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

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