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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/deadline.h>
 49 #include <linux/sched/mm.h>
 50 #include <linux/sched/task.h>
 51 #include <linux/seq_file.h>
 52 #include <linux/security.h>
 53 #include <linux/slab.h>
 54 #include <linux/spinlock.h>
 55 #include <linux/stat.h>
 56 #include <linux/string.h>
 57 #include <linux/time.h>
 58 #include <linux/time64.h>
 59 #include <linux/backing-dev.h>
 60 #include <linux/sort.h>
 61 #include <linux/oom.h>
 62 #include <linux/sched/isolation.h>
 63 #include <linux/uaccess.h>
 64 #include <linux/atomic.h>
 65 #include <linux/mutex.h>
 66 #include <linux/cgroup.h>
 67 #include <linux/wait.h>
 68 
 69 DEFINE_STATIC_KEY_FALSE(cpusets_pre_enable_key);
 70 DEFINE_STATIC_KEY_FALSE(cpusets_enabled_key);
 71 
 72 /* See "Frequency meter" comments, below. */
 73 
 74 struct fmeter {
 75         int cnt;                /* unprocessed events count */
 76         int val;                /* most recent output value */
 77         time64_t time;          /* clock (secs) when val computed */
 78         spinlock_t lock;        /* guards read or write of above */
 79 };
 80 
 81 struct cpuset {
 82         struct cgroup_subsys_state css;
 83 
 84         unsigned long flags;            /* "unsigned long" so bitops work */
 85 
 86         /*
 87          * On default hierarchy:
 88          *
 89          * The user-configured masks can only be changed by writing to
 90          * cpuset.cpus and cpuset.mems, and won't be limited by the
 91          * parent masks.
 92          *
 93          * The effective masks is the real masks that apply to the tasks
 94          * in the cpuset. They may be changed if the configured masks are
 95          * changed or hotplug happens.
 96          *
 97          * effective_mask == configured_mask & parent's effective_mask,
 98          * and if it ends up empty, it will inherit the parent's mask.
 99          *
100          *
101          * On legacy hierachy:
102          *
103          * The user-configured masks are always the same with effective masks.
104          */
105 
106         /* user-configured CPUs and Memory Nodes allow to tasks */
107         cpumask_var_t cpus_allowed;
108         nodemask_t mems_allowed;
109 
110         /* effective CPUs and Memory Nodes allow to tasks */
111         cpumask_var_t effective_cpus;
112         nodemask_t effective_mems;
113 
114         /*
115          * CPUs allocated to child sub-partitions (default hierarchy only)
116          * - CPUs granted by the parent = effective_cpus U subparts_cpus
117          * - effective_cpus and subparts_cpus are mutually exclusive.
118          *
119          * effective_cpus contains only onlined CPUs, but subparts_cpus
120          * may have offlined ones.
121          */
122         cpumask_var_t subparts_cpus;
123 
124         /*
125          * This is old Memory Nodes tasks took on.
126          *
127          * - top_cpuset.old_mems_allowed is initialized to mems_allowed.
128          * - A new cpuset's old_mems_allowed is initialized when some
129          *   task is moved into it.
130          * - old_mems_allowed is used in cpuset_migrate_mm() when we change
131          *   cpuset.mems_allowed and have tasks' nodemask updated, and
132          *   then old_mems_allowed is updated to mems_allowed.
133          */
134         nodemask_t old_mems_allowed;
135 
136         struct fmeter fmeter;           /* memory_pressure filter */
137 
138         /*
139          * Tasks are being attached to this cpuset.  Used to prevent
140          * zeroing cpus/mems_allowed between ->can_attach() and ->attach().
141          */
142         int attach_in_progress;
143 
144         /* partition number for rebuild_sched_domains() */
145         int pn;
146 
147         /* for custom sched domain */
148         int relax_domain_level;
149 
150         /* number of CPUs in subparts_cpus */
151         int nr_subparts_cpus;
152 
153         /* partition root state */
154         int partition_root_state;
155 
156         /*
157          * Default hierarchy only:
158          * use_parent_ecpus - set if using parent's effective_cpus
159          * child_ecpus_count - # of children with use_parent_ecpus set
160          */
161         int use_parent_ecpus;
162         int child_ecpus_count;
163 };
164 
165 /*
166  * Partition root states:
167  *
168  *   0 - not a partition root
169  *
170  *   1 - partition root
171  *
172  *  -1 - invalid partition root
173  *       None of the cpus in cpus_allowed can be put into the parent's
174  *       subparts_cpus. In this case, the cpuset is not a real partition
175  *       root anymore.  However, the CPU_EXCLUSIVE bit will still be set
176  *       and the cpuset can be restored back to a partition root if the
177  *       parent cpuset can give more CPUs back to this child cpuset.
178  */
179 #define PRS_DISABLED            0
180 #define PRS_ENABLED             1
181 #define PRS_ERROR               -1
182 
183 /*
184  * Temporary cpumasks for working with partitions that are passed among
185  * functions to avoid memory allocation in inner functions.
186  */
187 struct tmpmasks {
188         cpumask_var_t addmask, delmask; /* For partition root */
189         cpumask_var_t new_cpus;         /* For update_cpumasks_hier() */
190 };
191 
192 static inline struct cpuset *css_cs(struct cgroup_subsys_state *css)
193 {
194         return css ? container_of(css, struct cpuset, css) : NULL;
195 }
196 
197 /* Retrieve the cpuset for a task */
198 static inline struct cpuset *task_cs(struct task_struct *task)
199 {
200         return css_cs(task_css(task, cpuset_cgrp_id));
201 }
202 
203 static inline struct cpuset *parent_cs(struct cpuset *cs)
204 {
205         return css_cs(cs->css.parent);
206 }
207 
208 /* bits in struct cpuset flags field */
209 typedef enum {
210         CS_ONLINE,
211         CS_CPU_EXCLUSIVE,
212         CS_MEM_EXCLUSIVE,
213         CS_MEM_HARDWALL,
214         CS_MEMORY_MIGRATE,
215         CS_SCHED_LOAD_BALANCE,
216         CS_SPREAD_PAGE,
217         CS_SPREAD_SLAB,
218 } cpuset_flagbits_t;
219 
220 /* convenient tests for these bits */
221 static inline bool is_cpuset_online(struct cpuset *cs)
222 {
223         return test_bit(CS_ONLINE, &cs->flags) && !css_is_dying(&cs->css);
224 }
225 
226 static inline int is_cpu_exclusive(const struct cpuset *cs)
227 {
228         return test_bit(CS_CPU_EXCLUSIVE, &cs->flags);
229 }
230 
231 static inline int is_mem_exclusive(const struct cpuset *cs)
232 {
233         return test_bit(CS_MEM_EXCLUSIVE, &cs->flags);
234 }
235 
236 static inline int is_mem_hardwall(const struct cpuset *cs)
237 {
238         return test_bit(CS_MEM_HARDWALL, &cs->flags);
239 }
240 
241 static inline int is_sched_load_balance(const struct cpuset *cs)
242 {
243         return test_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
244 }
245 
246 static inline int is_memory_migrate(const struct cpuset *cs)
247 {
248         return test_bit(CS_MEMORY_MIGRATE, &cs->flags);
249 }
250 
251 static inline int is_spread_page(const struct cpuset *cs)
252 {
253         return test_bit(CS_SPREAD_PAGE, &cs->flags);
254 }
255 
256 static inline int is_spread_slab(const struct cpuset *cs)
257 {
258         return test_bit(CS_SPREAD_SLAB, &cs->flags);
259 }
260 
261 static inline int is_partition_root(const struct cpuset *cs)
262 {
263         return cs->partition_root_state > 0;
264 }
265 
266 static struct cpuset top_cpuset = {
267         .flags = ((1 << CS_ONLINE) | (1 << CS_CPU_EXCLUSIVE) |
268                   (1 << CS_MEM_EXCLUSIVE)),
269         .partition_root_state = PRS_ENABLED,
270 };
271 
272 /**
273  * cpuset_for_each_child - traverse online children of a cpuset
274  * @child_cs: loop cursor pointing to the current child
275  * @pos_css: used for iteration
276  * @parent_cs: target cpuset to walk children of
277  *
278  * Walk @child_cs through the online children of @parent_cs.  Must be used
279  * with RCU read locked.
280  */
281 #define cpuset_for_each_child(child_cs, pos_css, parent_cs)             \
282         css_for_each_child((pos_css), &(parent_cs)->css)                \
283                 if (is_cpuset_online(((child_cs) = css_cs((pos_css)))))
284 
285 /**
286  * cpuset_for_each_descendant_pre - pre-order walk of a cpuset's descendants
287  * @des_cs: loop cursor pointing to the current descendant
288  * @pos_css: used for iteration
289  * @root_cs: target cpuset to walk ancestor of
290  *
291  * Walk @des_cs through the online descendants of @root_cs.  Must be used
292  * with RCU read locked.  The caller may modify @pos_css by calling
293  * css_rightmost_descendant() to skip subtree.  @root_cs is included in the
294  * iteration and the first node to be visited.
295  */
296 #define cpuset_for_each_descendant_pre(des_cs, pos_css, root_cs)        \
297         css_for_each_descendant_pre((pos_css), &(root_cs)->css)         \
298                 if (is_cpuset_online(((des_cs) = css_cs((pos_css)))))
299 
300 /*
301  * There are two global locks guarding cpuset structures - cpuset_mutex and
302  * callback_lock. We also require taking task_lock() when dereferencing a
303  * task's cpuset pointer. See "The task_lock() exception", at the end of this
304  * comment.
305  *
306  * A task must hold both locks to modify cpusets.  If a task holds
307  * cpuset_mutex, then it blocks others wanting that mutex, ensuring that it
308  * is the only task able to also acquire callback_lock and be able to
309  * modify cpusets.  It can perform various checks on the cpuset structure
310  * first, knowing nothing will change.  It can also allocate memory while
311  * just holding cpuset_mutex.  While it is performing these checks, various
312  * callback routines can briefly acquire callback_lock to query cpusets.
313  * Once it is ready to make the changes, it takes callback_lock, blocking
314  * everyone else.
315  *
316  * Calls to the kernel memory allocator can not be made while holding
317  * callback_lock, as that would risk double tripping on callback_lock
318  * from one of the callbacks into the cpuset code from within
319  * __alloc_pages().
320  *
321  * If a task is only holding callback_lock, then it has read-only
322  * access to cpusets.
323  *
324  * Now, the task_struct fields mems_allowed and mempolicy may be changed
325  * by other task, we use alloc_lock in the task_struct fields to protect
326  * them.
327  *
328  * The cpuset_common_file_read() handlers only hold callback_lock across
329  * small pieces of code, such as when reading out possibly multi-word
330  * cpumasks and nodemasks.
331  *
332  * Accessing a task's cpuset should be done in accordance with the
333  * guidelines for accessing subsystem state in kernel/cgroup.c
334  */
335 
336 DEFINE_STATIC_PERCPU_RWSEM(cpuset_rwsem);
337 
338 void cpuset_read_lock(void)
339 {
340         percpu_down_read(&cpuset_rwsem);
341 }
342 
343 void cpuset_read_unlock(void)
344 {
345         percpu_up_read(&cpuset_rwsem);
346 }
347 
348 static DEFINE_SPINLOCK(callback_lock);
349 
350 static struct workqueue_struct *cpuset_migrate_mm_wq;
351 
352 /*
353  * CPU / memory hotplug is handled asynchronously.
354  */
355 static void cpuset_hotplug_workfn(struct work_struct *work);
356 static DECLARE_WORK(cpuset_hotplug_work, cpuset_hotplug_workfn);
357 
358 static DECLARE_WAIT_QUEUE_HEAD(cpuset_attach_wq);
359 
360 /*
361  * Cgroup v2 behavior is used when on default hierarchy or the
362  * cgroup_v2_mode flag is set.
363  */
364 static inline bool is_in_v2_mode(void)
365 {
366         return cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||
367               (cpuset_cgrp_subsys.root->flags & CGRP_ROOT_CPUSET_V2_MODE);
368 }
369 
370 /*
371  * Return in pmask the portion of a cpusets's cpus_allowed that
372  * are online.  If none are online, walk up the cpuset hierarchy
373  * until we find one that does have some online cpus.
374  *
375  * One way or another, we guarantee to return some non-empty subset
376  * of cpu_online_mask.
377  *
378  * Call with callback_lock or cpuset_mutex held.
379  */
380 static void guarantee_online_cpus(struct cpuset *cs, struct cpumask *pmask)
381 {
382         while (!cpumask_intersects(cs->effective_cpus, cpu_online_mask)) {
383                 cs = parent_cs(cs);
384                 if (unlikely(!cs)) {
385                         /*
386                          * The top cpuset doesn't have any online cpu as a
387                          * consequence of a race between cpuset_hotplug_work
388                          * and cpu hotplug notifier.  But we know the top
389                          * cpuset's effective_cpus is on its way to to be
390                          * identical to cpu_online_mask.
391                          */
392                         cpumask_copy(pmask, cpu_online_mask);
393                         return;
394                 }
395         }
396         cpumask_and(pmask, cs->effective_cpus, cpu_online_mask);
397 }
398 
399 /*
400  * Return in *pmask the portion of a cpusets's mems_allowed that
401  * are online, with memory.  If none are online with memory, walk
402  * up the cpuset hierarchy until we find one that does have some
403  * online mems.  The top cpuset always has some mems online.
404  *
405  * One way or another, we guarantee to return some non-empty subset
406  * of node_states[N_MEMORY].
407  *
408  * Call with callback_lock or cpuset_mutex held.
409  */
410 static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask)
411 {
412         while (!nodes_intersects(cs->effective_mems, node_states[N_MEMORY]))
413                 cs = parent_cs(cs);
414         nodes_and(*pmask, cs->effective_mems, node_states[N_MEMORY]);
415 }
416 
417 /*
418  * update task's spread flag if cpuset's page/slab spread flag is set
419  *
420  * Call with callback_lock or cpuset_mutex held.
421  */
422 static void cpuset_update_task_spread_flag(struct cpuset *cs,
423                                         struct task_struct *tsk)
424 {
425         if (is_spread_page(cs))
426                 task_set_spread_page(tsk);
427         else
428                 task_clear_spread_page(tsk);
429 
430         if (is_spread_slab(cs))
431                 task_set_spread_slab(tsk);
432         else
433                 task_clear_spread_slab(tsk);
434 }
435 
436 /*
437  * is_cpuset_subset(p, q) - Is cpuset p a subset of cpuset q?
438  *
439  * One cpuset is a subset of another if all its allowed CPUs and
440  * Memory Nodes are a subset of the other, and its exclusive flags
441  * are only set if the other's are set.  Call holding cpuset_mutex.
442  */
443 
444 static int is_cpuset_subset(const struct cpuset *p, const struct cpuset *q)
445 {
446         return  cpumask_subset(p->cpus_allowed, q->cpus_allowed) &&
447                 nodes_subset(p->mems_allowed, q->mems_allowed) &&
448                 is_cpu_exclusive(p) <= is_cpu_exclusive(q) &&
449                 is_mem_exclusive(p) <= is_mem_exclusive(q);
450 }
451 
452 /**
453  * alloc_cpumasks - allocate three cpumasks for cpuset
454  * @cs:  the cpuset that have cpumasks to be allocated.
455  * @tmp: the tmpmasks structure pointer
456  * Return: 0 if successful, -ENOMEM otherwise.
457  *
458  * Only one of the two input arguments should be non-NULL.
459  */
460 static inline int alloc_cpumasks(struct cpuset *cs, struct tmpmasks *tmp)
461 {
462         cpumask_var_t *pmask1, *pmask2, *pmask3;
463 
464         if (cs) {
465                 pmask1 = &cs->cpus_allowed;
466                 pmask2 = &cs->effective_cpus;
467                 pmask3 = &cs->subparts_cpus;
468         } else {
469                 pmask1 = &tmp->new_cpus;
470                 pmask2 = &tmp->addmask;
471                 pmask3 = &tmp->delmask;
472         }
473 
474         if (!zalloc_cpumask_var(pmask1, GFP_KERNEL))
475                 return -ENOMEM;
476 
477         if (!zalloc_cpumask_var(pmask2, GFP_KERNEL))
478                 goto free_one;
479 
480         if (!zalloc_cpumask_var(pmask3, GFP_KERNEL))
481                 goto free_two;
482 
483         return 0;
484 
485 free_two:
486         free_cpumask_var(*pmask2);
487 free_one:
488         free_cpumask_var(*pmask1);
489         return -ENOMEM;
490 }
491 
492 /**
493  * free_cpumasks - free cpumasks in a tmpmasks structure
494  * @cs:  the cpuset that have cpumasks to be free.
