cpuset.c

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/*
 *  kernel/cpuset.c
 *
 *  Processor and Memory placement constraints for sets of tasks.
 *
 *  Copyright (C) 2003 BULL SA.
 *  Copyright (C) 2004-2007 Silicon Graphics, Inc.
 *  Copyright (C) 2006 Google, Inc
 *
 *  Portions derived from Patrick Mochel's sysfs code.
 *  sysfs is Copyright (c) 2001-3 Patrick Mochel
 *
 *  2003-10-10 Written by Simon Derr.
 *  2003-10-22 Updates by Stephen Hemminger.
 *  2004 May-July Rework by Paul Jackson.
 *  2006 Rework by Paul Menage to use generic cgroups
 *  2008 Rework of the scheduler domains and CPU hotplug handling
 *       by Max Krasnyansky
 *
 *  This file is subject to the terms and conditions of the GNU General Public
 *  License.  See the file COPYING in the main directory of the Linux
 *  distribution for more details.
 */

#include <linux/cpu.h>
#include <linux/cpumask.h>
#include <linux/cpuset.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/kmod.h>
#include <linux/list.h>
#include <linux/mempolicy.h>
#include <linux/mm.h>
#include <linux/memory.h>
#include <linux/export.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/pagemap.h>
#include <linux/proc_fs.h>
#include <linux/rcupdate.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/security.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/time.h>
#include <linux/backing-dev.h>
#include <linux/sort.h>

#include <asm/uaccess.h>
#include <linux/atomic.h>
#include <linux/mutex.h>
#include <linux/workqueue.h>
#include <linux/cgroup.h>

/*
 * Workqueue for cpuset related tasks.
 *
 * Using kevent workqueue may cause deadlock when memory_migrate
 * is set. So we create a separate workqueue thread for cpuset.
 */
static struct workqueue_struct *cpuset_wq;

/*
 * Tracks how many cpusets are currently defined in system.
 * When there is only one cpuset (the root cpuset) we can
 * short circuit some hooks.
 */
int number_of_cpusets __read_mostly;

/* Forward declare cgroup structures */
struct cgroup_subsys cpuset_subsys;
struct cpuset;

/* See "Frequency meter" comments, below. */

struct fmeter {
    int cnt;        /* unprocessed events count */
    int val;        /* most recent output value */
    time_t time;        /* clock (secs) when val computed */
    spinlock_t lock;    /* guards read or write of above */
};

struct cpuset {
    struct cgroup_subsys_state css;

    unsigned long flags;        /* "unsigned long" so bitops work */
    cpumask_var_t cpus_allowed; /* CPUs allowed to tasks in cpuset */
    nodemask_t mems_allowed;    /* Memory Nodes allowed to tasks */

    struct cpuset *parent;      /* my parent */

    struct fmeter fmeter;       /* memory_pressure filter */

    /* partition number for rebuild_sched_domains() */
    int pn;

    /* for custom sched domain */
    int relax_domain_level;

    /* used for walking a cpuset hierarchy */
    struct list_head stack_list;
};

/* Retrieve the cpuset for a cgroup */
static inline struct cpuset *cgroup_cs(struct cgroup *cont)
{
    return container_of(cgroup_subsys_state(cont, cpuset_subsys_id),
                struct cpuset, css);
}

/* Retrieve the cpuset for a task */
static inline struct cpuset *task_cs(struct task_struct *task)
{
    return container_of(task_subsys_state(task, cpuset_subsys_id),
                struct cpuset, css);
}

#ifdef CONFIG_NUMA
static inline bool task_has_mempolicy(struct task_struct *task)
{
    return task->mempolicy;
}
#else
static inline bool task_has_mempolicy(struct task_struct *task)
{
    return false;
}
#endif


/* bits in struct cpuset flags field */
typedef enum {
    CS_CPU_EXCLUSIVE,
    CS_MEM_EXCLUSIVE,
    CS_MEM_HARDWALL,
    CS_MEMORY_MIGRATE,
    CS_SCHED_LOAD_BALANCE,
    CS_SPREAD_PAGE,
    CS_SPREAD_SLAB,
} cpuset_flagbits_t;

/* the type of hotplug event */
enum hotplug_event {
    CPUSET_CPU_OFFLINE,
    CPUSET_MEM_OFFLINE,
};

/* convenient tests for these bits */
static inline int is_cpu_exclusive(const struct cpuset *cs)
{
    return test_bit(CS_CPU_EXCLUSIVE, &cs->flags);
}

static inline int is_mem_exclusive(const struct cpuset *cs)
{
    return test_bit(CS_MEM_EXCLUSIVE, &cs->flags);
}

static inline int is_mem_hardwall(const struct cpuset *cs)
{
    return test_bit(CS_MEM_HARDWALL, &cs->flags);
}

static inline int is_sched_load_balance(const struct cpuset *cs)
{
    return test_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
}

static inline int is_memory_migrate(const struct cpuset *cs)
{
    return test_bit(CS_MEMORY_MIGRATE, &cs->flags);
}

static inline int is_spread_page(const struct cpuset *cs)
{
    return test_bit(CS_SPREAD_PAGE, &cs->flags);
}

static inline int is_spread_slab(const struct cpuset *cs)
{
    return test_bit(CS_SPREAD_SLAB, &cs->flags);
}

static struct cpuset top_cpuset = {
    .flags = ((1 << CS_CPU_EXCLUSIVE) | (1 << CS_MEM_EXCLUSIVE)),
};

/*
 * There are two global mutexes guarding cpuset structures.  The first
 * is the main control groups cgroup_mutex, accessed via
 * cgroup_lock()/cgroup_unlock().  The second is the cpuset-specific
 * callback_mutex, below. They can nest.  It is ok to first take
 * cgroup_mutex, then nest callback_mutex.  We also require taking
 * task_lock() when dereferencing a task's cpuset pointer.  See "The
 * task_lock() exception", at the end of this comment.
 *
 * A task must hold both mutexes to modify cpusets.  If a task
 * holds cgroup_mutex, then it blocks others wanting that mutex,
 * ensuring that it is the only task able to also acquire callback_mutex
 * and be able to modify cpusets.  It can perform various checks on
 * the cpuset structure first, knowing nothing will change.  It can
 * also allocate memory while just holding cgroup_mutex.  While it is
 * performing these checks, various callback routines can briefly
 * acquire callback_mutex to query cpusets.  Once it is ready to make
 * the changes, it takes callback_mutex, blocking everyone else.
 *
 * Calls to the kernel memory allocator can not be made while holding
 * callback_mutex, as that would risk double tripping on callback_mutex
 * from one of the callbacks into the cpuset code from within
 * __alloc_pages().
 *
 * If a task is only holding callback_mutex, then it has read-only
 * access to cpusets.
 *
 * Now, the task_struct fields mems_allowed and mempolicy may be changed
 * by other task, we use alloc_lock in the task_struct fields to protect
 * them.
 *
 * The cpuset_common_file_read() handlers only hold callback_mutex across
 * small pieces of code, such as when reading out possibly multi-word
 * cpumasks and nodemasks.
 *
 * Accessing a task's cpuset should be done in accordance with the
 * guidelines for accessing subsystem state in kernel/cgroup.c
 */

static DEFINE_MUTEX(callback_mutex);

/*
 * cpuset_buffer_lock protects both the cpuset_name and cpuset_nodelist
 * buffers.  They are statically allocated to prevent using excess stack
 * when calling cpuset_print_task_mems_allowed().
 */
#define CPUSET_NAME_LEN     (128)
#define CPUSET_NODELIST_LEN (256)
static char cpuset_name[CPUSET_NAME_LEN];
static char cpuset_nodelist[CPUSET_NODELIST_LEN];
static DEFINE_SPINLOCK(cpuset_buffer_lock);

/*
 * This is ugly, but preserves the userspace API for existing cpuset
 * users. If someone tries to mount the "cpuset" filesystem, we
 * silently switch it to mount "cgroup" instead
 */
static struct dentry *cpuset_mount(struct file_system_type *fs_type,
             int flags, const char *unused_dev_name, void *data)
{
    struct file_system_type *cgroup_fs = get_fs_type("cgroup");
    struct dentry *ret = ERR_PTR(-ENODEV);
    if (cgroup_fs) {
        char mountopts[] =
            "cpuset,noprefix,"
            "release_agent=/sbin/cpuset_release_agent";
        ret = cgroup_fs->mount(cgroup_fs, flags,
                       unused_dev_name, mountopts);
        put_filesystem(cgroup_fs);
    }
    return ret;
}

static struct file_system_type cpuset_fs_type = {
    .name = "cpuset",
    .mount = cpuset_mount,
};

/*
 * Return in pmask the portion of a cpusets's cpus_allowed that
 * are online.  If none are online, walk up the cpuset hierarchy
 * until we find one that does have some online cpus.  If we get
 * all the way to the top and still haven't found any online cpus,
 * return cpu_online_mask.  Or if passed a NULL cs from an exit'ing
 * task, return cpu_online_mask.
 *
 * One way or another, we guarantee to return some non-empty subset
 * of cpu_online_mask.
 *
 * Call with callback_mutex held.
 */

static void guarantee_online_cpus(const struct cpuset *cs,
                  struct cpumask *pmask)
{
    while (cs && !cpumask_intersects(cs->cpus_allowed, cpu_online_mask))
        cs = cs->parent;
    if (cs)
        cpumask_and(pmask, cs->cpus_allowed, cpu_online_mask);
    else
        cpumask_copy(pmask, cpu_online_mask);
    BUG_ON(!cpumask_intersects(pmask, cpu_online_mask));
}

