_u64,
2549                 .private = FILE_MEM_EXCLUSIVE,
2550         },
2551 
2552         {
2553                 .name = "mem_hardwall",
2554                 .read_u64 = cpuset_read_u64,
2555                 .write_u64 = cpuset_write_u64,
2556                 .private = FILE_MEM_HARDWALL,
2557         },
2558 
2559         {
2560                 .name = "sched_load_balance",
2561                 .read_u64 = cpuset_read_u64,
2562                 .write_u64 = cpuset_write_u64,
2563                 .private = FILE_SCHED_LOAD_BALANCE,
2564         },
2565 
2566         {
2567                 .name = "sched_relax_domain_level",
2568                 .read_s64 = cpuset_read_s64,
2569                 .write_s64 = cpuset_write_s64,
2570                 .private = FILE_SCHED_RELAX_DOMAIN_LEVEL,
2571         },
2572 
2573         {
2574                 .name = "memory_migrate",
2575                 .read_u64 = cpuset_read_u64,
2576                 .write_u64 = cpuset_write_u64,
2577                 .private = FILE_MEMORY_MIGRATE,
2578         },
2579 
2580         {
2581                 .name = "memory_pressure",
2582                 .read_u64 = cpuset_read_u64,
2583                 .private = FILE_MEMORY_PRESSURE,
2584         },
2585 
2586         {
2587                 .name = "memory_spread_page",
2588                 .read_u64 = cpuset_read_u64,
2589                 .write_u64 = cpuset_write_u64,
2590                 .private = FILE_SPREAD_PAGE,
2591         },
2592 
2593         {
2594                 .name = "memory_spread_slab",
2595                 .read_u64 = cpuset_read_u64,
2596                 .write_u64 = cpuset_write_u64,
2597                 .private = FILE_SPREAD_SLAB,
2598         },
2599 
2600         {
2601                 .name = "memory_pressure_enabled",
2602                 .flags = CFTYPE_ONLY_ON_ROOT,
2603                 .read_u64 = cpuset_read_u64,
2604                 .write_u64 = cpuset_write_u64,
2605                 .private = FILE_MEMORY_PRESSURE_ENABLED,
2606         },
2607 
2608         { }     /* terminate */
2609 };
2610 
2611 /*
2612  * This is currently a minimal set for the default hierarchy. It can be
2613  * expanded later on by migrating more features and control files from v1.
2614  */
2615 static struct cftype dfl_files[] = {
2616         {
2617                 .name = "cpus",
2618                 .seq_show = cpuset_common_seq_show,
2619                 .write = cpuset_write_resmask,
2620                 .max_write_len = (100U + 6 * NR_CPUS),
2621                 .private = FILE_CPULIST,
2622                 .flags = CFTYPE_NOT_ON_ROOT,
2623         },
2624 
2625         {
2626                 .name = "mems",
2627                 .seq_show = cpuset_common_seq_show,
2628                 .write = cpuset_write_resmask,
2629                 .max_write_len = (100U + 6 * MAX_NUMNODES),
2630                 .private = FILE_MEMLIST,
2631                 .flags = CFTYPE_NOT_ON_ROOT,
2632         },
2633 
2634         {
2635                 .name = "cpus.effective",
2636                 .seq_show = cpuset_common_seq_show,
2637                 .private = FILE_EFFECTIVE_CPULIST,
2638         },
2639 
2640         {
2641                 .name = "mems.effective",
2642                 .seq_show = cpuset_common_seq_show,
2643                 .private = FILE_EFFECTIVE_MEMLIST,
2644         },
2645 
2646         {
2647                 .name = "cpus.partition",
2648                 .seq_show = sched_partition_show,
2649                 .write = sched_partition_write,
2650                 .private = FILE_PARTITION_ROOT,
2651                 .flags = CFTYPE_NOT_ON_ROOT,
2652         },
2653 
2654         {
2655                 .name = "cpus.subpartitions",
2656                 .seq_show = cpuset_common_seq_show,
2657                 .private = FILE_SUBPARTS_CPULIST,
2658                 .flags = CFTYPE_DEBUG,
2659         },
2660 
2661         { }     /* terminate */
2662 };
2663 
2664 
2665 /*
2666  *      cpuset_css_alloc - allocate a cpuset css
2667  *      cgrp:   control group that the new cpuset will be part of
2668  */
2669 
2670 static struct cgroup_subsys_state *
2671 cpuset_css_alloc(struct cgroup_subsys_state *parent_css)
2672 {
2673         struct cpuset *cs;
2674 
2675         if (!parent_css)
2676                 return &top_cpuset.css;
2677 
2678         cs = kzalloc(sizeof(*cs), GFP_KERNEL);
2679         if (!cs)
2680                 return ERR_PTR(-ENOMEM);
2681 
2682         if (alloc_cpumasks(cs, NULL)) {
2683                 kfree(cs);
2684                 return ERR_PTR(-ENOMEM);
2685         }
2686 
2687         set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
2688         nodes_clear(cs->mems_allowed);
2689         nodes_clear(cs->effective_mems);
2690         fmeter_init(&cs->fmeter);
2691         cs->relax_domain_level = -1;
2692 
2693         return &cs->css;
2694 }
2695 
2696 static int cpuset_css_online(struct cgroup_subsys_state *css)
2697 {
2698         struct cpuset *cs = css_cs(css);
2699         struct cpuset *parent = parent_cs(cs);
2700         struct cpuset *tmp_cs;
2701         struct cgroup_subsys_state *pos_css;
2702 
2703         if (!parent)
2704                 return 0;
2705 
2706         mutex_lock(&cpuset_mutex);
2707 
2708         set_bit(CS_ONLINE, &cs->flags);
2709         if (is_spread_page(parent))
2710                 set_bit(CS_SPREAD_PAGE, &cs->flags);
2711         if (is_spread_slab(parent))
2712                 set_bit(CS_SPREAD_SLAB, &cs->flags);
2713 
2714         cpuset_inc();
2715 
2716         spin_lock_irq(&callback_lock);
2717         if (is_in_v2_mode()) {
2718                 cpumask_copy(cs->effective_cpus, parent->effective_cpus);
2719                 cs->effective_mems = parent->effective_mems;
2720                 cs->use_parent_ecpus = true;
2721                 parent->child_ecpus_count++;
2722         }
2723         spin_unlock_irq(&callback_lock);
2724 
2725         if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags))
2726                 goto out_unlock;
2727 
2728         /*
2729          * Clone @parent's configuration if CGRP_CPUSET_CLONE_CHILDREN is
2730          * set.  This flag handling is implemented in cgroup core for
2731          * histrical reasons - the flag may be specified during mount.