495  * @tmp: the tmpmasks structure pointer
496  */
497 static inline void free_cpumasks(struct cpuset *cs, struct tmpmasks *tmp)
498 {
499         if (cs) {
500                 free_cpumask_var(cs->cpus_allowed);
501                 free_cpumask_var(cs->effective_cpus);
502                 free_cpumask_var(cs->subparts_cpus);
503         }
504         if (tmp) {
505                 free_cpumask_var(tmp->new_cpus);
506                 free_cpumask_var(tmp->addmask);
507                 free_cpumask_var(tmp->delmask);
508         }
509 }
510 
511 /**
512  * alloc_trial_cpuset - allocate a trial cpuset
513  * @cs: the cpuset that the trial cpuset duplicates
514  */
515 static struct cpuset *alloc_trial_cpuset(struct cpuset *cs)
516 {
517         struct cpuset *trial;
518 
519         trial = kmemdup(cs, sizeof(*cs), GFP_KERNEL);
520         if (!trial)
521                 return NULL;
522 
523         if (alloc_cpumasks(trial, NULL)) {
524                 kfree(trial);
525                 return NULL;
526         }
527 
528         cpumask_copy(trial->cpus_allowed, cs->cpus_allowed);
529         cpumask_copy(trial->effective_cpus, cs->effective_cpus);
530         return trial;
531 }
532 
533 /**
534  * free_cpuset - free the cpuset
535  * @cs: the cpuset to be freed
536  */
537 static inline void free_cpuset(struct cpuset *cs)
538 {
539         free_cpumasks(cs, NULL);
540         kfree(cs);
541 }
542 
543 /*
544  * validate_change() - Used to validate that any proposed cpuset change
545  *                     follows the structural rules for cpusets.
546  *
547  * If we replaced the flag and mask values of the current cpuset
548  * (cur) with those values in the trial cpuset (trial), would
549  * our various subset and exclusive rules still be valid?  Presumes
550  * cpuset_mutex held.
551  *
552  * 'cur' is the address of an actual, in-use cpuset.  Operations
553  * such as list traversal that depend on the actual address of the
554  * cpuset in the list must use cur below, not trial.
555  *
556  * 'trial' is the address of bulk structure copy of cur, with
557  * perhaps one or more of the fields cpus_allowed, mems_allowed,
558  * or flags changed to new, trial values.
559  *
560  * Return 0 if valid, -errno if not.
561  */
562 
563 static int validate_change(struct cpuset *cur, struct cpuset *trial)
564 {
565         struct cgroup_subsys_state *css;
566         struct cpuset *c, *par;
567         int ret;
568 
569         rcu_read_lock();
570 
571         /* Each of our child cpusets must be a subset of us */
572         ret = -EBUSY;
573         cpuset_for_each_child(c, css, cur)
574                 if (!is_cpuset_subset(c, trial))
575                         goto out;
576 
577         /* Remaining checks don't apply to root cpuset */
578         ret = 0;
579         if (cur == &top_cpuset)
580                 goto out;
581 
582         par = parent_cs(cur);
583 
584         /* On legacy hiearchy, we must be a subset of our parent cpuset. */
585         ret = -EACCES;
586         if (!is_in_v2_mode() && !is_cpuset_subset(trial, par))
587                 goto out;
588 
589         /*
590          * If either I or some sibling (!= me) is exclusive, we can't
591          * overlap
592          */
593         ret = -EINVAL;
594         cpuset_for_each_child(c, css, par) {
595                 if ((is_cpu_exclusive(trial) || is_cpu_exclusive(c)) &&
596                     c != cur &&
597                     cpumask_intersects(trial->cpus_allowed, c->cpus_allowed))
598                         goto out;
599                 if ((is_mem_exclusive(trial) || is_mem_exclusive(c)) &&
600                     c != cur &&
601                     nodes_intersects(trial->mems_allowed, c->mems_allowed))
602                         goto out;
603         }
604 
605         /*
606          * Cpusets with tasks - existing or newly being attached - can't
607          * be changed to have empty cpus_allowed or mems_allowed.
608          */
609         ret = -ENOSPC;
610         if ((cgroup_is_populated(cur->css.cgroup) || cur->attach_in_progress)) {
611                 if (!cpumask_empty(cur->cpus_allowed) &&
612                     cpumask_empty(trial->cpus_allowed))
613                         goto out;
614                 if (!nodes_empty(cur->mems_allowed) &&
615                     nodes_empty(trial->mems_allowed))
616                         goto out;
617         }
618 
619         /*
620          * We can't shrink if we won't have enough room for SCHED_DEADLINE
621          * tasks.
622          */
623         ret = -EBUSY;
624         if (is_cpu_exclusive(cur) &&
625             !cpuset_cpumask_can_shrink(cur->cpus_allowed,
626                                        trial->cpus_allowed))
627                 goto out;
628 
629         ret = 0;
630 out:
631         rcu_read_unlock();
632         return ret;
633 }
634 
635 #ifdef CONFIG_SMP
636 /*
637  * Helper routine for generate_sched_domains().
638  * Do cpusets a, b have overlapping effective cpus_allowed masks?
639  */
640 static int cpusets_overlap(struct cpuset *a, struct cpuset *b)
641 {
642         return cpumask_intersects(a->effective_cpus, b->effective_cpus);
643 }
644 
645 static void
646 update_domain_attr(struct sched_domain_attr *dattr, struct cpuset *c)
647 {
648         if (dattr->relax_domain_level < c->relax_domain_level)
649                 dattr->relax_domain_level = c->relax_domain_level;
650         return;
651 }
652 
653 static void update_domain_attr_tree(struct sched_domain_attr *dattr,
654                                     struct cpuset *root_cs)
655 {
656         struct cpuset *cp;
657         struct cgroup_subsys_state *pos_css;
658 
659         rcu_read_lock();
660         cpuset_for_each_descendant_pre(cp, pos_css, root_cs) {
661                 /* skip the whole subtree if @cp doesn't have any CPU */
662                 if (cpumask_empty(cp->cpus_allowed)) {
663                         pos_css = css_rightmost_descendant(pos_css);
664                         continue;
665                 }
666 
667                 if (is_sched_load_balance(cp))
668                         update_domain_attr(dattr, cp);
669         }
670         rcu_read_unlock();
671 }
672 
673 /* Must be called with cpuset_mutex held.  */
674 static inline int nr_cpusets(void)
675 {
676         /* jump label reference count + the top-level cpuset */
677         return static_key_count(&cpusets_enabled_key.key) + 1;
678 }
679 
680 /*
681  * generate_sched_domains()
682  *
683  * This function builds a partial partition of the systems CPUs
684  * A 'partial partition' is a set of non-overlapping subsets whose
685  * union is a subset of that set.
686  * The output of this function needs to be passed to kernel/sched/core.c
687  * partition_sched_domains() routine, which will rebuild the scheduler's
688  * load balancing domains (sched domains) as specified by that partial
689  * partition.
690  *
691  * See "What is sched_load_balance" in Documentation/admin-guide/cgroup-v1/cpusets.rst
692  * for a background explanation of this.
693  *
694  * Does not return errors, on the theory that the callers of this
695  * routine would rather not worry about failures to rebuild sched
696  * domains when operating in the severe memory shortage situations
697  * that could cause allocation failures below.
698  *
699  * Must be called with cpuset_mutex held.
700  *
701  * The three key local variables below are:
702  *    cp - cpuset pointer, used (together with pos_css) to perform a
703  *         top-down scan of all cpusets. For our purposes, rebuilding
704  *         the schedulers sched domains, we can ignore !is_sched_load_
705  *         balance cpusets.
706  *  csa  - (for CpuSet Array) Array of pointers to all the cpusets
707  *         that need to be load balanced, for convenient iterative
708  *         access by the subsequent code that finds the best partition,
709  *         i.e the set of domains (subsets) of CPUs such that the
710  *         cpus_allowed of every cpuset marked is_sched_load_balance
711  *         is a subset of one of these domains, while there are as
712  *         many such domains as possible, each as small as possible.
713  * doms  - Conversion of 'csa' to an array of cpumasks, for passing to
714  *         the kernel/sched/core.c routine partition_sched_domains() in a
715  *         convenient format, that can be easily compared to the prior
716  *         value to determine what partition elements (sched domains)
717  *         were changed (added or removed.)
718  *
719  * Finding the best partition (set of domains):
720  *      The triple nested loops below over i, j, k scan over the
721  *      load balanced cpusets (using the array of cpuset pointers in
722  *      csa[]) looking for pairs of cpusets that have overlapping
723  *      cpus_allowed, but which don't have the same 'pn' partition
724  *      number and gives them in the same partition number.  It keeps
725  *      looping on the 'restart' label until it can no longer find
726  *      any such pairs.
727  *
728  *      The union of the cpus_allowed masks from the set of
729  *      all cpusets having the same 'pn' value then form the one
730  *      element of the partition (one sched domain) to be passed to
731  *      partition_sched_domains().
732  */
733 static int generate_sched_domains(cpumask_var_t **domains,
734                         struct sched_domain_attr **attributes)
735 {
736         struct cpuset *cp;      /* top-down scan of cpusets */
737         struct cpuset **csa;    /* array of all cpuset ptrs */
738         int csn;                /* how many cpuset ptrs in csa so far */
739         int i, j, k;            /* indices for partition finding loops */
740         cpumask_var_t *doms;    /* resulting partition; i.e. sched domains */
741         struct sched_domain_attr *dattr;  /* attributes for custom domains */
742         int ndoms = 0;          /* number of sched domains in result */
743         int nslot;              /* next empty doms[] struct cpumask slot */
744         struct cgroup_subsys_state *pos_css;
745         bool root_load_balance = is_sched_load_balance(&top_cpuset);
746 
747         doms = NULL;
748         dattr = NULL;
749         csa = NULL;
750 
751         /* Special case for the 99% of systems with one, full, sched domain */
752         if (root_load_balance && !top_cpuset.nr_subparts_cpus) {
753                 ndoms = 1;
754                 doms = alloc_sched_domains(ndoms);
755                 if (!doms)
756                         goto done;
757 
758                 dattr = kmalloc(sizeof(struct sched_domain_attr), GFP_KERNEL);
759                 if (dattr) {
760                         *dattr = SD_ATTR_INIT;
761                         update_domain_attr_tree(dattr, &top_cpuset);
762                 }
763                 cpumask_and(doms[0], top_cpuset.effective_cpus,
764                             housekeeping_cpumask(HK_FLAG_DOMAIN));
765 
766                 goto done;
767         }
768 
769         csa = kmalloc_array(nr_cpusets(), sizeof(cp), GFP_KERNEL);
770         if (!csa)
771                 goto done;
772         csn = 0;
773 
774         rcu_read_lock();
775         if (root_load_balance)
776                 csa[csn++] = &top_cpuset;
777         cpuset_for_each_descendant_pre(cp, pos_css, &top_cpuset) {
778                 if (cp == &top_cpuset)
779                         continue;
780                 /*
781                  * Continue traversing beyond @cp iff @cp has some CPUs and
782                  * isn't load balancing.  The former is obvious.  The
783                  * latter: All child cpusets contain a subset of the
784                  * parent's cpus, so just skip them, and then we call
785                  * update_domain_attr_tree() to calc relax_domain_level of
786                  * the corresponding sched domain.
787                  *
788                  * If root is load-balancing, we can skip @cp if it
789                  * is a subset of the root's effective_cpus.
790                  */
791                 if (!cpumask_empty(cp->cpus_allowed) &&
792                     !(is_sched_load_balance(cp) &&
793                       cpumask_intersects(cp->cpus_allowed,
794                                          housekeeping_cpumask(HK_FLAG_DOMAIN))))
795                         continue;
796 
797                 if (root_load_balance &&
798                     cpumask_subset(cp->cpus_allowed, top_cpuset.effective_cpus))
799                         continue;
800 
801                 if (is_sched_load_balance(cp) &&
802                     !cpumask_empty(cp->effective_cpus))
803                         csa[csn++] = cp;
804 
805                 /* skip @cp's subtree if not a partition root */
806                 if (!is_partition_root(cp))
807                         pos_css = css_rightmost_descendant(pos_css);
808         }
809         rcu_read_unlock();
810 
811         for (i = 0; i < csn; i++)
812                 csa[i]->pn = i;
813         ndoms = csn;
814 
815 restart:
816         /* Find the best partition (set of sched domains) */
817         for (i = 0; i < csn; i++) {
818                 struct cpuset *a = csa[i];
819                 int apn = a->pn;
820 
821                 for (j = 0; j < csn; j++) {
822                         struct cpuset *b = csa[j];
823                         int bpn = b->pn;
824 
825                         if (apn != bpn && cpusets_overlap(a, b)) {
826                                 for (k = 0; k < csn; k++) {
827                                         struct cpuset *c = csa[k];
828 
829                                         if (c->pn == bpn)
830                                                 c->pn = apn;
831                                 }
832                                 ndoms--;        /* one less element */
833                                 goto restart;
834                         }
835                 }
836         }
837 
838         /*
839          * Now we know how many domains to create.
840          * Convert <csn, csa> to <ndoms, doms> and populate cpu masks.
841          */
842         doms = alloc_sched_domains(ndoms);
843         if (!doms)
844                 goto done;
845 
846         /*
847          * The rest of the code, including the scheduler, can deal with
848          * dattr==NULL case. No need to abort if alloc fails.
849          */
850         dattr = kmalloc_array(ndoms, sizeof(struct sched_domain_attr),
851                               GFP_KERNEL);
852 
853         for (nslot = 0, i = 0; i < csn; i++) {
854                 struct cpuset *a = csa[i];
855                 struct cpumask *dp;
856                 int apn = a->pn;
857 
858                 if (apn < 0) {
859                         /* Skip completed partitions */
860                         continue;
861                 }
862 
863                 dp = doms[nslot];
864 
865                 if (nslot == ndoms) {
866                         static int warnings = 10;
867                         if (warnings) {
868                                 pr_warn("rebuild_sched_domains confused: nslot %d, ndoms %d, csn %d, i %d, apn %d\n",
869                                         nslot, ndoms, csn, i, apn);
870                                 warnings--;
871                         }
872                         continue;
873                 }
874 
875                 cpumask_clear(dp);
876                 if (dattr)
877                         *(dattr + nslot) = SD_ATTR_INIT;
878                 for (j = i; j < csn; j++) {
879                         struct cpuset *b = csa[j];
880 
881                         if (apn == b->pn) {
882                                 cpumask_or(dp, dp, b->effective_cpus);
883                                 cpumask_and(dp, dp, housekeeping_cpumask(HK_FLAG_DOMAIN));
884                                 if (dattr)
885                                         update_domain_attr_tree(dattr + nslot, b);
886 
887                                 /* Done with this partition */
888                                 b->pn = -1;
889                         }
890                 }
891                 nslot++;
892         }
893         BUG_ON(nslot != ndoms);
894 
895 done:
896         kfree(csa);
897 
898         /*
899          * Fallback to the default domain if kmalloc() failed.
900          * See comments in partition_sched_domains().
901          */
902         if (doms == NULL)
903                 ndoms = 1;
904 
905         *domains    = doms;
906         *attributes = dattr;
907         return ndoms;
908 }
909 
910 static void update_tasks_root_domain(struct cpuset *cs)
911 {
912         struct css_task_iter it;
913         struct task_struct *task;
914 
915         css_task_iter_start(&cs->css, 0, &it);
916 
917         while ((task = css_task_iter_next(&it)))
918                 dl_add_task_root_domain(task);
919 
920         css_task_iter_end(&it);
921 }
922 
923 static void rebuild_root_domains(void)
924 {
925         struct cpuset *cs = NULL;
926         struct cgroup_subsys_state *pos_css;
927 
928         percpu_rwsem_assert_held(&cpuset_rwsem);
929         lockdep_assert_cpus_held();
930         lockdep_assert_held(&sched_domains_mutex);
931 
932         rcu_read_lock();
933 
934         /*
935          * Clear default root domain DL accounting, it will be computed again
936          * if a task belongs to it.
937          */
938         dl_clear_root_domain(&def_root_domain);
939 
940         cpuset_for_each_descendant_pre(cs, pos_css, &top_cpuset) {
941 
942                 if (cpumask_empty(cs->effective_cpus)) {
943                         pos_css = css_rightmost_descendant(pos_css);
944                         continue;
945                 }
946 
947                 css_get(&cs->css);
948 
949                 rcu_read_unlock();
950 
951                 update_tasks_root_domain(cs);
952 
953                 rcu_read_lock();
954                 css_put(&cs->css);
955         }
956         rcu_read_unlock();
957 }
958 
959 static void
960 partition_and_rebuild_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
961                                     struct sched_domain_attr *dattr_new)
962 {
963         mutex_lock(&sched_domains_mutex);
964         partition_sched_domains_locked(ndoms_new, doms_new, dattr_new);
965         rebuild_root_domains();
966         mutex_unlock(&sched_domains_mutex);
967 }
968 
969 /*
970  * Rebuild scheduler domains.
971  *
972  * If the flag 'sched_load_balance' of any cpuset with non-empty
973  * 'cpus' changes, or if the 'cpus' allowed changes in any cpuset
974  * which has that flag enabled, or if any cpuset with a non-empty
975  * 'cpus' is removed, then call this routine to rebuild the
976  * scheduler's dynamic sched domains.
977  *
978  * Call with cpuset_mutex held.  Takes get_online_cpus().
979  */
980 static void rebuild_sched_domains_locked(void)
981 {
982         struct sched_domain_attr *attr;
983         cpumask_var_t *doms;
984         int ndoms;
985 
986         lockdep_assert_cpus_held();
987         percpu_rwsem_assert_held(&cpuset_rwsem);
988 
989         /*
990          * We have raced with CPU hotplug. Don't do anything to avoid
991          * passing doms with offlined cpu to partition_sched_domains().