/*
 * Return in *pmask the portion of a cpusets's mems_allowed that
 * are online, with memory.  If none are online with memory, walk
 * up the cpuset hierarchy until we find one that does have some
 * online mems.  If we get all the way to the top and still haven't
 * found any online mems, return node_states[N_HIGH_MEMORY].
 *
 * One way or another, we guarantee to return some non-empty subset
 * of node_states[N_HIGH_MEMORY].
 *
 * Call with callback_mutex held.
 */

static void guarantee_online_mems(const struct cpuset *cs, nodemask_t *pmask)
{
    while (cs && !nodes_intersects(cs->mems_allowed,
                    node_states[N_HIGH_MEMORY]))
        cs = cs->parent;
    if (cs)
        nodes_and(*pmask, cs->mems_allowed,
                    node_states[N_HIGH_MEMORY]);
    else
        *pmask = node_states[N_HIGH_MEMORY];
    BUG_ON(!nodes_intersects(*pmask, node_states[N_HIGH_MEMORY]));
}

/*
 * update task's spread flag if cpuset's page/slab spread flag is set
 *
 * Called with callback_mutex/cgroup_mutex held
 */
static void cpuset_update_task_spread_flag(struct cpuset *cs,
                    struct task_struct *tsk)
{
    if (is_spread_page(cs))
        tsk->flags |= PF_SPREAD_PAGE;
    else
        tsk->flags &= ~PF_SPREAD_PAGE;
    if (is_spread_slab(cs))
        tsk->flags |= PF_SPREAD_SLAB;
    else
        tsk->flags &= ~PF_SPREAD_SLAB;
}

/*
 * is_cpuset_subset(p, q) - Is cpuset p a subset of cpuset q?
 *
 * One cpuset is a subset of another if all its allowed CPUs and
 * Memory Nodes are a subset of the other, and its exclusive flags
 * are only set if the other's are set.  Call holding cgroup_mutex.
 */

static int is_cpuset_subset(const struct cpuset *p, const struct cpuset *q)
{
    return  cpumask_subset(p->cpus_allowed, q->cpus_allowed) &&
        nodes_subset(p->mems_allowed, q->mems_allowed) &&
        is_cpu_exclusive(p) <= is_cpu_exclusive(q) &&
        is_mem_exclusive(p) <= is_mem_exclusive(q);
}

static struct cpuset *alloc_trial_cpuset(const struct cpuset *cs)
{
    struct cpuset *trial;

    trial = kmemdup(cs, sizeof(*cs), GFP_KERNEL);
    if (!trial)
        return NULL;

    if (!alloc_cpumask_var(&trial->cpus_allowed, GFP_KERNEL)) {
        kfree(trial);
        return NULL;
    }
    cpumask_copy(trial->cpus_allowed, cs->cpus_allowed);

    return trial;
}

static void free_trial_cpuset(struct cpuset *trial)
{
    free_cpumask_var(trial->cpus_allowed);
    kfree(trial);
}

/*
 * validate_change() - Used to validate that any proposed cpuset change
 *             follows the structural rules for cpusets.
 *
 * If we replaced the flag and mask values of the current cpuset
 * (cur) with those values in the trial cpuset (trial), would
 * our various subset and exclusive rules still be valid?  Presumes
 * cgroup_mutex held.
 *
 * 'cur' is the address of an actual, in-use cpuset.  Operations
 * such as list traversal that depend on the actual address of the
 * cpuset in the list must use cur below, not trial.
 *
 * 'trial' is the address of bulk structure copy of cur, with
 * perhaps one or more of the fields cpus_allowed, mems_allowed,
 * or flags changed to new, trial values.
 *
 * Return 0 if valid, -errno if not.
 */

static int validate_change(const struct cpuset *cur, const struct cpuset *trial)
{
    struct cgroup *cont;
    struct cpuset *c, *par;

    /* Each of our child cpusets must be a subset of us */
    list_for_each_entry(cont, &cur->css.cgroup->children, sibling) {
        if (!is_cpuset_subset(cgroup_cs(cont), trial))
            return -EBUSY;
    }

    /* Remaining checks don't apply to root cpuset */
    if (cur == &top_cpuset)
        return 0;

    par = cur->parent;

    /* We must be a subset of our parent cpuset */
    if (!is_cpuset_subset(trial, par))
        return -EACCES;

    /*
     * If either I or some sibling (!= me) is exclusive, we can't
     * overlap
     */
    list_for_each_entry(cont, &par->css.cgroup->children, sibling) {
        c = cgroup_cs(cont);
        if ((is_cpu_exclusive(trial) || is_cpu_exclusive(c)) &&
            c != cur &&
            cpumask_intersects(trial->cpus_allowed, c->cpus_allowed))
            return -EINVAL;
        if ((is_mem_exclusive(trial) || is_mem_exclusive(c)) &&
            c != cur &&
            nodes_intersects(trial->mems_allowed, c->mems_allowed))
            return -EINVAL;
    }

    /* Cpusets with tasks can't have empty cpus_allowed or mems_allowed */
    if (cgroup_task_count(cur->css.cgroup)) {
        if (cpumask_empty(trial->cpus_allowed) ||
            nodes_empty(trial->mems_allowed)) {
            return -ENOSPC;
        }
    }

    return 0;
}

#ifdef CONFIG_SMP
/*
 * Helper routine for generate_sched_domains().
 * Do cpusets a, b have overlapping cpus_allowed masks?
 */
static int cpusets_overlap(struct cpuset *a, struct cpuset *b)
{
    return cpumask_intersects(a->cpus_allowed, b->cpus_allowed);
}

static void
update_domain_attr(struct sched_domain_attr *dattr, struct cpuset *c)
{
    if (dattr->relax_domain_level < c->relax_domain_level)
        dattr->relax_domain_level = c->relax_domain_level;
    return;
}

static void
update_domain_attr_tree(struct sched_domain_attr *dattr, struct cpuset *c)
{
    LIST_HEAD(q);

    list_add(&c->stack_list, &q);
    while (!list_empty(&q)) {
        struct cpuset *cp;
        struct cgroup *cont;
        struct cpuset *child;

        cp = list_first_entry(&q, struct cpuset, stack_list);
        list_del(q.next);

        if (cpumask_empty(cp->cpus_allowed))
            continue;

        if (is_sched_load_balance(cp))
            update_domain_attr(dattr, cp);

        list_for_each_entry(cont, &cp->css.cgroup->children, sibling) {
            child = cgroup_cs(cont);
            list_add_tail(&child->stack_list, &q);
        }
    }
}

/*
 * generate_sched_domains()
 *
 * This function builds a partial partition of the systems CPUs
 * A 'partial partition' is a set of non-overlapping subsets whose
 * union is a subset of that set.
 * The output of this function needs to be passed to kernel/sched.c
 * partition_sched_domains() routine, which will rebuild the scheduler's
 * load balancing domains (sched domains) as specified by that partial
 * partition.
 *
 * See "What is sched_load_balance" in Documentation/cgroups/cpusets.txt
 * for a background explanation of this.
 *
 * Does not return errors, on the theory that the callers of this
 * routine would rather not worry about failures to rebuild sched
 * domains when operating in the severe memory shortage situations
 * that could cause allocation failures below.
 *
 * Must be called with cgroup_lock held.
 *
 * The three key local variables below are:
 *    q  - a linked-list queue of cpuset pointers, used to implement a
 *     top-down scan of all cpusets.  This scan loads a pointer
 *     to each cpuset marked is_sched_load_balance into the
 *     array 'csa'.  For our purposes, rebuilding the schedulers
 *     sched domains, we can ignore !is_sched_load_balance cpusets.
 *  csa  - (for CpuSet Array) Array of pointers to all the cpusets
 *     that need to be load balanced, for convenient iterative
 *     access by the subsequent code that finds the best partition,
 *     i.e the set of domains (subsets) of CPUs such that the
 *     cpus_allowed of every cpuset marked is_sched_load_balance
 *     is a subset of one of these domains, while there are as
 *     many such domains as possible, each as small as possible.
 * doms  - Conversion of 'csa' to an array of cpumasks, for passing to
 *     the kernel/sched.c routine partition_sched_domains() in a
 *     convenient format, that can be easily compared to the prior
 *     value to determine what partition elements (sched domains)
 *     were changed (added or removed.)
 *
 * Finding the best partition (set of domains):
 *  The triple nested loops below over i, j, k scan over the
 *  load balanced cpusets (using the array of cpuset pointers in
 *  csa[]) looking for pairs of cpusets that have overlapping
 *  cpus_allowed, but which don't have the same 'pn' partition
 *  number and gives them in the same partition number.  It keeps
 *  looping on the 'restart' label until it can no longer find
 *  any such pairs.
 *
 *  The union of the cpus_allowed masks from the set of
 *  all cpusets having the same 'pn' value then form the one
 *  element of the partition (one sched domain) to be passed to
 *  partition_sched_domains().
 */
static int generate_sched_domains(cpumask_var_t **domains,
            struct sched_domain_attr **attributes)
{
    LIST_HEAD(q);       /* queue of cpusets to be scanned */
    struct cpuset *cp;  /* scans q */
    struct cpuset **csa;    /* array of all cpuset ptrs */
    int csn;        /* how many cpuset ptrs in csa so far */
    int i, j, k;        /* indices for partition finding loops */
    cpumask_var_t *doms;    /* resulting partition; i.e. sched domains */
    struct sched_domain_attr *dattr;  /* attributes for custom domains */
    int ndoms = 0;      /* number of sched domains in result */
    int nslot;      /* next empty doms[] struct cpumask slot */

    doms = NULL;
    dattr = NULL;
    csa = NULL;

