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Linux/kernel/cpuset.c

  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/namei.h>
 43 #include <linux/pagemap.h>
 44 #include <linux/proc_fs.h>
 45 #include <linux/rcupdate.h>
 46 #include <linux/sched.h>
 47 #include <linux/seq_file.h>
 48 #include <linux/security.h>
 49 #include <linux/slab.h>
 50 #include <linux/spinlock.h>
 51 #include <linux/stat.h>
 52 #include <linux/string.h>
 53 #include <linux/time.h>
 54 #include <linux/time64.h>
 55 #include <linux/backing-dev.h>
 56 #include <linux/sort.h>
 57 
 58 #include <asm/uaccess.h>
 59 #include <linux/atomic.h>
 60 #include <linux/mutex.h>
 61 #include <linux/cgroup.h>
 62 #include <linux/wait.h>
 63 
 64 DEFINE_STATIC_KEY_FALSE(cpusets_enabled_key);
 65 
 66 /* See "Frequency meter" comments, below. */
 67 
 68 struct fmeter {
 69         int cnt;                /* unprocessed events count */
 70         int val;                /* most recent output value */
 71         time64_t time;          /* clock (secs) when val computed */
 72         spinlock_t lock;        /* guards read or write of above */
 73 };
 74 
 75 struct cpuset {
 76         struct cgroup_subsys_state css;
 77 
 78         unsigned long flags;            /* "unsigned long" so bitops work */
 79 
 80         /*
 81          * On default hierarchy:
 82          *
 83          * The user-configured masks can only be changed by writing to
 84          * cpuset.cpus and cpuset.mems, and won't be limited by the
 85          * parent masks.
 86          *
 87          * The effective masks is the real masks that apply to the tasks
 88          * in the cpuset. They may be changed if the configured masks are
 89          * changed or hotplug happens.
 90          *
 91          * effective_mask == configured_mask & parent's effective_mask,
 92          * and if it ends up empty, it will inherit the parent's mask.
 93          *
 94          *
 95          * On legacy hierachy:
 96          *
 97          * The user-configured masks are always the same with effective masks.
 98          */
 99 
100         /* user-configured CPUs and Memory Nodes allow to tasks */
101         cpumask_var_t cpus_allowed;
102         nodemask_t mems_allowed;
103 
104         /* effective CPUs and Memory Nodes allow to tasks */
105         cpumask_var_t effective_cpus;
106         nodemask_t effective_mems;
107 
108         /*
109          * This is old Memory Nodes tasks took on.
110          *
111          * - top_cpuset.old_mems_allowed is initialized to mems_allowed.
112          * - A new cpuset's old_mems_allowed is initialized when some
113          *   task is moved into it.
114          * - old_mems_allowed is used in cpuset_migrate_mm() when we change
115          *   cpuset.mems_allowed and have tasks' nodemask updated, and
116          *   then old_mems_allowed is updated to mems_allowed.
117          */
118         nodemask_t old_mems_allowed;
119 
120         struct fmeter fmeter;           /* memory_pressure filter */
121 
122         /*
123          * Tasks are being attached to this cpuset.  Used to prevent
124          * zeroing cpus/mems_allowed between ->can_attach() and ->attach().
125          */
126         int attach_in_progress;
127 
128         /* partition number for rebuild_sched_domains() */
129         int pn;
130 
131         /* for custom sched domain */
132         int relax_domain_level;
133 };
134 
135 static inline struct cpuset *css_cs(struct cgroup_subsys_state *css)
136 {
137         return css ? container_of(css, struct cpuset, css) : NULL;
138 }
139 
140 /* Retrieve the cpuset for a task */
141 static inline struct cpuset *task_cs(struct task_struct *task)
142 {
143         return css_cs(task_css(task, cpuset_cgrp_id));
144 }
145 
146 static inline struct cpuset *parent_cs(struct cpuset *cs)
147 {
148         return css_cs(cs->css.parent);
149 }
150 
151 #ifdef CONFIG_NUMA
152 static inline bool task_has_mempolicy(struct task_struct *task)
153 {
154         return task->mempolicy;
155 }
156 #else
157 static inline bool task_has_mempolicy(struct task_struct *task)
158 {
159         return false;
160 }
161 #endif
162 
163 
164 /* bits in struct cpuset flags field */
165 typedef enum {
166         CS_ONLINE,
167         CS_CPU_EXCLUSIVE,
168         CS_MEM_EXCLUSIVE,
169         CS_MEM_HARDWALL,
170         CS_MEMORY_MIGRATE,
171         CS_SCHED_LOAD_BALANCE,
172         CS_SPREAD_PAGE,
173         CS_SPREAD_SLAB,
174 } cpuset_flagbits_t;
175 
176 /* convenient tests for these bits */
177 static inline bool is_cpuset_online(const struct cpuset *cs)
178 {
179         return test_bit(CS_ONLINE, &cs->flags);
180 }
181 
182 static inline int is_cpu_exclusive(const struct cpuset *cs)
183 {
184         return test_bit(CS_CPU_EXCLUSIVE, &cs->flags);
185 }
186 
187 static inline int is_mem_exclusive(const struct cpuset *cs)
188 {
189         return test_bit(CS_MEM_EXCLUSIVE, &cs->flags);
190 }
191 
192 static inline int is_mem_hardwall(const struct cpuset *cs)
193 {
194         return test_bit(CS_MEM_HARDWALL, &cs->flags);
195 }
196 
197 static inline int is_sched_load_balance(const struct cpuset *cs)
198 {
199         return test_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
200 }
201 
202 static inline int is_memory_migrate(const struct cpuset *cs)
203 {
204         return test_bit(CS_MEMORY_MIGRATE, &cs->flags);
205 }
206 
207 static inline int is_spread_page(const struct cpuset *cs)
208 {
209         return test_bit(CS_SPREAD_PAGE, &cs->flags);
210 }
211 
212 static inline int is_spread_slab(const struct cpuset *cs)
213 {
214         return test_bit(CS_SPREAD_SLAB, &cs->flags);
215 }
216 
217 static struct cpuset top_cpuset = {
218         .flags = ((1 << CS_ONLINE) | (1 << CS_CPU_EXCLUSIVE) |
219                   (1 << CS_MEM_EXCLUSIVE)),
220 };
221 
222 /**
223  * cpuset_for_each_child - traverse online children of a cpuset
224  * @child_cs: loop cursor pointing to the current child
225  * @pos_css: used for iteration
226  * @parent_cs: target cpuset to walk children of
227  *
228  * Walk @child_cs through the online children of @parent_cs.  Must be used
229  * with RCU read locked.
230  */
231 #define cpuset_for_each_child(child_cs, pos_css, parent_cs)             \
232         css_for_each_child((pos_css), &(parent_cs)->css)                \
233                 if (is_cpuset_online(((child_cs) = css_cs((pos_css)))))
234 
235 /**
236  * cpuset_for_each_descendant_pre - pre-order walk of a cpuset's descendants
237  * @des_cs: loop cursor pointing to the current descendant
238  * @pos_css: used for iteration
239  * @root_cs: target cpuset to walk ancestor of
240  *
241  * Walk @des_cs through the online descendants of @root_cs.  Must be used
242  * with RCU read locked.  The caller may modify @pos_css by calling
243  * css_rightmost_descendant() to skip subtree.  @root_cs is included in the
244  * iteration and the first node to be visited.
245  */
246 #define cpuset_for_each_descendant_pre(des_cs, pos_css, root_cs)        \
247         css_for_each_descendant_pre((pos_css), &(root_cs)->css)         \
248                 if (is_cpuset_online(((des_cs) = css_cs((pos_css)))))
249 
250 /*
251  * There are two global locks guarding cpuset structures - cpuset_mutex and
252  * callback_lock. We also require taking task_lock() when dereferencing a
253  * task's cpuset pointer. See "The task_lock() exception", at the end of this
254  * comment.
255  *
256  * A task must hold both locks to modify cpusets.  If a task holds
257  * cpuset_mutex, then it blocks others wanting that mutex, ensuring that it
258  * is the only task able to also acquire callback_lock and be able to
259  * modify cpusets.  It can perform various checks on the cpuset structure
260  * first, knowing nothing will change.  It can also allocate memory while
261  * just holding cpuset_mutex.  While it is performing these checks, various
262  * callback routines can briefly acquire callback_lock to query cpusets.
263  * Once it is ready to make the changes, it takes callback_lock, blocking
264  * everyone else.
265  *
266  * Calls to the kernel memory allocator can not be made while holding
267  * callback_lock, as that would risk double tripping on callback_lock
268  * from one of the callbacks into the cpuset code from within
269  * __alloc_pages().
270  *
271  * If a task is only holding callback_lock, then it has read-only
272  * access to cpusets.
273  *
274  * Now, the task_struct fields mems_allowed and mempolicy may be changed
275  * by other task, we use alloc_lock in the task_struct fields to protect
276  * them.
277  *
278  * The cpuset_common_file_read() handlers only hold callback_lock across
279  * small pieces of code, such as when reading out possibly multi-word
280  * cpumasks and nodemasks.
281  *
282  * Accessing a task's cpuset should be done in accordance with the
283  * guidelines for accessing subsystem state in kernel/cgroup.c
284  */
285 
286 static DEFINE_MUTEX(cpuset_mutex);
287 static DEFINE_SPINLOCK(callback_lock);
288 
289 static struct workqueue_struct *cpuset_migrate_mm_wq;
290 
291 /*
292  * CPU / memory hotplug is handled asynchronously.
293  */
294 static void cpuset_hotplug_workfn(struct work_struct *work);
295 static DECLARE_WORK(cpuset_hotplug_work, cpuset_hotplug_workfn);
296 
297 static DECLARE_WAIT_QUEUE_HEAD(cpuset_attach_wq);
298 
299 /*
300  * This is ugly, but preserves the userspace API for existing cpuset
301  * users. If someone tries to mount the "cpuset" filesystem, we
302  * silently switch it to mount "cgroup" instead
303  */
304 static struct dentry *cpuset_mount(struct file_system_type *fs_type,
305                          int flags, const char *unused_dev_name, void *data)
306 {
307         struct file_system_type *cgroup_fs = get_fs_type("cgroup");
308         struct dentry *ret = ERR_PTR(-ENODEV);
309         if (cgroup_fs) {
310                 char mountopts[] =
311                         "cpuset,noprefix,"
312                         "release_agent=/sbin/cpuset_release_agent";
313                 ret = cgroup_fs->mount(cgroup_fs, flags,
314                                            unused_dev_name, mountopts);
315                 put_filesystem(cgroup_fs);
316         }
317         return ret;
318 }
319 
320 static struct file_system_type cpuset_fs_type = {
321         .name = "cpuset",
322         .mount = cpuset_mount,
323 };
324 
325 /*
326  * Return in pmask the portion of a cpusets's cpus_allowed that
327  * are online.  If none are online, walk up the cpuset hierarchy
328  * until we find one that does have some online cpus.
329  *
330  * One way or another, we guarantee to return some non-empty subset
331  * of cpu_online_mask.
332  *
333  * Call with callback_lock or cpuset_mutex held.
334  */
335 static void guarantee_online_cpus(struct cpuset *cs, struct cpumask *pmask)
336 {
337         while (!cpumask_intersects(cs->effective_cpus, cpu_online_mask)) {
338                 cs = parent_cs(cs);
339                 if (unlikely(!cs)) {
340                         /*
341                          * The top cpuset doesn't have any online cpu as a
342                          * consequence of a race between cpuset_hotplug_work
343                          * and cpu hotplug notifier.  But we know the top
344                          * cpuset's effective_cpus is on its way to to be
345                          * identical to cpu_online_mask.
346                          */
347                         cpumask_copy(pmask, cpu_online_mask);
348                         return;
349                 }
350         }
351         cpumask_and(pmask, cs->effective_cpus, cpu_online_mask);
352 }
353 
354 /*
355  * Return in *pmask the portion of a cpusets's mems_allowed that
356  * are online, with memory.  If none are online with memory, walk
357  * up the cpuset hierarchy until we find one that does have some
358  * online mems.  The top cpuset always has some mems online.
359  *
360  * One way or another, we guarantee to return some non-empty subset
361  * of node_states[N_MEMORY].
362  *
363  * Call with callback_lock or cpuset_mutex held.
364  */
365 static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask)
366 {
367         while (!nodes_intersects(cs->effective_mems, node_states[N_MEMORY]))
368                 cs = parent_cs(cs);
369         nodes_and(*pmask, cs->effective_mems, node_states[N_MEMORY]);
370 }
371 
372 /*
373  * update task's spread flag if cpuset's page/slab spread flag is set
374  *
375  * Call with callback_lock or cpuset_mutex held.
376  */
377 static void cpuset_update_task_spread_flag(struct cpuset *cs,
378                                         struct task_struct *tsk)
379 {
380         if (is_spread_page(cs))
381                 task_set_spread_page(tsk);
382         else
383                 task_clear_spread_page(tsk);
384 
385         if (is_spread_slab(cs))
386                 task_set_spread_slab(tsk);
387         else
388                 task_clear_spread_slab(tsk);
389 }
390 
391 /*
392  * is_cpuset_subset(p, q) - Is cpuset p a subset of cpuset q?