2732          *
2733          * Currently, if any sibling cpusets have exclusive cpus or mem, we
2734          * refuse to clone the configuration - thereby refusing the task to
2735          * be entered, and as a result refusing the sys_unshare() or
2736          * clone() which initiated it.  If this becomes a problem for some
2737          * users who wish to allow that scenario, then this could be
2738          * changed to grant parent->cpus_allowed-sibling_cpus_exclusive
2739          * (and likewise for mems) to the new cgroup.
2740          */
2741         rcu_read_lock();
2742         cpuset_for_each_child(tmp_cs, pos_css, parent) {
2743                 if (is_mem_exclusive(tmp_cs) || is_cpu_exclusive(tmp_cs)) {
2744                         rcu_read_unlock();
2745                         goto out_unlock;
2746                 }
2747         }
2748         rcu_read_unlock();
2749 
2750         spin_lock_irq(&callback_lock);
2751         cs->mems_allowed = parent->mems_allowed;
2752         cs->effective_mems = parent->mems_allowed;
2753         cpumask_copy(cs->cpus_allowed, parent->cpus_allowed);
2754         cpumask_copy(cs->effective_cpus, parent->cpus_allowed);
2755         spin_unlock_irq(&callback_lock);
2756 out_unlock:
2757         mutex_unlock(&cpuset_mutex);
2758         return 0;
2759 }
2760 
2761 /*
2762  * If the cpuset being removed has its flag 'sched_load_balance'
2763  * enabled, then simulate turning sched_load_balance off, which
2764  * will call rebuild_sched_domains_locked(). That is not needed
2765  * in the default hierarchy where only changes in partition
2766  * will cause repartitioning.
2767  *
2768  * If the cpuset has the 'sched.partition' flag enabled, simulate
2769  * turning 'sched.partition" off.
2770  */
2771 
2772 static void cpuset_css_offline(struct cgroup_subsys_state *css)
2773 {
2774         struct cpuset *cs = css_cs(css);
2775 
2776         mutex_lock(&cpuset_mutex);
2777 
2778         if (is_partition_root(cs))
2779                 update_prstate(cs, 0);
2780 
2781         if (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
2782             is_sched_load_balance(cs))
2783                 update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
2784 
2785         if (cs->use_parent_ecpus) {
2786                 struct cpuset *parent = parent_cs(cs);
2787 
2788                 cs->use_parent_ecpus = false;
2789                 parent->child_ecpus_count--;
2790         }
2791 
2792         cpuset_dec();
2793         clear_bit(CS_ONLINE, &cs->flags);
2794 
2795         mutex_unlock(&cpuset_mutex);
2796 }
2797 
2798 static void cpuset_css_free(struct cgroup_subsys_state *css)
2799 {
2800         struct cpuset *cs = css_cs(css);
2801 
2802         free_cpuset(cs);
2803 }
2804 
2805 static void cpuset_bind(struct cgroup_subsys_state *root_css)
2806 {
2807         mutex_lock(&cpuset_mutex);
2808         spin_lock_irq(&callback_lock);
2809 
2810         if (is_in_v2_mode()) {
2811                 cpumask_copy(top_cpuset.cpus_allowed, cpu_possible_mask);
2812                 top_cpuset.mems_allowed = node_possible_map;
2813         } else {
2814                 cpumask_copy(top_cpuset.cpus_allowed,
2815                              top_cpuset.effective_cpus);
2816                 top_cpuset.mems_allowed = top_cpuset.effective_mems;
2817         }
2818 
2819         spin_unlock_irq(&callback_lock);
2820         mutex_unlock(&cpuset_mutex);
2821 }
2822 
2823 /*
2824  * Make sure the new task conform to the current state of its parent,
2825  * which could have been changed by cpuset just after it inherits the
2826  * state from the parent and before it sits on the cgroup's task list.