    /* Special case for the 99% of systems with one, full, sched domain */
    if (is_sched_load_balance(&top_cpuset)) {
        ndoms = 1;
        doms = alloc_sched_domains(ndoms);
        if (!doms)
            goto done;

        dattr = kmalloc(sizeof(struct sched_domain_attr), GFP_KERNEL);
        if (dattr) {
            *dattr = SD_ATTR_INIT;
            update_domain_attr_tree(dattr, &top_cpuset);
        }
        cpumask_copy(doms[0], top_cpuset.cpus_allowed);

        goto done;
    }

    csa = kmalloc(number_of_cpusets * sizeof(cp), GFP_KERNEL);
    if (!csa)
        goto done;
    csn = 0;

    list_add(&top_cpuset.stack_list, &q);
    while (!list_empty(&q)) {
        struct cgroup *cont;
        struct cpuset *child;   /* scans child cpusets of cp */

        cp = list_first_entry(&q, struct cpuset, stack_list);
        list_del(q.next);

        if (cpumask_empty(cp->cpus_allowed))
            continue;

        /*
         * All child cpusets contain a subset of the parent's cpus, so
         * just skip them, and then we call update_domain_attr_tree()
         * to calc relax_domain_level of the corresponding sched
         * domain.
         */
        if (is_sched_load_balance(cp)) {
            csa[csn++] = cp;
            continue;
        }

        list_for_each_entry(cont, &cp->css.cgroup->children, sibling) {
            child = cgroup_cs(cont);
            list_add_tail(&child->stack_list, &q);
        }
    }

    for (i = 0; i < csn; i++)
        csa[i]->pn = i;
    ndoms = csn;

restart:
    /* Find the best partition (set of sched domains) */
    for (i = 0; i < csn; i++) {
        struct cpuset *a = csa[i];
        int apn = a->pn;

        for (j = 0; j < csn; j++) {
            struct cpuset *b = csa[j];
            int bpn = b->pn;

            if (apn != bpn && cpusets_overlap(a, b)) {
                for (k = 0; k < csn; k++) {
                    struct cpuset *c = csa[k];

                    if (c->pn == bpn)
                        c->pn = apn;
                }
                ndoms--;    /* one less element */
                goto restart;
            }
        }
    }

    /*
     * Now we know how many domains to create.
     * Convert <csn, csa> to <ndoms, doms> and populate cpu masks.
     */
    doms = alloc_sched_domains(ndoms);
    if (!doms)
        goto done;

    /*
     * The rest of the code, including the scheduler, can deal with
     * dattr==NULL case. No need to abort if alloc fails.
     */
    dattr = kmalloc(ndoms * sizeof(struct sched_domain_attr), GFP_KERNEL);

    for (nslot = 0, i = 0; i < csn; i++) {
        struct cpuset *a = csa[i];
        struct cpumask *dp;
        int apn = a->pn;

        if (apn < 0) {
            /* Skip completed partitions */
            continue;
        }

        dp = doms[nslot];

        if (nslot == ndoms) {
            static int warnings = 10;
            if (warnings) {
                printk(KERN_WARNING
                 "rebuild_sched_domains confused:"
                  " nslot %d, ndoms %d, csn %d, i %d,"
                  " apn %d\n",
                  nslot, ndoms, csn, i, apn);
                warnings--;
            }
            continue;
        }

        cpumask_clear(dp);
        if (dattr)
            *(dattr + nslot) = SD_ATTR_INIT;
        for (j = i; j < csn; j++) {
            struct cpuset *b = csa[j];

            if (apn == b->pn) {
                cpumask_or(dp, dp, b->cpus_allowed);
                if (dattr)
                    update_domain_attr_tree(dattr + nslot, b);

                /* Done with this partition */
                b->pn = -1;
            }
        }
        nslot++;
    }
    BUG_ON(nslot != ndoms);

done:
    kfree(csa);

    /*
     * Fallback to the default domain if kmalloc() failed.
     * See comments in partition_sched_domains().
     */
    if (doms == NULL)
        ndoms = 1;

    *domains    = doms;
    *attributes = dattr;
    return ndoms;
}

/*
 * Rebuild scheduler domains.
 *
 * Call with neither cgroup_mutex held nor within get_online_cpus().
 * Takes both cgroup_mutex and get_online_cpus().
 *
 * Cannot be directly called from cpuset code handling changes
 * to the cpuset pseudo-filesystem, because it cannot be called
 * from code that already holds cgroup_mutex.
 */
static void do_rebuild_sched_domains(struct work_struct *unused)
{
    struct sched_domain_attr *attr;
    cpumask_var_t *doms;
    int ndoms;

    get_online_cpus();

    /* Generate domain masks and attrs */
    cgroup_lock();
    ndoms = generate_sched_domains(&doms, &attr);
    cgroup_unlock();

    /* Have scheduler rebuild the domains */
    partition_sched_domains(ndoms, doms, attr);

    put_online_cpus();
}
#else /* !CONFIG_SMP */
static void do_rebuild_sched_domains(struct work_struct *unused)
{
}

static int generate_sched_domains(cpumask_var_t **domains,
            struct sched_domain_attr **attributes)
{
    *domains = NULL;
    return 1;
}
#endif /* CONFIG_SMP */

static DECLARE_WORK(rebuild_sched_domains_work, do_rebuild_sched_domains);

/*
 * Rebuild scheduler domains, asynchronously via workqueue.
 *
 * If the flag 'sched_load_balance' of any cpuset with non-empty
 * 'cpus' changes, or if the 'cpus' allowed changes in any cpuset
 * which has that flag enabled, or if any cpuset with a non-empty
 * 'cpus' is removed, then call this routine to rebuild the
 * scheduler's dynamic sched domains.
 *
 * The rebuild_sched_domains() and partition_sched_domains()
 * routines must nest cgroup_lock() inside get_online_cpus(),
 * but such cpuset changes as these must nest that locking the
 * other way, holding cgroup_lock() for much of the code.
 *
 * So in order to avoid an ABBA deadlock, the cpuset code handling
 * these user changes delegates the actual sched domain rebuilding
 * to a separate workqueue thread, which ends up processing the
 * above do_rebuild_sched_domains() function.
 */
static void async_rebuild_sched_domains(void)
{
    queue_work(cpuset_wq, &rebuild_sched_domains_work);
}

/*
 * Accomplishes the same scheduler domain rebuild as the above
 * async_rebuild_sched_domains(), however it directly calls the
 * rebuild routine synchronously rather than calling it via an
 * asynchronous work thread.
 *
 * This can only be called from code that is not holding
 * cgroup_mutex (not nested in a cgroup_lock() call.)
 */
void rebuild_sched_domains(void)
{
    do_rebuild_sched_domains(NULL);
}

static int cpuset_test_cpumask(struct task_struct *tsk,
                   struct cgroup_scanner *scan)
{
    return !cpumask_equal(&tsk->cpus_allowed,
            (cgroup_cs(scan->cg))->cpus_allowed);
}

static void cpuset_change_cpumask(struct task_struct *tsk,
                  struct cgroup_scanner *scan)
{
    set_cpus_allowed_ptr(tsk, ((cgroup_cs(scan->cg))->cpus_allowed));
}

static void update_tasks_cpumask(struct cpuset *cs, struct ptr_heap *heap)
{
    struct cgroup_scanner scan;

    scan.cg = cs->css.cgroup;
    scan.test_task = cpuset_test_cpumask;
    scan.process_task = cpuset_change_cpumask;
    scan.heap = heap;
    cgroup_scan_tasks(&scan);
}

static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
              const char *buf)
{
    struct ptr_heap heap;
    int retval;
    int is_load_balanced;

    /* top_cpuset.cpus_allowed tracks cpu_online_mask; it's read-only */
    if (cs == &top_cpuset)
        return -EACCES;

    /*
     * An empty cpus_allowed is ok only if the cpuset has no tasks.
     * Since cpulist_parse() fails on an empty mask, we special case
     * that parsing.  The validate_change() call ensures that cpusets
     * with tasks have cpus.
     */
    if (!*buf) {
        cpumask_clear(trialcs->cpus_allowed);
    } else {
        retval = cpulist_parse(buf, trialcs->cpus_allowed);
        if (retval < 0)
            return retval;

        if (!cpumask_subset(trialcs->cpus_allowed, cpu_active_mask))
            return -EINVAL;
    }
    retval = validate_change(cs, trialcs);
    if (retval < 0)
        return retval;

    /* Nothing to do if the cpus didn't change */
    if (cpumask_equal(cs->cpus_allowed, trialcs->cpus_allowed))
        return 0;

    retval = heap_init(&heap, PAGE_SIZE, GFP_KERNEL, NULL);
    if (retval)
        return retval;

    is_load_balanced = is_sched_load_balance(trialcs);

    mutex_lock(&callback_mutex);
    cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
    mutex_unlock(&callback_mutex);