393  *
394  * One cpuset is a subset of another if all its allowed CPUs and
395  * Memory Nodes are a subset of the other, and its exclusive flags
396  * are only set if the other's are set.  Call holding cpuset_mutex.
397  */
398 
399 static int is_cpuset_subset(const struct cpuset *p, const struct cpuset *q)
400 {
401         return  cpumask_subset(p->cpus_allowed, q->cpus_allowed) &&
402                 nodes_subset(p->mems_allowed, q->mems_allowed) &&
403                 is_cpu_exclusive(p) <= is_cpu_exclusive(q) &&
404                 is_mem_exclusive(p) <= is_mem_exclusive(q);
405 }
406 
407 /**
408  * alloc_trial_cpuset - allocate a trial cpuset
409  * @cs: the cpuset that the trial cpuset duplicates
410  */
411 static struct cpuset *alloc_trial_cpuset(struct cpuset *cs)
412 {
413         struct cpuset *trial;
414 
415         trial = kmemdup(cs, sizeof(*cs), GFP_KERNEL);
416         if (!trial)
417                 return NULL;
418 
419         if (!alloc_cpumask_var(&trial->cpus_allowed, GFP_KERNEL))
420                 goto free_cs;
421         if (!alloc_cpumask_var(&trial->effective_cpus, GFP_KERNEL))
422                 goto free_cpus;
423 
424         cpumask_copy(trial->cpus_allowed, cs->cpus_allowed);
425         cpumask_copy(trial->effective_cpus, cs->effective_cpus);
426         return trial;
427 
428 free_cpus:
429         free_cpumask_var(trial->cpus_allowed);
430 free_cs:
431         kfree(trial);
432         return NULL;
433 }
434 
435 /**
436  * free_trial_cpuset - free the trial cpuset
437  * @trial: the trial cpuset to be freed
438  */
439 static void free_trial_cpuset(struct cpuset *trial)
440 {
441         free_cpumask_var(trial->effective_cpus);
442         free_cpumask_var(trial->cpus_allowed);
443         kfree(trial);
444 }
445 
446 /*
447  * validate_change() - Used to validate that any proposed cpuset change
448  *                     follows the structural rules for cpusets.
449  *
450  * If we replaced the flag and mask values of the current cpuset
451  * (cur) with those values in the trial cpuset (trial), would
452  * our various subset and exclusive rules still be valid?  Presumes
453  * cpuset_mutex held.
454  *
455  * 'cur' is the address of an actual, in-use cpuset.  Operations
456  * such as list traversal that depend on the actual address of the
457  * cpuset in the list must use cur below, not trial.
458  *
459  * 'trial' is the address of bulk structure copy of cur, with
460  * perhaps one or more of the fields cpus_allowed, mems_allowed,
461  * or flags changed to new, trial values.
462  *
463  * Return 0 if valid, -errno if not.
464  */
465 
466 static int validate_change(struct cpuset *cur, struct cpuset *trial)
467 {
468         struct cgroup_subsys_state *css;
469         struct cpuset *c, *par;
470         int ret;
471 
472         rcu_read_lock();
473 
474         /* Each of our child cpusets must be a subset of us */
475         ret = -EBUSY;
476         cpuset_for_each_child(c, css, cur)
477                 if (!is_cpuset_subset(c, trial))
478                         goto out;
479 
480         /* Remaining checks don't apply to root cpuset */
481         ret = 0;
482         if (cur == &top_cpuset)
483                 goto out;
484 
485         par = parent_cs(cur);
486 
487         /* On legacy hiearchy, we must be a subset of our parent cpuset. */
488         ret = -EACCES;
489         if (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
490             !is_cpuset_subset(trial, par))
491                 goto out;
492 
493         /*
494          * If either I or some sibling (!= me) is exclusive, we can't
495          * overlap
496          */
497         ret = -EINVAL;
498         cpuset_for_each_child(c, css, par) {
499                 if ((is_cpu_exclusive(trial) || is_cpu_exclusive(c)) &&
500                     c != cur &&
501                     cpumask_intersects(trial->cpus_allowed, c->cpus_allowed))
502                         goto out;
503                 if ((is_mem_exclusive(trial) || is_mem_exclusive(c)) &&
504                     c != cur &&
505                     nodes_intersects(trial->mems_allowed, c->mems_allowed))
506                         goto out;
507         }
508 
509         /*
510          * Cpusets with tasks - existing or newly being attached - can't
511          * be changed to have empty cpus_allowed or mems_allowed.
512          */
513         ret = -ENOSPC;
514         if ((cgroup_is_populated(cur->css.cgroup) || cur->attach_in_progress)) {
515                 if (!cpumask_empty(cur->cpus_allowed) &&
516                     cpumask_empty(trial->cpus_allowed))
517                         goto out;
518                 if (!nodes_empty(cur->mems_allowed) &&
519                     nodes_empty(trial->mems_allowed))
520                         goto out;
521         }
522 
523         /*
524          * We can't shrink if we won't have enough room for SCHED_DEADLINE
525          * tasks.
526          */
527         ret = -EBUSY;
528         if (is_cpu_exclusive(cur) &&
529             !cpuset_cpumask_can_shrink(cur->cpus_allowed,
530                                        trial->cpus_allowed))
531                 goto out;
532 
533         ret = 0;
534 out:
535         rcu_read_unlock();
536         return ret;
537 }
538 
539 #ifdef CONFIG_SMP
540 /*
541  * Helper routine for generate_sched_domains().
542  * Do cpusets a, b have overlapping effective cpus_allowed masks?
543  */
544 static int cpusets_overlap(struct cpuset *a, struct cpuset *b)
545 {
546         return cpumask_intersects(a->effective_cpus, b->effective_cpus);
547 }
548 
549 static void
550 update_domain_attr(struct sched_domain_attr *dattr, struct cpuset *c)
551 {
552         if (dattr->relax_domain_level < c->relax_domain_level)
553                 dattr->relax_domain_level = c->relax_domain_level;
554         return;
555 }
556 
557 static void update_domain_attr_tree(struct sched_domain_attr *dattr,
558                                     struct cpuset *root_cs)
559 {
560         struct cpuset *cp;
561         struct cgroup_subsys_state *pos_css;
562 
563         rcu_read_lock();
564         cpuset_for_each_descendant_pre(cp, pos_css, root_cs) {
565                 /* skip the whole subtree if @cp doesn't have any CPU */
566                 if (cpumask_empty(cp->cpus_allowed)) {
567                         pos_css = css_rightmost_descendant(pos_css);
568                         continue;
569                 }
570 
571                 if (is_sched_load_balance(cp))
572                         update_domain_attr(dattr, cp);
573         }
574         rcu_read_unlock();
575 }
576 
577 /*
578  * generate_sched_domains()
579  *
580  * This function builds a partial partition of the systems CPUs
581  * A 'partial partition' is a set of non-overlapping subsets whose
582  * union is a subset of that set.
583  * The output of this function needs to be passed to kernel/sched/core.c
584  * partition_sched_domains() routine, which will rebuild the scheduler's
585  * load balancing domains (sched domains) as specified by that partial
586  * partition.
587  *
588  * See "What is sched_load_balance" in Documentation/cgroups/cpusets.txt
589  * for a background explanation of this.
590  *
591  * Does not return errors, on the theory that the callers of this
592  * routine would rather not worry about failures to rebuild sched
593  * domains when operating in the severe memory shortage situations
594  * that could cause allocation failures below.
595  *
596  * Must be called with cpuset_mutex held.
597  *
598  * The three key local variables below are:
599  *    q  - a linked-list queue of cpuset pointers, used to implement a
600  *         top-down scan of all cpusets.  This scan loads a pointer
601  *         to each cpuset marked is_sched_load_balance into the
602  *         array 'csa'.  For our purposes, rebuilding the schedulers
603  *         sched domains, we can ignore !is_sched_load_balance cpusets.
604  *  csa  - (for CpuSet Array) Array of pointers to all the cpusets
605  *         that need to be load balanced, for convenient iterative
606  *         access by the subsequent code that finds the best partition,
607  *         i.e the set of domains (subsets) of CPUs such that the
608  *         cpus_allowed of every cpuset marked is_sched_load_balance
609  *         is a subset of one of these domains, while there are as
610  *         many such domains as possible, each as small as possible.
611  * doms  - Conversion of 'csa' to an array of cpumasks, for passing to
612  *         the kernel/sched/core.c routine partition_sched_domains() in a
613  *         convenient format, that can be easily compared to the prior
614  *         value to determine what partition elements (sched domains)
615  *         were changed (added or removed.)
616  *
617  * Finding the best partition (set of domains):
618  *      The triple nested loops below over i, j, k scan over the
619  *      load balanced cpusets (using the array of cpuset pointers in
620  *      csa[]) looking for pairs of cpusets that have overlapping
621  *      cpus_allowed, but which don't have the same 'pn' partition
622  *      number and gives them in the same partition number.  It keeps
623  *      looping on the 'restart' label until it can no longer find
624  *      any such pairs.
625  *
626  *      The union of the cpus_allowed masks from the set of
627  *      all cpusets having the same 'pn' value then form the one
628  *      element of the partition (one sched domain) to be passed to
629  *      partition_sched_domains().
630  */
631 static int generate_sched_domains(cpumask_var_t **domains,
632                         struct sched_domain_attr **attributes)
633 {
634         struct cpuset *cp;      /* scans q */
635         struct cpuset **csa;    /* array of all cpuset ptrs */
636         int csn;                /* how many cpuset ptrs in csa so far */
637         int i, j, k;            /* indices for partition finding loops */
638         cpumask_var_t *doms;    /* resulting partition; i.e. sched domains */
639         cpumask_var_t non_isolated_cpus;  /* load balanced CPUs */
640         struct sched_domain_attr *dattr;  /* attributes for custom domains */
641         int ndoms = 0;          /* number of sched domains in result */
642         int nslot;              /* next empty doms[] struct cpumask slot */
643         struct cgroup_subsys_state *pos_css;
644 
645         doms = NULL;
646         dattr = NULL;
647         csa = NULL;
648 
649         if (!alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL))
650                 goto done;
651         cpumask_andnot(non_isolated_cpus, cpu_possible_mask, cpu_isolated_map);
652 
653         /* Special case for the 99% of systems with one, full, sched domain */
654         if (is_sched_load_balance(&top_cpuset)) {
655                 ndoms = 1;
656                 doms = alloc_sched_domains(ndoms);
657                 if (!doms)
658                         goto done;
659 
660                 dattr = kmalloc(sizeof(struct sched_domain_attr), GFP_KERNEL);
661                 if (dattr) {
662                         *dattr = SD_ATTR_INIT;
663                         update_domain_attr_tree(dattr, &top_cpuset);
664                 }
665                 cpumask_and(doms[0], top_cpuset.effective_cpus,
666                                      non_isolated_cpus);
667 
668                 goto done;
669         }
670 
671         csa = kmalloc(nr_cpusets() * sizeof(cp), GFP_KERNEL);
672         if (!csa)
673                 goto done;
674         csn = 0;
675 
676         rcu_read_lock();
677         cpuset_for_each_descendant_pre(cp, pos_css, &top_cpuset) {
678                 if (cp == &top_cpuset)
679                         continue;
680                 /*
681                  * Continue traversing beyond @cp iff @cp has some CPUs and
682                  * isn't load balancing.  The former is obvious.  The
683                  * latter: All child cpusets contain a subset of the
684                  * parent's cpus, so just skip them, and then we call
685                  * update_domain_attr_tree() to calc relax_domain_level of
686                  * the corresponding sched domain.
687                  */
688                 if (!cpumask_empty(cp->cpus_allowed) &&
689                     !(is_sched_load_balance(cp) &&
690                       cpumask_intersects(cp->cpus_allowed, non_isolated_cpus)))
691                         continue;
692 
693                 if (is_sched_load_balance(cp))
694                         csa[csn++] = cp;
695 
696                 /* skip @cp's subtree */
697                 pos_css = css_rightmost_descendant(pos_css);
698         }
699         rcu_read_unlock();
700 
701         for (i = 0; i < csn; i++)
702                 csa[i]->pn = i;
703         ndoms = csn;
704 
705 restart:
706         /* Find the best partition (set of sched domains) */
707         for (i = 0; i < csn; i++) {
708                 struct cpuset *a = csa[i];
709                 int apn = a->pn;
710 
711                 for (j = 0; j < csn; j++) {
712                         struct cpuset *b = csa[j];
713                         int bpn = b->pn;
714 
715                         if (apn != bpn && cpusets_overlap(a, b)) {
716                                 for (k = 0; k < csn; k++) {
717                                         struct cpuset *c = csa[k];
718 
719                                         if (c->pn == bpn)
720                                                 c->pn = apn;
721                                 }
722                                 ndoms--;        /* one less element */
723                                 goto restart;
724                         }
725                 }
726         }
727 
728         /*
729          * Now we know how many domains to create.
730          * Convert <csn, csa> to <ndoms, doms> and populate cpu masks.