2827  */
2828 static void cpuset_fork(struct task_struct *task)
2829 {
2830         if (task_css_is_root(task, cpuset_cgrp_id))
2831                 return;
2832 
2833         set_cpus_allowed_ptr(task, &current->cpus_allowed);
2834         task->mems_allowed = current->mems_allowed;
2835 }
2836 
2837 struct cgroup_subsys cpuset_cgrp_subsys = {
2838         .css_alloc      = cpuset_css_alloc,
2839         .css_online     = cpuset_css_online,
2840         .css_offline    = cpuset_css_offline,
2841         .css_free       = cpuset_css_free,
2842         .can_attach     = cpuset_can_attach,
2843         .cancel_attach  = cpuset_cancel_attach,
2844         .attach         = cpuset_attach,
2845         .post_attach    = cpuset_post_attach,
2846         .bind           = cpuset_bind,
2847         .fork           = cpuset_fork,
2848         .legacy_cftypes = legacy_files,
2849         .dfl_cftypes    = dfl_files,
2850         .early_init     = true,
2851         .threaded       = true,
2852 };
2853 
2854 /**
2855  * cpuset_init - initialize cpusets at system boot
2856  *
2857  * Description: Initialize top_cpuset and the cpuset internal file system,
2858  **/
2859 
2860 int __init cpuset_init(void)
2861 {
2862         int err = 0;
2863 
2864         BUG_ON(!alloc_cpumask_var(&top_cpuset.cpus_allowed, GFP_KERNEL));
2865         BUG_ON(!alloc_cpumask_var(&top_cpuset.effective_cpus, GFP_KERNEL));
2866         BUG_ON(!zalloc_cpumask_var(&top_cpuset.subparts_cpus, GFP_KERNEL));
2867 
2868         cpumask_setall(top_cpuset.cpus_allowed);
2869         nodes_setall(top_cpuset.mems_allowed);
2870         cpumask_setall(top_cpuset.effective_cpus);
2871         nodes_setall(top_cpuset.effective_mems);
2872 
2873         fmeter_init(&top_cpuset.fmeter);
2874         set_bit(CS_SCHED_LOAD_BALANCE, &top_cpuset.flags);
2875         top_cpuset.relax_domain_level = -1;
2876 
2877         err = register_filesystem(&cpuset_fs_type);
2878         if (err < 0)
2879                 return err;
2880 
2881         BUG_ON(!alloc_cpumask_var(&cpus_attach, GFP_KERNEL));
2882 
2883         return 0;
2884 }
2885 
2886 /*
2887  * If CPU and/or memory hotplug handlers, below, unplug any CPUs
2888  * or memory nodes, we need to walk over the cpuset hierarchy,
2889  * removing that CPU or node from all cpusets.  If this removes the
2890  * last CPU or node from a cpuset, then move the tasks in the empty
2891  * cpuset to its next-highest non-empty parent.
2892  */
2893 static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
2894 {
2895         struct cpuset *parent;
2896 
2897         /*
2898          * Find its next-highest non-empty parent, (top cpuset
2899          * has online cpus, so can't be empty).
2900          */
2901         parent = parent_cs(cs);
2902         while (cpumask_empty(parent->cpus_allowed) ||
2903                         nodes_empty(parent->mems_allowed))
2904                 parent = parent_cs(parent);
2905 
2906         if (cgroup_transfer_tasks(parent->css.cgroup, cs->css.cgroup)) {
2907                 pr_err("cpuset: failed to transfer tasks out of empty cpuset ");
2908                 pr_cont_cgroup_name(cs->css.cgroup);
2909                 pr_cont("\n");
2910         }
2911 }
2912 
2913 static void
2914 hotplug_update_tasks_legacy(struct cpuset *cs,
2915                             struct cpumask *new_cpus, nodemask_t *new_mems,
2916                             bool cpus_updated, bool mems_updated)
2917 {
2918         bool is_empty;
2919 
2920         spin_lock_irq(&callback_lock);
2921         cpumask_copy(cs->cpus_allowed, new_cpus);
2922         cpumask_copy(cs->effective_cpus, new_cpus);
2923         cs->mems_allowed = *new_mems;
2924         cs->effective_mems = *new_mems;
2925         spin_unlock_irq(&callback_lock);
2926 
2927         /*
2928          * Don't call update_tasks_cpumask() if the cpuset becomes empty,
2929          * as the tasks will be migratecd to an ancestor.
2930          */
2931         if (cpus_updated && !cpumask_empty(cs->cpus_allowed))
2932                 update_tasks_cpumask(cs);
2933         if (mems_updated && !nodes_empty(cs->mems_allowed))
2934                 update_tasks_nodemask(cs);
2935 
2936         is_empty = cpumask_empty(cs->cpus_allowed) ||
2937                    nodes_empty(cs->mems_allowed);
2938 
2939         mutex_unlock(&cpuset_mutex);
2940 
2941         /*
2942          * Move tasks to the nearest ancestor with execution resources,
2943          * This is full cgroup operation which will also call back into
2944          * cpuset. Should be done outside any lock.