    /*
     * Scan tasks in the cpuset, and update the cpumasks of any
     * that need an update.
     */
    update_tasks_cpumask(cs, &heap);

    heap_free(&heap);

    if (is_load_balanced)
        async_rebuild_sched_domains();
    return 0;
}

/*
 * cpuset_migrate_mm
 *
 *    Migrate memory region from one set of nodes to another.
 *
 *    Temporarilly set tasks mems_allowed to target nodes of migration,
 *    so that the migration code can allocate pages on these nodes.
 *
 *    Call holding cgroup_mutex, so current's cpuset won't change
 *    during this call, as manage_mutex holds off any cpuset_attach()
 *    calls.  Therefore we don't need to take task_lock around the
 *    call to guarantee_online_mems(), as we know no one is changing
 *    our task's cpuset.
 *
 *    While the mm_struct we are migrating is typically from some
 *    other task, the task_struct mems_allowed that we are hacking
 *    is for our current task, which must allocate new pages for that
 *    migrating memory region.
 */

static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
                            const nodemask_t *to)
{
    struct task_struct *tsk = current;

    tsk->mems_allowed = *to;

    do_migrate_pages(mm, from, to, MPOL_MF_MOVE_ALL);

    guarantee_online_mems(task_cs(tsk),&tsk->mems_allowed);
}

/*
 * cpuset_change_task_nodemask - change task's mems_allowed and mempolicy
 * @tsk: the task to change
 * @newmems: new nodes that the task will be set
 *
 * In order to avoid seeing no nodes if the old and new nodes are disjoint,
 * we structure updates as setting all new allowed nodes, then clearing newly
 * disallowed ones.
 */
static void cpuset_change_task_nodemask(struct task_struct *tsk,
                    nodemask_t *newmems)
{
    bool need_loop;

    /*
     * Allow tasks that have access to memory reserves because they have
     * been OOM killed to get memory anywhere.
     */
    if (unlikely(test_thread_flag(TIF_MEMDIE)))
        return;
    if (current->flags & PF_EXITING) /* Let dying task have memory */
        return;

    task_lock(tsk);
    /*
     * Determine if a loop is necessary if another thread is doing
     * get_mems_allowed().  If at least one node remains unchanged and
     * tsk does not have a mempolicy, then an empty nodemask will not be
     * possible when mems_allowed is larger than a word.
     */
    need_loop = task_has_mempolicy(tsk) ||
            !nodes_intersects(*newmems, tsk->mems_allowed);

    if (need_loop)
        write_seqcount_begin(&tsk->mems_allowed_seq);

    nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems);
    mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP1);

    mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP2);
    tsk->mems_allowed = *newmems;

    if (need_loop)
        write_seqcount_end(&tsk->mems_allowed_seq);

    task_unlock(tsk);
}

/*
 * Update task's mems_allowed and rebind its mempolicy and vmas' mempolicy
 * of it to cpuset's new mems_allowed, and migrate pages to new nodes if
 * memory_migrate flag is set. Called with cgroup_mutex held.
 */
static void cpuset_change_nodemask(struct task_struct *p,
                   struct cgroup_scanner *scan)
{
    struct mm_struct *mm;
    struct cpuset *cs;
    int migrate;
    const nodemask_t *oldmem = scan->data;
    static nodemask_t newmems;  /* protected by cgroup_mutex */

    cs = cgroup_cs(scan->cg);
    guarantee_online_mems(cs, &newmems);

    cpuset_change_task_nodemask(p, &newmems);

    mm = get_task_mm(p);
    if (!mm)
        return;

    migrate = is_memory_migrate(cs);

    mpol_rebind_mm(mm, &cs->mems_allowed);
    if (migrate)
        cpuset_migrate_mm(mm, oldmem, &cs->mems_allowed);
    mmput(mm);
}

static void *cpuset_being_rebound;

static void update_tasks_nodemask(struct cpuset *cs, const nodemask_t *oldmem,
                 struct ptr_heap *heap)
{
    struct cgroup_scanner scan;

    cpuset_being_rebound = cs;      /* causes mpol_dup() rebind */

    scan.cg = cs->css.cgroup;
    scan.test_task = NULL;
    scan.process_task = cpuset_change_nodemask;
    scan.heap = heap;
    scan.data = (nodemask_t *)oldmem;

    /*
     * The mpol_rebind_mm() call takes mmap_sem, which we couldn't
     * take while holding tasklist_lock.  Forks can happen - the
     * mpol_dup() cpuset_being_rebound check will catch such forks,
     * and rebind their vma mempolicies too.  Because we still hold
     * the global cgroup_mutex, we know that no other rebind effort
     * will be contending for the global variable cpuset_being_rebound.
     * It's ok if we rebind the same mm twice; mpol_rebind_mm()
     * is idempotent.  Also migrate pages in each mm to new nodes.
     */
    cgroup_scan_tasks(&scan);

    /* We're done rebinding vmas to this cpuset's new mems_allowed. */
    cpuset_being_rebound = NULL;
}

/*
 * Handle user request to change the 'mems' memory placement
 * of a cpuset.  Needs to validate the request, update the
 * cpusets mems_allowed, and for each task in the cpuset,
 * update mems_allowed and rebind task's mempolicy and any vma
 * mempolicies and if the cpuset is marked 'memory_migrate',
 * migrate the tasks pages to the new memory.
 *
 * Call with cgroup_mutex held.  May take callback_mutex during call.
 * Will take tasklist_lock, scan tasklist for tasks in cpuset cs,
 * lock each such tasks mm->mmap_sem, scan its vma's and rebind
 * their mempolicies to the cpusets new mems_allowed.
 */
static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
               const char *buf)
{
    NODEMASK_ALLOC(nodemask_t, oldmem, GFP_KERNEL);
    int retval;
    struct ptr_heap heap;

    if (!oldmem)
        return -ENOMEM;

    /*
     * top_cpuset.mems_allowed tracks node_stats[N_HIGH_MEMORY];
     * it's read-only
     */
    if (cs == &top_cpuset) {
        retval = -EACCES;
        goto done;
    }

    /*
     * An empty mems_allowed is ok iff there are no tasks in the cpuset.
     * Since nodelist_parse() fails on an empty mask, we special case
     * that parsing.  The validate_change() call ensures that cpusets
     * with tasks have memory.
     */
    if (!*buf) {
        nodes_clear(trialcs->mems_allowed);
    } else {
        retval = nodelist_parse(buf, trialcs->mems_allowed);
        if (retval < 0)
            goto done;

        if (!nodes_subset(trialcs->mems_allowed,
                node_states[N_HIGH_MEMORY])) {
            retval =  -EINVAL;
            goto done;
        }
    }
    *oldmem = cs->mems_allowed;
    if (nodes_equal(*oldmem, trialcs->mems_allowed)) {
        retval = 0;     /* Too easy - nothing to do */
        goto done;
    }
    retval = validate_change(cs, trialcs);
    if (retval < 0)
        goto done;

    retval = heap_init(&heap, PAGE_SIZE, GFP_KERNEL, NULL);
    if (retval < 0)
        goto done;

    mutex_lock(&callback_mutex);
    cs->mems_allowed = trialcs->mems_allowed;
    mutex_unlock(&callback_mutex);

    update_tasks_nodemask(cs, oldmem, &heap);

    heap_free(&heap);
done:
    NODEMASK_FREE(oldmem);
    return retval;
}

int current_cpuset_is_being_rebound(void)
{
    return task_cs(current) == cpuset_being_rebound;
}

static int update_relax_domain_level(struct cpuset *cs, s64 val)
{
#ifdef CONFIG_SMP
    if (val < -1 || val >= sched_domain_level_max)
        return -EINVAL;
#endif

    if (val != cs->relax_domain_level) {
        cs->relax_domain_level = val;
        if (!cpumask_empty(cs->cpus_allowed) &&
            is_sched_load_balance(cs))
            async_rebuild_sched_domains();
    }

    return 0;
}

/*
 * cpuset_change_flag - make a task's spread flags the same as its cpuset's
 * @tsk: task to be updated
 * @scan: struct cgroup_scanner containing the cgroup of the task
 *
 * Called by cgroup_scan_tasks() for each task in a cgroup.
 *
 * We don't need to re-check for the cgroup/cpuset membership, since we're
 * holding cgroup_lock() at this point.
 */
static void cpuset_change_flag(struct task_struct *tsk,
                struct cgroup_scanner *scan)
{
    cpuset_update_task_spread_flag(cgroup_cs(scan->cg), tsk);
}

/*
 * update_tasks_flags - update the spread flags of tasks in the cpuset.
 * @cs: the cpuset in which each task's spread flags needs to be changed
 * @heap: if NULL, defer allocating heap memory to cgroup_scan_tasks()
 *
 * Called with cgroup_mutex held
 *
 * The cgroup_scan_tasks() function will scan all the tasks in a cgroup,
 * calling callback functions for each.
 *
 * No return value. It's guaranteed that cgroup_scan_tasks() always returns 0
 * if @heap != NULL.
 */
static void update_tasks_flags(struct cpuset *cs, struct ptr_heap *heap)
{
    struct cgroup_scanner scan;

    scan.cg = cs->css.cgroup;
    scan.test_task = NULL;
    scan.process_task = cpuset_change_flag;
    scan.heap = heap;
    cgroup_scan_tasks(&scan);
}

/*
 * update_flag - read a 0 or a 1 in a file and update associated flag
 * bit:     the bit to update (see cpuset_flagbits_t)
 * cs:      the cpuset to update
 * turning_on:  whether the flag is being set or cleared
 *
 * Call with cgroup_mutex held.
 */

static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
               int turning_on)
{
    struct cpuset *trialcs;
    int balance_flag_changed;
    int spread_flag_changed;
    struct ptr_heap heap;
    int err;

    trialcs = alloc_trial_cpuset(cs);
    if (!trialcs)
        return -ENOMEM;

    if (turning_on)
        set_bit(bit, &trialcs->flags);
    else
        clear_bit(bit, &trialcs->flags);

    err = validate_change(cs, trialcs);
    if (err < 0)
        goto out;

    err = heap_init(&heap, PAGE_SIZE, GFP_KERNEL, NULL);
    if (err < 0)
        goto out;

    balance_flag_changed = (is_sched_load_balance(cs) !=
                is_sched_load_balance(trialcs));

    spread_flag_changed = ((is_spread_slab(cs) != is_spread_slab(trialcs))
            || (is_spread_page(cs) != is_spread_page(trialcs)));

    mutex_lock(&callback_mutex);
    cs->flags = trialcs->flags;
    mutex_unlock(&callback_mutex);

    if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed)
        async_rebuild_sched_domains();

    if (spread_flag_changed)
        update_tasks_flags(cs, &heap);
    heap_free(&heap);
out:
    free_trial_cpuset(trialcs);
    return err;
}