731          */
732         doms = alloc_sched_domains(ndoms);
733         if (!doms)
734                 goto done;
735 
736         /*
737          * The rest of the code, including the scheduler, can deal with
738          * dattr==NULL case. No need to abort if alloc fails.
739          */
740         dattr = kmalloc(ndoms * sizeof(struct sched_domain_attr), GFP_KERNEL);
741 
742         for (nslot = 0, i = 0; i < csn; i++) {
743                 struct cpuset *a = csa[i];
744                 struct cpumask *dp;
745                 int apn = a->pn;
746 
747                 if (apn < 0) {
748                         /* Skip completed partitions */
749                         continue;
750                 }
751 
752                 dp = doms[nslot];
753 
754                 if (nslot == ndoms) {
755                         static int warnings = 10;
756                         if (warnings) {
757                                 pr_warn("rebuild_sched_domains confused: nslot %d, ndoms %d, csn %d, i %d, apn %d\n",
758                                         nslot, ndoms, csn, i, apn);
759                                 warnings--;
760                         }
761                         continue;
762                 }
763 
764                 cpumask_clear(dp);
765                 if (dattr)
766                         *(dattr + nslot) = SD_ATTR_INIT;
767                 for (j = i; j < csn; j++) {
768                         struct cpuset *b = csa[j];
769 
770                         if (apn == b->pn) {
771                                 cpumask_or(dp, dp, b->effective_cpus);
772                                 cpumask_and(dp, dp, non_isolated_cpus);
773                                 if (dattr)
774                                         update_domain_attr_tree(dattr + nslot, b);
775 
776                                 /* Done with this partition */
777                                 b->pn = -1;
778                         }
779                 }
780                 nslot++;
781         }
782         BUG_ON(nslot != ndoms);
783 
784 done:
785         free_cpumask_var(non_isolated_cpus);
786         kfree(csa);
787 
788         /*
789          * Fallback to the default domain if kmalloc() failed.
790          * See comments in partition_sched_domains().
791          */
792         if (doms == NULL)
793                 ndoms = 1;
794 
795         *domains    = doms;
796         *attributes = dattr;
797         return ndoms;
798 }
799 
800 /*
801  * Rebuild scheduler domains.
802  *
803  * If the flag 'sched_load_balance' of any cpuset with non-empty
804  * 'cpus' changes, or if the 'cpus' allowed changes in any cpuset
805  * which has that flag enabled, or if any cpuset with a non-empty
806  * 'cpus' is removed, then call this routine to rebuild the
807  * scheduler's dynamic sched domains.
808  *
809  * Call with cpuset_mutex held.  Takes get_online_cpus().
810  */
811 static void rebuild_sched_domains_locked(void)
812 {
813         struct sched_domain_attr *attr;
814         cpumask_var_t *doms;
815         int ndoms;
816 
817         lockdep_assert_held(&cpuset_mutex);
818         get_online_cpus();
819 
820         /*
821          * We have raced with CPU hotplug. Don't do anything to avoid
822          * passing doms with offlined cpu to partition_sched_domains().
823          * Anyways, hotplug work item will rebuild sched domains.
824          */
825         if (!cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
826                 goto out;
827 
828         /* Generate domain masks and attrs */
829         ndoms = generate_sched_domains(&doms, &attr);
830 
831         /* Have scheduler rebuild the domains */
832         partition_sched_domains(ndoms, doms, attr);
833 out:
834         put_online_cpus();
835 }
836 #else /* !CONFIG_SMP */
837 static void rebuild_sched_domains_locked(void)
838 {
839 }
840 #endif /* CONFIG_SMP */
841 
842 void rebuild_sched_domains(void)
843 {
844         mutex_lock(&cpuset_mutex);
845         rebuild_sched_domains_locked();
846         mutex_unlock(&cpuset_mutex);
847 }
848 
849 /**
850  * update_tasks_cpumask - Update the cpumasks of tasks in the cpuset.
851  * @cs: the cpuset in which each task's cpus_allowed mask needs to be changed
852  *
853  * Iterate through each task of @cs updating its cpus_allowed to the
854  * effective cpuset's.  As this function is called with cpuset_mutex held,
855  * cpuset membership stays stable.
856  */
857 static void update_tasks_cpumask(struct cpuset *cs)
858 {
859         struct css_task_iter it;
860         struct task_struct *task;
861 
862         css_task_iter_start(&cs->css, &it);
863         while ((task = css_task_iter_next(&it)))
864                 set_cpus_allowed_ptr(task, cs->effective_cpus);
865         css_task_iter_end(&it);
866 }
867 
868 /*
869  * update_cpumasks_hier - Update effective cpumasks and tasks in the subtree
870  * @cs: the cpuset to consider
871  * @new_cpus: temp variable for calculating new effective_cpus
872  *
873  * When congifured cpumask is changed, the effective cpumasks of this cpuset
874  * and all its descendants need to be updated.
875  *
876  * On legacy hierachy, effective_cpus will be the same with cpu_allowed.
877  *
878  * Called with cpuset_mutex held
879  */
880 static void update_cpumasks_hier(struct cpuset *cs, struct cpumask *new_cpus)
881 {
882         struct cpuset *cp;
883         struct cgroup_subsys_state *pos_css;
884         bool need_rebuild_sched_domains = false;
885 
886         rcu_read_lock();
887         cpuset_for_each_descendant_pre(cp, pos_css, cs) {
888                 struct cpuset *parent = parent_cs(cp);
889 
890                 cpumask_and(new_cpus, cp->cpus_allowed, parent->effective_cpus);
891 
892                 /*
893                  * If it becomes empty, inherit the effective mask of the
894                  * parent, which is guaranteed to have some CPUs.
895                  */
896                 if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
897                     cpumask_empty(new_cpus))
898                         cpumask_copy(new_cpus, parent->effective_cpus);
899 
900                 /* Skip the whole subtree if the cpumask remains the same. */
901                 if (cpumask_equal(new_cpus, cp->effective_cpus)) {
902                         pos_css = css_rightmost_descendant(pos_css);
903                         continue;
904                 }
905 
906                 if (!css_tryget_online(&cp->css))
907                         continue;
908                 rcu_read_unlock();
909 
910                 spin_lock_irq(&callback_lock);
911                 cpumask_copy(cp->effective_cpus, new_cpus);
912                 spin_unlock_irq(&callback_lock);
913 
914                 WARN_ON(!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
915                         !cpumask_equal(cp->cpus_allowed, cp->effective_cpus));
916 
917                 update_tasks_cpumask(cp);
918 
919                 /*
920                  * If the effective cpumask of any non-empty cpuset is changed,
921                  * we need to rebuild sched domains.
922                  */
923                 if (!cpumask_empty(cp->cpus_allowed) &&
924                     is_sched_load_balance(cp))
925                         need_rebuild_sched_domains = true;
926 
927                 rcu_read_lock();
928                 css_put(&cp->css);
929         }
930         rcu_read_unlock();
931 
932         if (need_rebuild_sched_domains)
933                 rebuild_sched_domains_locked();
934 }
935 
936 /**
937  * update_cpumask - update the cpus_allowed mask of a cpuset and all tasks in it
938  * @cs: the cpuset to consider
939  * @trialcs: trial cpuset
940  * @buf: buffer of cpu numbers written to this cpuset
941  */
942 static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
943                           const char *buf)
944 {
945         int retval;
946 
947         /* top_cpuset.cpus_allowed tracks cpu_online_mask; it's read-only */
948         if (cs == &top_cpuset)
949                 return -EACCES;
950 
951         /*
952          * An empty cpus_allowed is ok only if the cpuset has no tasks.
953          * Since cpulist_parse() fails on an empty mask, we special case
954          * that parsing.  The validate_change() call ensures that cpusets
955          * with tasks have cpus.
956          */
957         if (!*buf) {
958                 cpumask_clear(trialcs->cpus_allowed);
959         } else {
960                 retval = cpulist_parse(buf, trialcs->cpus_allowed);
961                 if (retval < 0)
962                         return retval;
963 
964                 if (!cpumask_subset(trialcs->cpus_allowed,
965                                     top_cpuset.cpus_allowed))
966                         return -EINVAL;
967         }
968 
969         /* Nothing to do if the cpus didn't change */
970         if (cpumask_equal(cs->cpus_allowed, trialcs->cpus_allowed))
971                 return 0;
972 
973         retval = validate_change(cs, trialcs);
974         if (retval < 0)
975                 return retval;
976 
977         spin_lock_irq(&callback_lock);
978         cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
979         spin_unlock_irq(&callback_lock);
980 
981         /* use trialcs->cpus_allowed as a temp variable */
982         update_cpumasks_hier(cs, trialcs->cpus_allowed);
983         return 0;
984 }
985 
986 /*
987  * Migrate memory region from one set of nodes to another.  This is
988  * performed asynchronously as it can be called from process migration path
989  * holding locks involved in process management.  All mm migrations are
990  * performed in the queued order and can be waited for by flushing
991  * cpuset_migrate_mm_wq.
992  */
993 
994 struct cpuset_migrate_mm_work {
995         struct work_struct      work;
996         struct mm_struct        *mm;
997         nodemask_t              from;
998         nodemask_t              to;
999 };
1000 
1001 static void cpuset_migrate_mm_workfn(struct work_struct *work)
1002 {
1003         struct cpuset_migrate_mm_work *mwork =
1004                 container_of(work, struct cpuset_migrate_mm_work, work);
1005 
1006         /* on a wq worker, no need to worry about %current's mems_allowed */
1007         do_migrate_pages(mwork->mm, &mwork->from, &mwork->to, MPOL_MF_MOVE_ALL);
1008         mmput(mwork->mm);
1009         kfree(mwork);
1010 }
1011 
1012 static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
1013                                                         const nodemask_t *to)
1014 {
1015         struct cpuset_migrate_mm_work *mwork;
1016 
1017         mwork = kzalloc(sizeof(*mwork), GFP_KERNEL);
1018         if (mwork) {
1019                 mwork->mm = mm;
1020                 mwork->from = *from;
1021                 mwork->to = *to;
1022                 INIT_WORK(&mwork->work, cpuset_migrate_mm_workfn);
1023                 queue_work(cpuset_migrate_mm_wq, &mwork->work);
1024         } else {
1025                 mmput(mm);
1026         }
1027 }
1028 
1029 static void cpuset_post_attach(void)
1030 {
1031         flush_workqueue(cpuset_migrate_mm_wq);
1032 }
1033 
1034 /*
1035  * cpuset_change_task_nodemask - change task's mems_allowed and mempolicy
1036  * @tsk: the task to change
1037  * @newmems: new nodes that the task will be set
1038  *
1039  * In order to avoid seeing no nodes if the old and new nodes are disjoint,
1040  * we structure updates as setting all new allowed nodes, then clearing newly
1041  * disallowed ones.
1042  */
1043 static void cpuset_change_task_nodemask(struct task_struct *tsk,
1044                                         nodemask_t *newmems)
1045 {
1046         bool need_loop;
1047 
1048         task_lock(tsk);
1049         /*
1050          * Determine if a loop is necessary if another thread is doing
1051          * read_mems_allowed_begin().  If at least one node remains unchanged and
1052          * tsk does not have a mempolicy, then an empty nodemask will not be
1053          * possible when mems_allowed is larger than a word.
1054          */
1055         need_loop = task_has_mempolicy(tsk) ||
1056                         !nodes_intersects(*newmems, tsk->mems_allowed);
1057 
1058         if (need_loop) {
1059                 local_irq_disable();
1060                 write_seqcount_begin(&tsk->mems_allowed_seq);
1061         }
1062 
1063         nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems);
1064         mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP1);
1065 
1066         mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP2);
1067         tsk->mems_allowed = *newmems;
1068 
1069         if (need_loop) {
1070                 write_seqcount_end(&tsk->mems_allowed_seq);
1071                 local_irq_enable();
1072         }
1073 
1074         task_unlock(tsk);
1075 }
1076 
1077 static void *cpuset_being_rebound;
1078 
1079 /**
1080  * update_tasks_nodemask - Update the nodemasks of tasks in the cpuset.
1081  * @cs: the cpuset in which each task's mems_allowed mask needs to be changed
1082  *
1083  * Iterate through each task of @cs updating its mems_allowed to the
1084  * effective cpuset's.  As this function is called with cpuset_mutex held,
1085  * cpuset membership stays stable.
1086  */
1087 static void update_tasks_nodemask(struct cpuset *cs)
1088 {
1089         static nodemask_t newmems;      /* protected by cpuset_mutex */
1090         struct css_task_iter it;
1091         struct task_struct *task;
1092 
1093         cpuset_being_rebound = cs;              /* causes mpol_dup() rebind */
1094 
1095         guarantee_online_mems(cs, &newmems);
1096 
1097         /*
1098          * The mpol_rebind_mm() call takes mmap_sem, which we couldn't
1099          * take while holding tasklist_lock.  Forks can happen - the
1100          * mpol_dup() cpuset_being_rebound check will catch such forks,
1101          * and rebind their vma mempolicies too.  Because we still hold
1102          * the global cpuset_mutex, we know that no other rebind effort
1103          * will be contending for the global variable cpuset_being_rebound.