2945          */
2946         if (is_empty)
2947                 remove_tasks_in_empty_cpuset(cs);
2948 
2949         mutex_lock(&cpuset_mutex);
2950 }
2951 
2952 static void
2953 hotplug_update_tasks(struct cpuset *cs,
2954                      struct cpumask *new_cpus, nodemask_t *new_mems,
2955                      bool cpus_updated, bool mems_updated)
2956 {
2957         if (cpumask_empty(new_cpus))
2958                 cpumask_copy(new_cpus, parent_cs(cs)->effective_cpus);
2959         if (nodes_empty(*new_mems))
2960                 *new_mems = parent_cs(cs)->effective_mems;
2961 
2962         spin_lock_irq(&callback_lock);
2963         cpumask_copy(cs->effective_cpus, new_cpus);
2964         cs->effective_mems = *new_mems;
2965         spin_unlock_irq(&callback_lock);
2966 
2967         if (cpus_updated)
2968                 update_tasks_cpumask(cs);
2969         if (mems_updated)
2970                 update_tasks_nodemask(cs);
2971 }
2972 
2973 static bool force_rebuild;
2974 
2975 void cpuset_force_rebuild(void)
2976 {
2977         force_rebuild = true;
2978 }
2979 
2980 /**
2981  * cpuset_hotplug_update_tasks - update tasks in a cpuset for hotunplug
2982  * @cs: cpuset in interest
2983  * @tmp: the tmpmasks structure pointer
2984  *
2985  * Compare @cs's cpu and mem masks against top_cpuset and if some have gone
2986  * offline, update @cs accordingly.  If @cs ends up with no CPU or memory,
2987  * all its tasks are moved to the nearest ancestor with both resources.
2988  */
2989 static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
2990 {
2991         static cpumask_t new_cpus;
2992         static nodemask_t new_mems;
2993         bool cpus_updated;
2994         bool mems_updated;
2995         struct cpuset *parent;
2996 retry:
2997         wait_event(cpuset_attach_wq, cs->attach_in_progress == 0);
2998 
2999         mutex_lock(&cpuset_mutex);
3000 
3001         /*
3002          * We have raced with task attaching. We wait until attaching
3003          * is finished, so we won't attach a task to an empty cpuset.
3004          */
3005         if (cs->attach_in_progress) {
3006                 mutex_unlock(&cpuset_mutex);
3007                 goto retry;
3008         }
3009 
3010         parent =  parent_cs(cs);
3011         compute_effective_cpumask(&new_cpus, cs, parent);
3012         nodes_and(new_mems, cs->mems_allowed, parent->effective_mems);
3013 
3014         if (cs->nr_subparts_cpus)
3015                 /*
3016                  * Make sure that CPUs allocated to child partitions
3017                  * do not show up in effective_cpus.
3018                  */
3019                 cpumask_andnot(&new_cpus, &new_cpus, cs->subparts_cpus);
3020 
3021         if (!tmp || !cs->partition_root_state)
3022                 goto update_tasks;
3023 
3024         /*
3025          * In the unlikely event that a partition root has empty
3026          * effective_cpus or its parent becomes erroneous, we have to
3027          * transition it to the erroneous state.
3028          */
3029         if (is_partition_root(cs) && (cpumask_empty(&new_cpus) ||
3030            (parent->partition_root_state == PRS_ERROR))) {
3031                 if (cs->nr_subparts_cpus) {
3032                         cs->nr_subparts_cpus = 0;
3033                         cpumask_clear(cs->subparts_cpus);
3034                         compute_effective_cpumask(&new_cpus, cs, parent);
3035                 }
3036 
3037                 /*
3038                  * If the effective_cpus is empty because the child
3039                  * partitions take away all the CPUs, we can keep
3040                  * the current partition and let the child partitions
3041                  * fight for available CPUs.
3042                  */
3043                 if ((parent->partition_root_state == PRS_ERROR) ||
3044                      cpumask_empty(&new_cpus)) {
3045                         update_parent_subparts_cpumask(cs, partcmd_disable,
3046                                                        NULL, tmp);
3047                         cs->partition_root_state = PRS_ERROR;
3048                 }
3049                 cpuset_force_rebuild();
3050         }
3051 
3052         /*
3053          * On the other hand, an erroneous partition root may be transitioned
3054          * back to a regular one or a partition root with no CPU allocated
3055          * from the parent may change to erroneous.
3056          */
3057         if (is_partition_root(parent) &&
3058            ((cs->partition_root_state == PRS_ERROR) ||
3059             !cpumask_intersects(&new_cpus, parent->subparts_cpus)) &&
3060              update_parent_subparts_cpumask(cs, partcmd_update, NULL, tmp))
3061                 cpuset_force_rebuild();
3062 
3063 update_tasks:
3064         cpus_updated = !cpumask_equal(&new_cpus, cs->effective_cpus);
3065         mems_updated = !nodes_equal(new_mems, cs->effective_mems);
3066 
3067         if (is_in_v2_mode())
3068                 hotplug_update_tasks(cs, &new_cpus, &new_mems,
3069                                      cpus_updated, mems_updated);
3070         else
3071                 hotplug_update_tasks_legacy(cs, &new_cpus, &new_mems,
3072                                             cpus_updated, mems_updated);
3073 
3074         mutex_unlock(&cpuset_mutex);
3075 }
3076 
3077 /**
3078  * cpuset_hotplug_workfn - handle CPU/memory hotunplug for a cpuset
3079  *
3080  * This function is called after either CPU or memory configuration has
3081  * changed and updates cpuset accordingly.  The top_cpuset is always
3082  * synchronized to cpu_active_mask and N_MEMORY, which is necessary in
3083  * order to make cpusets transparent (of no affect) on systems that are
3084  * actively using CPU hotplug but making no active use of cpusets.
3085  *
3086  * Non-root cpusets are only affected by offlining.  If any CPUs or memory
3087  * nodes have been taken down, cpuset_hotplug_update_tasks() is invoked on
3088  * all descendants.