992          * Anyways, hotplug work item will rebuild sched domains.
993          */
994         if (!top_cpuset.nr_subparts_cpus &&
995             !cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
996                 return;
997 
998         if (top_cpuset.nr_subparts_cpus &&
999            !cpumask_subset(top_cpuset.effective_cpus, cpu_active_mask))
1000                 return;
1001 
1002         /* Generate domain masks and attrs */
1003         ndoms = generate_sched_domains(&doms, &attr);
1004 
1005         /* Have scheduler rebuild the domains */
1006         partition_and_rebuild_sched_domains(ndoms, doms, attr);
1007 }
1008 #else /* !CONFIG_SMP */
1009 static void rebuild_sched_domains_locked(void)
1010 {
1011 }
1012 #endif /* CONFIG_SMP */
1013 
1014 void rebuild_sched_domains(void)
1015 {
1016         get_online_cpus();
1017         percpu_down_write(&cpuset_rwsem);
1018         rebuild_sched_domains_locked();
1019         percpu_up_write(&cpuset_rwsem);
1020         put_online_cpus();
1021 }
1022 
1023 /**
1024  * update_tasks_cpumask - Update the cpumasks of tasks in the cpuset.
1025  * @cs: the cpuset in which each task's cpus_allowed mask needs to be changed
1026  *
1027  * Iterate through each task of @cs updating its cpus_allowed to the
1028  * effective cpuset's.  As this function is called with cpuset_mutex held,
1029  * cpuset membership stays stable.
1030  */
1031 static void update_tasks_cpumask(struct cpuset *cs)
1032 {
1033         struct css_task_iter it;
1034         struct task_struct *task;
1035 
1036         css_task_iter_start(&cs->css, 0, &it);
1037         while ((task = css_task_iter_next(&it)))
1038                 set_cpus_allowed_ptr(task, cs->effective_cpus);
1039         css_task_iter_end(&it);
1040 }
1041 
1042 /**
1043  * compute_effective_cpumask - Compute the effective cpumask of the cpuset
1044  * @new_cpus: the temp variable for the new effective_cpus mask
1045  * @cs: the cpuset the need to recompute the new effective_cpus mask
1046  * @parent: the parent cpuset
1047  *
1048  * If the parent has subpartition CPUs, include them in the list of
1049  * allowable CPUs in computing the new effective_cpus mask. Since offlined
1050  * CPUs are not removed from subparts_cpus, we have to use cpu_active_mask
1051  * to mask those out.
1052  */
1053 static void compute_effective_cpumask(struct cpumask *new_cpus,
1054                                       struct cpuset *cs, struct cpuset *parent)
1055 {
1056         if (parent->nr_subparts_cpus) {
1057                 cpumask_or(new_cpus, parent->effective_cpus,
1058                            parent->subparts_cpus);
1059                 cpumask_and(new_cpus, new_cpus, cs->cpus_allowed);
1060                 cpumask_and(new_cpus, new_cpus, cpu_active_mask);
1061         } else {
1062                 cpumask_and(new_cpus, cs->cpus_allowed, parent->effective_cpus);
1063         }
1064 }
1065 
1066 /*
1067  * Commands for update_parent_subparts_cpumask
1068  */
1069 enum subparts_cmd {
1070         partcmd_enable,         /* Enable partition root         */
1071         partcmd_disable,        /* Disable partition root        */
1072         partcmd_update,         /* Update parent's subparts_cpus */
1073 };
1074 
1075 /**
1076  * update_parent_subparts_cpumask - update subparts_cpus mask of parent cpuset
1077  * @cpuset:  The cpuset that requests change in partition root state
1078  * @cmd:     Partition root state change command
1079  * @newmask: Optional new cpumask for partcmd_update
1080  * @tmp:     Temporary addmask and delmask
1081  * Return:   0, 1 or an error code
1082  *
1083  * For partcmd_enable, the cpuset is being transformed from a non-partition
1084  * root to a partition root. The cpus_allowed mask of the given cpuset will
1085  * be put into parent's subparts_cpus and taken away from parent's
1086  * effective_cpus. The function will return 0 if all the CPUs listed in
1087  * cpus_allowed can be granted or an error code will be returned.
1088  *
1089  * For partcmd_disable, the cpuset is being transofrmed from a partition
1090  * root back to a non-partition root. any CPUs in cpus_allowed that are in
1091  * parent's subparts_cpus will be taken away from that cpumask and put back
1092  * into parent's effective_cpus. 0 should always be returned.
1093  *
1094  * For partcmd_update, if the optional newmask is specified, the cpu
1095  * list is to be changed from cpus_allowed to newmask. Otherwise,
1096  * cpus_allowed is assumed to remain the same. The cpuset should either
1097  * be a partition root or an invalid partition root. The partition root
1098  * state may change if newmask is NULL and none of the requested CPUs can
1099  * be granted by the parent. The function will return 1 if changes to
1100  * parent's subparts_cpus and effective_cpus happen or 0 otherwise.
1101  * Error code should only be returned when newmask is non-NULL.
1102  *
1103  * The partcmd_enable and partcmd_disable commands are used by
1104  * update_prstate(). The partcmd_update command is used by
1105  * update_cpumasks_hier() with newmask NULL and update_cpumask() with
1106  * newmask set.
1107  *
1108  * The checking is more strict when enabling partition root than the
1109  * other two commands.
1110  *
1111  * Because of the implicit cpu exclusive nature of a partition root,
1112  * cpumask changes that violates the cpu exclusivity rule will not be
1113  * permitted when checked by validate_change(). The validate_change()
1114  * function will also prevent any changes to the cpu list if it is not
1115  * a superset of children's cpu lists.
1116  */
1117 static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
1118                                           struct cpumask *newmask,
1119                                           struct tmpmasks *tmp)
1120 {
1121         struct cpuset *parent = parent_cs(cpuset);
1122         int adding;     /* Moving cpus from effective_cpus to subparts_cpus */
1123         int deleting;   /* Moving cpus from subparts_cpus to effective_cpus */
1124         bool part_error = false;        /* Partition error? */
1125 
1126         percpu_rwsem_assert_held(&cpuset_rwsem);
1127 
1128         /*
1129          * The parent must be a partition root.
1130          * The new cpumask, if present, or the current cpus_allowed must
1131          * not be empty.
1132          */
1133         if (!is_partition_root(parent) ||
1134            (newmask && cpumask_empty(newmask)) ||
1135            (!newmask && cpumask_empty(cpuset->cpus_allowed)))
1136                 return -EINVAL;
1137 
1138         /*
1139          * Enabling/disabling partition root is not allowed if there are
1140          * online children.
1141          */
1142         if ((cmd != partcmd_update) && css_has_online_children(&cpuset->css))
1143                 return -EBUSY;
1144 
1145         /*
1146          * Enabling partition root is not allowed if not all the CPUs
1147          * can be granted from parent's effective_cpus or at least one
1148          * CPU will be left after that.
1149          */
1150         if ((cmd == partcmd_enable) &&
1151            (!cpumask_subset(cpuset->cpus_allowed, parent->effective_cpus) ||
1152              cpumask_equal(cpuset->cpus_allowed, parent->effective_cpus)))
1153                 return -EINVAL;
1154 
1155         /*
1156          * A cpumask update cannot make parent's effective_cpus become empty.
1157          */
1158         adding = deleting = false;
1159         if (cmd == partcmd_enable) {
1160                 cpumask_copy(tmp->addmask, cpuset->cpus_allowed);
1161                 adding = true;
1162         } else if (cmd == partcmd_disable) {
1163                 deleting = cpumask_and(tmp->delmask, cpuset->cpus_allowed,
1164                                        parent->subparts_cpus);
1165         } else if (newmask) {
1166                 /*
1167                  * partcmd_update with newmask:
1168                  *
1169                  * delmask = cpus_allowed & ~newmask & parent->subparts_cpus
1170                  * addmask = newmask & parent->effective_cpus
1171                  *                   & ~parent->subparts_cpus
1172                  */
1173                 cpumask_andnot(tmp->delmask, cpuset->cpus_allowed, newmask);
1174                 deleting = cpumask_and(tmp->delmask, tmp->delmask,
1175                                        parent->subparts_cpus);
1176 
1177                 cpumask_and(tmp->addmask, newmask, parent->effective_cpus);
1178                 adding = cpumask_andnot(tmp->addmask, tmp->addmask,
1179                                         parent->subparts_cpus);
1180                 /*
1181                  * Return error if the new effective_cpus could become empty.
1182                  */
1183                 if (adding &&
1184                     cpumask_equal(parent->effective_cpus, tmp->addmask)) {
1185                         if (!deleting)
1186                                 return -EINVAL;
1187                         /*
1188                          * As some of the CPUs in subparts_cpus might have
1189                          * been offlined, we need to compute the real delmask
1190                          * to confirm that.
1191                          */
1192                         if (!cpumask_and(tmp->addmask, tmp->delmask,
1193                                          cpu_active_mask))
1194                                 return -EINVAL;
1195                         cpumask_copy(tmp->addmask, parent->effective_cpus);
1196                 }
1197         } else {
1198                 /*
1199                  * partcmd_update w/o newmask:
1200                  *
1201                  * addmask = cpus_allowed & parent->effectiveb_cpus
1202                  *
1203                  * Note that parent's subparts_cpus may have been
1204                  * pre-shrunk in case there is a change in the cpu list.
1205                  * So no deletion is needed.
1206                  */
1207                 adding = cpumask_and(tmp->addmask, cpuset->cpus_allowed,
1208                                      parent->effective_cpus);
1209                 part_error = cpumask_equal(tmp->addmask,
1210                                            parent->effective_cpus);
1211         }
1212 
1213         if (cmd == partcmd_update) {
1214                 int prev_prs = cpuset->partition_root_state;
1215 
1216                 /*
1217                  * Check for possible transition between PRS_ENABLED
1218                  * and PRS_ERROR.
1219                  */
1220                 switch (cpuset->partition_root_state) {
1221                 case PRS_ENABLED:
1222                         if (part_error)
1223                                 cpuset->partition_root_state = PRS_ERROR;
1224                         break;
1225                 case PRS_ERROR:
1226                         if (!part_error)
1227                                 cpuset->partition_root_state = PRS_ENABLED;
1228                         break;
1229                 }
1230                 /*
1231                  * Set part_error if previously in invalid state.
1232                  */
1233                 part_error = (prev_prs == PRS_ERROR);
1234         }
1235 
1236         if (!part_error && (cpuset->partition_root_state == PRS_ERROR))
1237                 return 0;       /* Nothing need to be done */
1238 
1239         if (cpuset->partition_root_state == PRS_ERROR) {
1240                 /*
1241                  * Remove all its cpus from parent's subparts_cpus.
1242                  */
1243                 adding = false;
1244                 deleting = cpumask_and(tmp->delmask, cpuset->cpus_allowed,
1245                                        parent->subparts_cpus);
1246         }
1247 
1248         if (!adding && !deleting)
1249                 return 0;
1250 
1251         /*
1252          * Change the parent's subparts_cpus.
1253          * Newly added CPUs will be removed from effective_cpus and
1254          * newly deleted ones will be added back to effective_cpus.
1255          */
1256         spin_lock_irq(&callback_lock);
1257         if (adding) {
1258                 cpumask_or(parent->subparts_cpus,
1259                            parent->subparts_cpus, tmp->addmask);
1260                 cpumask_andnot(parent->effective_cpus,
1261                                parent->effective_cpus, tmp->addmask);
1262         }
1263         if (deleting) {
1264                 cpumask_andnot(parent->subparts_cpus,
1265                                parent->subparts_cpus, tmp->delmask);
1266                 /*
1267                  * Some of the CPUs in subparts_cpus might have been offlined.
1268                  */
1269                 cpumask_and(tmp->delmask, tmp->delmask, cpu_active_mask);
1270                 cpumask_or(parent->effective_cpus,
1271                            parent->effective_cpus, tmp->delmask);
1272         }
1273 
1274         parent->nr_subparts_cpus = cpumask_weight(parent->subparts_cpus);
1275         spin_unlock_irq(&callback_lock);
1276 
1277         return cmd == partcmd_update;
1278 }
1279 
1280 /*
1281  * update_cpumasks_hier - Update effective cpumasks and tasks in the subtree
1282  * @cs:  the cpuset to consider
1283  * @tmp: temp variables for calculating effective_cpus & partition setup
1284  *
1285  * When congifured cpumask is changed, the effective cpumasks of this cpuset
1286  * and all its descendants need to be updated.
1287  *
1288  * On legacy hierachy, effective_cpus will be the same with cpu_allowed.
1289  *
1290  * Called with cpuset_mutex held
1291  */
1292 static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
1293 {
1294         struct cpuset *cp;
1295         struct cgroup_subsys_state *pos_css;
1296         bool need_rebuild_sched_domains = false;
1297 
1298         rcu_read_lock();
1299         cpuset_for_each_descendant_pre(cp, pos_css, cs) {
1300                 struct cpuset *parent = parent_cs(cp);
1301 
1302                 compute_effective_cpumask(tmp->new_cpus, cp, parent);
1303 
1304                 /*
1305                  * If it becomes empty, inherit the effective mask of the
1306                  * parent, which is guaranteed to have some CPUs.
1307                  */
1308                 if (is_in_v2_mode() && cpumask_empty(tmp->new_cpus)) {
1309                         cpumask_copy(tmp->new_cpus, parent->effective_cpus);
1310                         if (!cp->use_parent_ecpus) {
1311                                 cp->use_parent_ecpus = true;
1312                                 parent->child_ecpus_count++;
1313                         }
1314                 } else if (cp->use_parent_ecpus) {
1315                         cp->use_parent_ecpus = false;
1316                         WARN_ON_ONCE(!parent->child_ecpus_count);
1317                         parent->child_ecpus_count--;
1318                 }
1319 
1320                 /*
1321                  * Skip the whole subtree if the cpumask remains the same
1322                  * and has no partition root state.
1323                  */
1324                 if (!cp->partition_root_state &&
1325                     cpumask_equal(tmp->new_cpus, cp->effective_cpus)) {
1326                         pos_css = css_rightmost_descendant(pos_css);
1327                         continue;
1328                 }
1329 
1330                 /*
1331                  * update_parent_subparts_cpumask() should have been called
1332                  * for cs already in update_cpumask(). We should also call
1333                  * update_tasks_cpumask() again for tasks in the parent
1334                  * cpuset if the parent's subparts_cpus changes.
1335                  */
1336                 if ((cp != cs) && cp->partition_root_state) {
1337                         switch (parent->partition_root_state) {
1338                         case PRS_DISABLED:
1339                                 /*
1340                                  * If parent is not a partition root or an
1341                                  * invalid partition root, clear the state
1342                                  * state and the CS_CPU_EXCLUSIVE flag.
1343                                  */
1344                                 WARN_ON_ONCE(cp->partition_root_state
1345                                              != PRS_ERROR);
1346                                 cp->partition_root_state = 0;
1347 
1348                                 /*
1349                                  * clear_bit() is an atomic operation and
1350                                  * readers aren't interested in the state
1351                                  * of CS_CPU_EXCLUSIVE anyway. So we can
1352                                  * just update the flag without holding
1353                                  * the callback_lock.
1354                                  */
1355                                 clear_bit(CS_CPU_EXCLUSIVE, &cp->flags);
1356                                 break;
1357 
1358                         case PRS_ENABLED:
1359                                 if (update_parent_subparts_cpumask(cp, partcmd_update, NULL, tmp))
1360                                         update_tasks_cpumask(parent);
1361                                 break;
1362 
1363                         case PRS_ERROR:
1364                                 /*
1365                                  * When parent is invalid, it has to be too.
1366                                  */
1367                                 cp->partition_root_state = PRS_ERROR;
1368                                 if (cp->nr_subparts_cpus) {
1369                                         cp->nr_subparts_cpus = 0;
1370                                         cpumask_clear(cp->subparts_cpus);
1371                                 }
1372                                 break;
1373                         }
1374                 }
1375 
1376                 if (!css_tryget_online(&cp->css))
1377                         continue;
1378                 rcu_read_unlock();
1379 
1380                 spin_lock_irq(&callback_lock);
1381 
1382                 cpumask_copy(cp->effective_cpus, tmp->new_cpus);
1383                 if (cp->nr_subparts_cpus &&
1384                    (cp->partition_root_state != PRS_ENABLED)) {
1385                         cp->nr_subparts_cpus = 0;
1386                         cpumask_clear(cp->subparts_cpus);
1387                 } else if (cp->nr_subparts_cpus) {
1388                         /*
1389                          * Make sure that effective_cpus & subparts_cpus
1390                          * are mutually exclusive.
1391                          *
1392                          * In the unlikely event that effective_cpus
1393                          * becomes empty. we clear cp->nr_subparts_cpus and
1394                          * let its child partition roots to compete for
1395                          * CPUs again.