1104          * It's ok if we rebind the same mm twice; mpol_rebind_mm()
1105          * is idempotent.  Also migrate pages in each mm to new nodes.
1106          */
1107         css_task_iter_start(&cs->css, &it);
1108         while ((task = css_task_iter_next(&it))) {
1109                 struct mm_struct *mm;
1110                 bool migrate;
1111 
1112                 cpuset_change_task_nodemask(task, &newmems);
1113 
1114                 mm = get_task_mm(task);
1115                 if (!mm)
1116                         continue;
1117 
1118                 migrate = is_memory_migrate(cs);
1119 
1120                 mpol_rebind_mm(mm, &cs->mems_allowed);
1121                 if (migrate)
1122                         cpuset_migrate_mm(mm, &cs->old_mems_allowed, &newmems);
1123                 else
1124                         mmput(mm);
1125         }
1126         css_task_iter_end(&it);
1127 
1128         /*
1129          * All the tasks' nodemasks have been updated, update
1130          * cs->old_mems_allowed.
1131          */
1132         cs->old_mems_allowed = newmems;
1133 
1134         /* We're done rebinding vmas to this cpuset's new mems_allowed. */
1135         cpuset_being_rebound = NULL;
1136 }
1137 
1138 /*
1139  * update_nodemasks_hier - Update effective nodemasks and tasks in the subtree
1140  * @cs: the cpuset to consider
1141  * @new_mems: a temp variable for calculating new effective_mems
1142  *
1143  * When configured nodemask is changed, the effective nodemasks of this cpuset
1144  * and all its descendants need to be updated.
1145  *
1146  * On legacy hiearchy, effective_mems will be the same with mems_allowed.
1147  *
1148  * Called with cpuset_mutex held
1149  */
1150 static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems)
1151 {
1152         struct cpuset *cp;
1153         struct cgroup_subsys_state *pos_css;
1154 
1155         rcu_read_lock();
1156         cpuset_for_each_descendant_pre(cp, pos_css, cs) {
1157                 struct cpuset *parent = parent_cs(cp);
1158 
1159                 nodes_and(*new_mems, cp->mems_allowed, parent->effective_mems);
1160 
1161                 /*
1162                  * If it becomes empty, inherit the effective mask of the
1163                  * parent, which is guaranteed to have some MEMs.
1164                  */
1165                 if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
1166                     nodes_empty(*new_mems))
1167                         *new_mems = parent->effective_mems;
1168 
1169                 /* Skip the whole subtree if the nodemask remains the same. */
1170                 if (nodes_equal(*new_mems, cp->effective_mems)) {
1171                         pos_css = css_rightmost_descendant(pos_css);
1172                         continue;
1173                 }
1174 
1175                 if (!css_tryget_online(&cp->css))
1176                         continue;
1177                 rcu_read_unlock();
1178 
1179                 spin_lock_irq(&callback_lock);
1180                 cp->effective_mems = *new_mems;
1181                 spin_unlock_irq(&callback_lock);
1182 
1183                 WARN_ON(!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
1184                         !nodes_equal(cp->mems_allowed, cp->effective_mems));
1185 
1186                 update_tasks_nodemask(cp);
1187 
1188                 rcu_read_lock();
1189                 css_put(&cp->css);
1190         }
1191         rcu_read_unlock();
1192 }
1193 
1194 /*
1195  * Handle user request to change the 'mems' memory placement
1196  * of a cpuset.  Needs to validate the request, update the
1197  * cpusets mems_allowed, and for each task in the cpuset,
1198  * update mems_allowed and rebind task's mempolicy and any vma
1199  * mempolicies and if the cpuset is marked 'memory_migrate',
1200  * migrate the tasks pages to the new memory.
1201  *
1202  * Call with cpuset_mutex held. May take callback_lock during call.
1203  * Will take tasklist_lock, scan tasklist for tasks in cpuset cs,
1204  * lock each such tasks mm->mmap_sem, scan its vma's and rebind
1205  * their mempolicies to the cpusets new mems_allowed.
1206  */
1207 static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
1208                            const char *buf)
1209 {
1210         int retval;
1211 
1212         /*
1213          * top_cpuset.mems_allowed tracks node_stats[N_MEMORY];
1214          * it's read-only
1215          */
1216         if (cs == &top_cpuset) {
1217                 retval = -EACCES;
1218                 goto done;
1219         }
1220 
1221         /*
1222          * An empty mems_allowed is ok iff there are no tasks in the cpuset.
1223          * Since nodelist_parse() fails on an empty mask, we special case
1224          * that parsing.  The validate_change() call ensures that cpusets
1225          * with tasks have memory.
1226          */
1227         if (!*buf) {
1228                 nodes_clear(trialcs->mems_allowed);
1229         } else {
1230                 retval = nodelist_parse(buf, trialcs->mems_allowed);
1231                 if (retval < 0)
1232                         goto done;
1233 
1234                 if (!nodes_subset(trialcs->mems_allowed,
1235                                   top_cpuset.mems_allowed)) {
1236                         retval = -EINVAL;
1237                         goto done;
1238                 }
1239         }
1240 
1241         if (nodes_equal(cs->mems_allowed, trialcs->mems_allowed)) {
1242                 retval = 0;             /* Too easy - nothing to do */
1243                 goto done;
1244         }
1245         retval = validate_change(cs, trialcs);
1246         if (retval < 0)
1247                 goto done;
1248 
1249         spin_lock_irq(&callback_lock);
1250         cs->mems_allowed = trialcs->mems_allowed;
1251         spin_unlock_irq(&callback_lock);
1252 
1253         /* use trialcs->mems_allowed as a temp variable */
1254         update_nodemasks_hier(cs, &trialcs->mems_allowed);
1255 done:
1256         return retval;
1257 }
1258 
1259 int current_cpuset_is_being_rebound(void)
1260 {
1261         int ret;
1262 
1263         rcu_read_lock();
1264         ret = task_cs(current) == cpuset_being_rebound;
1265         rcu_read_unlock();
1266 
1267         return ret;
1268 }
1269 
1270 static int update_relax_domain_level(struct cpuset *cs, s64 val)
1271 {
1272 #ifdef CONFIG_SMP
1273         if (val < -1 || val >= sched_domain_level_max)
1274                 return -EINVAL;
1275 #endif
1276 
1277         if (val != cs->relax_domain_level) {
1278                 cs->relax_domain_level = val;
1279                 if (!cpumask_empty(cs->cpus_allowed) &&
1280                     is_sched_load_balance(cs))
1281                         rebuild_sched_domains_locked();
1282         }
1283 
1284         return 0;
1285 }
1286 
1287 /**
1288  * update_tasks_flags - update the spread flags of tasks in the cpuset.
1289  * @cs: the cpuset in which each task's spread flags needs to be changed
1290  *
1291  * Iterate through each task of @cs updating its spread flags.  As this
1292  * function is called with cpuset_mutex held, cpuset membership stays
1293  * stable.
1294  */
1295 static void update_tasks_flags(struct cpuset *cs)
1296 {
1297         struct css_task_iter it;
1298         struct task_struct *task;
1299 
1300         css_task_iter_start(&cs->css, &it);
1301         while ((task = css_task_iter_next(&it)))
1302                 cpuset_update_task_spread_flag(cs, task);
1303         css_task_iter_end(&it);
1304 }
1305 
1306 /*
1307  * update_flag - read a 0 or a 1 in a file and update associated flag
1308  * bit:         the bit to update (see cpuset_flagbits_t)
1309  * cs:          the cpuset to update
1310  * turning_on:  whether the flag is being set or cleared
1311  *
1312  * Call with cpuset_mutex held.
1313  */
1314 
1315 static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
1316                        int turning_on)
1317 {
1318         struct cpuset *trialcs;
1319         int balance_flag_changed;
1320         int spread_flag_changed;
1321         int err;
1322 
1323         trialcs = alloc_trial_cpuset(cs);
1324         if (!trialcs)
1325                 return -ENOMEM;
1326 
1327         if (turning_on)
1328                 set_bit(bit, &trialcs->flags);
1329         else
1330                 clear_bit(bit, &trialcs->flags);
1331 
1332         err = validate_change(cs, trialcs);
1333         if (err < 0)
1334                 goto out;
1335 
1336         balance_flag_changed = (is_sched_load_balance(cs) !=
1337                                 is_sched_load_balance(trialcs));
1338 
1339         spread_flag_changed = ((is_spread_slab(cs) != is_spread_slab(trialcs))
1340                         || (is_spread_page(cs) != is_spread_page(trialcs)));
1341 
1342         spin_lock_irq(&callback_lock);
1343         cs->flags = trialcs->flags;
1344         spin_unlock_irq(&callback_lock);
1345 
1346         if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed)
1347                 rebuild_sched_domains_locked();
1348 
1349         if (spread_flag_changed)
1350                 update_tasks_flags(cs);
1351 out:
1352         free_trial_cpuset(trialcs);
1353         return err;
1354 }
1355 
1356 /*
1357  * Frequency meter - How fast is some event occurring?
1358  *
1359  * These routines manage a digitally filtered, constant time based,
1360  * event frequency meter.  There are four routines:
1361  *   fmeter_init() - initialize a frequency meter.
1362  *   fmeter_markevent() - called each time the event happens.
1363  *   fmeter_getrate() - returns the recent rate of such events.
1364  *   fmeter_update() - internal routine used to update fmeter.
1365  *
1366  * A common data structure is passed to each of these routines,
1367  * which is used to keep track of the state required to manage the
1368  * frequency meter and its digital filter.
1369  *
1370  * The filter works on the number of events marked per unit time.
1371  * The filter is single-pole low-pass recursive (IIR).  The time unit
1372  * is 1 second.  Arithmetic is done using 32-bit integers scaled to
1373  * simulate 3 decimal digits of precision (multiplied by 1000).
1374  *
1375  * With an FM_COEF of 933, and a time base of 1 second, the filter
1376  * has a half-life of 10 seconds, meaning that if the events quit
1377  * happening, then the rate returned from the fmeter_getrate()
1378  * will be cut in half each 10 seconds, until it converges to zero.
1379  *
1380  * It is not worth doing a real infinitely recursive filter.  If more
1381  * than FM_MAXTICKS ticks have elapsed since the last filter event,
1382  * just compute FM_MAXTICKS ticks worth, by which point the level
1383  * will be stable.
1384  *
1385  * Limit the count of unprocessed events to FM_MAXCNT, so as to avoid
1386  * arithmetic overflow in the fmeter_update() routine.
1387  *
1388  * Given the simple 32 bit integer arithmetic used, this meter works
1389  * best for reporting rates between one per millisecond (msec) and
1390  * one per 32 (approx) seconds.  At constant rates faster than one
1391  * per msec it maxes out at values just under 1,000,000.  At constant
1392  * rates between one per msec, and one per second it will stabilize
1393  * to a value N*1000, where N is the rate of events per second.
1394  * At constant rates between one per second and one per 32 seconds,
1395  * it will be choppy, moving up on the seconds that have an event,
1396  * and then decaying until the next event.  At rates slower than
1397  * about one in 32 seconds, it decays all the way back to zero between
1398  * each event.
1399  */
1400 
1401 #define FM_COEF 933             /* coefficient for half-life of 10 secs */
1402 #define FM_MAXTICKS ((u32)99)   /* useless computing more ticks than this */
1403 #define FM_MAXCNT 1000000       /* limit cnt to avoid overflow */
1404 #define FM_SCALE 1000           /* faux fixed point scale */
1405 
1406 /* Initialize a frequency meter */
1407 static void fmeter_init(struct fmeter *fmp)
1408 {
1409         fmp->cnt = 0;
1410         fmp->val = 0;
1411         fmp->time = 0;
1412         spin_lock_init(&fmp->lock);
1413 }
1414 
1415 /* Internal meter update - process cnt events and update value */
1416 static void fmeter_update(struct fmeter *fmp)
1417 {
1418         time64_t now;
1419         u32 ticks;
1420 
1421         now = ktime_get_seconds();
1422         ticks = now - fmp->time;
1423 
1424         if (ticks == 0)
1425                 return;
1426 
1427         ticks = min(FM_MAXTICKS, ticks);
1428         while (ticks-- > 0)
1429                 fmp->val = (FM_COEF * fmp->val) / FM_SCALE;
1430         fmp->time = now;
1431 
1432         fmp->val += ((FM_SCALE - FM_COEF) * fmp->cnt) / FM_SCALE;
1433         fmp->cnt = 0;
1434 }
1435 
1436 /* Process any previous ticks, then bump cnt by one (times scale). */
1437 static void fmeter_markevent(struct fmeter *fmp)
1438 {
1439         spin_lock(&fmp->lock);
1440         fmeter_update(fmp);
1441         fmp->cnt = min(FM_MAXCNT, fmp->cnt + FM_SCALE);
1442         spin_unlock(&fmp->lock);
1443 }
1444 
1445 /* Process any previous ticks, then return current value. */
1446 static int fmeter_getrate(struct fmeter *fmp)
1447 {
1448         int val;
1449 
1450         spin_lock(&fmp->lock);
1451         fmeter_update(fmp);
1452         val = fmp->val;
1453         spin_unlock(&fmp->lock);
1454         return val;
1455 }
1456 
1457 static struct cpuset *cpuset_attach_old_cs;
1458 
1459 /* Called by cgroups to determine if a cpuset is usable; cpuset_mutex held */
1460 static int cpuset_can_attach(struct cgroup_taskset *tset)
1461 {
1462         struct cgroup_subsys_state *css;
1463         struct cpuset *cs;
1464         struct task_struct *task;
1465         int ret;
1466 
1467         /* used later by cpuset_attach() */
1468         cpuset_attach_old_cs = task_cs(cgroup_taskset_first(tset, &css));
1469         cs = css_cs(css);
1470 
1471         mutex_lock(&cpuset_mutex);
1472 
1473         /* allow moving tasks into an empty cpuset if on default hierarchy */
1474         ret = -ENOSPC;
1475         if (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
1476             (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed)))
1477                 goto out_unlock;
1478 
1479         cgroup_taskset_for_each(task, css, tset) {
1480                 ret = task_can_attach(task, cs->cpus_allowed);
1481                 if (ret)
1482                         goto out_unlock;
1483                 ret = security_task_setscheduler(task);
1484                 if (ret)
1485                         goto out_unlock;
1486         }
1487 
1488         /*
1489          * Mark attach is in progress.  This makes validate_change() fail
1490          * changes which zero cpus/mems_allowed.