3089  *
3090  * Note that CPU offlining during suspend is ignored.  We don't modify
3091  * cpusets across suspend/resume cycles at all.
3092  */
3093 static void cpuset_hotplug_workfn(struct work_struct *work)
3094 {
3095         static cpumask_t new_cpus;
3096         static nodemask_t new_mems;
3097         bool cpus_updated, mems_updated;
3098         bool on_dfl = is_in_v2_mode();
3099         struct tmpmasks tmp, *ptmp = NULL;
3100 
3101         if (on_dfl && !alloc_cpumasks(NULL, &tmp))
3102                 ptmp = &tmp;
3103 
3104         mutex_lock(&cpuset_mutex);
3105 
3106         /* fetch the available cpus/mems and find out which changed how */
3107         cpumask_copy(&new_cpus, cpu_active_mask);
3108         new_mems = node_states[N_MEMORY];
3109 
3110         /*
3111          * If subparts_cpus is populated, it is likely that the check below
3112          * will produce a false positive on cpus_updated when the cpu list
3113          * isn't changed. It is extra work, but it is better to be safe.
3114          */
3115         cpus_updated = !cpumask_equal(top_cpuset.effective_cpus, &new_cpus);
3116         mems_updated = !nodes_equal(top_cpuset.effective_mems, new_mems);
3117 
3118         /* synchronize cpus_allowed to cpu_active_mask */
3119         if (cpus_updated) {
3120                 spin_lock_irq(&callback_lock);
3121                 if (!on_dfl)
3122                         cpumask_copy(top_cpuset.cpus_allowed, &new_cpus);
3123                 /*
3124                  * Make sure that CPUs allocated to child partitions
3125                  * do not show up in effective_cpus. If no CPU is left,
3126                  * we clear the subparts_cpus & let the child partitions
3127                  * fight for the CPUs again.
3128                  */
3129                 if (top_cpuset.nr_subparts_cpus) {
3130                         if (cpumask_subset(&new_cpus,
3131                                            top_cpuset.subparts_cpus)) {
3132                                 top_cpuset.nr_subparts_cpus = 0;
3133                                 cpumask_clear(top_cpuset.subparts_cpus);
3134                         } else {
3135                                 cpumask_andnot(&new_cpus, &new_cpus,
3136                                                top_cpuset.subparts_cpus);
3137                         }
3138                 }
3139                 cpumask_copy(top_cpuset.effective_cpus, &new_cpus);
3140                 spin_unlock_irq(&callback_lock);
3141                 /* we don't mess with cpumasks of tasks in top_cpuset */
3142         }
3143 
3144         /* synchronize mems_allowed to N_MEMORY */
3145         if (mems_updated) {
3146                 spin_lock_irq(&callback_lock);
3147                 if (!on_dfl)
3148                         top_cpuset.mems_allowed = new_mems;
3149                 top_cpuset.effective_mems = new_mems;
3150                 spin_unlock_irq(&callback_lock);
3151                 update_tasks_nodemask(&top_cpuset);
3152         }
3153 
3154         mutex_unlock(&cpuset_mutex);
3155 
3156         /* if cpus or mems changed, we need to propagate to descendants */
3157         if (cpus_updated || mems_updated) {
3158                 struct cpuset *cs;
3159                 struct cgroup_subsys_state *pos_css;
3160 
3161                 rcu_read_lock();
3162                 cpuset_for_each_descendant_pre(cs, pos_css, &top_cpuset) {
3163                         if (cs == &top_cpuset || !css_tryget_online(&cs->css))
3164                                 continue;
3165                         rcu_read_unlock();
3166 
3167                         cpuset_hotplug_update_tasks(cs, ptmp);
3168 
3169                         rcu_read_lock();
3170                         css_put(&cs->css);
3171                 }
3172                 rcu_read_unlock();
3173         }
3174 
3175         /* rebuild sched domains if cpus_allowed has changed */
3176         if (cpus_updated || force_rebuild) {
3177                 force_rebuild = false;
3178                 rebuild_sched_domains();
3179         }
3180 
3181         free_cpumasks(NULL, ptmp);
3182 }
3183 
3184 void cpuset_update_active_cpus(void)
3185 {
3186         /*
3187          * We're inside cpu hotplug critical region which usually nests
3188          * inside cgroup synchronization.  Bounce actual hotplug processing
3189          * to a work item to avoid reverse locking order.
3190          */
3191         schedule_work(&cpuset_hotplug_work);
3192 }
3193 
3194 void cpuset_wait_for_hotplug(void)
3195 {
3196         flush_work(&cpuset_hotplug_work);
3197 }
3198 
3199 /*
3200  * Keep top_cpuset.mems_allowed tracking node_states[N_MEMORY].
3201  * Call this routine anytime after node_states[N_MEMORY] changes.
3202  * See cpuset_update_active_cpus() for CPU hotplug handling.