/*
 * Frequency meter - How fast is some event occurring?
 *
 * These routines manage a digitally filtered, constant time based,
 * event frequency meter.  There are four routines:
 *   fmeter_init() - initialize a frequency meter.
 *   fmeter_markevent() - called each time the event happens.
 *   fmeter_getrate() - returns the recent rate of such events.
 *   fmeter_update() - internal routine used to update fmeter.
 *
 * A common data structure is passed to each of these routines,
 * which is used to keep track of the state required to manage the
 * frequency meter and its digital filter.
 *
 * The filter works on the number of events marked per unit time.
 * The filter is single-pole low-pass recursive (IIR).  The time unit
 * is 1 second.  Arithmetic is done using 32-bit integers scaled to
 * simulate 3 decimal digits of precision (multiplied by 1000).
 *
 * With an FM_COEF of 933, and a time base of 1 second, the filter
 * has a half-life of 10 seconds, meaning that if the events quit
 * happening, then the rate returned from the fmeter_getrate()
 * will be cut in half each 10 seconds, until it converges to zero.
 *
 * It is not worth doing a real infinitely recursive filter.  If more
 * than FM_MAXTICKS ticks have elapsed since the last filter event,
 * just compute FM_MAXTICKS ticks worth, by which point the level
 * will be stable.
 *
 * Limit the count of unprocessed events to FM_MAXCNT, so as to avoid
 * arithmetic overflow in the fmeter_update() routine.
 *
 * Given the simple 32 bit integer arithmetic used, this meter works
 * best for reporting rates between one per millisecond (msec) and
 * one per 32 (approx) seconds.  At constant rates faster than one
 * per msec it maxes out at values just under 1,000,000.  At constant
 * rates between one per msec, and one per second it will stabilize
 * to a value N*1000, where N is the rate of events per second.
 * At constant rates between one per second and one per 32 seconds,
 * it will be choppy, moving up on the seconds that have an event,
 * and then decaying until the next event.  At rates slower than
 * about one in 32 seconds, it decays all the way back to zero between
 * each event.
 */

#define FM_COEF 933     /* coefficient for half-life of 10 secs */
#define FM_MAXTICKS ((time_t)99) /* useless computing more ticks than this */
#define FM_MAXCNT 1000000   /* limit cnt to avoid overflow */
#define FM_SCALE 1000       /* faux fixed point scale */

/* Initialize a frequency meter */
static void fmeter_init(struct fmeter *fmp)
{
    fmp->cnt = 0;
    fmp->val = 0;
    fmp->time = 0;
    spin_lock_init(&fmp->lock);
}

/* Internal meter update - process cnt events and update value */
static void fmeter_update(struct fmeter *fmp)
{
    time_t now = get_seconds();
    time_t ticks = now - fmp->time;

    if (ticks == 0)
        return;

    ticks = min(FM_MAXTICKS, ticks);
    while (ticks-- > 0)
        fmp->val = (FM_COEF * fmp->val) / FM_SCALE;
    fmp->time = now;

    fmp->val += ((FM_SCALE - FM_COEF) * fmp->cnt) / FM_SCALE;
    fmp->cnt = 0;
}

/* Process any previous ticks, then bump cnt by one (times scale). */
static void fmeter_markevent(struct fmeter *fmp)
{
    spin_lock(&fmp->lock);
    fmeter_update(fmp);
    fmp->cnt = min(FM_MAXCNT, fmp->cnt + FM_SCALE);
    spin_unlock(&fmp->lock);
}

/* Process any previous ticks, then return current value. */
static int fmeter_getrate(struct fmeter *fmp)
{
    int val;

    spin_lock(&fmp->lock);
    fmeter_update(fmp);
    val = fmp->val;
    spin_unlock(&fmp->lock);
    return val;
}

/*
 * Protected by cgroup_lock. The nodemasks must be stored globally because
 * dynamically allocating them is not allowed in can_attach, and they must
 * persist until attach.
 */
static cpumask_var_t cpus_attach;
static nodemask_t cpuset_attach_nodemask_from;
static nodemask_t cpuset_attach_nodemask_to;

/* Called by cgroups to determine if a cpuset is usable; cgroup_mutex held */
static int cpuset_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
{
    struct cpuset *cs = cgroup_cs(cgrp);
    struct task_struct *task;
    int ret;

    if (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
        return -ENOSPC;

    cgroup_taskset_for_each(task, cgrp, tset) {
        /*
         * Kthreads bound to specific cpus cannot be moved to a new
         * cpuset; we cannot change their cpu affinity and
         * isolating such threads by their set of allowed nodes is
         * unnecessary.  Thus, cpusets are not applicable for such
         * threads.  This prevents checking for success of
         * set_cpus_allowed_ptr() on all attached tasks before
         * cpus_allowed may be changed.
         */
        if (task->flags & PF_THREAD_BOUND)
            return -EINVAL;
        if ((ret = security_task_setscheduler(task)))
            return ret;
    }

    /* prepare for attach */
    if (cs == &top_cpuset)
        cpumask_copy(cpus_attach, cpu_possible_mask);
    else
        guarantee_online_cpus(cs, cpus_attach);

    guarantee_online_mems(cs, &cpuset_attach_nodemask_to);

    return 0;
}

static void cpuset_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
{
    struct mm_struct *mm;
    struct task_struct *task;
    struct task_struct *leader = cgroup_taskset_first(tset);
    struct cgroup *oldcgrp = cgroup_taskset_cur_cgroup(tset);
    struct cpuset *cs = cgroup_cs(cgrp);
    struct cpuset *oldcs = cgroup_cs(oldcgrp);

    cgroup_taskset_for_each(task, cgrp, tset) {
        /*
         * can_attach beforehand should guarantee that this doesn't
         * fail.  TODO: have a better way to handle failure here
         */
        WARN_ON_ONCE(set_cpus_allowed_ptr(task, cpus_attach));

        cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to);
        cpuset_update_task_spread_flag(cs, task);
    }

    /*
     * Change mm, possibly for multiple threads in a threadgroup. This is
     * expensive and may sleep.
     */
    cpuset_attach_nodemask_from = oldcs->mems_allowed;
    cpuset_attach_nodemask_to = cs->mems_allowed;
    mm = get_task_mm(leader);
    if (mm) {
        mpol_rebind_mm(mm, &cpuset_attach_nodemask_to);
        if (is_memory_migrate(cs))
            cpuset_migrate_mm(mm, &cpuset_attach_nodemask_from,
                      &cpuset_attach_nodemask_to);
        mmput(mm);
    }
}

/* The various types of files and directories in a cpuset file system */

typedef enum {
    FILE_MEMORY_MIGRATE,
    FILE_CPULIST,
    FILE_MEMLIST,
    FILE_CPU_EXCLUSIVE,
    FILE_MEM_EXCLUSIVE,
    FILE_MEM_HARDWALL,
    FILE_SCHED_LOAD_BALANCE,
    FILE_SCHED_RELAX_DOMAIN_LEVEL,
    FILE_MEMORY_PRESSURE_ENABLED,
    FILE_MEMORY_PRESSURE,
    FILE_SPREAD_PAGE,
    FILE_SPREAD_SLAB,
} cpuset_filetype_t;

static int cpuset_write_u64(struct cgroup *cgrp, struct cftype *cft, u64 val)
{
    int retval = 0;
    struct cpuset *cs = cgroup_cs(cgrp);
    cpuset_filetype_t type = cft->private;

    if (!cgroup_lock_live_group(cgrp))
        return -ENODEV;

    switch (type) {
    case FILE_CPU_EXCLUSIVE:
        retval = update_flag(CS_CPU_EXCLUSIVE, cs, val);
        break;
    case FILE_MEM_EXCLUSIVE:
        retval = update_flag(CS_MEM_EXCLUSIVE, cs, val);
        break;
    case FILE_MEM_HARDWALL:
        retval = update_flag(CS_MEM_HARDWALL, cs, val);
        break;
    case FILE_SCHED_LOAD_BALANCE:
        retval = update_flag(CS_SCHED_LOAD_BALANCE, cs, val);
        break;
    case FILE_MEMORY_MIGRATE:
        retval = update_flag(CS_MEMORY_MIGRATE, cs, val);
        break;
    case FILE_MEMORY_PRESSURE_ENABLED:
        cpuset_memory_pressure_enabled = !!val;
        break;
    case FILE_MEMORY_PRESSURE:
        retval = -EACCES;
        break;
    case FILE_SPREAD_PAGE:
        retval = update_flag(CS_SPREAD_PAGE, cs, val);
        break;
    case FILE_SPREAD_SLAB:
        retval = update_flag(CS_SPREAD_SLAB, cs, val);
        break;
    default:
        retval = -EINVAL;
        break;
    }
    cgroup_unlock();
    return retval;
}

static int cpuset_write_s64(struct cgroup *cgrp, struct cftype *cft, s64 val)
{
    int retval = 0;
    struct cpuset *cs = cgroup_cs(cgrp);
    cpuset_filetype_t type = cft->private;

    if (!cgroup_lock_live_group(cgrp))
        return -ENODEV;

    switch (type) {
    case FILE_SCHED_RELAX_DOMAIN_LEVEL:
        retval = update_relax_domain_level(cs, val);
        break;
    default:
        retval = -EINVAL;
        break;
    }
    cgroup_unlock();
    return retval;
}