1491          */
1492         cs->attach_in_progress++;
1493         ret = 0;
1494 out_unlock:
1495         mutex_unlock(&cpuset_mutex);
1496         return ret;
1497 }
1498 
1499 static void cpuset_cancel_attach(struct cgroup_taskset *tset)
1500 {
1501         struct cgroup_subsys_state *css;
1502         struct cpuset *cs;
1503 
1504         cgroup_taskset_first(tset, &css);
1505         cs = css_cs(css);
1506 
1507         mutex_lock(&cpuset_mutex);
1508         css_cs(css)->attach_in_progress--;
1509         mutex_unlock(&cpuset_mutex);
1510 }
1511 
1512 /*
1513  * Protected by cpuset_mutex.  cpus_attach is used only by cpuset_attach()
1514  * but we can't allocate it dynamically there.  Define it global and
1515  * allocate from cpuset_init().
1516  */
1517 static cpumask_var_t cpus_attach;
1518 
1519 static void cpuset_attach(struct cgroup_taskset *tset)
1520 {
1521         /* static buf protected by cpuset_mutex */
1522         static nodemask_t cpuset_attach_nodemask_to;
1523         struct task_struct *task;
1524         struct task_struct *leader;
1525         struct cgroup_subsys_state *css;
1526         struct cpuset *cs;
1527         struct cpuset *oldcs = cpuset_attach_old_cs;
1528 
1529         cgroup_taskset_first(tset, &css);
1530         cs = css_cs(css);
1531 
1532         mutex_lock(&cpuset_mutex);
1533 
1534         /* prepare for attach */
1535         if (cs == &top_cpuset)
1536                 cpumask_copy(cpus_attach, cpu_possible_mask);
1537         else
1538                 guarantee_online_cpus(cs, cpus_attach);
1539 
1540         guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
1541 
1542         cgroup_taskset_for_each(task, css, tset) {
1543                 /*
1544                  * can_attach beforehand should guarantee that this doesn't
1545                  * fail.  TODO: have a better way to handle failure here
1546                  */
1547                 WARN_ON_ONCE(set_cpus_allowed_ptr(task, cpus_attach));
1548 
1549                 cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to);
1550                 cpuset_update_task_spread_flag(cs, task);
1551         }
1552 
1553         /*
1554          * Change mm for all threadgroup leaders. This is expensive and may
1555          * sleep and should be moved outside migration path proper.
1556          */
1557         cpuset_attach_nodemask_to = cs->effective_mems;
1558         cgroup_taskset_for_each_leader(leader, css, tset) {
1559                 struct mm_struct *mm = get_task_mm(leader);
1560 
1561                 if (mm) {
1562                         mpol_rebind_mm(mm, &cpuset_attach_nodemask_to);
1563 
1564                         /*
1565                          * old_mems_allowed is the same with mems_allowed
1566                          * here, except if this task is being moved
1567                          * automatically due to hotplug.  In that case
1568                          * @mems_allowed has been updated and is empty, so
1569                          * @old_mems_allowed is the right nodesets that we
1570                          * migrate mm from.
1571                          */
1572                         if (is_memory_migrate(cs))
1573                                 cpuset_migrate_mm(mm, &oldcs->old_mems_allowed,
1574                                                   &cpuset_attach_nodemask_to);
1575                         else
1576                                 mmput(mm);
1577                 }
1578         }
1579 
1580         cs->old_mems_allowed = cpuset_attach_nodemask_to;
1581 
1582         cs->attach_in_progress--;
1583         if (!cs->attach_in_progress)
1584                 wake_up(&cpuset_attach_wq);
1585 
1586         mutex_unlock(&cpuset_mutex);
1587 }
1588 
1589 /* The various types of files and directories in a cpuset file system */
1590 
1591 typedef enum {
1592         FILE_MEMORY_MIGRATE,
1593         FILE_CPULIST,
1594         FILE_MEMLIST,
1595         FILE_EFFECTIVE_CPULIST,
1596         FILE_EFFECTIVE_MEMLIST,
1597         FILE_CPU_EXCLUSIVE,
1598         FILE_MEM_EXCLUSIVE,
1599         FILE_MEM_HARDWALL,
1600         FILE_SCHED_LOAD_BALANCE,
1601         FILE_SCHED_RELAX_DOMAIN_LEVEL,
1602         FILE_MEMORY_PRESSURE_ENABLED,
1603         FILE_MEMORY_PRESSURE,
1604         FILE_SPREAD_PAGE,
1605         FILE_SPREAD_SLAB,
1606 } cpuset_filetype_t;
1607 
1608 static int cpuset_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
1609                             u64 val)
1610 {
1611         struct cpuset *cs = css_cs(css);
1612         cpuset_filetype_t type = cft->private;
1613         int retval = 0;
1614 
1615         mutex_lock(&cpuset_mutex);
1616         if (!is_cpuset_online(cs)) {
1617                 retval = -ENODEV;
1618                 goto out_unlock;
1619         }
1620 
1621         switch (type) {
1622         case FILE_CPU_EXCLUSIVE:
1623                 retval = update_flag(CS_CPU_EXCLUSIVE, cs, val);
1624                 break;
1625         case FILE_MEM_EXCLUSIVE:
1626                 retval = update_flag(CS_MEM_EXCLUSIVE, cs, val);
1627                 break;
1628         case FILE_MEM_HARDWALL:
1629                 retval = update_flag(CS_MEM_HARDWALL, cs, val);
1630                 break;
1631         case FILE_SCHED_LOAD_BALANCE:
1632                 retval = update_flag(CS_SCHED_LOAD_BALANCE, cs, val);
1633                 break;
1634         case FILE_MEMORY_MIGRATE:
1635                 retval = update_flag(CS_MEMORY_MIGRATE, cs, val);
1636                 break;
1637         case FILE_MEMORY_PRESSURE_ENABLED:
1638                 cpuset_memory_pressure_enabled = !!val;
1639                 break;
1640         case FILE_SPREAD_PAGE:
1641                 retval = update_flag(CS_SPREAD_PAGE, cs, val);
1642                 break;
1643         case FILE_SPREAD_SLAB:
1644                 retval = update_flag(CS_SPREAD_SLAB, cs, val);
1645                 break;
1646         default:
1647                 retval = -EINVAL;
1648                 break;
1649         }
1650 out_unlock:
1651         mutex_unlock(&cpuset_mutex);
1652         return retval;
1653 }
1654 
1655 static int cpuset_write_s64(struct cgroup_subsys_state *css, struct cftype *cft,
1656                             s64 val)
1657 {
1658         struct cpuset *cs = css_cs(css);
1659         cpuset_filetype_t type = cft->private;
1660         int retval = -ENODEV;
1661 
1662         mutex_lock(&cpuset_mutex);
1663         if (!is_cpuset_online(cs))
1664                 goto out_unlock;
1665 
1666         switch (type) {
1667         case FILE_SCHED_RELAX_DOMAIN_LEVEL:
1668                 retval = update_relax_domain_level(cs, val);
1669                 break;
1670         default:
1671                 retval = -EINVAL;
1672                 break;
1673         }
1674 out_unlock:
1675         mutex_unlock(&cpuset_mutex);
1676         return retval;
1677 }
1678 
1679 /*
1680  * Common handling for a write to a "cpus" or "mems" file.
1681  */
1682 static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
1683                                     char *buf, size_t nbytes, loff_t off)
1684 {
1685         struct cpuset *cs = css_cs(of_css(of));
1686         struct cpuset *trialcs;
1687         int retval = -ENODEV;
1688 
1689         buf = strstrip(buf);
1690 
1691         /*
1692          * CPU or memory hotunplug may leave @cs w/o any execution
1693          * resources, in which case the hotplug code asynchronously updates
1694          * configuration and transfers all tasks to the nearest ancestor
1695          * which can execute.
1696          *
1697          * As writes to "cpus" or "mems" may restore @cs's execution
1698          * resources, wait for the previously scheduled operations before
1699          * proceeding, so that we don't end up keep removing tasks added
1700          * after execution capability is restored.
1701          *
1702          * cpuset_hotplug_work calls back into cgroup core via
1703          * cgroup_transfer_tasks() and waiting for it from a cgroupfs
1704          * operation like this one can lead to a deadlock through kernfs
1705          * active_ref protection.  Let's break the protection.  Losing the
1706          * protection is okay as we check whether @cs is online after
1707          * grabbing cpuset_mutex anyway.  This only happens on the legacy
1708          * hierarchies.
1709          */
1710         css_get(&cs->css);
1711         kernfs_break_active_protection(of->kn);
1712         flush_work(&cpuset_hotplug_work);
1713 
1714         mutex_lock(&cpuset_mutex);
1715         if (!is_cpuset_online(cs))
1716                 goto out_unlock;
1717 
1718         trialcs = alloc_trial_cpuset(cs);
1719         if (!trialcs) {
1720                 retval = -ENOMEM;
1721                 goto out_unlock;
1722         }
1723 
1724         switch (of_cft(of)->private) {
1725         case FILE_CPULIST:
1726                 retval = update_cpumask(cs, trialcs, buf);
1727                 break;
1728         case FILE_MEMLIST:
1729                 retval = update_nodemask(cs, trialcs, buf);
1730                 break;
1731         default:
1732                 retval = -EINVAL;
1733                 break;
1734         }
1735 
1736         free_trial_cpuset(trialcs);
1737 out_unlock:
1738         mutex_unlock(&cpuset_mutex);
1739         kernfs_unbreak_active_protection(of->kn);
1740         css_put(&cs->css);
1741         flush_workqueue(cpuset_migrate_mm_wq);
1742         return retval ?: nbytes;
1743 }
1744 
1745 /*
1746  * These ascii lists should be read in a single call, by using a user
1747  * buffer large enough to hold the entire map.  If read in smaller
1748  * chunks, there is no guarantee of atomicity.  Since the display format
1749  * used, list of ranges of sequential numbers, is variable length,
1750  * and since these maps can change value dynamically, one could read
1751  * gibberish by doing partial reads while a list was changing.