3203  */
3204 static int cpuset_track_online_nodes(struct notifier_block *self,
3205                                 unsigned long action, void *arg)
3206 {
3207         schedule_work(&cpuset_hotplug_work);
3208         return NOTIFY_OK;
3209 }
3210 
3211 static struct notifier_block cpuset_track_online_nodes_nb = {
3212         .notifier_call = cpuset_track_online_nodes,
3213         .priority = 10,         /* ??! */
3214 };
3215 
3216 /**
3217  * cpuset_init_smp - initialize cpus_allowed
3218  *
3219  * Description: Finish top cpuset after cpu, node maps are initialized
3220  */
3221 void __init cpuset_init_smp(void)
3222 {
3223         cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
3224         top_cpuset.mems_allowed = node_states[N_MEMORY];
3225         top_cpuset.old_mems_allowed = top_cpuset.mems_allowed;
3226 
3227         cpumask_copy(top_cpuset.effective_cpus, cpu_active_mask);
3228         top_cpuset.effective_mems = node_states[N_MEMORY];
3229 
3230         register_hotmemory_notifier(&cpuset_track_online_nodes_nb);
3231 
3232         cpuset_migrate_mm_wq = alloc_ordered_workqueue("cpuset_migrate_mm", 0);
3233         BUG_ON(!cpuset_migrate_mm_wq);
3234 }
3235 
3236 /**
3237  * cpuset_cpus_allowed - return cpus_allowed mask from a tasks cpuset.
3238  * @tsk: pointer to task_struct from which to obtain cpuset->cpus_allowed.
3239  * @pmask: pointer to struct cpumask variable to receive cpus_allowed set.
3240  *
3241  * Description: Returns the cpumask_var_t cpus_allowed of the cpuset
3242  * attached to the specified @tsk.  Guaranteed to return some non-empty
3243  * subset of cpu_online_mask, even if this means going outside the
3244  * tasks cpuset.
3245  **/
3246 
3247 void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask)
3248 {
3249         unsigned long flags;
3250 
3251         spin_lock_irqsave(&callback_lock, flags);
3252         rcu_read_lock();
3253         guarantee_online_cpus(task_cs(tsk), pmask);
3254         rcu_read_unlock();
3255         spin_unlock_irqrestore(&callback_lock, flags);
3256 }
3257 
3258 void cpuset_cpus_allowed_fallback(struct task_struct *tsk)
3259 {
3260         rcu_read_lock();
3261         do_set_cpus_allowed(tsk, task_cs(tsk)->effective_cpus);
3262         rcu_read_unlock();
3263 
3264         /*
3265          * We own tsk->cpus_allowed, nobody can change it under us.
3266          *
3267          * But we used cs && cs->cpus_allowed lockless and thus can
3268          * race with cgroup_attach_task() or update_cpumask() and get
3269          * the wrong tsk->cpus_allowed. However, both cases imply the
3270          * subsequent cpuset_change_cpumask()->set_cpus_allowed_ptr()
3271          * which takes task_rq_lock().
3272          *
3273          * If we are called after it dropped the lock we must see all
3274          * changes in tsk_cs()->cpus_allowed. Otherwise we can temporary
3275          * set any mask even if it is not right from task_cs() pov,
3276          * the pending set_cpus_allowed_ptr() will fix things.
3277          *
3278          * select_fallback_rq() will fix things ups and set cpu_possible_mask
3279          * if required.
3280          */
3281 }
3282 
3283 void __init cpuset_init_current_mems_allowed(void)
3284 {
3285         nodes_setall(current->mems_allowed);
3286 }
3287 
3288 /**
3289  * cpuset_mems_allowed - return mems_allowed mask from a tasks cpuset.
3290  * @tsk: pointer to task_struct from which to obtain cpuset->mems_allowed.
3291  *
3292  * Description: Returns the nodemask_t mems_allowed of the cpuset
3293  * attached to the specified @tsk.  Guaranteed to return some non-empty
3294  * subset of node_states[N_MEMORY], even if this means going outside the
3295  * tasks cpuset.
3296  **/
3297 
3298 nodemask_t cpuset_mems_allowed(struct task_struct *tsk)
3299 {
3300         nodemask_t mask;
3301         unsigned long flags;
3302 
3303         spin_lock_irqsave(&callback_lock, flags);
3304         rcu_read_lock();
3305         guarantee_online_mems(task_cs(tsk), &mask);
3306         rcu_read_unlock();
3307         spin_unlock_irqrestore(&callback_lock, flags);
3308 
3309         return mask;
3310 }
3311 
3312 /**
3313  * cpuset_nodemask_valid_mems_allowed - check nodemask vs. curremt mems_allowed
3314  * @nodemask: the nodemask to be checked
3315  *
3316  * Are any of the nodes in the nodemask allowed in current->mems_allowed?
3317  */
3318 int cpuset_nodemask_valid_mems_allowed(nodemask_t *nodemask)
3319 {
3320         return nodes_intersects(*nodemask, current->mems_allowed);
3321 }
3322 
3323 /*
3324  * nearest_hardwall_ancestor() - Returns the nearest mem_exclusive or
3325  * mem_hardwall ancestor to the specified cpuset.  Call holding
3326  * callback_lock.  If no ancestor is mem_exclusive or mem_hardwall
3327  * (an unusual configuration), then returns the root cpuset.
3328  */
3329 static struct cpuset *nearest_hardwall_ancestor(struct cpuset *cs)
3330 {
3331         while (!(is_mem_exclusive(cs) || is_mem_hardwall(cs)) && parent_cs(cs))
3332                 cs = parent_cs(cs);
3333         return cs;
3334 }
3335 
3336 /**
3337  * cpuset_node_allowed - Can we allocate on a memory node?
3338  * @node: is this an allowed node?