1396                          */
1397                         cpumask_andnot(cp->effective_cpus, cp->effective_cpus,
1398                                        cp->subparts_cpus);
1399                         if (cpumask_empty(cp->effective_cpus)) {
1400                                 cpumask_copy(cp->effective_cpus, tmp->new_cpus);
1401                                 cpumask_clear(cp->subparts_cpus);
1402                                 cp->nr_subparts_cpus = 0;
1403                         } else if (!cpumask_subset(cp->subparts_cpus,
1404                                                    tmp->new_cpus)) {
1405                                 cpumask_andnot(cp->subparts_cpus,
1406                                         cp->subparts_cpus, tmp->new_cpus);
1407                                 cp->nr_subparts_cpus
1408                                         = cpumask_weight(cp->subparts_cpus);
1409                         }
1410                 }
1411                 spin_unlock_irq(&callback_lock);
1412 
1413                 WARN_ON(!is_in_v2_mode() &&
1414                         !cpumask_equal(cp->cpus_allowed, cp->effective_cpus));
1415 
1416                 update_tasks_cpumask(cp);
1417 
1418                 /*
1419                  * On legacy hierarchy, if the effective cpumask of any non-
1420                  * empty cpuset is changed, we need to rebuild sched domains.
1421                  * On default hierarchy, the cpuset needs to be a partition
1422                  * root as well.
1423                  */
1424                 if (!cpumask_empty(cp->cpus_allowed) &&
1425                     is_sched_load_balance(cp) &&
1426                    (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||
1427                     is_partition_root(cp)))
1428                         need_rebuild_sched_domains = true;
1429 
1430                 rcu_read_lock();
1431                 css_put(&cp->css);
1432         }
1433         rcu_read_unlock();
1434 
1435         if (need_rebuild_sched_domains)
1436                 rebuild_sched_domains_locked();
1437 }
1438 
1439 /**
1440  * update_sibling_cpumasks - Update siblings cpumasks
1441  * @parent:  Parent cpuset
1442  * @cs:      Current cpuset
1443  * @tmp:     Temp variables
1444  */
1445 static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
1446                                     struct tmpmasks *tmp)
1447 {
1448         struct cpuset *sibling;
1449         struct cgroup_subsys_state *pos_css;
1450 
1451         /*
1452          * Check all its siblings and call update_cpumasks_hier()
1453          * if their use_parent_ecpus flag is set in order for them
1454          * to use the right effective_cpus value.
1455          */
1456         rcu_read_lock();
1457         cpuset_for_each_child(sibling, pos_css, parent) {
1458                 if (sibling == cs)
1459                         continue;
1460                 if (!sibling->use_parent_ecpus)
1461                         continue;
1462 
1463                 update_cpumasks_hier(sibling, tmp);
1464         }
1465         rcu_read_unlock();
1466 }
1467 
1468 /**
1469  * update_cpumask - update the cpus_allowed mask of a cpuset and all tasks in it
1470  * @cs: the cpuset to consider
1471  * @trialcs: trial cpuset
1472  * @buf: buffer of cpu numbers written to this cpuset
1473  */
1474 static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
1475                           const char *buf)
1476 {
1477         int retval;
1478         struct tmpmasks tmp;
1479 
1480         /* top_cpuset.cpus_allowed tracks cpu_online_mask; it's read-only */
1481         if (cs == &top_cpuset)
1482                 return -EACCES;
1483 
1484         /*
1485          * An empty cpus_allowed is ok only if the cpuset has no tasks.
1486          * Since cpulist_parse() fails on an empty mask, we special case
1487          * that parsing.  The validate_change() call ensures that cpusets
1488          * with tasks have cpus.
1489          */
1490         if (!*buf) {
1491                 cpumask_clear(trialcs->cpus_allowed);
1492         } else {
1493                 retval = cpulist_parse(buf, trialcs->cpus_allowed);
1494                 if (retval < 0)
1495                         return retval;
1496 
1497                 if (!cpumask_subset(trialcs->cpus_allowed,
1498                                     top_cpuset.cpus_allowed))
1499                         return -EINVAL;
1500         }
1501 
1502         /* Nothing to do if the cpus didn't change */
1503         if (cpumask_equal(cs->cpus_allowed, trialcs->cpus_allowed))
1504                 return 0;
1505 
1506         retval = validate_change(cs, trialcs);
1507         if (retval < 0)
1508                 return retval;
1509 
1510 #ifdef CONFIG_CPUMASK_OFFSTACK
1511         /*
1512          * Use the cpumasks in trialcs for tmpmasks when they are pointers
1513          * to allocated cpumasks.
1514          */
1515         tmp.addmask  = trialcs->subparts_cpus;
1516         tmp.delmask  = trialcs->effective_cpus;
1517         tmp.new_cpus = trialcs->cpus_allowed;
1518 #endif
1519 
1520         if (cs->partition_root_state) {
1521                 /* Cpumask of a partition root cannot be empty */
1522                 if (cpumask_empty(trialcs->cpus_allowed))
1523                         return -EINVAL;
1524                 if (update_parent_subparts_cpumask(cs, partcmd_update,
1525                                         trialcs->cpus_allowed, &tmp) < 0)
1526                         return -EINVAL;
1527         }
1528 
1529         spin_lock_irq(&callback_lock);
1530         cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
1531 
1532         /*
1533          * Make sure that subparts_cpus is a subset of cpus_allowed.
1534          */
1535         if (cs->nr_subparts_cpus) {
1536                 cpumask_andnot(cs->subparts_cpus, cs->subparts_cpus,
1537                                cs->cpus_allowed);
1538                 cs->nr_subparts_cpus = cpumask_weight(cs->subparts_cpus);
1539         }
1540         spin_unlock_irq(&callback_lock);
1541 
1542         update_cpumasks_hier(cs, &tmp);
1543 
1544         if (cs->partition_root_state) {
1545                 struct cpuset *parent = parent_cs(cs);
1546 
1547                 /*
1548                  * For partition root, update the cpumasks of sibling
1549                  * cpusets if they use parent's effective_cpus.
1550                  */
1551                 if (parent->child_ecpus_count)
1552                         update_sibling_cpumasks(parent, cs, &tmp);
1553         }
1554         return 0;
1555 }
1556 
1557 /*
1558  * Migrate memory region from one set of nodes to another.  This is
1559  * performed asynchronously as it can be called from process migration path
1560  * holding locks involved in process management.  All mm migrations are
1561  * performed in the queued order and can be waited for by flushing
1562  * cpuset_migrate_mm_wq.
1563  */
1564 
1565 struct cpuset_migrate_mm_work {
1566         struct work_struct      work;
1567         struct mm_struct        *mm;
1568         nodemask_t              from;
1569         nodemask_t              to;
1570 };
1571 
1572 static void cpuset_migrate_mm_workfn(struct work_struct *work)
1573 {
1574         struct cpuset_migrate_mm_work *mwork =
1575                 container_of(work, struct cpuset_migrate_mm_work, work);
1576 
1577         /* on a wq worker, no need to worry about %current's mems_allowed */
1578         do_migrate_pages(mwork->mm, &mwork->from, &mwork->to, MPOL_MF_MOVE_ALL);
1579         mmput(mwork->mm);
1580         kfree(mwork);
1581 }
1582 
1583 static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
1584                                                         const nodemask_t *to)
1585 {
1586         struct cpuset_migrate_mm_work *mwork;
1587 
1588         mwork = kzalloc(sizeof(*mwork), GFP_KERNEL);
1589         if (mwork) {
1590                 mwork->mm = mm;
1591                 mwork->from = *from;
1592                 mwork->to = *to;
1593                 INIT_WORK(&mwork->work, cpuset_migrate_mm_workfn);
1594                 queue_work(cpuset_migrate_mm_wq, &mwork->work);
1595         } else {
1596                 mmput(mm);
1597         }
1598 }
1599 
1600 static void cpuset_post_attach(void)
1601 {
1602         flush_workqueue(cpuset_migrate_mm_wq);
1603 }
1604 
1605 /*
1606  * cpuset_change_task_nodemask - change task's mems_allowed and mempolicy
1607  * @tsk: the task to change
1608  * @newmems: new nodes that the task will be set
1609  *
1610  * We use the mems_allowed_seq seqlock to safely update both tsk->mems_allowed
1611  * and rebind an eventual tasks' mempolicy. If the task is allocating in
1612  * parallel, it might temporarily see an empty intersection, which results in
1613  * a seqlock check and retry before OOM or allocation failure.
1614  */
1615 static void cpuset_change_task_nodemask(struct task_struct *tsk,
1616                                         nodemask_t *newmems)
1617 {
1618         task_lock(tsk);
1619 
1620         local_irq_disable();
1621         write_seqcount_begin(&tsk->mems_allowed_seq);
1622 
1623         nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems);
1624         mpol_rebind_task(tsk, newmems);
1625         tsk->mems_allowed = *newmems;
1626 
1627         write_seqcount_end(&tsk->mems_allowed_seq);
1628         local_irq_enable();
1629 
1630         task_unlock(tsk);
1631 }
1632 
1633 static void *cpuset_being_rebound;
1634 
1635 /**
1636  * update_tasks_nodemask - Update the nodemasks of tasks in the cpuset.
1637  * @cs: the cpuset in which each task's mems_allowed mask needs to be changed
1638  *
1639  * Iterate through each task of @cs updating its mems_allowed to the
1640  * effective cpuset's.  As this function is called with cpuset_mutex held,
1641  * cpuset membership stays stable.
1642  */
1643 static void update_tasks_nodemask(struct cpuset *cs)
1644 {
1645         static nodemask_t newmems;      /* protected by cpuset_mutex */
1646         struct css_task_iter it;
1647         struct task_struct *task;
1648 
1649         cpuset_being_rebound = cs;              /* causes mpol_dup() rebind */
1650 
1651         guarantee_online_mems(cs, &newmems);
1652 
1653         /*
1654          * The mpol_rebind_mm() call takes mmap_sem, which we couldn't
1655          * take while holding tasklist_lock.  Forks can happen - the
1656          * mpol_dup() cpuset_being_rebound check will catch such forks,
1657          * and rebind their vma mempolicies too.  Because we still hold
1658          * the global cpuset_mutex, we know that no other rebind effort
1659          * will be contending for the global variable cpuset_being_rebound.
1660          * It's ok if we rebind the same mm twice; mpol_rebind_mm()
1661          * is idempotent.  Also migrate pages in each mm to new nodes.
1662          */
1663         css_task_iter_start(&cs->css, 0, &it);
1664         while ((task = css_task_iter_next(&it))) {
1665                 struct mm_struct *mm;
1666                 bool migrate;
1667 
1668                 cpuset_change_task_nodemask(task, &newmems);
1669 
1670                 mm = get_task_mm(task);
1671                 if (!mm)
1672                         continue;
1673 
1674                 migrate = is_memory_migrate(cs);
1675 
1676                 mpol_rebind_mm(mm, &cs->mems_allowed);
1677                 if (migrate)
1678                         cpuset_migrate_mm(mm, &cs->old_mems_allowed, &newmems);
1679                 else
1680                         mmput(mm);
1681         }
1682         css_task_iter_end(&it);
1683 
1684         /*
1685          * All the tasks' nodemasks have been updated, update
1686          * cs->old_mems_allowed.
1687          */
1688         cs->old_mems_allowed = newmems;
1689 
1690         /* We're done rebinding vmas to this cpuset's new mems_allowed. */
1691         cpuset_being_rebound = NULL;
1692 }
1693 
1694 /*
1695  * update_nodemasks_hier - Update effective nodemasks and tasks in the subtree
1696  * @cs: the cpuset to consider
1697  * @new_mems: a temp variable for calculating new effective_mems
1698  *
1699  * When configured nodemask is changed, the effective nodemasks of this cpuset
1700  * and all its descendants need to be updated.
1701  *
1702  * On legacy hiearchy, effective_mems will be the same with mems_allowed.
1703  *
1704  * Called with cpuset_mutex held
1705  */
1706 static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems)
1707 {
1708         struct cpuset *cp;
1709         struct cgroup_subsys_state *pos_css;
1710 
1711         rcu_read_lock();
1712         cpuset_for_each_descendant_pre(cp, pos_css, cs) {
1713                 struct cpuset *parent = parent_cs(cp);
1714 
1715                 nodes_and(*new_mems, cp->mems_allowed, parent->effective_mems);
1716 
1717                 /*
1718                  * If it becomes empty, inherit the effective mask of the
1719                  * parent, which is guaranteed to have some MEMs.
1720                  */
1721                 if (is_in_v2_mode() && nodes_empty(*new_mems))
1722                         *new_mems = parent->effective_mems;
1723 
1724                 /* Skip the whole subtree if the nodemask remains the same. */
1725                 if (nodes_equal(*new_mems, cp->effective_mems)) {
1726                         pos_css = css_rightmost_descendant(pos_css);
1727                         continue;
1728                 }
1729 
1730                 if (!css_tryget_online(&cp->css))
1731                         continue;
1732                 rcu_read_unlock();
1733 
1734                 spin_lock_irq(&callback_lock);
1735                 cp->effective_mems = *new_mems;
1736                 spin_unlock_irq(&callback_lock);
1737 
1738                 WARN_ON(!is_in_v2_mode() &&
1739                         !nodes_equal(cp->mems_allowed, cp->effective_mems));
1740 
1741                 update_tasks_nodemask(cp);
1742 
1743                 rcu_read_lock();
1744                 css_put(&cp->css);
1745         }
1746         rcu_read_unlock();
1747 }
1748 
1749 /*
1750  * Handle user request to change the 'mems' memory placement
1751  * of a cpuset.  Needs to validate the request, update the
1752  * cpusets mems_allowed, and for each task in the cpuset,
1753  * update mems_allowed and rebind task's mempolicy and any vma
1754  * mempolicies and if the cpuset is marked 'memory_migrate',
1755  * migrate the tasks pages to the new memory.
1756  *
1757  * Call with cpuset_mutex held. May take callback_lock during call.
1758  * Will take tasklist_lock, scan tasklist for tasks in cpuset cs,
1759  * lock each such tasks mm->mmap_sem, scan its vma's and rebind
1760  * their mempolicies to the cpusets new mems_allowed.
1761  */
1762 static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
1763                            const char *buf)
1764 {
1765         int retval;
1766 
1767         /*
1768          * top_cpuset.mems_allowed tracks node_stats[N_MEMORY];
1769          * it's read-only
1770          */
1771         if (cs == &top_cpuset) {
1772                 retval = -EACCES;
1773                 goto done;
1774         }
1775 
1776         /*
1777          * An empty mems_allowed is ok iff there are no tasks in the cpuset.
1778          * Since nodelist_parse() fails on an empty mask, we special case
1779          * that parsing.  The validate_change() call ensures that cpusets
1780          * with tasks have memory.
1781          */
1782         if (!*buf) {
1783                 nodes_clear(trialcs->mems_allowed);
1784         } else {
1785                 retval = nodelist_parse(buf, trialcs->mems_allowed);
1786                 if (retval < 0)
1787                         goto done;
1788 
1789                 if (!nodes_subset(trialcs->mems_allowed,
1790                                   top_cpuset.mems_allowed)) {
1791                         retval = -EINVAL;
1792                         goto done;
1793                 }
1794         }
1795 
1796         if (nodes_equal(cs->mems_allowed, trialcs->mems_allowed)) {
1797                 retval = 0;             /* Too easy - nothing to do */
1798                 goto done;
1799         }
1800         retval = validate_change(cs, trialcs);
1801         if (retval < 0)
1802                 goto done;
1803 
1804         spin_lock_irq(&callback_lock);
1805         cs->mems_allowed = trialcs->mems_allowed;
1806         spin_unlock_irq(&callback_lock);
1807 
1808         /* use trialcs->mems_allowed as a temp variable */
1809         update_nodemasks_hier(cs, &trialcs->mems_allowed);
1810 done:
1811         return retval;
1812 }
1813 
1814 bool current_cpuset_is_being_rebound(void)
1815 {
1816         bool ret;
1817 
1818         rcu_read_lock();
1819         ret = task_cs(current) == cpuset_being_rebound;
1820         rcu_read_unlock();
1821 
1822         return ret;
1823 }
1824 
1825 static int update_relax_domain_level(struct cpuset *cs, s64 val)
1826 {
1827 #ifdef CONFIG_SMP
1828         if (val < -1 || val >= sched_domain_level_max)
1829                 return -EINVAL;
1830 #endif
1831 
1832         if (val != cs->relax_domain_level) {
1833                 cs->relax_domain_level = val;
1834                 if (!cpumask_empty(cs->cpus_allowed) &&
1835                     is_sched_load_balance(cs))
1836                         rebuild_sched_domains_locked();
1837         }
1838 
1839         return 0;
1840 }
1841 
1842 /**
1843  * update_tasks_flags - update the spread flags of tasks in the cpuset.
1844  * @cs: the cpuset in which each task's spread flags needs to be changed
1845  *
1846  * Iterate through each task of @cs updating its spread flags.  As this
1847  * function is called with cpuset_mutex held, cpuset membership stays
1848  * stable.
1849  */
1850 static void update_tasks_flags(struct cpuset *cs)
1851 {
1852         struct css_task_iter it;
1853         struct task_struct *task;
1854 
1855         css_task_iter_start(&cs->css, 0, &it);
1856         while ((task = css_task_iter_next(&it)))
1857                 cpuset_update_task_spread_flag(cs, task);
1858         css_task_iter_end(&it);
1859 }
1860 
1861 /*
1862  * update_flag - read a 0 or a 1 in a file and update associated flag
1863  * bit:         the bit to update (see cpuset_flagbits_t)
1864  * cs:          the cpuset to update
1865  * turning_on:  whether the flag is being set or cleared
1866  *
1867  * Call with cpuset_mutex held.
