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

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