3339  * @gfp_mask: memory allocation flags
3340  *
3341  * If we're in interrupt, yes, we can always allocate.  If @node is set in
3342  * current's mems_allowed, yes.  If it's not a __GFP_HARDWALL request and this
3343  * node is set in the nearest hardwalled cpuset ancestor to current's cpuset,
3344  * yes.  If current has access to memory reserves as an oom victim, yes.
3345  * Otherwise, no.
3346  *
3347  * GFP_USER allocations are marked with the __GFP_HARDWALL bit,
3348  * and do not allow allocations outside the current tasks cpuset
3349  * unless the task has been OOM killed.
3350  * GFP_KERNEL allocations are not so marked, so can escape to the
3351  * nearest enclosing hardwalled ancestor cpuset.
3352  *
3353  * Scanning up parent cpusets requires callback_lock.  The
3354  * __alloc_pages() routine only calls here with __GFP_HARDWALL bit
3355  * _not_ set if it's a GFP_KERNEL allocation, and all nodes in the
3356  * current tasks mems_allowed came up empty on the first pass over
3357  * the zonelist.  So only GFP_KERNEL allocations, if all nodes in the
3358  * cpuset are short of memory, might require taking the callback_lock.
3359  *
3360  * The first call here from mm/page_alloc:get_page_from_freelist()
3361  * has __GFP_HARDWALL set in gfp_mask, enforcing hardwall cpusets,
3362  * so no allocation on a node outside the cpuset is allowed (unless
3363  * in interrupt, of course).
3364  *
3365  * The second pass through get_page_from_freelist() doesn't even call
3366  * here for GFP_ATOMIC calls.  For those calls, the __alloc_pages()
3367  * variable 'wait' is not set, and the bit ALLOC_CPUSET is not set
3368  * in alloc_flags.  That logic and the checks below have the combined
3369  * affect that:
3370  *      in_interrupt - any node ok (current task context irrelevant)
3371  *      GFP_ATOMIC   - any node ok
3372  *      tsk_is_oom_victim   - any node ok
3373  *      GFP_KERNEL   - any node in enclosing hardwalled cpuset ok
3374  *      GFP_USER     - only nodes in current tasks mems allowed ok.
3375  */
3376 bool __cpuset_node_allowed(int node, gfp_t gfp_mask)
3377 {
3378         struct cpuset *cs;              /* current cpuset ancestors */
3379         int allowed;                    /* is allocation in zone z allowed? */
3380         unsigned long flags;
3381 
3382         if (in_interrupt())
3383                 return true;
3384         if (node_isset(node, current->mems_allowed))
3385                 return true;
3386         /*
3387          * Allow tasks that have access to memory reserves because they have
3388          * been OOM killed to get memory anywhere.
3389          */
3390         if (unlikely(tsk_is_oom_victim(current)))
3391                 return true;
3392         if (gfp_mask & __GFP_HARDWALL)  /* If hardwall request, stop here */
3393                 return false;
3394 
3395         if (current->flags & PF_EXITING) /* Let dying task have memory */
3396                 return true;
3397 
3398         /* Not hardwall and node outside mems_allowed: scan up cpusets */
3399         spin_lock_irqsave(&callback_lock, flags);
3400 
3401         rcu_read_lock();
3402         cs = nearest_hardwall_ancestor(task_cs(current));
3403         allowed = node_isset(node, cs->mems_allowed);
3404         rcu_read_unlock();
3405 
3406         spin_unlock_irqrestore(&callback_lock, flags);
3407         return allowed;
3408 }
3409 
3410 /**
3411  * cpuset_mem_spread_node() - On which node to begin search for a file page
3412  * cpuset_slab_spread_node() - On which node to begin search for a slab page
3413  *
3414  * If a task is marked PF_SPREAD_PAGE or PF_SPREAD_SLAB (as for
3415  * tasks in a cpuset with is_spread_page or is_spread_slab set),
3416  * and if the memory allocation used cpuset_mem_spread_node()
3417  * to determine on which node to start looking, as it will for
3418  * certain page cache or slab cache pages such as used for file
3419  * system buffers and inode caches, then instead of starting on the
3420  * local node to look for a free page, rather spread the starting
3421  * node around the tasks mems_allowed nodes.
3422  *
3423  * We don't have to worry about the returned node being offline
3424  * because "it can't happen", and even if it did, it would be ok.
3425  *
3426  * The routines calling guarantee_online_mems() are careful to
3427  * only set nodes in task->mems_allowed that are online.  So it
3428  * should not be possible for the following code to return an
3429  * offline node.  But if it did, that would be ok, as this routine
3430  * is not returning the node where the allocation must be, only
3431  * the node where the search should start.  The zonelist passed to
3432  * __alloc_pages() will include all nodes.  If the slab allocator
3433  * is passed an offline node, it will fall back to the local node.
3434  * See kmem_cache_alloc_node().