1868  */
1869 
1870 static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
1871                        int turning_on)
1872 {
1873         struct cpuset *trialcs;
1874         int balance_flag_changed;
1875         int spread_flag_changed;
1876         int err;
1877 
1878         trialcs = alloc_trial_cpuset(cs);
1879         if (!trialcs)
1880                 return -ENOMEM;
1881 
1882         if (turning_on)
1883                 set_bit(bit, &trialcs->flags);
1884         else
1885                 clear_bit(bit, &trialcs->flags);
1886 
1887         err = validate_change(cs, trialcs);
1888         if (err < 0)
1889                 goto out;
1890 
1891         balance_flag_changed = (is_sched_load_balance(cs) !=
1892                                 is_sched_load_balance(trialcs));
1893 
1894         spread_flag_changed = ((is_spread_slab(cs) != is_spread_slab(trialcs))
1895                         || (is_spread_page(cs) != is_spread_page(trialcs)));
1896 
1897         spin_lock_irq(&callback_lock);
1898         cs->flags = trialcs->flags;
1899         spin_unlock_irq(&callback_lock);
1900 
1901         if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed)
1902                 rebuild_sched_domains_locked();
1903 
1904         if (spread_flag_changed)
1905                 update_tasks_flags(cs);
1906 out:
1907         free_cpuset(trialcs);
1908         return err;
1909 }
1910 
1911 /*
1912  * update_prstate - update partititon_root_state
1913  * cs:  the cpuset to update
1914  * val: 0 - disabled, 1 - enabled
1915  *
1916  * Call with cpuset_mutex held.
1917  */
1918 static int update_prstate(struct cpuset *cs, int val)
1919 {
1920         int err;
1921         struct cpuset *parent = parent_cs(cs);
1922         struct tmpmasks tmp;
1923 
1924         if ((val != 0) && (val != 1))
1925                 return -EINVAL;
1926         if (val == cs->partition_root_state)
1927                 return 0;
1928 
1929         /*
1930          * Cannot force a partial or invalid partition root to a full
1931          * partition root.
1932          */
1933         if (val && cs->partition_root_state)
1934                 return -EINVAL;
1935 
1936         if (alloc_cpumasks(NULL, &tmp))
1937                 return -ENOMEM;
1938 
1939         err = -EINVAL;
1940         if (!cs->partition_root_state) {
1941                 /*
1942                  * Turning on partition root requires setting the
1943                  * CS_CPU_EXCLUSIVE bit implicitly as well and cpus_allowed
1944                  * cannot be NULL.
1945                  */
1946                 if (cpumask_empty(cs->cpus_allowed))
1947                         goto out;
1948 
1949                 err = update_flag(CS_CPU_EXCLUSIVE, cs, 1);
1950                 if (err)
1951                         goto out;
1952 
1953                 err = update_parent_subparts_cpumask(cs, partcmd_enable,
1954                                                      NULL, &tmp);
1955                 if (err) {
1956                         update_flag(CS_CPU_EXCLUSIVE, cs, 0);
1957                         goto out;
1958                 }
1959                 cs->partition_root_state = PRS_ENABLED;
1960         } else {
1961                 /*
1962                  * Turning off partition root will clear the
1963                  * CS_CPU_EXCLUSIVE bit.
1964                  */
1965                 if (cs->partition_root_state == PRS_ERROR) {
1966                         cs->partition_root_state = 0;
1967                         update_flag(CS_CPU_EXCLUSIVE, cs, 0);
1968                         err = 0;
1969                         goto out;
1970                 }
1971 
1972                 err = update_parent_subparts_cpumask(cs, partcmd_disable,
1973                                                      NULL, &tmp);
1974                 if (err)
1975                         goto out;
1976 
1977                 cs->partition_root_state = 0;
1978 
1979                 /* Turning off CS_CPU_EXCLUSIVE will not return error */
1980                 update_flag(CS_CPU_EXCLUSIVE, cs, 0);
1981         }
1982 
1983         /*
1984          * Update cpumask of parent's tasks except when it is the top
1985          * cpuset as some system daemons cannot be mapped to other CPUs.
1986          */
1987         if (parent != &top_cpuset)
1988                 update_tasks_cpumask(parent);
1989 
1990         if (parent->child_ecpus_count)
1991                 update_sibling_cpumasks(parent, cs, &tmp);
1992 
1993         rebuild_sched_domains_locked();
1994 out:
1995         free_cpumasks(NULL, &tmp);
1996         return err;
1997 }
1998 
1999 /*
2000  * Frequency meter - How fast is some event occurring?
2001  *
2002  * These routines manage a digitally filtered, constant time based,
2003  * event frequency meter.  There are four routines:
2004  *   fmeter_init() - initialize a frequency meter.
2005  *   fmeter_markevent() - called each time the event happens.
2006  *   fmeter_getrate() - returns the recent rate of such events.
2007  *   fmeter_update() - internal routine used to update fmeter.
2008  *
2009  * A common data structure is passed to each of these routines,
2010  * which is used to keep track of the state required to manage the
2011  * frequency meter and its digital filter.
2012  *
2013  * The filter works on the number of events marked per unit time.
2014  * The filter is single-pole low-pass recursive (IIR).  The time unit
2015  * is 1 second.  Arithmetic is done using 32-bit integers scaled to
2016  * simulate 3 decimal digits of precision (multiplied by 1000).
2017  *
2018  * With an FM_COEF of 933, and a time base of 1 second, the filter
2019  * has a half-life of 10 seconds, meaning that if the events quit
2020  * happening, then the rate returned from the fmeter_getrate()
2021  * will be cut in half each 10 seconds, until it converges to zero.
2022  *
2023  * It is not worth doing a real infinitely recursive filter.  If more
2024  * than FM_MAXTICKS ticks have elapsed since the last filter event,
2025  * just compute FM_MAXTICKS ticks worth, by which point the level
2026  * will be stable.
2027  *
2028  * Limit the count of unprocessed events to FM_MAXCNT, so as to avoid
2029  * arithmetic overflow in the fmeter_update() routine.
2030  *
2031  * Given the simple 32 bit integer arithmetic used, this meter works
2032  * best for reporting rates between one per millisecond (msec) and
2033  * one per 32 (approx) seconds.  At constant rates faster than one
2034  * per msec it maxes out at values just under 1,000,000.  At constant
2035  * rates between one per msec, and one per second it will stabilize
2036  * to a value N*1000, where N is the rate of events per second.
2037  * At constant rates between one per second and one per 32 seconds,
2038  * it will be choppy, moving up on the seconds that have an event,
2039  * and then decaying until the next event.  At rates slower than
2040  * about one in 32 seconds, it decays all the way back to zero between
2041  * each event.
2042  */
2043 
2044 #define FM_COEF 933             /* coefficient for half-life of 10 secs */
2045 #define FM_MAXTICKS ((u32)99)   /* useless computing more ticks than this */
2046 #define FM_MAXCNT 1000000       /* limit cnt to avoid overflow */
2047 #define FM_SCALE 1000           /* faux fixed point scale */
2048 
2049 /* Initialize a frequency meter */
2050 static void fmeter_init(struct fmeter *fmp)
2051 {
2052         fmp->cnt = 0;
2053         fmp->val = 0;
2054         fmp->time = 0;
2055         spin_lock_init(&fmp->lock);
2056 }
2057 
2058 /* Internal meter update - process cnt events and update value */
2059 static void fmeter_update(struct fmeter *fmp)
2060 {
2061         time64_t now;
2062         u32 ticks;
2063 
2064         now = ktime_get_seconds();
2065         ticks = now - fmp->time;
2066 
2067         if (ticks == 0)
2068                 return;
2069 
2070         ticks = min(FM_MAXTICKS, ticks);
2071         while (ticks-- > 0)
2072                 fmp->val = (FM_COEF * fmp->val) / FM_SCALE;
2073         fmp->time = now;
2074 
2075         fmp->val += ((FM_SCALE - FM_COEF) * fmp->cnt) / FM_SCALE;
2076         fmp->cnt = 0;
2077 }
2078 
2079 /* Process any previous ticks, then bump cnt by one (times scale). */
2080 static void fmeter_markevent(struct fmeter *fmp)
2081 {
2082         spin_lock(&fmp->lock);
2083         fmeter_update(fmp);
2084         fmp->cnt = min(FM_MAXCNT, fmp->cnt + FM_SCALE);
2085         spin_unlock(&fmp->lock);
2086 }
2087 
2088 /* Process any previous ticks, then return current value. */
2089 static int fmeter_getrate(struct fmeter *fmp)
2090 {
2091         int val;
2092 
2093         spin_lock(&fmp->lock);
2094         fmeter_update(fmp);
2095         val = fmp->val;
2096         spin_unlock(&fmp->lock);
2097         return val;
2098 }
2099 
2100 static struct cpuset *cpuset_attach_old_cs;
2101 
2102 /* Called by cgroups to determine if a cpuset is usable; cpuset_mutex held */
2103 static int cpuset_can_attach(struct cgroup_taskset *tset)
2104 {
2105         struct cgroup_subsys_state *css;
2106         struct cpuset *cs;
2107         struct task_struct *task;
2108         int ret;
2109 
2110         /* used later by cpuset_attach() */
2111         cpuset_attach_old_cs = task_cs(cgroup_taskset_first(tset, &css));
2112         cs = css_cs(css);
2113 
2114         percpu_down_write(&cpuset_rwsem);
2115 
2116         /* allow moving tasks into an empty cpuset if on default hierarchy */
2117         ret = -ENOSPC;
2118         if (!is_in_v2_mode() &&
2119             (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed)))
2120                 goto out_unlock;
2121 
2122         cgroup_taskset_for_each(task, css, tset) {
2123                 ret = task_can_attach(task, cs->cpus_allowed);
2124                 if (ret)
2125                         goto out_unlock;
2126                 ret = security_task_setscheduler(task);
2127                 if (ret)
2128                         goto out_unlock;
2129         }
2130 
2131         /*
2132          * Mark attach is in progress.  This makes validate_change() fail
2133          * changes which zero cpus/mems_allowed.
2134          */
2135         cs->attach_in_progress++;
2136         ret = 0;
2137 out_unlock:
2138         percpu_up_write(&cpuset_rwsem);
2139         return ret;
2140 }
2141 
2142 static void cpuset_cancel_attach(struct cgroup_taskset *tset)
2143 {
2144         struct cgroup_subsys_state *css;
2145 
2146         cgroup_taskset_first(tset, &css);
2147 
2148         percpu_down_write(&cpuset_rwsem);
2149         css_cs(css)->attach_in_progress--;
2150         percpu_up_write(&cpuset_rwsem);
2151 }
2152 
2153 /*
2154  * Protected by cpuset_mutex.  cpus_attach is used only by cpuset_attach()
2155  * but we can't allocate it dynamically there.  Define it global and
2156  * allocate from cpuset_init().
2157  */
2158 static cpumask_var_t cpus_attach;
2159 
2160 static void cpuset_attach(struct cgroup_taskset *tset)
2161 {
2162         /* static buf protected by cpuset_mutex */
2163         static nodemask_t cpuset_attach_nodemask_to;
2164         struct task_struct *task;
2165         struct task_struct *leader;
2166         struct cgroup_subsys_state *css;
2167         struct cpuset *cs;
2168         struct cpuset *oldcs = cpuset_attach_old_cs;
2169 
2170         cgroup_taskset_first(tset, &css);
2171         cs = css_cs(css);
2172 
2173         percpu_down_write(&cpuset_rwsem);
2174 
2175         /* prepare for attach */
2176         if (cs == &top_cpuset)
2177                 cpumask_copy(cpus_attach, cpu_possible_mask);
2178         else
2179                 guarantee_online_cpus(cs, cpus_attach);
2180 
2181         guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
2182 
2183         cgroup_taskset_for_each(task, css, tset) {
2184                 /*
2185                  * can_attach beforehand should guarantee that this doesn't
2186                  * fail.  TODO: have a better way to handle failure here
2187                  */
2188                 WARN_ON_ONCE(set_cpus_allowed_ptr(task, cpus_attach));
2189 
2190                 cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to);
2191                 cpuset_update_task_spread_flag(cs, task);
2192         }
2193 
2194         /*
2195          * Change mm for all threadgroup leaders. This is expensive and may
2196          * sleep and should be moved outside migration path proper.
2197          */
2198         cpuset_attach_nodemask_to = cs->effective_mems;
2199         cgroup_taskset_for_each_leader(leader, css, tset) {
2200                 struct mm_struct *mm = get_task_mm(leader);
2201 
2202                 if (mm) {
2203                         mpol_rebind_mm(mm, &cpuset_attach_nodemask_to);
2204 
2205                         /*
2206                          * old_mems_allowed is the same with mems_allowed
2207                          * here, except if this task is being moved
2208                          * automatically due to hotplug.  In that case
2209                          * @mems_allowed has been updated and is empty, so
2210                          * @old_mems_allowed is the right nodesets that we
2211                          * migrate mm from.
2212                          */
2213                         if (is_memory_migrate(cs))
2214                                 cpuset_migrate_mm(mm, &oldcs->old_mems_allowed,
2215                                                   &cpuset_attach_nodemask_to);
2216                         else
2217                                 mmput(mm);
2218                 }
2219         }
2220 
2221         cs->old_mems_allowed = cpuset_attach_nodemask_to;
2222 
2223         cs->attach_in_progress--;
2224         if (!cs->attach_in_progress)
2225                 wake_up(&cpuset_attach_wq);
2226 
2227         percpu_up_write(&cpuset_rwsem);
2228 }
2229 
2230 /* The various types of files and directories in a cpuset file system */
2231 
2232 typedef enum {
2233         FILE_MEMORY_MIGRATE,
2234         FILE_CPULIST,
2235         FILE_MEMLIST,
2236         FILE_EFFECTIVE_CPULIST,
2237         FILE_EFFECTIVE_MEMLIST,
2238         FILE_SUBPARTS_CPULIST,
2239         FILE_CPU_EXCLUSIVE,
2240         FILE_MEM_EXCLUSIVE,
2241         FILE_MEM_HARDWALL,
2242         FILE_SCHED_LOAD_BALANCE,
2243         FILE_PARTITION_ROOT,
2244         FILE_SCHED_RELAX_DOMAIN_LEVEL,
2245         FILE_MEMORY_PRESSURE_ENABLED,
2246         FILE_MEMORY_PRESSURE,
2247         FILE_SPREAD_PAGE,
2248         FILE_SPREAD_SLAB,
2249 } cpuset_filetype_t;
2250 
2251 static int cpuset_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
2252                             u64 val)
2253 {
2254         struct cpuset *cs = css_cs(css);
2255         cpuset_filetype_t type = cft->private;
2256         int retval = 0;
2257 
2258         get_online_cpus();
2259         percpu_down_write(&cpuset_rwsem);
2260         if (!is_cpuset_online(cs)) {
2261                 retval = -ENODEV;
2262                 goto out_unlock;
2263         }
2264 
2265         switch (type) {
2266         case FILE_CPU_EXCLUSIVE:
2267                 retval = update_flag(CS_CPU_EXCLUSIVE, cs, val);
2268                 break;
2269         case FILE_MEM_EXCLUSIVE:
2270                 retval = update_flag(CS_MEM_EXCLUSIVE, cs, val);
2271                 break;
2272         case FILE_MEM_HARDWALL:
2273                 retval = update_flag(CS_MEM_HARDWALL, cs, val);
2274                 break;
2275         case FILE_SCHED_LOAD_BALANCE:
2276                 retval = update_flag(CS_SCHED_LOAD_BALANCE, cs, val);
2277                 break;
2278         case FILE_MEMORY_MIGRATE:
2279                 retval = update_flag(CS_MEMORY_MIGRATE, cs, val);
2280                 break;
2281         case FILE_MEMORY_PRESSURE_ENABLED:
2282                 cpuset_memory_pressure_enabled = !!val;
2283                 break;
2284         case FILE_SPREAD_PAGE:
2285                 retval = update_flag(CS_SPREAD_PAGE, cs, val);
2286                 break;
2287         case FILE_SPREAD_SLAB:
2288                 retval = update_flag(CS_SPREAD_SLAB, cs, val);
2289                 break;
2290         default:
2291                 retval = -EINVAL;
2292                 break;
2293         }
2294 out_unlock:
2295         percpu_up_write(&cpuset_rwsem);
2296         put_online_cpus();
2297         return retval;
2298 }
2299 
2300 static int cpuset_write_s64(struct cgroup_subsys_state *css, struct cftype *cft,
2301                             s64 val)
2302 {
2303         struct cpuset *cs = css_cs(css);
2304         cpuset_filetype_t type = cft->private;
2305         int retval = -ENODEV;
2306 
2307         get_online_cpus();
2308         percpu_down_write(&cpuset_rwsem);
2309         if (!is_cpuset_online(cs))
2310                 goto out_unlock;
2311 
2312         switch (type) {
2313         case FILE_SCHED_RELAX_DOMAIN_LEVEL:
2314                 retval = update_relax_domain_level(cs, val);
2315                 break;
2316         default:
2317                 retval = -EINVAL;
2318                 break;
2319         }
2320 out_unlock:
2321         percpu_up_write(&cpuset_rwsem);
2322         put_online_cpus();
2323         return retval;
2324 }
2325 
2326 /*
2327  * Common handling for a write to a "cpus" or "mems" file.