/*
 * Common handling for a write to a "cpus" or "mems" file.
 */
static int cpuset_write_resmask(struct cgroup *cgrp, struct cftype *cft,
                const char *buf)
{
    int retval = 0;
    struct cpuset *cs = cgroup_cs(cgrp);
    struct cpuset *trialcs;

    if (!cgroup_lock_live_group(cgrp))
        return -ENODEV;

    trialcs = alloc_trial_cpuset(cs);
    if (!trialcs) {
        retval = -ENOMEM;
        goto out;
    }

    switch (cft->private) {
    case FILE_CPULIST:
        retval = update_cpumask(cs, trialcs, buf);
        break;
    case FILE_MEMLIST:
        retval = update_nodemask(cs, trialcs, buf);
        break;
    default:
        retval = -EINVAL;
        break;
    }

    free_trial_cpuset(trialcs);
out:
    cgroup_unlock();
    return retval;
}

/*
 * These ascii lists should be read in a single call, by using a user
 * buffer large enough to hold the entire map.  If read in smaller
 * chunks, there is no guarantee of atomicity.  Since the display format
 * used, list of ranges of sequential numbers, is variable length,
 * and since these maps can change value dynamically, one could read
 * gibberish by doing partial reads while a list was changing.
 * A single large read to a buffer that crosses a page boundary is
 * ok, because the result being copied to user land is not recomputed
 * across a page fault.
 */

static size_t cpuset_sprintf_cpulist(char *page, struct cpuset *cs)
{
    size_t count;

    mutex_lock(&callback_mutex);
    count = cpulist_scnprintf(page, PAGE_SIZE, cs->cpus_allowed);
    mutex_unlock(&callback_mutex);

    return count;
}

static size_t cpuset_sprintf_memlist(char *page, struct cpuset *cs)
{
    size_t count;

    mutex_lock(&callback_mutex);
    count = nodelist_scnprintf(page, PAGE_SIZE, cs->mems_allowed);
    mutex_unlock(&callback_mutex);

    return count;
}

static ssize_t cpuset_common_file_read(struct cgroup *cont,
                       struct cftype *cft,
                       struct file *file,
                       char __user *buf,
                       size_t nbytes, loff_t *ppos)
{
    struct cpuset *cs = cgroup_cs(cont);
    cpuset_filetype_t type = cft->private;
    char *page;
    ssize_t retval = 0;
    char *s;

    if (!(page = (char *)__get_free_page(GFP_TEMPORARY)))
        return -ENOMEM;

    s = page;

    switch (type) {
    case FILE_CPULIST:
        s += cpuset_sprintf_cpulist(s, cs);
        break;
    case FILE_MEMLIST:
        s += cpuset_sprintf_memlist(s, cs);
        break;
    default:
        retval = -EINVAL;
        goto out;
    }
    *s++ = '\n';

    retval = simple_read_from_buffer(buf, nbytes, ppos, page, s - page);
out:
    free_page((unsigned long)page);
    return retval;
}

static u64 cpuset_read_u64(struct cgroup *cont, struct cftype *cft)
{
    struct cpuset *cs = cgroup_cs(cont);
    cpuset_filetype_t type = cft->private;
    switch (type) {
    case FILE_CPU_EXCLUSIVE:
        return is_cpu_exclusive(cs);
    case FILE_MEM_EXCLUSIVE:
        return is_mem_exclusive(cs);
    case FILE_MEM_HARDWALL:
        return is_mem_hardwall(cs);
    case FILE_SCHED_LOAD_BALANCE:
        return is_sched_load_balance(cs);
    case FILE_MEMORY_MIGRATE:
        return is_memory_migrate(cs);
    case FILE_MEMORY_PRESSURE_ENABLED:
        return cpuset_memory_pressure_enabled;
    case FILE_MEMORY_PRESSURE:
        return fmeter_getrate(&cs->fmeter);
    case FILE_SPREAD_PAGE:
        return is_spread_page(cs);
    case FILE_SPREAD_SLAB:
        return is_spread_slab(cs);
    default:
        BUG();
    }

    /* Unreachable but makes gcc happy */
    return 0;
}

static s64 cpuset_read_s64(struct cgroup *cont, struct cftype *cft)
{
    struct cpuset *cs = cgroup_cs(cont);
    cpuset_filetype_t type = cft->private;
    switch (type) {
    case FILE_SCHED_RELAX_DOMAIN_LEVEL:
        return cs->relax_domain_level;
    default:
        BUG();
    }

    /* Unrechable but makes gcc happy */
    return 0;
}


/*
 * for the common functions, 'private' gives the type of file
 */

static struct cftype files[] = {
    {
        .name = "cpus",
        .read = cpuset_common_file_read,
        .write_string = cpuset_write_resmask,
        .max_write_len = (100U + 6 * NR_CPUS),
        .private = FILE_CPULIST,
    },

    {
        .name = "mems",
        .read = cpuset_common_file_read,
        .write_string = cpuset_write_resmask,
        .max_write_len = (100U + 6 * MAX_NUMNODES),
        .private = FILE_MEMLIST,
    },

    {
        .name = "cpu_exclusive",
        .read_u64 = cpuset_read_u64,
        .write_u64 = cpuset_write_u64,
        .private = FILE_CPU_EXCLUSIVE,
    },

    {
        .name = "mem_exclusive",
        .read_u64 = cpuset_read_u64,
        .write_u64 = cpuset_write_u64,
        .private = FILE_MEM_EXCLUSIVE,
    },

    {
        .name = "mem_hardwall",
        .read_u64 = cpuset_read_u64,
        .write_u64 = cpuset_write_u64,
        .private = FILE_MEM_HARDWALL,
    },

    {
        .name = "sched_load_balance",
        .read_u64 = cpuset_read_u64,
        .write_u64 = cpuset_write_u64,
        .private = FILE_SCHED_LOAD_BALANCE,
    },

    {
        .name = "sched_relax_domain_level",
        .read_s64 = cpuset_read_s64,
        .write_s64 = cpuset_write_s64,
        .private = FILE_SCHED_RELAX_DOMAIN_LEVEL,
    },

    {
        .name = "memory_migrate",
        .read_u64 = cpuset_read_u64,
        .write_u64 = cpuset_write_u64,
        .private = FILE_MEMORY_MIGRATE,
    },

    {
        .name = "memory_pressure",
        .read_u64 = cpuset_read_u64,
        .write_u64 = cpuset_write_u64,
        .private = FILE_MEMORY_PRESSURE,
        .mode = S_IRUGO,
    },

    {
        .name = "memory_spread_page",
        .read_u64 = cpuset_read_u64,
        .write_u64 = cpuset_write_u64,
        .private = FILE_SPREAD_PAGE,
    },

    {
        .name = "memory_spread_slab",
        .read_u64 = cpuset_read_u64,
        .write_u64 = cpuset_write_u64,
        .private = FILE_SPREAD_SLAB,
    },

    {
        .name = "memory_pressure_enabled",
        .flags = CFTYPE_ONLY_ON_ROOT,
        .read_u64 = cpuset_read_u64,
        .write_u64 = cpuset_write_u64,
        .private = FILE_MEMORY_PRESSURE_ENABLED,
    },

    { } /* terminate */
};

/*
 * post_clone() is called during cgroup_create() when the
 * clone_children mount argument was specified.  The cgroup
 * can not yet have any tasks.
 *
 * Currently we refuse to set up the cgroup - thereby
 * refusing the task to be entered, and as a result refusing
 * the sys_unshare() or clone() which initiated it - if any
 * sibling cpusets have exclusive cpus or mem.
 *
 * If this becomes a problem for some users who wish to
 * allow that scenario, then cpuset_post_clone() could be
 * changed to grant parent->cpus_allowed-sibling_cpus_exclusive
 * (and likewise for mems) to the new cgroup. Called with cgroup_mutex
 * held.
 */
static void cpuset_post_clone(struct cgroup *cgroup)
{
    struct cgroup *parent, *child;
    struct cpuset *cs, *parent_cs;

    parent = cgroup->parent;
    list_for_each_entry(child, &parent->children, sibling) {
        cs = cgroup_cs(child);
        if (is_mem_exclusive(cs) || is_cpu_exclusive(cs))
            return;
    }
    cs = cgroup_cs(cgroup);
    parent_cs = cgroup_cs(parent);

    mutex_lock(&callback_mutex);
    cs->mems_allowed = parent_cs->mems_allowed;
    cpumask_copy(cs->cpus_allowed, parent_cs->cpus_allowed);
    mutex_unlock(&callback_mutex);
    return;
}