3435  */
3436 
3437 static int cpuset_spread_node(int *rotor)
3438 {
3439         return *rotor = next_node_in(*rotor, current->mems_allowed);
3440 }
3441 
3442 int cpuset_mem_spread_node(void)
3443 {
3444         if (current->cpuset_mem_spread_rotor == NUMA_NO_NODE)
3445                 current->cpuset_mem_spread_rotor =
3446                         node_random(&current->mems_allowed);
3447 
3448         return cpuset_spread_node(&current->cpuset_mem_spread_rotor);
3449 }
3450 
3451 int cpuset_slab_spread_node(void)
3452 {
3453         if (current->cpuset_slab_spread_rotor == NUMA_NO_NODE)
3454                 current->cpuset_slab_spread_rotor =
3455                         node_random(&current->mems_allowed);
3456 
3457         return cpuset_spread_node(&current->cpuset_slab_spread_rotor);
3458 }
3459 
3460 EXPORT_SYMBOL_GPL(cpuset_mem_spread_node);
3461 
3462 /**
3463  * cpuset_mems_allowed_intersects - Does @tsk1's mems_allowed intersect @tsk2's?
3464  * @tsk1: pointer to task_struct of some task.
3465  * @tsk2: pointer to task_struct of some other task.
3466  *
3467  * Description: Return true if @tsk1's mems_allowed intersects the
3468  * mems_allowed of @tsk2.  Used by the OOM killer to determine if
3469  * one of the task's memory usage might impact the memory available
3470  * to the other.
3471  **/
3472 
3473 int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
3474                                    const struct task_struct *tsk2)
3475 {
3476         return nodes_intersects(tsk1->mems_allowed, tsk2->mems_allowed);
3477 }
3478 
3479 /**
3480  * cpuset_print_current_mems_allowed - prints current's cpuset and mems_allowed
3481  *
3482  * Description: Prints current's name, cpuset name, and cached copy of its
3483  * mems_allowed to the kernel log.
3484  */
3485 void cpuset_print_current_mems_allowed(void)
3486 {
3487         struct cgroup *cgrp;
3488 
3489         rcu_read_lock();
3490 
3491         cgrp = task_cs(current)->css.cgroup;
3492         pr_cont(",cpuset=");
3493         pr_cont_cgroup_name(cgrp);
3494         pr_cont(",mems_allowed=%*pbl",
3495                 nodemask_pr_args(&current->mems_allowed));
3496 
3497         rcu_read_unlock();
3498 }
3499 
3500 /*
3501  * Collection of memory_pressure is suppressed unless
3502  * this flag is enabled by writing "1" to the special
3503  * cpuset file 'memory_pressure_enabled' in the root cpuset.
3504  */
3505 
3506 int cpuset_memory_pressure_enabled __read_mostly;
3507 
3508 /**
3509  * cpuset_memory_pressure_bump - keep stats of per-cpuset reclaims.
3510  *
3511  * Keep a running average of the rate of synchronous (direct)
3512  * page reclaim efforts initiated by tasks in each cpuset.
3513  *
3514  * This represents the rate at which some task in the cpuset
3515  * ran low on memory on all nodes it was allowed to use, and
3516  * had to enter the kernels page reclaim code in an effort to
3517  * create more free memory by tossing clean pages or swapping
3518  * or writing dirty pages.
3519  *
3520  * Display to user space in the per-cpuset read-only file
3521  * "memory_pressure".  Value displayed is an integer
3522  * representing the recent rate of entry into the synchronous
3523  * (direct) page reclaim by any task attached to the cpuset.
3524  **/
3525 
3526 void __cpuset_memory_pressure_bump(void)
3527 {
3528         rcu_read_lock();
3529         fmeter_markevent(&task_cs(current)->fmeter);
3530         rcu_read_unlock();
3531 }
3532 
3533 #ifdef CONFIG_PROC_PID_CPUSET
3534 /*
3535  * proc_cpuset_show()
3536  *  - Print tasks cpuset path into seq_file.
3537  *  - Used for /proc/<pid>/cpuset.
3538  *  - No need to task_lock(tsk) on this tsk->cpuset reference, as it
3539  *    doesn't really matter if tsk->cpuset changes after we read it,
3540  *    and we take cpuset_mutex, keeping cpuset_attach() from changing it
3541  *    anyway.
3542  */
3543 int proc_cpuset_show(struct seq_file *m, struct pid_namespace *ns,
3544                      struct pid *pid, struct task_struct *tsk)
3545 {
3546         char *buf;
3547         struct cgroup_subsys_state *css;
3548         int retval;
3549 
3550         retval = -ENOMEM;
3551         buf = kmalloc(PATH_MAX, GFP_KERNEL);
3552         if (!buf)
3553                 goto out;
3554 
3555         css = task_get_css(tsk, cpuset_cgrp_id);
3556         retval = cgroup_path_ns(css->cgroup, buf, PATH_MAX,
3557                                 current->nsproxy->cgroup_ns);
3558         css_put(css);
3559         if (retval >= PATH_MAX)
3560                 retval = -ENAMETOOLONG;
3561         if (retval < 0)
3562                 goto out_free;
3563         seq_puts(m, buf);
3564         seq_putc(m, '\n');
3565         retval = 0;
3566 out_free:
3567         kfree(buf);
3568 out:
3569         return retval;
3570 }
3571 #endif /* CONFIG_PROC_PID_CPUSET */
3572 
3573 /* Display task mems_allowed in /proc/<pid>/status file. */
3574 void cpuset_task_status_allowed(struct seq_file *m, struct task_struct *task)
3575 {
3576         seq_printf(m, "Mems_allowed:\t%*pb\n",
3577                    nodemask_pr_args(&task->mems_allowed));
3578         seq_printf(m, "Mems_allowed_list:\t%*pbl\n",
3579                    nodemask_pr_args(&task->mems_allowed));
3580 }
3581 

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