2328  */
2329 static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
2330                                     char *buf, size_t nbytes, loff_t off)
2331 {
2332         struct cpuset *cs = css_cs(of_css(of));
2333         struct cpuset *trialcs;
2334         int retval = -ENODEV;
2335 
2336         buf = strstrip(buf);
2337 
2338         /*
2339          * CPU or memory hotunplug may leave @cs w/o any execution
2340          * resources, in which case the hotplug code asynchronously updates
2341          * configuration and transfers all tasks to the nearest ancestor
2342          * which can execute.
2343          *
2344          * As writes to "cpus" or "mems" may restore @cs's execution
2345          * resources, wait for the previously scheduled operations before
2346          * proceeding, so that we don't end up keep removing tasks added
2347          * after execution capability is restored.
2348          *
2349          * cpuset_hotplug_work calls back into cgroup core via
2350          * cgroup_transfer_tasks() and waiting for it from a cgroupfs
2351          * operation like this one can lead to a deadlock through kernfs
2352          * active_ref protection.  Let's break the protection.  Losing the
2353          * protection is okay as we check whether @cs is online after
2354          * grabbing cpuset_mutex anyway.  This only happens on the legacy
2355          * hierarchies.
2356          */
2357         css_get(&cs->css);
2358         kernfs_break_active_protection(of->kn);
2359         flush_work(&cpuset_hotplug_work);
2360 
2361         get_online_cpus();
2362         percpu_down_write(&cpuset_rwsem);
2363         if (!is_cpuset_online(cs))
2364                 goto out_unlock;
2365 
2366         trialcs = alloc_trial_cpuset(cs);
2367         if (!trialcs) {
2368                 retval = -ENOMEM;
2369                 goto out_unlock;
2370         }
2371 
2372         switch (of_cft(of)->private) {
2373         case FILE_CPULIST:
2374                 retval = update_cpumask(cs, trialcs, buf);
2375                 break;
2376         case FILE_MEMLIST:
2377                 retval = update_nodemask(cs, trialcs, buf);
2378                 break;
2379         default:
2380                 retval = -EINVAL;
2381                 break;
2382         }
2383 
2384         free_cpuset(trialcs);
2385 out_unlock:
2386         percpu_up_write(&cpuset_rwsem);
2387         put_online_cpus();
2388         kernfs_unbreak_active_protection(of->kn);
2389         css_put(&cs->css);
2390         flush_workqueue(cpuset_migrate_mm_wq);
2391         return retval ?: nbytes;
2392 }
2393 
2394 /*
2395  * These ascii lists should be read in a single call, by using a user
2396  * buffer large enough to hold the entire map.  If read in smaller
2397  * chunks, there is no guarantee of atomicity.  Since the display format
2398  * used, list of ranges of sequential numbers, is variable length,
2399  * and since these maps can change value dynamically, one could read
2400  * gibberish by doing partial reads while a list was changing.
2401  */
2402 static int cpuset_common_seq_show(struct seq_file *sf, void *v)
2403 {
2404         struct cpuset *cs = css_cs(seq_css(sf));
2405         cpuset_filetype_t type = seq_cft(sf)->private;
2406         int ret = 0;
2407 
2408         spin_lock_irq(&callback_lock);
2409 
2410         switch (type) {
2411         case FILE_CPULIST:
2412                 seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->cpus_allowed));
2413                 break;
2414         case FILE_MEMLIST:
2415                 seq_printf(sf, "%*pbl\n", nodemask_pr_args(&cs->mems_allowed));
2416                 break;
2417         case FILE_EFFECTIVE_CPULIST:
2418                 seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->effective_cpus));
2419                 break;
2420         case FILE_EFFECTIVE_MEMLIST:
2421                 seq_printf(sf, "%*pbl\n", nodemask_pr_args(&cs->effective_mems));
2422                 break;
2423         case FILE_SUBPARTS_CPULIST:
2424                 seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->subparts_cpus));
2425                 break;
2426         default:
2427                 ret = -EINVAL;
2428         }
2429 
2430         spin_unlock_irq(&callback_lock);
2431         return ret;
2432 }
2433 
2434 static u64 cpuset_read_u64(struct cgroup_subsys_state *css, struct cftype *cft)
2435 {
2436         struct cpuset *cs = css_cs(css);
2437         cpuset_filetype_t type = cft->private;
2438         switch (type) {
2439         case FILE_CPU_EXCLUSIVE:
2440                 return is_cpu_exclusive(cs);
2441         case FILE_MEM_EXCLUSIVE:
2442                 return is_mem_exclusive(cs);
2443         case FILE_MEM_HARDWALL:
2444                 return is_mem_hardwall(cs);
2445         case FILE_SCHED_LOAD_BALANCE:
2446                 return is_sched_load_balance(cs);
2447         case FILE_MEMORY_MIGRATE:
2448                 return is_memory_migrate(cs);
2449         case FILE_MEMORY_PRESSURE_ENABLED:
2450                 return cpuset_memory_pressure_enabled;
2451         case FILE_MEMORY_PRESSURE:
2452                 return fmeter_getrate(&cs->fmeter);
2453         case FILE_SPREAD_PAGE:
2454                 return is_spread_page(cs);
2455         case FILE_SPREAD_SLAB:
2456                 return is_spread_slab(cs);
2457         default:
2458                 BUG();
2459         }
2460 
2461         /* Unreachable but makes gcc happy */
2462         return 0;
2463 }
2464 
2465 static s64 cpuset_read_s64(struct cgroup_subsys_state *css, struct cftype *cft)
2466 {
2467         struct cpuset *cs = css_cs(css);
2468         cpuset_filetype_t type = cft->private;
2469         switch (type) {
2470         case FILE_SCHED_RELAX_DOMAIN_LEVEL:
2471                 return cs->relax_domain_level;
2472         default:
2473                 BUG();
2474         }
2475 
2476         /* Unrechable but makes gcc happy */
2477         return 0;
2478 }
2479 
2480 static int sched_partition_show(struct seq_file *seq, void *v)
2481 {
2482         struct cpuset *cs = css_cs(seq_css(seq));
2483 
2484         switch (cs->partition_root_state) {
2485         case PRS_ENABLED:
2486                 seq_puts(seq, "root\n");
2487                 break;
2488         case PRS_DISABLED:
2489                 seq_puts(seq, "member\n");
2490                 break;
2491         case PRS_ERROR:
2492                 seq_puts(seq, "root invalid\n");
2493                 break;
2494         }
2495         return 0;
2496 }
2497 
2498 static ssize_t sched_partition_write(struct kernfs_open_file *of, char *buf,
2499                                      size_t nbytes, loff_t off)
2500 {
2501         struct cpuset *cs = css_cs(of_css(of));
2502         int val;
2503         int retval = -ENODEV;
2504 
2505         buf = strstrip(buf);
2506 
2507         /*
2508          * Convert "root" to ENABLED, and convert "member" to DISABLED.
2509          */
2510         if (!strcmp(buf, "root"))
2511                 val = PRS_ENABLED;
2512         else if (!strcmp(buf, "member"))
2513                 val = PRS_DISABLED;
2514         else
2515                 return -EINVAL;
2516 
2517         css_get(&cs->css);
2518         get_online_cpus();
2519         percpu_down_write(&cpuset_rwsem);
2520         if (!is_cpuset_online(cs))
2521                 goto out_unlock;
2522 
2523         retval = update_prstate(cs, val);
2524 out_unlock:
2525         percpu_up_write(&cpuset_rwsem);
2526         put_online_cpus();
2527         css_put(&cs->css);
2528         return retval ?: nbytes;
2529 }
2530 
2531 /*
2532  * for the common functions, 'private' gives the type of file
2533  */
2534 
2535 static struct cftype legacy_files[] = {
2536         {
2537                 .name = "cpus",
2538                 .seq_show = cpuset_common_seq_show,
2539                 .write = cpuset_write_resmask,
2540                 .max_write_len = (100U + 6 * NR_CPUS),
2541                 .private = FILE_CPULIST,
2542         },
2543 
2544         {
2545                 .name = "mems",
2546                 .seq_show = cpuset_common_seq_show,
2547                 .write = cpuset_write_resmask,
2548                 .max_write_len = (100U + 6 * MAX_NUMNODES),
2549                 .private = FILE_MEMLIST,
2550         },
2551 
2552         {
2553                 .name = "effective_cpus",
2554                 .seq_show = cpuset_common_seq_show,
2555                 .private = FILE_EFFECTIVE_CPULIST,
2556         },
2557 
2558         {
2559                 .name = "effective_mems",
2560                 .seq_show = cpuset_common_seq_show,
2561                 .private = FILE_EFFECTIVE_MEMLIST,
2562         },
2563 
2564         {
2565                 .name = "cpu_exclusive",
2566                 .read_u64 = cpuset_read_u64,
2567                 .write_u64 = cpuset_write_u64,
2568                 .private = FILE_CPU_EXCLUSIVE,
2569         },
2570 
2571         {
2572                 .name = "mem_exclusive",
2573                 .read_u64 = cpuset_read_u64,
2574                 .write_u64 = cpuset_write_u64,
2575                 .private = FILE_MEM_EXCLUSIVE,
2576         },
2577 
2578         {
2579                 .name = "mem_hardwall",
2580                 .read_u64 = cpuset_read_u64,
2581                 .write_u64 = cpuset_write_u64,
2582                 .private = FILE_MEM_HARDWALL,
2583         },
2584 
2585         {
2586                 .name = "sched_load_balance",
2587                 .read_u64 = cpuset_read_u64,
2588                 .write_u64 = cpuset_write_u64,
2589                 .private = FILE_SCHED_LOAD_BALANCE,
2590         },
2591 
2592         {
2593                 .name = "sched_relax_domain_level",
2594                 .read_s64 = cpuset_read_s64,
2595                 .write_s64 = cpuset_write_s64,
2596                 .private = FILE_SCHED_RELAX_DOMAIN_LEVEL,
2597         },
2598 
2599         {
2600                 .name = "memory_migrate",
2601                 .read_u64 = cpuset_read_u64,
2602                 .write_u64 = cpuset_write_u64,
2603                 .private = FILE_MEMORY_MIGRATE,
2604         },
2605 
2606         {
2607                 .name = "memory_pressure",
2608                 .read_u64 = cpuset_read_u64,
2609                 .private = FILE_MEMORY_PRESSURE,
2610         },
2611 
2612         {
2613                 .name = "memory_spread_page",
2614                 .read_u64 = cpuset_read_u64,
2615                 .write_u64 = cpuset_write_u64,
2616                 .private = FILE_SPREAD_PAGE,
2617         },
2618 
2619         {
2620                 .name = "memory_spread_slab",
2621                 .read_u64 = cpuset_read_u64,
2622                 .write_u64 = cpuset_write_u64,
2623                 .private = FILE_SPREAD_SLAB,
2624         },
2625 
2626         {
2627                 .name = "memory_pressure_enabled",
2628                 .flags = CFTYPE_ONLY_ON_ROOT,
2629                 .read_u64 = cpuset_read_u64,
2630                 .write_u64 = cpuset_write_u64,
2631                 .private = FILE_MEMORY_PRESSURE_ENABLED,
2632         },
2633 
2634         { }     /* terminate */
2635 };
2636 
2637 /*
2638  * This is currently a minimal set for the default hierarchy. It can be
2639  * expanded later on by migrating more features and control files from v1.
2640  */
2641 static struct cftype dfl_files[] = {
2642         {
2643                 .name = "cpus",
2644                 .seq_show = cpuset_common_seq_show,
2645                 .write = cpuset_write_resmask,
2646                 .max_write_len = (100U + 6 * NR_CPUS),
2647                 .private = FILE_CPULIST,
2648                 .flags = CFTYPE_NOT_ON_ROOT,
2649         },
2650 
2651         {
2652                 .name = "mems",
2653                 .seq_show = cpuset_common_seq_show,
2654                 .write = cpuset_write_resmask,
2655                 .max_write_len = (100U + 6 * MAX_NUMNODES),
2656                 .private = FILE_MEMLIST,
2657                 .flags = CFTYPE_NOT_ON_ROOT,
2658         },
2659 
2660         {
2661                 .name = "cpus.effective",
2662                 .seq_show = cpuset_common_seq_show,
2663                 .private = FILE_EFFECTIVE_CPULIST,
2664         },
2665 
2666         {
2667                 .name = "mems.effective",
2668                 .seq_show = cpuset_common_seq_show,
2669                 .private = FILE_EFFECTIVE_MEMLIST,
2670         },
2671 
2672         {
2673                 .name = "cpus.partition",
2674                 .seq_show = sched_partition_show,
2675                 .write = sched_partition_write,
2676                 .private = FILE_PARTITION_ROOT,
2677                 .flags = CFTYPE_NOT_ON_ROOT,
2678         },
2679 
2680         {
2681                 .name = "cpus.subpartitions",
2682                 .seq_show = cpuset_common_seq_show,
2683                 .private = FILE_SUBPARTS_CPULIST,
2684                 .flags = CFTYPE_DEBUG,
2685         },
2686 
2687         { }     /* terminate */
2688 };
2689 
2690 
2691 /*
2692  *      cpuset_css_alloc - allocate a cpuset css
2693  *      cgrp:   control group that the new cpuset will be part of
2694  */
2695 
2696 static struct cgroup_subsys_state *
2697 cpuset_css_alloc(struct cgroup_subsys_state *parent_css)
2698 {
2699         struct cpuset *cs;
2700 
2701         if (!parent_css)
2702                 return &top_cpuset.css;
2703 
2704         cs = kzalloc(sizeof(*cs), GFP_KERNEL);
2705         if (!cs)
2706                 return ERR_PTR(-ENOMEM);
2707 
2708         if (alloc_cpumasks(cs, NULL)) {
2709                 kfree(cs);
2710                 return ERR_PTR(-ENOMEM);
2711         }
2712 
2713         set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
2714         nodes_clear(cs->mems_allowed);
2715         nodes_clear(cs->effective_mems);
2716         fmeter_init(&cs->fmeter);
2717         cs->relax_domain_level = -1;
2718 
2719         return &cs->css;
2720 }
2721 
2722 static int cpuset_css_online(struct cgroup_subsys_state *css)
2723 {
2724         struct cpuset *cs = css_cs(css);
2725         struct cpuset *parent = parent_cs(cs);
2726         struct cpuset *tmp_cs;
2727         struct cgroup_subsys_state *pos_css;
2728 
2729         if (!parent)
2730                 return 0;
2731 
2732         get_online_cpus();
2733         percpu_down_write(&cpuset_rwsem);
2734 
2735         set_bit(CS_ONLINE, &cs->flags);
2736         if (is_spread_page(parent))
2737                 set_bit(CS_SPREAD_PAGE, &cs->flags);
2738         if (is_spread_slab(parent))
2739                 set_bit(CS_SPREAD_SLAB, &cs->flags);
2740 
2741         cpuset_inc();
2742 
2743         spin_lock_irq(&callback_lock);
2744         if (is_in_v2_mode()) {
2745                 cpumask_copy(cs->effective_cpus, parent->effective_cpus);
2746                 cs->effective_mems = parent->effective_mems;
2747                 cs->use_parent_ecpus = true;
2748                 parent->child_ecpus_count++;
2749         }
2750         spin_unlock_irq(&callback_lock);
2751 
2752         if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags))
2753                 goto out_unlock;
2754 
2755         /*
2756          * Clone @parent's configuration if CGRP_CPUSET_CLONE_CHILDREN is
2757          * set.  This flag handling is implemented in cgroup core for
2758          * histrical reasons - the flag may be specified during mount.
2759          *
2760          * Currently, if any sibling cpusets have exclusive cpus or mem, we
2761          * refuse to clone the configuration - thereby refusing the task to
2762          * be entered, and as a result refusing the sys_unshare() or
2763          * clone() which initiated it.  If this becomes a problem for some
2764          * users who wish to allow that scenario, then this could be
2765          * changed to grant parent->cpus_allowed-sibling_cpus_exclusive
2766          * (and likewise for mems) to the new cgroup.
2767          */
2768         rcu_read_lock();
2769         cpuset_for_each_child(tmp_cs, pos_css, parent) {
2770                 if (is_mem_exclusive(tmp_cs) || is_cpu_exclusive(tmp_cs)) {
2771                         rcu_read_unlock();
2772                         goto out_unlock;
2773                 }
2774         }
2775         rcu_read_unlock();
2776 
2777         spin_lock_irq(&callback_lock);
2778         cs->mems_allowed = parent->mems_allowed;
2779         cs->effective_mems = parent->mems_allowed;
2780         cpumask_copy(cs->cpus_allowed, parent->cpus_allowed);
2781         cpumask_copy(cs->effective_cpus, parent->cpus_allowed);
2782         spin_unlock_irq(&callback_lock);
2783 out_unlock:
2784         percpu_up_write(&cpuset_rwsem);
2785         put_online_cpus();
2786         return 0;
2787 }
2788 
2789 /*
2790  * If the cpuset being removed has its flag 'sched_load_balance'
2791  * enabled, then simulate turning sched_load_balance off, which
2792  * will call rebuild_sched_domains_locked(). That is not needed
2793  * in the default hierarchy where only changes in partition
2794  * will cause repartitioning.