1752  */
1753 static int cpuset_common_seq_show(struct seq_file *sf, void *v)
1754 {
1755         struct cpuset *cs = css_cs(seq_css(sf));
1756         cpuset_filetype_t type = seq_cft(sf)->private;
1757         int ret = 0;
1758 
1759         spin_lock_irq(&callback_lock);
1760 
1761         switch (type) {
1762         case FILE_CPULIST:
1763                 seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->cpus_allowed));
1764                 break;
1765         case FILE_MEMLIST:
1766                 seq_printf(sf, "%*pbl\n", nodemask_pr_args(&cs->mems_allowed));
1767                 break;
1768         case FILE_EFFECTIVE_CPULIST:
1769                 seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->effective_cpus));
1770                 break;
1771         case FILE_EFFECTIVE_MEMLIST:
1772                 seq_printf(sf, "%*pbl\n", nodemask_pr_args(&cs->effective_mems));
1773                 break;
1774         default:
1775                 ret = -EINVAL;
1776         }
1777 
1778         spin_unlock_irq(&callback_lock);
1779         return ret;
1780 }
1781 
1782 static u64 cpuset_read_u64(struct cgroup_subsys_state *css, struct cftype *cft)
1783 {
1784         struct cpuset *cs = css_cs(css);
1785         cpuset_filetype_t type = cft->private;
1786         switch (type) {
1787         case FILE_CPU_EXCLUSIVE:
1788                 return is_cpu_exclusive(cs);
1789         case FILE_MEM_EXCLUSIVE:
1790                 return is_mem_exclusive(cs);
1791         case FILE_MEM_HARDWALL:
1792                 return is_mem_hardwall(cs);
1793         case FILE_SCHED_LOAD_BALANCE:
1794                 return is_sched_load_balance(cs);
1795         case FILE_MEMORY_MIGRATE:
1796                 return is_memory_migrate(cs);
1797         case FILE_MEMORY_PRESSURE_ENABLED:
1798                 return cpuset_memory_pressure_enabled;
1799         case FILE_MEMORY_PRESSURE:
1800                 return fmeter_getrate(&cs->fmeter);
1801         case FILE_SPREAD_PAGE:
1802                 return is_spread_page(cs);
1803         case FILE_SPREAD_SLAB:
1804                 return is_spread_slab(cs);
1805         default:
1806                 BUG();
1807         }
1808 
1809         /* Unreachable but makes gcc happy */
1810         return 0;
1811 }
1812 
1813 static s64 cpuset_read_s64(struct cgroup_subsys_state *css, struct cftype *cft)
1814 {
1815         struct cpuset *cs = css_cs(css);
1816         cpuset_filetype_t type = cft->private;
1817         switch (type) {
1818         case FILE_SCHED_RELAX_DOMAIN_LEVEL:
1819                 return cs->relax_domain_level;
1820         default:
1821                 BUG();
1822         }
1823 
1824         /* Unrechable but makes gcc happy */
1825         return 0;
1826 }
1827 
1828 
1829 /*
1830  * for the common functions, 'private' gives the type of file
1831  */
1832 
1833 static struct cftype files[] = {
1834         {
1835                 .name = "cpus",
1836                 .seq_show = cpuset_common_seq_show,
1837                 .write = cpuset_write_resmask,
1838                 .max_write_len = (100U + 6 * NR_CPUS),
1839                 .private = FILE_CPULIST,
1840         },
1841 
1842         {
1843                 .name = "mems",
1844                 .seq_show = cpuset_common_seq_show,
1845                 .write = cpuset_write_resmask,
1846                 .max_write_len = (100U + 6 * MAX_NUMNODES),
1847                 .private = FILE_MEMLIST,
1848         },
1849 
1850         {
1851                 .name = "effective_cpus",
1852                 .seq_show = cpuset_common_seq_show,
1853                 .private = FILE_EFFECTIVE_CPULIST,
1854         },
1855 
1856         {
1857                 .name = "effective_mems",
1858                 .seq_show = cpuset_common_seq_show,
1859                 .private = FILE_EFFECTIVE_MEMLIST,
1860         },
1861 
1862         {
1863                 .name = "cpu_exclusive",
1864                 .read_u64 = cpuset_read_u64,
1865                 .write_u64 = cpuset_write_u64,
1866                 .private = FILE_CPU_EXCLUSIVE,
1867         },
1868 
1869         {
1870                 .name = "mem_exclusive",
1871                 .read_u64 = cpuset_read_u64,
1872                 .write_u64 = cpuset_write_u64,
1873                 .private = FILE_MEM_EXCLUSIVE,
1874         },
1875 
1876         {
1877                 .name = "mem_hardwall",
1878                 .read_u64 = cpuset_read_u64,
1879                 .write_u64 = cpuset_write_u64,
1880                 .private = FILE_MEM_HARDWALL,
1881         },
1882 
1883         {
1884                 .name = "sched_load_balance",
1885                 .read_u64 = cpuset_read_u64,
1886                 .write_u64 = cpuset_write_u64,
1887                 .private = FILE_SCHED_LOAD_BALANCE,
1888         },
1889 
1890         {
1891                 .name = "sched_relax_domain_level",
1892                 .read_s64 = cpuset_read_s64,
1893                 .write_s64 = cpuset_write_s64,
1894                 .private = FILE_SCHED_RELAX_DOMAIN_LEVEL,
1895         },
1896 
1897         {
1898                 .name = "memory_migrate",
1899                 .read_u64 = cpuset_read_u64,
1900                 .write_u64 = cpuset_write_u64,
1901                 .private = FILE_MEMORY_MIGRATE,
1902         },
1903 
1904         {
1905                 .name = "memory_pressure",
1906                 .read_u64 = cpuset_read_u64,
1907         },
1908 
1909         {
1910                 .name = "memory_spread_page",
1911                 .read_u64 = cpuset_read_u64,
1912                 .write_u64 = cpuset_write_u64,
1913                 .private = FILE_SPREAD_PAGE,
1914         },
1915 
1916         {
1917                 .name = "memory_spread_slab",
1918                 .read_u64 = cpuset_read_u64,
1919                 .write_u64 = cpuset_write_u64,
1920                 .private = FILE_SPREAD_SLAB,
1921         },
1922 
1923         {
1924                 .name = "memory_pressure_enabled",
1925                 .flags = CFTYPE_ONLY_ON_ROOT,
1926                 .read_u64 = cpuset_read_u64,
1927                 .write_u64 = cpuset_write_u64,
1928                 .private = FILE_MEMORY_PRESSURE_ENABLED,
1929         },
1930 
1931         { }     /* terminate */
1932 };
1933 
1934 /*
1935  *      cpuset_css_alloc - allocate a cpuset css
1936  *      cgrp:   control group that the new cpuset will be part of
1937  */
1938 
1939 static struct cgroup_subsys_state *
1940 cpuset_css_alloc(struct cgroup_subsys_state *parent_css)
1941 {
1942         struct cpuset *cs;
1943 
1944         if (!parent_css)
1945                 return &top_cpuset.css;
1946 
1947         cs = kzalloc(sizeof(*cs), GFP_KERNEL);
1948         if (!cs)
1949                 return ERR_PTR(-ENOMEM);
1950         if (!alloc_cpumask_var(&cs->cpus_allowed, GFP_KERNEL))
1951                 goto free_cs;
1952         if (!alloc_cpumask_var(&cs->effective_cpus, GFP_KERNEL))
1953                 goto free_cpus;
1954 
1955         set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
1956         cpumask_clear(cs->cpus_allowed);
1957         nodes_clear(cs->mems_allowed);
1958         cpumask_clear(cs->effective_cpus);
1959         nodes_clear(cs->effective_mems);
1960         fmeter_init(&cs->fmeter);
1961         cs->relax_domain_level = -1;
1962 
1963         return &cs->css;
1964 
1965 free_cpus:
1966         free_cpumask_var(cs->cpus_allowed);
1967 free_cs:
1968         kfree(cs);
1969         return ERR_PTR(-ENOMEM);
1970 }
1971 
1972 static int cpuset_css_online(struct cgroup_subsys_state *css)
1973 {
1974         struct cpuset *cs = css_cs(css);
1975         struct cpuset *parent = parent_cs(cs);
1976         struct cpuset *tmp_cs;
1977         struct cgroup_subsys_state *pos_css;
1978 
1979         if (!parent)
1980                 return 0;
1981 
1982         mutex_lock(&cpuset_mutex);
1983 
1984         set_bit(CS_ONLINE, &cs->flags);
1985         if (is_spread_page(parent))
1986                 set_bit(CS_SPREAD_PAGE, &cs->flags);
1987         if (is_spread_slab(parent))
1988                 set_bit(CS_SPREAD_SLAB, &cs->flags);
1989 
1990         cpuset_inc();
1991 
1992         spin_lock_irq(&callback_lock);
1993         if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys)) {
1994                 cpumask_copy(cs->effective_cpus, parent->effective_cpus);
1995                 cs->effective_mems = parent->effective_mems;
1996         }
1997         spin_unlock_irq(&callback_lock);
1998 
1999         if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags))
2000                 goto out_unlock;
2001 
2002         /*
2003          * Clone @parent's configuration if CGRP_CPUSET_CLONE_CHILDREN is
2004          * set.  This flag handling is implemented in cgroup core for
2005          * histrical reasons - the flag may be specified during mount.
2006          *
2007          * Currently, if any sibling cpusets have exclusive cpus or mem, we
2008          * refuse to clone the configuration - thereby refusing the task to
2009          * be entered, and as a result refusing the sys_unshare() or
2010          * clone() which initiated it.  If this becomes a problem for some
2011          * users who wish to allow that scenario, then this could be
2012          * changed to grant parent->cpus_allowed-sibling_cpus_exclusive
2013          * (and likewise for mems) to the new cgroup.
2014          */
2015         rcu_read_lock();
2016         cpuset_for_each_child(tmp_cs, pos_css, parent) {
2017                 if (is_mem_exclusive(tmp_cs) || is_cpu_exclusive(tmp_cs)) {
2018                         rcu_read_unlock();
2019                         goto out_unlock;
2020                 }
2021         }
2022         rcu_read_unlock();
2023 
2024         spin_lock_irq(&callback_lock);
2025         cs->mems_allowed = parent->mems_allowed;
2026         cs->effective_mems = parent->mems_allowed;
2027         cpumask_copy(cs->cpus_allowed, parent->cpus_allowed);
2028         cpumask_copy(cs->effective_cpus, parent->cpus_allowed);
2029         spin_unlock_irq(&callback_lock);
2030 out_unlock:
2031         mutex_unlock(&cpuset_mutex);
2032         return 0;
2033 }
2034 
2035 /*
2036  * If the cpuset being removed has its flag 'sched_load_balance'
2037  * enabled, then simulate turning sched_load_balance off, which
2038  * will call rebuild_sched_domains_locked().
2039  */
2040 
2041 static void cpuset_css_offline(struct cgroup_subsys_state *css)
2042 {
2043         struct cpuset *cs = css_cs(css);
2044 
2045         mutex_lock(&cpuset_mutex);
2046 
2047         if (is_sched_load_balance(cs))
2048                 update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
2049 
2050         cpuset_dec();
2051         clear_bit(CS_ONLINE, &cs->flags);
2052 
2053         mutex_unlock(&cpuset_mutex);
2054 }
2055 
2056 static void cpuset_css_free(struct cgroup_subsys_state *css)
2057 {
2058         struct cpuset *cs = css_cs(css);
2059 
2060         free_cpumask_var(cs->effective_cpus);
2061         free_cpumask_var(cs->cpus_allowed);
2062         kfree(cs);
2063 }
2064 
2065 static void cpuset_bind(struct cgroup_subsys_state *root_css)
2066 {
2067         mutex_lock(&cpuset_mutex);
2068         spin_lock_irq(&callback_lock);
2069 
2070         if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys)) {
2071                 cpumask_copy(top_cpuset.cpus_allowed, cpu_possible_mask);
2072                 top_cpuset.mems_allowed = node_possible_map;
2073         } else {
2074                 cpumask_copy(top_cpuset.cpus_allowed,
2075                              top_cpuset.effective_cpus);
2076                 top_cpuset.mems_allowed = top_cpuset.effective_mems;
2077         }
2078 
2079         spin_unlock_irq(&callback_lock);
2080         mutex_unlock(&cpuset_mutex);
2081 }
2082 
2083 /*
2084  * Make sure the new task conform to the current state of its parent,
2085  * which could have been changed by cpuset just after it inherits the
2086  * state from the parent and before it sits on the cgroup's task list.
2087  */
2088 static void cpuset_fork(struct task_struct *task)
2089 {
2090         if (task_css_is_root(task, cpuset_cgrp_id))
2091                 return;
2092 
2093         set_cpus_allowed_ptr(task, &current->cpus_allowed);
2094         task->mems_allowed = current->mems_allowed;
2095 }
2096 
2097 struct cgroup_subsys cpuset_cgrp_subsys = {
2098         .css_alloc      = cpuset_css_alloc,
2099         .css_online     = cpuset_css_online,
2100         .css_offline    = cpuset_css_offline,
2101         .css_free       = cpuset_css_free,
2102         .can_attach     = cpuset_can_attach,
2103         .cancel_attach  = cpuset_cancel_attach,
2104         .attach         = cpuset_attach,
2105         .post_attach    = cpuset_post_attach,
2106         .bind           = cpuset_bind,
2107         .fork           = cpuset_fork,
2108         .legacy_cftypes = files,
2109         .early_init     = true,
2110 };
2111 
2112 /**
2113  * cpuset_init - initialize cpusets at system boot
2114  *
2115  * Description: Initialize top_cpuset and the cpuset internal file system,
2116  **/
2117 
2118 int __init cpuset_init(void)
2119 {
2120         int err = 0;
2121 
2122         if (!alloc_cpumask_var(&top_cpuset.cpus_allowed, GFP_KERNEL))
2123                 BUG();
2124         if (!alloc_cpumask_var(&top_cpuset.effective_cpus, GFP_KERNEL))
2125                 BUG();
2126 
2127         cpumask_setall(top_cpuset.cpus_allowed);
2128         nodes_setall(top_cpuset.mems_allowed);
2129         cpumask_setall(top_cpuset.effective_cpus);
2130         nodes_setall(top_cpuset.effective_mems);
2131 
2132         fmeter_init(&top_cpuset.fmeter);
2133         set_bit(CS_SCHED_LOAD_BALANCE, &top_cpuset.flags);
2134         top_cpuset.relax_domain_level = -1;
2135 
2136         err = register_filesystem(&cpuset_fs_type);
2137         if (err < 0)
2138                 return err;
2139 
2140         if (!alloc_cpumask_var(&cpus_attach, GFP_KERNEL))
2141                 BUG();
2142 
2143         return 0;
2144 }
2145 
2146 /*
2147  * If CPU and/or memory hotplug handlers, below, unplug any CPUs
2148  * or memory nodes, we need to walk over the cpuset hierarchy,
2149  * removing that CPU or node from all cpusets.  If this removes the
2150  * last CPU or node from a cpuset, then move the tasks in the empty
2151  * cpuset to its next-highest non-empty parent.