/*
 *  cpuset_create - create a cpuset
 *  cont:   control group that the new cpuset will be part of
 */

static struct cgroup_subsys_state *cpuset_create(struct cgroup *cont)
{
    struct cpuset *cs;
    struct cpuset *parent;

    if (!cont->parent) {
        return &top_cpuset.css;
    }
    parent = cgroup_cs(cont->parent);
    cs = kmalloc(sizeof(*cs), GFP_KERNEL);
    if (!cs)
        return ERR_PTR(-ENOMEM);
    if (!alloc_cpumask_var(&cs->cpus_allowed, GFP_KERNEL)) {
        kfree(cs);
        return ERR_PTR(-ENOMEM);
    }

    cs->flags = 0;
    if (is_spread_page(parent))
        set_bit(CS_SPREAD_PAGE, &cs->flags);
    if (is_spread_slab(parent))
        set_bit(CS_SPREAD_SLAB, &cs->flags);
    set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
    cpumask_clear(cs->cpus_allowed);
    nodes_clear(cs->mems_allowed);
    fmeter_init(&cs->fmeter);
    cs->relax_domain_level = -1;

    cs->parent = parent;
    number_of_cpusets++;
    return &cs->css ;
}

/*
 * If the cpuset being removed has its flag 'sched_load_balance'
 * enabled, then simulate turning sched_load_balance off, which
 * will call async_rebuild_sched_domains().
 */

static void cpuset_destroy(struct cgroup *cont)
{
    struct cpuset *cs = cgroup_cs(cont);

    if (is_sched_load_balance(cs))
        update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);

    number_of_cpusets--;
    free_cpumask_var(cs->cpus_allowed);
    kfree(cs);
}

struct cgroup_subsys cpuset_subsys = {
    .name = "cpuset",
    .create = cpuset_create,
    .destroy = cpuset_destroy,
    .can_attach = cpuset_can_attach,
    .attach = cpuset_attach,
    .post_clone = cpuset_post_clone,
    .subsys_id = cpuset_subsys_id,
    .base_cftypes = files,
    .early_init = 1,
};

int __init cpuset_init(void)
{
    int err = 0;

    if (!alloc_cpumask_var(&top_cpuset.cpus_allowed, GFP_KERNEL))
        BUG();

    cpumask_setall(top_cpuset.cpus_allowed);
    nodes_setall(top_cpuset.mems_allowed);

    fmeter_init(&top_cpuset.fmeter);
    set_bit(CS_SCHED_LOAD_BALANCE, &top_cpuset.flags);
    top_cpuset.relax_domain_level = -1;

    err = register_filesystem(&cpuset_fs_type);
    if (err < 0)
        return err;

    if (!alloc_cpumask_var(&cpus_attach, GFP_KERNEL))
        BUG();

    number_of_cpusets = 1;
    return 0;
}

static void cpuset_do_move_task(struct task_struct *tsk,
                struct cgroup_scanner *scan)
{
    struct cgroup *new_cgroup = scan->data;

    cgroup_attach_task(new_cgroup, tsk);
}

static void move_member_tasks_to_cpuset(struct cpuset *from, struct cpuset *to)
{
    struct cgroup_scanner scan;

    scan.cg = from->css.cgroup;
    scan.test_task = NULL; /* select all tasks in cgroup */
    scan.process_task = cpuset_do_move_task;
    scan.heap = NULL;
    scan.data = to->css.cgroup;

    if (cgroup_scan_tasks(&scan))
        printk(KERN_ERR "move_member_tasks_to_cpuset: "
                "cgroup_scan_tasks failed\n");
}

/*
 * If CPU and/or memory hotplug handlers, below, unplug any CPUs
 * or memory nodes, we need to walk over the cpuset hierarchy,
 * removing that CPU or node from all cpusets.  If this removes the
 * last CPU or node from a cpuset, then move the tasks in the empty
 * cpuset to its next-highest non-empty parent.
 *
 * Called with cgroup_mutex held
 * callback_mutex must not be held, as cpuset_attach() will take it.
 */
static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
{
    struct cpuset *parent;

    /*
     * The cgroup's css_sets list is in use if there are tasks
     * in the cpuset; the list is empty if there are none;
     * the cs->css.refcnt seems always 0.
     */
    if (list_empty(&cs->css.cgroup->css_sets))
        return;

    /*
     * Find its next-highest non-empty parent, (top cpuset
     * has online cpus, so can't be empty).
     */
    parent = cs->parent;
    while (cpumask_empty(parent->cpus_allowed) ||
            nodes_empty(parent->mems_allowed))
        parent = parent->parent;

    move_member_tasks_to_cpuset(cs, parent);
}

/*
 * Helper function to traverse cpusets.
 * It can be used to walk the cpuset tree from top to bottom, completing
 * one layer before dropping down to the next (thus always processing a
 * node before any of its children).
 */
static struct cpuset *cpuset_next(struct list_head *queue)
{
    struct cpuset *cp;
    struct cpuset *child;   /* scans child cpusets of cp */
    struct cgroup *cont;

    if (list_empty(queue))
        return NULL;

    cp = list_first_entry(queue, struct cpuset, stack_list);
    list_del(queue->next);
    list_for_each_entry(cont, &cp->css.cgroup->children, sibling) {
        child = cgroup_cs(cont);
        list_add_tail(&child->stack_list, queue);
    }

    return cp;
}


/*
 * Walk the specified cpuset subtree upon a hotplug operation (CPU/Memory
 * online/offline) and update the cpusets accordingly.
 * For regular CPU/Mem hotplug, look for empty cpusets; the tasks of such
 * cpuset must be moved to a parent cpuset.
 *
 * Called with cgroup_mutex held.  We take callback_mutex to modify
 * cpus_allowed and mems_allowed.
 *
 * This walk processes the tree from top to bottom, completing one layer
 * before dropping down to the next.  It always processes a node before
 * any of its children.
 *
 * In the case of memory hot-unplug, it will remove nodes from N_HIGH_MEMORY
 * if all present pages from a node are offlined.
 */
static void
scan_cpusets_upon_hotplug(struct cpuset *root, enum hotplug_event event)
{
    LIST_HEAD(queue);
    struct cpuset *cp;      /* scans cpusets being updated */
    static nodemask_t oldmems;  /* protected by cgroup_mutex */

    list_add_tail((struct list_head *)&root->stack_list, &queue);

    switch (event) {
    case CPUSET_CPU_OFFLINE:
        while ((cp = cpuset_next(&queue)) != NULL) {

            /* Continue past cpusets with all cpus online */
            if (cpumask_subset(cp->cpus_allowed, cpu_active_mask))
                continue;

            /* Remove offline cpus from this cpuset. */
            mutex_lock(&callback_mutex);
            cpumask_and(cp->cpus_allowed, cp->cpus_allowed,
                            cpu_active_mask);
            mutex_unlock(&callback_mutex);

            /* Move tasks from the empty cpuset to a parent */
            if (cpumask_empty(cp->cpus_allowed))
                remove_tasks_in_empty_cpuset(cp);
            else
                update_tasks_cpumask(cp, NULL);
        }
        break;

    case CPUSET_MEM_OFFLINE:
        while ((cp = cpuset_next(&queue)) != NULL) {

            /* Continue past cpusets with all mems online */
            if (nodes_subset(cp->mems_allowed,
                    node_states[N_HIGH_MEMORY]))
                continue;

            oldmems = cp->mems_allowed;

            /* Remove offline mems from this cpuset. */
            mutex_lock(&callback_mutex);
            nodes_and(cp->mems_allowed, cp->mems_allowed,
                        node_states[N_HIGH_MEMORY]);
            mutex_unlock(&callback_mutex);

            /* Move tasks from the empty cpuset to a parent */
            if (nodes_empty(cp->mems_allowed))
                remove_tasks_in_empty_cpuset(cp);
            else
                update_tasks_nodemask(cp, &oldmems, NULL);
        }
    }
}

/*
 * The top_cpuset tracks what CPUs and Memory Nodes are online,
 * period.  This is necessary in order to make cpusets transparent
 * (of no affect) on systems that are actively using CPU hotplug
 * but making no active use of cpusets.
 *
 * The only exception to this is suspend/resume, where we don't
 * modify cpusets at all.
 *
 * This routine ensures that top_cpuset.cpus_allowed tracks
 * cpu_active_mask on each CPU hotplug (cpuhp) event.
 *
 * Called within get_online_cpus().  Needs to call cgroup_lock()
 * before calling generate_sched_domains().
 *
 * @cpu_online: Indicates whether this is a CPU online event (true) or
 * a CPU offline event (false).
 */
void cpuset_update_active_cpus(bool cpu_online)
{
    struct sched_domain_attr *attr;
    cpumask_var_t *doms;
    int ndoms;

    cgroup_lock();
    mutex_lock(&callback_mutex);
    cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
    mutex_unlock(&callback_mutex);

    if (!cpu_online)
        scan_cpusets_upon_hotplug(&top_cpuset, CPUSET_CPU_OFFLINE);

    ndoms = generate_sched_domains(&doms, &attr);
    cgroup_unlock();

    /* Have scheduler rebuild the domains */
    partition_sched_domains(ndoms, doms, attr);
}

#ifdef CONFIG_MEMORY_HOTPLUG
/*
 * Keep top_cpuset.mems_allowed tracking node_states[N_HIGH_MEMORY].
 * Call this routine anytime after node_states[N_HIGH_MEMORY] changes.
 * See cpuset_update_active_cpus() for CPU hotplug handling.
 */
static int cpuset_track_online_nodes(struct notifier_block *self,
                unsigned long action, void *arg)
{
    static nodemask_t oldmems;  /* protected by cgroup_mutex */

    cgroup_lock();
    switch (action) {
    case MEM_ONLINE:
        oldmems = top_cpuset.mems_allowed;
        mutex_lock(&callback_mutex);
        top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY];
        mutex_unlock(&callback_mutex);
        update_tasks_nodemask(&top_cpuset, &oldmems, NULL);
        break;
    case MEM_OFFLINE:
        /*
         * needn't update top_cpuset.mems_allowed explicitly because
         * scan_cpusets_upon_hotplug() will update it.
         */
        scan_cpusets_upon_hotplug(&top_cpuset, CPUSET_MEM_OFFLINE);
        break;
    default:
        break;
    }
    cgroup_unlock();

    return NOTIFY_OK;
}
#endif

void __init cpuset_init_smp(void)
{
    cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
    top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY];

    hotplug_memory_notifier(cpuset_track_online_nodes, 10);

    cpuset_wq = create_singlethread_workqueue("cpuset");
    BUG_ON(!cpuset_wq);
}

void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask)
{
    mutex_lock(&callback_mutex);
    task_lock(tsk);
    guarantee_online_cpus(task_cs(tsk), pmask);
    task_unlock(tsk);
    mutex_unlock(&callback_mutex);
}

void cpuset_cpus_allowed_fallback(struct task_struct *tsk)
{
    const struct cpuset *cs;

    rcu_read_lock();
    cs = task_cs(tsk);
    if (cs)
        do_set_cpus_allowed(tsk, cs->cpus_allowed);
    rcu_read_unlock();