2795  *
2796  * If the cpuset has the 'sched.partition' flag enabled, simulate
2797  * turning 'sched.partition" off.
2798  */
2799 
2800 static void cpuset_css_offline(struct cgroup_subsys_state *css)
2801 {
2802         struct cpuset *cs = css_cs(css);
2803 
2804         get_online_cpus();
2805         percpu_down_write(&cpuset_rwsem);
2806 
2807         if (is_partition_root(cs))
2808                 update_prstate(cs, 0);
2809 
2810         if (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
2811             is_sched_load_balance(cs))
2812                 update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
2813 
2814         if (cs->use_parent_ecpus) {
2815                 struct cpuset *parent = parent_cs(cs);
2816 
2817                 cs->use_parent_ecpus = false;
2818                 parent->child_ecpus_count--;
2819         }
2820 
2821         cpuset_dec();
2822         clear_bit(CS_ONLINE, &cs->flags);
2823 
2824         percpu_up_write(&cpuset_rwsem);
2825         put_online_cpus();
2826 }
2827 
2828 static void cpuset_css_free(struct cgroup_subsys_state *css)
2829 {
2830         struct cpuset *cs = css_cs(css);
2831 
2832         free_cpuset(cs);
2833 }
2834 
2835 static void cpuset_bind(struct cgroup_subsys_state *root_css)
2836 {
2837         percpu_down_write(&cpuset_rwsem);
2838         spin_lock_irq(&callback_lock);
2839 
2840         if (is_in_v2_mode()) {
2841                 cpumask_copy(top_cpuset.cpus_allowed, cpu_possible_mask);
2842                 top_cpuset.mems_allowed = node_possible_map;
2843         } else {
2844                 cpumask_copy(top_cpuset.cpus_allowed,
2845                              top_cpuset.effective_cpus);
2846                 top_cpuset.mems_allowed = top_cpuset.effective_mems;
2847         }
2848 
2849         spin_unlock_irq(&callback_lock);
2850         percpu_up_write(&cpuset_rwsem);
2851 }
2852 
2853 /*
2854  * Make sure the new task conform to the current state of its parent,
2855  * which could have been changed by cpuset just after it inherits the
2856  * state from the parent and before it sits on the cgroup's task list.
2857  */
2858 static void cpuset_fork(struct task_struct *task)
2859 {
2860         if (task_css_is_root(task, cpuset_cgrp_id))
2861                 return;
2862 
2863         set_cpus_allowed_ptr(task, current->cpus_ptr);
2864         task->mems_allowed = current->mems_allowed;
2865 }
2866 
2867 struct cgroup_subsys cpuset_cgrp_subsys = {
2868         .css_alloc      = cpuset_css_alloc,
2869         .css_online     = cpuset_css_online,
2870         .css_offline    = cpuset_css_offline,
2871         .css_free       = cpuset_css_free,
2872         .can_attach     = cpuset_can_attach,
2873         .cancel_attach  = cpuset_cancel_attach,
2874         .attach         = cpuset_attach,
2875         .post_attach    = cpuset_post_attach,
2876         .bind           = cpuset_bind,
2877         .fork           = cpuset_fork,
2878         .legacy_cftypes = legacy_files,
2879         .dfl_cftypes    = dfl_files,
2880         .early_init     = true,
2881         .threaded       = true,
2882 };
2883 
2884 /**
2885  * cpuset_init - initialize cpusets at system boot
2886  *
2887  * Description: Initialize top_cpuset
2888  **/
2889 
2890 int __init cpuset_init(void)
2891 {
2892         BUG_ON(percpu_init_rwsem(&cpuset_rwsem));
2893 
2894         BUG_ON(!alloc_cpumask_var(&top_cpuset.cpus_allowed, GFP_KERNEL));
2895         BUG_ON(!alloc_cpumask_var(&top_cpuset.effective_cpus, GFP_KERNEL));
2896         BUG_ON(!zalloc_cpumask_var(&top_cpuset.subparts_cpus, GFP_KERNEL));
2897 
2898         cpumask_setall(top_cpuset.cpus_allowed);
2899         nodes_setall(top_cpuset.mems_allowed);
2900         cpumask_setall(top_cpuset.effective_cpus);
2901         nodes_setall(top_cpuset.effective_mems);
2902 
2903         fmeter_init(&top_cpuset.fmeter);
2904         set_bit(CS_SCHED_LOAD_BALANCE, &top_cpuset.flags);
2905         top_cpuset.relax_domain_level = -1;
2906 
2907         BUG_ON(!alloc_cpumask_var(&cpus_attach, GFP_KERNEL));
2908 
2909         return 0;
2910 }
2911 
2912 /*
2913  * If CPU and/or memory hotplug handlers, below, unplug any CPUs
2914  * or memory nodes, we need to walk over the cpuset hierarchy,
2915  * removing that CPU or node from all cpusets.  If this removes the
2916  * last CPU or node from a cpuset, then move the tasks in the empty
2917  * cpuset to its next-highest non-empty parent.
2918  */
2919 static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
2920 {
2921         struct cpuset *parent;
2922 
2923         /*
2924          * Find its next-highest non-empty parent, (top cpuset
2925          * has online cpus, so can't be empty).
2926          */
2927         parent = parent_cs(cs);
2928         while (cpumask_empty(parent->cpus_allowed) ||
2929                         nodes_empty(parent->mems_allowed))
2930                 parent = parent_cs(parent);
2931 
2932         if (cgroup_transfer_tasks(parent->css.cgroup, cs->css.cgroup)) {
2933                 pr_err("cpuset: failed to transfer tasks out of empty cpuset ");
2934                 pr_cont_cgroup_name(cs->css.cgroup);
2935                 pr_cont("\n");
2936         }
2937 }
2938 
2939 static void
2940 hotplug_update_tasks_legacy(struct cpuset *cs,
2941                             struct cpumask *new_cpus, nodemask_t *new_mems,
2942                             bool cpus_updated, bool mems_updated)
2943 {
2944         bool is_empty;
2945 
2946         spin_lock_irq(&callback_lock);
2947         cpumask_copy(cs->cpus_allowed, new_cpus);
2948         cpumask_copy(cs->effective_cpus, new_cpus);
2949         cs->mems_allowed = *new_mems;
2950         cs->effective_mems = *new_mems;
2951         spin_unlock_irq(&callback_lock);
2952 
2953         /*
2954          * Don't call update_tasks_cpumask() if the cpuset becomes empty,
2955          * as the tasks will be migratecd to an ancestor.
2956          */
2957         if (cpus_updated && !cpumask_empty(cs->cpus_allowed))
2958                 update_tasks_cpumask(cs);
2959         if (mems_updated && !nodes_empty(cs->mems_allowed))
2960                 update_tasks_nodemask(cs);
2961 
2962         is_empty = cpumask_empty(cs->cpus_allowed) ||
2963                    nodes_empty(cs->mems_allowed);
2964 
2965         percpu_up_write(&cpuset_rwsem);
2966 
2967         /*
2968          * Move tasks to the nearest ancestor with execution resources,
2969          * This is full cgroup operation which will also call back into
2970          * cpuset. Should be done outside any lock.
2971          */
2972         if (is_empty)
2973                 remove_tasks_in_empty_cpuset(cs);
2974 
2975         percpu_down_write(&cpuset_rwsem);
2976 }
2977 
2978 static void
2979 hotplug_update_tasks(struct cpuset *cs,
2980                      struct cpumask *new_cpus, nodemask_t *new_mems,
2981                      bool cpus_updated, bool mems_updated)
2982 {
2983         if (cpumask_empty(new_cpus))
2984                 cpumask_copy(new_cpus, parent_cs(cs)->effective_cpus);
2985         if (nodes_empty(*new_mems))
2986                 *new_mems = parent_cs(cs)->effective_mems;
2987 
2988         spin_lock_irq(&callback_lock);
2989         cpumask_copy(cs->effective_cpus, new_cpus);
2990         cs->effective_mems = *new_mems;
2991         spin_unlock_irq(&callback_lock);
2992 
2993         if (cpus_updated)
2994                 update_tasks_cpumask(cs);
2995         if (mems_updated)
2996                 update_tasks_nodemask(cs);
2997 }
2998 
2999 static bool force_rebuild;
3000 
3001 void cpuset_force_rebuild(void)
3002 {
3003         force_rebuild = true;
3004 }
3005 
3006 /**
3007  * cpuset_hotplug_update_tasks - update tasks in a cpuset for hotunplug
3008  * @cs: cpuset in interest
3009  * @tmp: the tmpmasks structure pointer
3010  *
3011  * Compare @cs's cpu and mem masks against top_cpuset and if some have gone
3012  * offline, update @cs accordingly.  If @cs ends up with no CPU or memory,
3013  * all its tasks are moved to the nearest ancestor with both resources.
3014  */
3015 static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
3016 {
3017         static cpumask_t new_cpus;
3018         static nodemask_t new_mems;
3019         bool cpus_updated;
3020         bool mems_updated;
3021         struct cpuset *parent;
3022 retry:
3023         wait_event(cpuset_attach_wq, cs->attach_in_progress == 0);
3024 
3025         percpu_down_write(&cpuset_rwsem);
3026 
3027         /*
3028          * We have raced with task attaching. We wait until attaching
3029          * is finished, so we won't attach a task to an empty cpuset.
3030          */
3031         if (cs->attach_in_progress) {
3032                 percpu_up_write(&cpuset_rwsem);
3033                 goto retry;
3034         }
3035 
3036         parent =  parent_cs(cs);
3037         compute_effective_cpumask(&new_cpus, cs, parent);
3038         nodes_and(new_mems, cs->mems_allowed, parent->effective_mems);
3039 
3040         if (cs->nr_subparts_cpus)
3041                 /*
3042                  * Make sure that CPUs allocated to child partitions
3043                  * do not show up in effective_cpus.
3044                  */
3045                 cpumask_andnot(&new_cpus, &new_cpus, cs->subparts_cpus);
3046 
3047         if (!tmp || !cs->partition_root_state)
3048                 goto update_tasks;
3049 
3050         /*
3051          * In the unlikely event that a partition root has empty
3052          * effective_cpus or its parent becomes erroneous, we have to
3053          * transition it to the erroneous state.
3054          */
3055         if (is_partition_root(cs) && (cpumask_empty(&new_cpus) ||
3056            (parent->partition_root_state == PRS_ERROR))) {
3057                 if (cs->nr_subparts_cpus) {
3058                         cs->nr_subparts_cpus = 0;
3059                         cpumask_clear(cs->subparts_cpus);
3060                         compute_effective_cpumask(&new_cpus, cs, parent);
3061                 }
3062 
3063                 /*
3064                  * If the effective_cpus is empty because the child
3065                  * partitions take away all the CPUs, we can keep
3066                  * the current partition and let the child partitions
3067                  * fight for available CPUs.
3068                  */
3069                 if ((parent->partition_root_state == PRS_ERROR) ||
3070                      cpumask_empty(&new_cpus)) {
3071                         update_parent_subparts_cpumask(cs, partcmd_disable,
3072                                                        NULL, tmp);
3073                         cs->partition_root_state = PRS_ERROR;
3074                 }
3075                 cpuset_force_rebuild();
3076         }
3077 
3078         /*
3079          * On the other hand, an erroneous partition root may be transitioned
3080          * back to a regular one or a partition root with no CPU allocated
3081          * from the parent may change to erroneous.
3082          */
3083         if (is_partition_root(parent) &&
3084            ((cs->partition_root_state == PRS_ERROR) ||
3085             !cpumask_intersects(&new_cpus, parent->subparts_cpus)) &&
3086              update_parent_subparts_cpumask(cs, partcmd_update, NULL, tmp))
3087                 cpuset_force_rebuild();
3088 
3089 update_tasks:
3090         cpus_updated = !cpumask_equal(&new_cpus, cs->effective_cpus);
3091         mems_updated = !nodes_equal(new_mems, cs->effective_mems);
3092 
3093         if (is_in_v2_mode())
3094                 hotplug_update_tasks(cs, &new_cpus, &new_mems,
3095                                      cpus_updated, mems_updated);
3096         else
3097                 hotplug_update_tasks_legacy(cs, &new_cpus, &new_mems,
3098                                             cpus_updated, mems_updated);
3099 
3100         percpu_up_write(&cpuset_rwsem);
3101 }
3102 
3103 /**
3104  * cpuset_hotplug_workfn - handle CPU/memory hotunplug for a cpuset
3105  *
3106  * This function is called after either CPU or memory configuration has
3107  * changed and updates cpuset accordingly.  The top_cpuset is always
3108  * synchronized to cpu_active_mask and N_MEMORY, which is necessary in
3109  * order to make cpusets transparent (of no affect) on systems that are
3110  * actively using CPU hotplug but making no active use of cpusets.
3111  *
3112  * Non-root cpusets are only affected by offlining.  If any CPUs or memory
3113  * nodes have been taken down, cpuset_hotplug_update_tasks() is invoked on
3114  * all descendants.
3115  *
3116  * Note that CPU offlining during suspend is ignored.  We don't modify
3117  * cpusets across suspend/resume cycles at all.
3118  */
3119 static void cpuset_hotplug_workfn(struct work_struct *work)
3120 {
3121         static cpumask_t new_cpus;
3122         static nodemask_t new_mems;
3123         bool cpus_updated, mems_updated;
3124         bool on_dfl = is_in_v2_mode();
3125         struct tmpmasks tmp, *ptmp = NULL;
3126 
3127         if (on_dfl && !alloc_cpumasks(NULL, &tmp))
3128                 ptmp = &tmp;
3129 
3130         percpu_down_write(&cpuset_rwsem);
3131 
3132         /* fetch the available cpus/mems and find out which changed how */
3133         cpumask_copy(&new_cpus, cpu_active_mask);
3134         new_mems = node_states[N_MEMORY];
3135 
3136         /*
3137          * If subparts_cpus is populated, it is likely that the check below
3138          * will produce a false positive on cpus_updated when the cpu list
3139          * isn't changed. It is extra work, but it is better to be safe.
3140          */
3141         cpus_updated = !cpumask_equal(top_cpuset.effective_cpus, &new_cpus);
3142         mems_updated = !nodes_equal(top_cpuset.effective_mems, new_mems);
3143 
3144         /* synchronize cpus_allowed to cpu_active_mask */
3145         if (cpus_updated) {
3146                 spin_lock_irq(&callback_lock);
3147                 if (!on_dfl)
3148                         cpumask_copy(top_cpuset.cpus_allowed, &new_cpus);
3149                 /*
3150                  * Make sure that CPUs allocated to child partitions
3151                  * do not show up in effective_cpus. If no CPU is left,
3152                  * we clear the subparts_cpus & let the child partitions
3153                  * fight for the CPUs again.
3154                  */
3155                 if (top_cpuset.nr_subparts_cpus) {
3156                         if (cpumask_subset(&new_cpus,
3157                                            top_cpuset.subparts_cpus)) {
3158                                 top_cpuset.nr_subparts_cpus = 0;
3159                                 cpumask_clear(top_cpuset.subparts_cpus);
3160                         } else {
3161                                 cpumask_andnot(&new_cpus, &new_cpus,
3162                                                top_cpuset.subparts_cpus);
3163                         }
3164                 }
3165                 cpumask_copy(top_cpuset.effective_cpus, &new_cpus);
3166                 spin_unlock_irq(&callback_lock);
3167                 /* we don't mess with cpumasks of tasks in top_cpuset */
3168         }
3169 
3170         /* synchronize mems_allowed to N_MEMORY */
3171         if (mems_updated) {
3172                 spin_lock_irq(&callback_lock);
3173                 if (!on_dfl)
3174                         top_cpuset.mems_allowed = new_mems;
3175                 top_cpuset.effective_mems = new_mems;
3176                 spin_unlock_irq(&callback_lock);
3177                 update_tasks_nodemask(&top_cpuset);
3178         }
3179 
3180         percpu_up_write(&cpuset_rwsem);
3181 
3182         /* if cpus or mems changed, we need to propagate to descendants */
3183         if (cpus_updated || mems_updated) {
3184                 struct cpuset *cs;
3185                 struct cgroup_subsys_state *pos_css;
3186 
3187                 rcu_read_lock();
3188                 cpuset_for_each_descendant_pre(cs, pos_css, &top_cpuset) {
3189                         if (cs == &top_cpuset || !css_tryget_online(&cs->css))
3190                                 continue;
3191                         rcu_read_unlock();
3192 
3193                         cpuset_hotplug_update_tasks(cs, ptmp);
3194 
3195                         rcu_read_lock();
3196                         css_put(&cs->css);
3197                 }
3198                 rcu_read_unlock();
3199         }
3200 
3201         /* rebuild sched domains if cpus_allowed has changed */
3202         if (cpus_updated || force_rebuild) {
3203                 force_rebuild = false;
3204                 rebuild_sched_domains();
3205         }
3206 
3207         free_cpumasks(NULL, ptmp);
3208 }
3209 
3210 void cpuset_update_active_cpus(void)
3211 {
3212         /*
3213          * We're inside cpu hotplug critical region which usually nests
3214          * inside cgroup synchronization.  Bounce actual hotplug processing
3215          * to a work item to avoid reverse locking order.
