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

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