2152  */
2153 static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
2154 {
2155         struct cpuset *parent;
2156 
2157         /*
2158          * Find its next-highest non-empty parent, (top cpuset
2159          * has online cpus, so can't be empty).
2160          */
2161         parent = parent_cs(cs);
2162         while (cpumask_empty(parent->cpus_allowed) ||
2163                         nodes_empty(parent->mems_allowed))
2164                 parent = parent_cs(parent);
2165 
2166         if (cgroup_transfer_tasks(parent->css.cgroup, cs->css.cgroup)) {
2167                 pr_err("cpuset: failed to transfer tasks out of empty cpuset ");
2168                 pr_cont_cgroup_name(cs->css.cgroup);
2169                 pr_cont("\n");
2170         }
2171 }
2172 
2173 static void
2174 hotplug_update_tasks_legacy(struct cpuset *cs,
2175                             struct cpumask *new_cpus, nodemask_t *new_mems,
2176                             bool cpus_updated, bool mems_updated)
2177 {
2178         bool is_empty;
2179 
2180         spin_lock_irq(&callback_lock);
2181         cpumask_copy(cs->cpus_allowed, new_cpus);
2182         cpumask_copy(cs->effective_cpus, new_cpus);
2183         cs->mems_allowed = *new_mems;
2184         cs->effective_mems = *new_mems;
2185         spin_unlock_irq(&callback_lock);
2186 
2187         /*
2188          * Don't call update_tasks_cpumask() if the cpuset becomes empty,
2189          * as the tasks will be migratecd to an ancestor.
2190          */
2191         if (cpus_updated && !cpumask_empty(cs->cpus_allowed))
2192                 update_tasks_cpumask(cs);
2193         if (mems_updated && !nodes_empty(cs->mems_allowed))
2194                 update_tasks_nodemask(cs);
2195 
2196         is_empty = cpumask_empty(cs->cpus_allowed) ||
2197                    nodes_empty(cs->mems_allowed);
2198 
2199         mutex_unlock(&cpuset_mutex);
2200 
2201         /*
2202          * Move tasks to the nearest ancestor with execution resources,
2203          * This is full cgroup operation which will also call back into
2204          * cpuset. Should be done outside any lock.
2205          */
2206         if (is_empty)
2207                 remove_tasks_in_empty_cpuset(cs);
2208 
2209         mutex_lock(&cpuset_mutex);
2210 }
2211 
2212 static void
2213 hotplug_update_tasks(struct cpuset *cs,
2214                      struct cpumask *new_cpus, nodemask_t *new_mems,
2215                      bool cpus_updated, bool mems_updated)
2216 {
2217         if (cpumask_empty(new_cpus))
2218                 cpumask_copy(new_cpus, parent_cs(cs)->effective_cpus);
2219         if (nodes_empty(*new_mems))
2220                 *new_mems = parent_cs(cs)->effective_mems;
2221 
2222         spin_lock_irq(&callback_lock);
2223         cpumask_copy(cs->effective_cpus, new_cpus);
2224         cs->effective_mems = *new_mems;
2225         spin_unlock_irq(&callback_lock);
2226 
2227         if (cpus_updated)
2228                 update_tasks_cpumask(cs);
2229         if (mems_updated)
2230                 update_tasks_nodemask(cs);
2231 }
2232 
2233 /**
2234  * cpuset_hotplug_update_tasks - update tasks in a cpuset for hotunplug
2235  * @cs: cpuset in interest
2236  *
2237  * Compare @cs's cpu and mem masks against top_cpuset and if some have gone
2238  * offline, update @cs accordingly.  If @cs ends up with no CPU or memory,
2239  * all its tasks are moved to the nearest ancestor with both resources.
2240  */
2241 static void cpuset_hotplug_update_tasks(struct cpuset *cs)
2242 {
2243         static cpumask_t new_cpus;
2244         static nodemask_t new_mems;
2245         bool cpus_updated;
2246         bool mems_updated;
2247 retry:
2248         wait_event(cpuset_attach_wq, cs->attach_in_progress == 0);
2249 
2250         mutex_lock(&cpuset_mutex);
2251 
2252         /*
2253          * We have raced with task attaching. We wait until attaching
2254          * is finished, so we won't attach a task to an empty cpuset.
2255          */
2256         if (cs->attach_in_progress) {
2257                 mutex_unlock(&cpuset_mutex);
2258                 goto retry;
2259         }
2260 
2261         cpumask_and(&new_cpus, cs->cpus_allowed, parent_cs(cs)->effective_cpus);
2262         nodes_and(new_mems, cs->mems_allowed, parent_cs(cs)->effective_mems);
2263 
2264         cpus_updated = !cpumask_equal(&new_cpus, cs->effective_cpus);
2265         mems_updated = !nodes_equal(new_mems, cs->effective_mems);
2266 
2267         if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys))
2268                 hotplug_update_tasks(cs, &new_cpus, &new_mems,
2269                                      cpus_updated, mems_updated);
2270         else
2271                 hotplug_update_tasks_legacy(cs, &new_cpus, &new_mems,
2272                                             cpus_updated, mems_updated);
2273 
2274         mutex_unlock(&cpuset_mutex);
2275 }
2276 
2277 /**
2278  * cpuset_hotplug_workfn - handle CPU/memory hotunplug for a cpuset
2279  *
2280  * This function is called after either CPU or memory configuration has
2281  * changed and updates cpuset accordingly.  The top_cpuset is always
2282  * synchronized to cpu_active_mask and N_MEMORY, which is necessary in
2283  * order to make cpusets transparent (of no affect) on systems that are
2284  * actively using CPU hotplug but making no active use of cpusets.
2285  *
2286  * Non-root cpusets are only affected by offlining.  If any CPUs or memory
2287  * nodes have been taken down, cpuset_hotplug_update_tasks() is invoked on
2288  * all descendants.
2289  *
2290  * Note that CPU offlining during suspend is ignored.  We don't modify
2291  * cpusets across suspend/resume cycles at all.
2292  */
2293 static void cpuset_hotplug_workfn(struct work_struct *work)
2294 {
2295         static cpumask_t new_cpus;
2296         static nodemask_t new_mems;
2297         bool cpus_updated, mems_updated;
2298         bool on_dfl = cgroup_subsys_on_dfl(cpuset_cgrp_subsys);
2299 
2300         mutex_lock(&cpuset_mutex);
2301 
2302         /* fetch the available cpus/mems and find out which changed how */
2303         cpumask_copy(&new_cpus, cpu_active_mask);
2304         new_mems = node_states[N_MEMORY];
2305 
2306         cpus_updated = !cpumask_equal(top_cpuset.effective_cpus, &new_cpus);
2307         mems_updated = !nodes_equal(top_cpuset.effective_mems, new_mems);
2308 
2309         /* synchronize cpus_allowed to cpu_active_mask */
2310         if (cpus_updated) {
2311                 spin_lock_irq(&callback_lock);
2312                 if (!on_dfl)
2313                         cpumask_copy(top_cpuset.cpus_allowed, &new_cpus);
2314                 cpumask_copy(top_cpuset.effective_cpus, &new_cpus);
2315                 spin_unlock_irq(&callback_lock);
2316                 /* we don't mess with cpumasks of tasks in top_cpuset */
2317         }
2318 
2319         /* synchronize mems_allowed to N_MEMORY */
2320         if (mems_updated) {
2321                 spin_lock_irq(&callback_lock);
2322                 if (!on_dfl)
2323                         top_cpuset.mems_allowed = new_mems;
2324                 top_cpuset.effective_mems = new_mems;
2325                 spin_unlock_irq(&callback_lock);
2326                 update_tasks_nodemask(&top_cpuset);
2327         }
2328 
2329         mutex_unlock(&cpuset_mutex);
2330 
2331         /* if cpus or mems changed, we need to propagate to descendants */
2332         if (cpus_updated || mems_updated) {
2333                 struct cpuset *cs;
2334                 struct cgroup_subsys_state *pos_css;
2335 
2336                 rcu_read_lock();
2337                 cpuset_for_each_descendant_pre(cs, pos_css, &top_cpuset) {
2338                         if (cs == &top_cpuset || !css_tryget_online(&cs->css))
2339                                 continue;
2340                         rcu_read_unlock();
2341 
2342                         cpuset_hotplug_update_tasks(cs);
2343 
2344                         rcu_read_lock();
2345                         css_put(&cs->css);
2346                 }
2347                 rcu_read_unlock();
2348         }
2349 
2350         /* rebuild sched domains if cpus_allowed has changed */
2351         if (cpus_updated)
2352                 rebuild_sched_domains();
2353 }
2354 
2355 void cpuset_update_active_cpus(bool cpu_online)
2356 {
2357         /*
2358          * We're inside cpu hotplug critical region which usually nests
2359          * inside cgroup synchronization.  Bounce actual hotplug processing
2360          * to a work item to avoid reverse locking order.
2361          *
2362          * We still need to do partition_sched_domains() synchronously;
2363          * otherwise, the scheduler will get confused and put tasks to the
2364          * dead CPU.  Fall back to the default single domain.
2365          * cpuset_hotplug_workfn() will rebuild it as necessary.
2366          */
2367         partition_sched_domains(1, NULL, NULL);
2368         schedule_work(&cpuset_hotplug_work);
2369 }
2370 
2371 /*
2372  * Keep top_cpuset.mems_allowed tracking node_states[N_MEMORY].
2373  * Call this routine anytime after node_states[N_MEMORY] changes.
2374  * See cpuset_update_active_cpus() for CPU hotplug handling.
2375  */
2376 static int cpuset_track_online_nodes(struct notifier_block *self,
2377                                 unsigned long action, void *arg)
2378 {
2379         schedule_work(&cpuset_hotplug_work);
2380         return NOTIFY_OK;
2381 }
2382 
2383 static struct notifier_block cpuset_track_online_nodes_nb = {
2384         .notifier_call = cpuset_track_online_nodes,
2385         .priority = 10,         /* ??! */
2386 };
2387 
2388 /**
2389  * cpuset_init_smp - initialize cpus_allowed
2390  *
2391  * Description: Finish top cpuset after cpu, node maps are initialized
2392  */
2393 void __init cpuset_init_smp(void)
2394 {
2395         cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
2396         top_cpuset.mems_allowed = node_states[N_MEMORY];
2397         top_cpuset.old_mems_allowed = top_cpuset.mems_allowed;
2398 
2399         cpumask_copy(top_cpuset.effective_cpus, cpu_active_mask);
2400         top_cpuset.effective_mems = node_states[N_MEMORY];
2401 
2402         register_hotmemory_notifier(&cpuset_track_online_nodes_nb);
2403 
2404         cpuset_migrate_mm_wq = alloc_ordered_workqueue("cpuset_migrate_mm", 0);
2405         BUG_ON(!cpuset_migrate_mm_wq);
2406 }
2407 
2408 /**
2409  * cpuset_cpus_allowed - return cpus_allowed mask from a tasks cpuset.
2410  * @tsk: pointer to task_struct from which to obtain cpuset->cpus_allowed.
2411  * @pmask: pointer to struct cpumask variable to receive cpus_allowed set.
2412  *
2413  * Description: Returns the cpumask_var_t cpus_allowed of the cpuset
2414  * attached to the specified @tsk.  Guaranteed to return some non-empty
2415  * subset of cpu_online_mask, even if this means going outside the
2416  * tasks cpuset.
2417  **/
2418 
2419 void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask)
2420 {
2421         unsigned long flags;
2422 
2423         spin_lock_irqsave(&callback_lock, flags);
2424         rcu_read_lock();
2425         guarantee_online_cpus(task_cs(tsk), pmask);
2426         rcu_read_unlock();
2427         spin_unlock_irqrestore(&callback_lock, flags);
2428 }
2429 
2430 void cpuset_cpus_allowed_fallback(struct task_struct *tsk)
2431 {
2432         rcu_read_lock();
2433         do_set_cpus_allowed(tsk, task_cs(tsk)->effective_cpus);
2434         rcu_read_unlock();
2435 
2436         /*
2437          * We own tsk->cpus_allowed, nobody can change it under us.
2438          *
2439          * But we used cs && cs->cpus_allowed lockless and thus can
2440          * race with cgroup_attach_task() or update_cpumask() and get
2441          * the wrong tsk->cpus_allowed. However, both cases imply the
2442          * subsequent cpuset_change_cpumask()->set_cpus_allowed_ptr()
2443          * which takes task_rq_lock().
2444          *
2445          * If we are called after it dropped the lock we must see all
2446          * changes in tsk_cs()->cpus_allowed. Otherwise we can temporary
2447          * set any mask even if it is not right from task_cs() pov,
2448          * the pending set_cpus_allowed_ptr() will fix things.