3216          */
3217         schedule_work(&cpuset_hotplug_work);
3218 }
3219 
3220 void cpuset_wait_for_hotplug(void)
3221 {
3222         flush_work(&cpuset_hotplug_work);
3223 }
3224 
3225 /*
3226  * Keep top_cpuset.mems_allowed tracking node_states[N_MEMORY].
3227  * Call this routine anytime after node_states[N_MEMORY] changes.
3228  * See cpuset_update_active_cpus() for CPU hotplug handling.
3229  */
3230 static int cpuset_track_online_nodes(struct notifier_block *self,
3231                                 unsigned long action, void *arg)
3232 {
3233         schedule_work(&cpuset_hotplug_work);
3234         return NOTIFY_OK;
3235 }
3236 
3237 static struct notifier_block cpuset_track_online_nodes_nb = {
3238         .notifier_call = cpuset_track_online_nodes,
3239         .priority = 10,         /* ??! */
3240 };
3241 
3242 /**
3243  * cpuset_init_smp - initialize cpus_allowed
3244  *
3245  * Description: Finish top cpuset after cpu, node maps are initialized
3246  */
3247 void __init cpuset_init_smp(void)
3248 {
3249         cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
3250         top_cpuset.mems_allowed = node_states[N_MEMORY];
3251         top_cpuset.old_mems_allowed = top_cpuset.mems_allowed;
3252 
3253         cpumask_copy(top_cpuset.effective_cpus, cpu_active_mask);
3254         top_cpuset.effective_mems = node_states[N_MEMORY];
3255 
3256         register_hotmemory_notifier(&cpuset_track_online_nodes_nb);
3257 
3258         cpuset_migrate_mm_wq = alloc_ordered_workqueue("cpuset_migrate_mm", 0);
3259         BUG_ON(!cpuset_migrate_mm_wq);
3260 }
3261 
3262 /**
3263  * cpuset_cpus_allowed - return cpus_allowed mask from a tasks cpuset.
3264  * @tsk: pointer to task_struct from which to obtain cpuset->cpus_allowed.
3265  * @pmask: pointer to struct cpumask variable to receive cpus_allowed set.
3266  *
3267  * Description: Returns the cpumask_var_t cpus_allowed of the cpuset
3268  * attached to the specified @tsk.  Guaranteed to return some non-empty
3269  * subset of cpu_online_mask, even if this means going outside the
3270  * tasks cpuset.
3271  **/
3272 
3273 void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask)
3274 {
3275         unsigned long flags;
3276 
3277         spin_lock_irqsave(&callback_lock, flags);
3278         rcu_read_lock();
3279         guarantee_online_cpus(task_cs(tsk), pmask);
3280         rcu_read_unlock();
3281         spin_unlock_irqrestore(&callback_lock, flags);
3282 }
3283 
3284 /**
3285  * cpuset_cpus_allowed_fallback - final fallback before complete catastrophe.
3286  * @tsk: pointer to task_struct with which the scheduler is struggling
3287  *
3288  * Description: In the case that the scheduler cannot find an allowed cpu in
3289  * tsk->cpus_allowed, we fall back to task_cs(tsk)->cpus_allowed. In legacy
3290  * mode however, this value is the same as task_cs(tsk)->effective_cpus,
3291  * which will not contain a sane cpumask during cases such as cpu hotplugging.
3292  * This is the absolute last resort for the scheduler and it is only used if
3293  * _every_ other avenue has been traveled.
3294  **/
3295 
3296 void cpuset_cpus_allowed_fallback(struct task_struct *tsk)
3297 {
3298         rcu_read_lock();
3299         do_set_cpus_allowed(tsk, is_in_v2_mode() ?
3300                 task_cs(tsk)->cpus_allowed : cpu_possible_mask);
3301         rcu_read_unlock();
3302 
3303         /*
3304          * We own tsk->cpus_allowed, nobody can change it under us.
3305          *
3306          * But we used cs && cs->cpus_allowed lockless and thus can
3307          * race with cgroup_attach_task() or update_cpumask() and get
3308          * the wrong tsk->cpus_allowed. However, both cases imply the
3309          * subsequent cpuset_change_cpumask()->set_cpus_allowed_ptr()
3310          * which takes task_rq_lock().
3311          *
3312          * If we are called after it dropped the lock we must see all
3313          * changes in tsk_cs()->cpus_allowed. Otherwise we can temporary
3314          * set any mask even if it is not right from task_cs() pov,
3315          * the pending set_cpus_allowed_ptr() will fix things.
3316          *
3317          * select_fallback_rq() will fix things ups and set cpu_possible_mask
3318          * if required.
3319          */
3320 }
3321 
3322 void __init cpuset_init_current_mems_allowed(void)
3323 {
3324         nodes_setall(current->mems_allowed);
3325 }
3326 
3327 /**
3328  * cpuset_mems_allowed - return mems_allowed mask from a tasks cpuset.
3329  * @tsk: pointer to task_struct from which to obtain cpuset->mems_allowed.
3330  *
3331  * Description: Returns the nodemask_t mems_allowed of the cpuset
3332  * attached to the specified @tsk.  Guaranteed to return some non-empty
3333  * subset of node_states[N_MEMORY], even if this means going outside the
3334  * tasks cpuset.
3335  **/
3336 
3337 nodemask_t cpuset_mems_allowed(struct task_struct *tsk)
3338 {
3339         nodemask_t mask;
3340         unsigned long flags;
3341 
3342         spin_lock_irqsave(&callback_lock, flags);
3343         rcu_read_lock();
3344         guarantee_online_mems(task_cs(tsk), &mask);
3345         rcu_read_unlock();
3346         spin_unlock_irqrestore(&callback_lock, flags);
3347 
3348         return mask;
3349 }
3350 
3351 /**
3352  * cpuset_nodemask_valid_mems_allowed - check nodemask vs. curremt mems_allowed
3353  * @nodemask: the nodemask to be checked
3354  *
3355  * Are any of the nodes in the nodemask allowed in current->mems_allowed?
3356  */
3357 int cpuset_nodemask_valid_mems_allowed(nodemask_t *nodemask)
3358 {
3359         return nodes_intersects(*nodemask, current->mems_allowed);
3360 }
3361 
3362 /*
3363  * nearest_hardwall_ancestor() - Returns the nearest mem_exclusive or
3364  * mem_hardwall ancestor to the specified cpuset.  Call holding
3365  * callback_lock.  If no ancestor is mem_exclusive or mem_hardwall
3366  * (an unusual configuration), then returns the root cpuset.
3367  */
3368 static struct cpuset *nearest_hardwall_ancestor(struct cpuset *cs)
3369 {
3370         while (!(is_mem_exclusive(cs) || is_mem_hardwall(cs)) && parent_cs(cs))
3371                 cs = parent_cs(cs);
3372         return cs;
3373 }
3374 
3375 /**
3376  * cpuset_node_allowed - Can we allocate on a memory node?
3377  * @node: is this an allowed node?
3378  * @gfp_mask: memory allocation flags
3379  *
3380  * If we're in interrupt, yes, we can always allocate.  If @node is set in
3381  * current's mems_allowed, yes.  If it's not a __GFP_HARDWALL request and this
3382  * node is set in the nearest hardwalled cpuset ancestor to current's cpuset,
3383  * yes.  If current has access to memory reserves as an oom victim, yes.
3384  * Otherwise, no.
3385  *
3386  * GFP_USER allocations are marked with the __GFP_HARDWALL bit,
3387  * and do not allow allocations outside the current tasks cpuset
3388  * unless the task has been OOM killed.
3389  * GFP_KERNEL allocations are not so marked, so can escape to the
3390  * nearest enclosing hardwalled ancestor cpuset.
3391  *
3392  * Scanning up parent cpusets requires callback_lock.  The
3393  * __alloc_pages() routine only calls here with __GFP_HARDWALL bit
3394  * _not_ set if it's a GFP_KERNEL allocation, and all nodes in the
3395  * current tasks mems_allowed came up empty on the first pass over
3396  * the zonelist.  So only GFP_KERNEL allocations, if all nodes in the
3397  * cpuset are short of memory, might require taking the callback_lock.
3398  *
3399  * The first call here from mm/page_alloc:get_page_from_freelist()
3400  * has __GFP_HARDWALL set in gfp_mask, enforcing hardwall cpusets,
3401  * so no allocation on a node outside the cpuset is allowed (unless
3402  * in interrupt, of course).
3403  *
3404  * The second pass through get_page_from_freelist() doesn't even call
3405  * here for GFP_ATOMIC calls.  For those calls, the __alloc_pages()
3406  * variable 'wait' is not set, and the bit ALLOC_CPUSET is not set
3407  * in alloc_flags.  That logic and the checks below have the combined
3408  * affect that:
3409  *      in_interrupt - any node ok (current task context irrelevant)
3410  *      GFP_ATOMIC   - any node ok
3411  *      tsk_is_oom_victim   - any node ok
3412  *      GFP_KERNEL   - any node in enclosing hardwalled cpuset ok
3413  *      GFP_USER     - only nodes in current tasks mems allowed ok.
3414  */
3415 bool __cpuset_node_allowed(int node, gfp_t gfp_mask)
3416 {
3417         struct cpuset *cs;              /* current cpuset ancestors */
3418         int allowed;                    /* is allocation in zone z allowed? */
3419         unsigned long flags;
3420 
3421         if (in_interrupt())
3422                 return true;
3423         if (node_isset(node, current->mems_allowed))
3424                 return true;
3425         /*
3426          * Allow tasks that have access to memory reserves because they have
3427          * been OOM killed to get memory anywhere.
3428          */
3429         if (unlikely(tsk_is_oom_victim(current)))
3430                 return true;
3431         if (gfp_mask & __GFP_HARDWALL)  /* If hardwall request, stop here */
3432                 return false;
3433 
3434         if (current->flags & PF_EXITING) /* Let dying task have memory */
3435                 return true;
3436 
3437         /* Not hardwall and node outside mems_allowed: scan up cpusets */
3438         spin_lock_irqsave(&callback_lock, flags);
3439 
3440         rcu_read_lock();
3441         cs = nearest_hardwall_ancestor(task_cs(current));
3442         allowed = node_isset(node, cs->mems_allowed);
3443         rcu_read_unlock();
3444 
3445         spin_unlock_irqrestore(&callback_lock, flags);
3446         return allowed;
3447 }
3448 
3449 /**
3450  * cpuset_mem_spread_node() - On which node to begin search for a file page
3451  * cpuset_slab_spread_node() - On which node to begin search for a slab page
3452  *
3453  * If a task is marked PF_SPREAD_PAGE or PF_SPREAD_SLAB (as for
3454  * tasks in a cpuset with is_spread_page or is_spread_slab set),
3455  * and if the memory allocation used cpuset_mem_spread_node()
3456  * to determine on which node to start looking, as it will for
3457  * certain page cache or slab cache pages such as used for file
3458  * system buffers and inode caches, then instead of starting on the
3459  * local node to look for a free page, rather spread the starting
3460  * node around the tasks mems_allowed nodes.
3461  *
3462  * We don't have to worry about the returned node being offline
3463  * because "it can't happen", and even if it did, it would be ok.
3464  *
3465  * The routines calling guarantee_online_mems() are careful to
3466  * only set nodes in task->mems_allowed that are online.  So it
3467  * should not be possible for the following code to return an
3468  * offline node.  But if it did, that would be ok, as this routine
3469  * is not returning the node where the allocation must be, only
3470  * the node where the search should start.  The zonelist passed to
3471  * __alloc_pages() will include all nodes.  If the slab allocator
3472  * is passed an offline node, it will fall back to the local node.
3473  * See kmem_cache_alloc_node().
3474  */
3475 
3476 static int cpuset_spread_node(int *rotor)
3477 {
3478         return *rotor = next_node_in(*rotor, current->mems_allowed);
3479 }
3480 
3481 int cpuset_mem_spread_node(void)
3482 {
3483         if (current->cpuset_mem_spread_rotor == NUMA_NO_NODE)
3484                 current->cpuset_mem_spread_rotor =
3485                         node_random(&current->mems_allowed);
3486 
3487         return cpuset_spread_node(&current->cpuset_mem_spread_rotor);
3488 }
3489 
3490 int cpuset_slab_spread_node(void)
3491 {
3492         if (current->cpuset_slab_spread_rotor == NUMA_NO_NODE)
3493                 current->cpuset_slab_spread_rotor =
3494                         node_random(&current->mems_allowed);
3495 
3496         return cpuset_spread_node(&current->cpuset_slab_spread_rotor);
3497 }
3498 
3499 EXPORT_SYMBOL_GPL(cpuset_mem_spread_node);
3500 
3501 /**
3502  * cpuset_mems_allowed_intersects - Does @tsk1's mems_allowed intersect @tsk2's?
3503  * @tsk1: pointer to task_struct of some task.
3504  * @tsk2: pointer to task_struct of some other task.
3505  *
3506  * Description: Return true if @tsk1's mems_allowed intersects the
3507  * mems_allowed of @tsk2.  Used by the OOM killer to determine if
3508  * one of the task's memory usage might impact the memory available
3509  * to the other.
3510  **/
3511 
3512 int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
3513                                    const struct task_struct *tsk2)
3514 {
3515         return nodes_intersects(tsk1->mems_allowed, tsk2->mems_allowed);
3516 }
3517 
3518 /**
3519  * cpuset_print_current_mems_allowed - prints current's cpuset and mems_allowed
3520  *
3521  * Description: Prints current's name, cpuset name, and cached copy of its
3522  * mems_allowed to the kernel log.
3523  */
3524 void cpuset_print_current_mems_allowed(void)
3525 {
3526         struct cgroup *cgrp;
3527 
3528         rcu_read_lock();
3529 
3530         cgrp = task_cs(current)->css.cgroup;
3531         pr_cont(",cpuset=");
3532         pr_cont_cgroup_name(cgrp);
3533         pr_cont(",mems_allowed=%*pbl",
3534                 nodemask_pr_args(&current->mems_allowed));
3535 
3536         rcu_read_unlock();
3537 }
3538 
3539 /*
3540  * Collection of memory_pressure is suppressed unless
3541  * this flag is enabled by writing "1" to the special
3542  * cpuset file 'memory_pressure_enabled' in the root cpuset.
3543  */
3544 
3545 int cpuset_memory_pressure_enabled __read_mostly;
3546 
3547 /**
3548  * cpuset_memory_pressure_bump - keep stats of per-cpuset reclaims.
3549  *
3550  * Keep a running average of the rate of synchronous (direct)
3551  * page reclaim efforts initiated by tasks in each cpuset.
3552  *
3553  * This represents the rate at which some task in the cpuset
3554  * ran low on memory on all nodes it was allowed to use, and
3555  * had to enter the kernels page reclaim code in an effort to
3556  * create more free memory by tossing clean pages or swapping
3557  * or writing dirty pages.
3558  *
3559  * Display to user space in the per-cpuset read-only file
3560  * "memory_pressure".  Value displayed is an integer
3561  * representing the recent rate of entry into the synchronous
3562  * (direct) page reclaim by any task attached to the cpuset.
3563  **/
3564 
3565 void __cpuset_memory_pressure_bump(void)
3566 {
3567         rcu_read_lock();
3568         fmeter_markevent(&task_cs(current)->fmeter);
3569         rcu_read_unlock();
3570 }
3571 
3572 #ifdef CONFIG_PROC_PID_CPUSET
3573 /*
3574  * proc_cpuset_show()
3575  *  - Print tasks cpuset path into seq_file.
3576  *  - Used for /proc/<pid>/cpuset.
3577  *  - No need to task_lock(tsk) on this tsk->cpuset reference, as it
3578  *    doesn't really matter if tsk->cpuset changes after we read it,
3579  *    and we take cpuset_mutex, keeping cpuset_attach() from changing it
3580  *    anyway.
3581  */
3582 int proc_cpuset_show(struct seq_file *m, struct pid_namespace *ns,
3583                      struct pid *pid, struct task_struct *tsk)
3584 {
3585         char *buf;
3586         struct cgroup_subsys_state *css;
3587         int retval;
3588 
3589         retval = -ENOMEM;
3590         buf = kmalloc(PATH_MAX, GFP_KERNEL);
3591         if (!buf)
3592                 goto out;
3593 
3594         css = task_get_css(tsk, cpuset_cgrp_id);
3595         retval = cgroup_path_ns(css->cgroup, buf, PATH_MAX,
3596                                 current->nsproxy->cgroup_ns);
3597         css_put(css);
3598         if (retval >= PATH_MAX)
3599                 retval = -ENAMETOOLONG;
3600         if (retval < 0)
3601                 goto out_free;
3602         seq_puts(m, buf);
3603         seq_putc(m, '\n');
3604         retval = 0;
3605 out_free:
3606         kfree(buf);
3607 out:
3608         return retval;
3609 }
3610 #endif /* CONFIG_PROC_PID_CPUSET */
3611 
3612 /* Display task mems_allowed in /proc/<pid>/status file. */
3613 void cpuset_task_status_allowed(struct seq_file *m, struct task_struct *task)
3614 {
3615         seq_printf(m, "Mems_allowed:\t%*pb\n",
3616                    nodemask_pr_args(&task->mems_allowed));
3617         seq_printf(m, "Mems_allowed_list:\t%*pbl\n",
3618                    nodemask_pr_args(&task->mems_allowed));
3619 }
3620 

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