    /*
     * We own tsk->cpus_allowed, nobody can change it under us.
     *
     * But we used cs && cs->cpus_allowed lockless and thus can
     * race with cgroup_attach_task() or update_cpumask() and get
     * the wrong tsk->cpus_allowed. However, both cases imply the
     * subsequent cpuset_change_cpumask()->set_cpus_allowed_ptr()
     * which takes task_rq_lock().
     *
     * If we are called after it dropped the lock we must see all
     * changes in tsk_cs()->cpus_allowed. Otherwise we can temporary
     * set any mask even if it is not right from task_cs() pov,
     * the pending set_cpus_allowed_ptr() will fix things.
     *
     * select_fallback_rq() will fix things ups and set cpu_possible_mask
     * if required.
     */
}

void cpuset_init_current_mems_allowed(void)
{
    nodes_setall(current->mems_allowed);
}

nodemask_t cpuset_mems_allowed(struct task_struct *tsk)
{
    nodemask_t mask;

    mutex_lock(&callback_mutex);
    task_lock(tsk);
    guarantee_online_mems(task_cs(tsk), &mask);
    task_unlock(tsk);
    mutex_unlock(&callback_mutex);

    return mask;
}

int cpuset_nodemask_valid_mems_allowed(nodemask_t *nodemask)
{
    return nodes_intersects(*nodemask, current->mems_allowed);
}

/*
 * nearest_hardwall_ancestor() - Returns the nearest mem_exclusive or
 * mem_hardwall ancestor to the specified cpuset.  Call holding
 * callback_mutex.  If no ancestor is mem_exclusive or mem_hardwall
 * (an unusual configuration), then returns the root cpuset.
 */
static const struct cpuset *nearest_hardwall_ancestor(const struct cpuset *cs)
{
    while (!(is_mem_exclusive(cs) || is_mem_hardwall(cs)) && cs->parent)
        cs = cs->parent;
    return cs;
}

int __cpuset_node_allowed_softwall(int node, gfp_t gfp_mask)
{
    const struct cpuset *cs;    /* current cpuset ancestors */
    int allowed;            /* is allocation in zone z allowed? */

    if (in_interrupt() || (gfp_mask & __GFP_THISNODE))
        return 1;
    might_sleep_if(!(gfp_mask & __GFP_HARDWALL));
    if (node_isset(node, current->mems_allowed))
        return 1;
    /*
     * Allow tasks that have access to memory reserves because they have
     * been OOM killed to get memory anywhere.
     */
    if (unlikely(test_thread_flag(TIF_MEMDIE)))
        return 1;
    if (gfp_mask & __GFP_HARDWALL)  /* If hardwall request, stop here */
        return 0;

    if (current->flags & PF_EXITING) /* Let dying task have memory */
        return 1;

    /* Not hardwall and node outside mems_allowed: scan up cpusets */
    mutex_lock(&callback_mutex);

    task_lock(current);
    cs = nearest_hardwall_ancestor(task_cs(current));
    task_unlock(current);

    allowed = node_isset(node, cs->mems_allowed);
    mutex_unlock(&callback_mutex);
    return allowed;
}

/*
 * cpuset_node_allowed_hardwall - Can we allocate on a memory node?
 * @node: is this an allowed node?
 * @gfp_mask: memory allocation flags
 *
 * If we're in interrupt, yes, we can always allocate.  If __GFP_THISNODE is
 * set, yes, we can always allocate.  If node is in our task's mems_allowed,
 * yes.  If the task has been OOM killed and has access to memory reserves as
 * specified by the TIF_MEMDIE flag, yes.
 * Otherwise, no.
 *
 * The __GFP_THISNODE placement logic is really handled elsewhere,
 * by forcibly using a zonelist starting at a specified node, and by
 * (in get_page_from_freelist()) refusing to consider the zones for
 * any node on the zonelist except the first.  By the time any such
 * calls get to this routine, we should just shut up and say 'yes'.
 *
 * Unlike the cpuset_node_allowed_softwall() variant, above,
 * this variant requires that the node be in the current task's
 * mems_allowed or that we're in interrupt.  It does not scan up the
 * cpuset hierarchy for the nearest enclosing mem_exclusive cpuset.
 * It never sleeps.
 */
int __cpuset_node_allowed_hardwall(int node, gfp_t gfp_mask)
{
    if (in_interrupt() || (gfp_mask & __GFP_THISNODE))
        return 1;
    if (node_isset(node, current->mems_allowed))
        return 1;
    /*
     * Allow tasks that have access to memory reserves because they have
     * been OOM killed to get memory anywhere.
     */
    if (unlikely(test_thread_flag(TIF_MEMDIE)))
        return 1;
    return 0;
}

void cpuset_unlock(void)
{
    mutex_unlock(&callback_mutex);
}

static int cpuset_spread_node(int *rotor)
{
    int node;

    node = next_node(*rotor, current->mems_allowed);
    if (node == MAX_NUMNODES)
        node = first_node(current->mems_allowed);
    *rotor = node;
    return node;
}

int cpuset_mem_spread_node(void)
{
    if (current->cpuset_mem_spread_rotor == NUMA_NO_NODE)
        current->cpuset_mem_spread_rotor =
            node_random(&current->mems_allowed);

    return cpuset_spread_node(&current->cpuset_mem_spread_rotor);
}

int cpuset_slab_spread_node(void)
{
    if (current->cpuset_slab_spread_rotor == NUMA_NO_NODE)
        current->cpuset_slab_spread_rotor =
            node_random(&current->mems_allowed);

    return cpuset_spread_node(&current->cpuset_slab_spread_rotor);
}

EXPORT_SYMBOL_GPL(cpuset_mem_spread_node);

int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
                   const struct task_struct *tsk2)
{
    return nodes_intersects(tsk1->mems_allowed, tsk2->mems_allowed);
}

void cpuset_print_task_mems_allowed(struct task_struct *tsk)
{
    struct dentry *dentry;

    dentry = task_cs(tsk)->css.cgroup->dentry;
    spin_lock(&cpuset_buffer_lock);
    snprintf(cpuset_name, CPUSET_NAME_LEN,
         dentry ? (const char *)dentry->d_name.name : "/");
    nodelist_scnprintf(cpuset_nodelist, CPUSET_NODELIST_LEN,
               tsk->mems_allowed);
    printk(KERN_INFO "%s cpuset=%s mems_allowed=%s\n",
           tsk->comm, cpuset_name, cpuset_nodelist);
    spin_unlock(&cpuset_buffer_lock);
}

/*
 * Collection of memory_pressure is suppressed unless
 * this flag is enabled by writing "1" to the special
 * cpuset file 'memory_pressure_enabled' in the root cpuset.
 */

int cpuset_memory_pressure_enabled __read_mostly;

void __cpuset_memory_pressure_bump(void)
{
    task_lock(current);
    fmeter_markevent(&task_cs(current)->fmeter);
    task_unlock(current);
}

#ifdef CONFIG_PROC_PID_CPUSET
/*
 * proc_cpuset_show()
 *  - Print tasks cpuset path into seq_file.
 *  - Used for /proc/<pid>/cpuset.
 *  - No need to task_lock(tsk) on this tsk->cpuset reference, as it
 *    doesn't really matter if tsk->cpuset changes after we read it,
 *    and we take cgroup_mutex, keeping cpuset_attach() from changing it
 *    anyway.
 */
static int proc_cpuset_show(struct seq_file *m, void *unused_v)
{
    struct pid *pid;
    struct task_struct *tsk;
    char *buf;
    struct cgroup_subsys_state *css;
    int retval;

    retval = -ENOMEM;
    buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
    if (!buf)
        goto out;

    retval = -ESRCH;
    pid = m->private;
    tsk = get_pid_task(pid, PIDTYPE_PID);
    if (!tsk)
        goto out_free;

    retval = -EINVAL;
    cgroup_lock();
    css = task_subsys_state(tsk, cpuset_subsys_id);
    retval = cgroup_path(css->cgroup, buf, PAGE_SIZE);
    if (retval < 0)
        goto out_unlock;
    seq_puts(m, buf);
    seq_putc(m, '\n');
out_unlock:
    cgroup_unlock();
    put_task_struct(tsk);
out_free:
    kfree(buf);
out:
    return retval;
}

static int cpuset_open(struct inode *inode, struct file *file)
{
    struct pid *pid = PROC_I(inode)->pid;
    return single_open(file, proc_cpuset_show, pid);
}

const struct file_operations proc_cpuset_operations = {
    .open       = cpuset_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = single_release,
};
#endif /* CONFIG_PROC_PID_CPUSET */

/* Display task mems_allowed in /proc/<pid>/status file. */
void cpuset_task_status_allowed(struct seq_file *m, struct task_struct *task)
{
    seq_printf(m, "Mems_allowed:\t");
    seq_nodemask(m, &task->mems_allowed);
    seq_printf(m, "\n");
    seq_printf(m, "Mems_allowed_list:\t");
    seq_nodemask_list(m, &task->mems_allowed);
    seq_printf(m, "\n");
}