2449          *
2450          * select_fallback_rq() will fix things ups and set cpu_possible_mask
2451          * if required.
2452          */
2453 }
2454 
2455 void __init cpuset_init_current_mems_allowed(void)
2456 {
2457         nodes_setall(current->mems_allowed);
2458 }
2459 
2460 /**
2461  * cpuset_mems_allowed - return mems_allowed mask from a tasks cpuset.
2462  * @tsk: pointer to task_struct from which to obtain cpuset->mems_allowed.
2463  *
2464  * Description: Returns the nodemask_t mems_allowed of the cpuset
2465  * attached to the specified @tsk.  Guaranteed to return some non-empty
2466  * subset of node_states[N_MEMORY], even if this means going outside the
2467  * tasks cpuset.
2468  **/
2469 
2470 nodemask_t cpuset_mems_allowed(struct task_struct *tsk)
2471 {
2472         nodemask_t mask;
2473         unsigned long flags;
2474 
2475         spin_lock_irqsave(&callback_lock, flags);
2476         rcu_read_lock();
2477         guarantee_online_mems(task_cs(tsk), &mask);
2478         rcu_read_unlock();
2479         spin_unlock_irqrestore(&callback_lock, flags);
2480 
2481         return mask;
2482 }
2483 
2484 /**
2485  * cpuset_nodemask_valid_mems_allowed - check nodemask vs. curremt mems_allowed
2486  * @nodemask: the nodemask to be checked
2487  *
2488  * Are any of the nodes in the nodemask allowed in current->mems_allowed?
2489  */
2490 int cpuset_nodemask_valid_mems_allowed(nodemask_t *nodemask)
2491 {
2492         return nodes_intersects(*nodemask, current->mems_allowed);
2493 }
2494 
2495 /*
2496  * nearest_hardwall_ancestor() - Returns the nearest mem_exclusive or
2497  * mem_hardwall ancestor to the specified cpuset.  Call holding
2498  * callback_lock.  If no ancestor is mem_exclusive or mem_hardwall
2499  * (an unusual configuration), then returns the root cpuset.
2500  */
2501 static struct cpuset *nearest_hardwall_ancestor(struct cpuset *cs)
2502 {
2503         while (!(is_mem_exclusive(cs) || is_mem_hardwall(cs)) && parent_cs(cs))
2504                 cs = parent_cs(cs);
2505         return cs;
2506 }
2507 
2508 /**
2509  * cpuset_node_allowed - Can we allocate on a memory node?
2510  * @node: is this an allowed node?
2511  * @gfp_mask: memory allocation flags
2512  *
2513  * If we're in interrupt, yes, we can always allocate.  If @node is set in
2514  * current's mems_allowed, yes.  If it's not a __GFP_HARDWALL request and this
2515  * node is set in the nearest hardwalled cpuset ancestor to current's cpuset,
2516  * yes.  If current has access to memory reserves due to TIF_MEMDIE, yes.
2517  * Otherwise, no.
2518  *
2519  * GFP_USER allocations are marked with the __GFP_HARDWALL bit,
2520  * and do not allow allocations outside the current tasks cpuset
2521  * unless the task has been OOM killed as is marked TIF_MEMDIE.
2522  * GFP_KERNEL allocations are not so marked, so can escape to the
2523  * nearest enclosing hardwalled ancestor cpuset.
2524  *
2525  * Scanning up parent cpusets requires callback_lock.  The
2526  * __alloc_pages() routine only calls here with __GFP_HARDWALL bit
2527  * _not_ set if it's a GFP_KERNEL allocation, and all nodes in the
2528  * current tasks mems_allowed came up empty on the first pass over
2529  * the zonelist.  So only GFP_KERNEL allocations, if all nodes in the
2530  * cpuset are short of memory, might require taking the callback_lock.
2531  *
2532  * The first call here from mm/page_alloc:get_page_from_freelist()
2533  * has __GFP_HARDWALL set in gfp_mask, enforcing hardwall cpusets,
2534  * so no allocation on a node outside the cpuset is allowed (unless
2535  * in interrupt, of course).
2536  *
2537  * The second pass through get_page_from_freelist() doesn't even call
2538  * here for GFP_ATOMIC calls.  For those calls, the __alloc_pages()
2539  * variable 'wait' is not set, and the bit ALLOC_CPUSET is not set
2540  * in alloc_flags.  That logic and the checks below have the combined
2541  * affect that:
2542  *      in_interrupt - any node ok (current task context irrelevant)
2543  *      GFP_ATOMIC   - any node ok
2544  *      TIF_MEMDIE   - any node ok
2545  *      GFP_KERNEL   - any node in enclosing hardwalled cpuset ok
2546  *      GFP_USER     - only nodes in current tasks mems allowed ok.
2547  */
2548 bool __cpuset_node_allowed(int node, gfp_t gfp_mask)
2549 {
2550         struct cpuset *cs;              /* current cpuset ancestors */
2551         int allowed;                    /* is allocation in zone z allowed? */
2552         unsigned long flags;
2553 
2554         if (in_interrupt())
2555                 return true;
2556         if (node_isset(node, current->mems_allowed))
2557                 return true;
2558         /*
2559          * Allow tasks that have access to memory reserves because they have
2560          * been OOM killed to get memory anywhere.
2561          */
2562         if (unlikely(test_thread_flag(TIF_MEMDIE)))
2563                 return true;
2564         if (gfp_mask & __GFP_HARDWALL)  /* If hardwall request, stop here */
2565                 return false;
2566 
2567         if (current->flags & PF_EXITING) /* Let dying task have memory */
2568                 return true;
2569 
2570         /* Not hardwall and node outside mems_allowed: scan up cpusets */
2571         spin_lock_irqsave(&callback_lock, flags);
2572 
2573         rcu_read_lock();
2574         cs = nearest_hardwall_ancestor(task_cs(current));
2575         allowed = node_isset(node, cs->mems_allowed);
2576         rcu_read_unlock();
2577 
2578         spin_unlock_irqrestore(&callback_lock, flags);
2579         return allowed;
2580 }
2581 
2582 /**
2583  * cpuset_mem_spread_node() - On which node to begin search for a file page
2584  * cpuset_slab_spread_node() - On which node to begin search for a slab page
2585  *
2586  * If a task is marked PF_SPREAD_PAGE or PF_SPREAD_SLAB (as for
2587  * tasks in a cpuset with is_spread_page or is_spread_slab set),
2588  * and if the memory allocation used cpuset_mem_spread_node()
2589  * to determine on which node to start looking, as it will for
2590  * certain page cache or slab cache pages such as used for file
2591  * system buffers and inode caches, then instead of starting on the
2592  * local node to look for a free page, rather spread the starting
2593  * node around the tasks mems_allowed nodes.
2594  *
2595  * We don't have to worry about the returned node being offline
2596  * because "it can't happen", and even if it did, it would be ok.
2597  *
2598  * The routines calling guarantee_online_mems() are careful to
2599  * only set nodes in task->mems_allowed that are online.  So it
2600  * should not be possible for the following code to return an
2601  * offline node.  But if it did, that would be ok, as this routine
2602  * is not returning the node where the allocation must be, only
2603  * the node where the search should start.  The zonelist passed to
2604  * __alloc_pages() will include all nodes.  If the slab allocator
2605  * is passed an offline node, it will fall back to the local node.
2606  * See kmem_cache_alloc_node().
2607  */
2608 
2609 static int cpuset_spread_node(int *rotor)
2610 {
2611         return *rotor = next_node_in(*rotor, current->mems_allowed);
2612 }
2613 
2614 int cpuset_mem_spread_node(void)
2615 {
2616         if (current->cpuset_mem_spread_rotor == NUMA_NO_NODE)
2617                 current->cpuset_mem_spread_rotor =
2618                         node_random(&current->mems_allowed);
2619 
2620         return cpuset_spread_node(&current->cpuset_mem_spread_rotor);
2621 }
2622 
2623 int cpuset_slab_spread_node(void)
2624 {
2625         if (current->cpuset_slab_spread_rotor == NUMA_NO_NODE)
2626                 current->cpuset_slab_spread_rotor =
2627                         node_random(&current->mems_allowed);
2628 
2629         return cpuset_spread_node(&current->cpuset_slab_spread_rotor);
2630 }
2631 
2632 EXPORT_SYMBOL_GPL(cpuset_mem_spread_node);
2633 
2634 /**
2635  * cpuset_mems_allowed_intersects - Does @tsk1's mems_allowed intersect @tsk2's?
2636  * @tsk1: pointer to task_struct of some task.
2637  * @tsk2: pointer to task_struct of some other task.
2638  *
2639  * Description: Return true if @tsk1's mems_allowed intersects the
2640  * mems_allowed of @tsk2.  Used by the OOM killer to determine if
2641  * one of the task's memory usage might impact the memory available
2642  * to the other.
2643  **/
2644 
2645 int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
2646                                    const struct task_struct *tsk2)
2647 {
2648         return nodes_intersects(tsk1->mems_allowed, tsk2->mems_allowed);
2649 }
2650 
2651 /**
2652  * cpuset_print_current_mems_allowed - prints current's cpuset and mems_allowed
2653  *
2654  * Description: Prints current's name, cpuset name, and cached copy of its
2655  * mems_allowed to the kernel log.
2656  */
2657 void cpuset_print_current_mems_allowed(void)
2658 {
2659         struct cgroup *cgrp;
2660 
2661         rcu_read_lock();
2662 
2663         cgrp = task_cs(current)->css.cgroup;
2664         pr_info("%s cpuset=", current->comm);
2665         pr_cont_cgroup_name(cgrp);
2666         pr_cont(" mems_allowed=%*pbl\n",
2667                 nodemask_pr_args(&current->mems_allowed));
2668 
2669         rcu_read_unlock();
2670 }
2671 
2672 /*
2673  * Collection of memory_pressure is suppressed unless
2674  * this flag is enabled by writing "1" to the special
2675  * cpuset file 'memory_pressure_enabled' in the root cpuset.
2676  */
2677 
2678 int cpuset_memory_pressure_enabled __read_mostly;
2679 
2680 /**
2681  * cpuset_memory_pressure_bump - keep stats of per-cpuset reclaims.
2682  *
2683  * Keep a running average of the rate of synchronous (direct)
2684  * page reclaim efforts initiated by tasks in each cpuset.
2685  *
2686  * This represents the rate at which some task in the cpuset
2687  * ran low on memory on all nodes it was allowed to use, and
2688  * had to enter the kernels page reclaim code in an effort to
2689  * create more free memory by tossing clean pages or swapping
2690  * or writing dirty pages.
2691  *
2692  * Display to user space in the per-cpuset read-only file
2693  * "memory_pressure".  Value displayed is an integer
2694  * representing the recent rate of entry into the synchronous
2695  * (direct) page reclaim by any task attached to the cpuset.
2696  **/
2697 
2698 void __cpuset_memory_pressure_bump(void)
2699 {
2700         rcu_read_lock();
2701         fmeter_markevent(&task_cs(current)->fmeter);
2702         rcu_read_unlock();
2703 }
2704 
2705 #ifdef CONFIG_PROC_PID_CPUSET
2706 /*
2707  * proc_cpuset_show()
2708  *  - Print tasks cpuset path into seq_file.
2709  *  - Used for /proc/<pid>/cpuset.
2710  *  - No need to task_lock(tsk) on this tsk->cpuset reference, as it
2711  *    doesn't really matter if tsk->cpuset changes after we read it,
2712  *    and we take cpuset_mutex, keeping cpuset_attach() from changing it
2713  *    anyway.
2714  */
2715 int proc_cpuset_show(struct seq_file *m, struct pid_namespace *ns,
2716                      struct pid *pid, struct task_struct *tsk)
2717 {
2718         char *buf, *p;
2719         struct cgroup_subsys_state *css;
2720         int retval;
2721 
2722         retval = -ENOMEM;
2723         buf = kmalloc(PATH_MAX, GFP_KERNEL);
2724         if (!buf)
2725                 goto out;
2726 
2727         retval = -ENAMETOOLONG;
2728         css = task_get_css(tsk, cpuset_cgrp_id);
2729         p = cgroup_path_ns(css->cgroup, buf, PATH_MAX,
2730                            current->nsproxy->cgroup_ns);
2731         css_put(css);
2732         if (!p)
2733                 goto out_free;
2734         seq_puts(m, p);
2735         seq_putc(m, '\n');
2736         retval = 0;
2737 out_free:
2738         kfree(buf);
2739 out:
2740         return retval;
2741 }
2742 #endif /* CONFIG_PROC_PID_CPUSET */
2743 
2744 /* Display task mems_allowed in /proc/<pid>/status file. */
2745 void cpuset_task_status_allowed(struct seq_file *m, struct task_struct *task)
2746 {
2747         seq_printf(m, "Mems_allowed:\t%*pb\n",
2748                    nodemask_pr_args(&task->mems_allowed));
2749         seq_printf(m, "Mems_allowed_list:\t%*pbl\n",
2750                    nodemask_pr_args(&task->mems_allowed));
2751 }
2752 

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