linux/kernel/cpuset.c
Paul Jackson 68860ec10b [PATCH] cpusets: automatic numa mempolicy rebinding
This patch automatically updates a tasks NUMA mempolicy when its cpuset
memory placement changes.  It does so within the context of the task,
without any need to support low level external mempolicy manipulation.

If a system is not using cpusets, or if running on a system with just the
root (all-encompassing) cpuset, then this remap is a no-op.  Only when a
task is moved between cpusets, or a cpusets memory placement is changed
does the following apply.  Otherwise, the main routine below,
rebind_policy() is not even called.

When mixing cpusets, scheduler affinity, and NUMA mempolicies, the
essential role of cpusets is to place jobs (several related tasks) on a set
of CPUs and Memory Nodes, the essential role of sched_setaffinity is to
manage a jobs processor placement within its allowed cpuset, and the
essential role of NUMA mempolicy (mbind, set_mempolicy) is to manage a jobs
memory placement within its allowed cpuset.

However, CPU affinity and NUMA memory placement are managed within the
kernel using absolute system wide numbering, not cpuset relative numbering.

This is ok until a job is migrated to a different cpuset, or what's the
same, a jobs cpuset is moved to different CPUs and Memory Nodes.

Then the CPU affinity and NUMA memory placement of the tasks in the job
need to be updated, to preserve their cpuset-relative position.  This can
be done for CPU affinity using sched_setaffinity() from user code, as one
task can modify anothers CPU affinity.  This cannot be done from an
external task for NUMA memory placement, as that can only be modified in
the context of the task using it.

However, it easy enough to remap a tasks NUMA mempolicy automatically when
a task is migrated, using the existing cpuset mechanism to trigger a
refresh of a tasks memory placement after its cpuset has changed.  All that
is needed is the old and new nodemask, and notice to the task that it needs
to rebind its mempolicy.  The tasks mems_allowed has the old mask, the
tasks cpuset has the new mask, and the existing
cpuset_update_current_mems_allowed() mechanism provides the notice.  The
bitmap/cpumask/nodemask remap operators provide the cpuset relative
calculations.

This patch leaves open a couple of issues:

 1) Updating vma and shmfs/tmpfs/hugetlbfs memory policies:

    These mempolicies may reference nodes outside of those allowed to
    the current task by its cpuset.  Tasks are migrated as part of jobs,
    which reside on what might be several cpusets in a subtree.  When such
    a job is migrated, all NUMA memory policy references to nodes within
    that cpuset subtree should be translated, and references to any nodes
    outside that subtree should be left untouched.  A future patch will
    provide the cpuset mechanism needed to mark such subtrees.  With that
    patch, we will be able to correctly migrate these other memory policies
    across a job migration.

 2) Updating cpuset, affinity and memory policies in user space:

    This is harder.  Any placement state stored in user space using
    system-wide numbering will be invalidated across a migration.  More
    work will be required to provide user code with a migration-safe means
    to manage its cpuset relative placement, while preserving the current
    API's that pass system wide numbers, not cpuset relative numbers across
    the kernel-user boundary.

Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-30 17:37:22 -08:00

1931 lines
53 KiB
C

/*
* kernel/cpuset.c
*
* Processor and Memory placement constraints for sets of tasks.
*
* Copyright (C) 2003 BULL SA.
* Copyright (C) 2004 Silicon Graphics, Inc.
*
* Portions derived from Patrick Mochel's sysfs code.
* sysfs is Copyright (c) 2001-3 Patrick Mochel
* Portions Copyright (c) 2004 Silicon Graphics, Inc.
*
* 2003-10-10 Written by Simon Derr <simon.derr@bull.net>
* 2003-10-22 Updates by Stephen Hemminger.
* 2004 May-July Rework by Paul Jackson <pj@sgi.com>
*
* 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/config.h>
#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/module.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/pagemap.h>
#include <linux/proc_fs.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/smp_lock.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 <asm/atomic.h>
#include <asm/semaphore.h>
#define CPUSET_SUPER_MAGIC 0x27e0eb
struct cpuset {
unsigned long flags; /* "unsigned long" so bitops work */
cpumask_t cpus_allowed; /* CPUs allowed to tasks in cpuset */
nodemask_t mems_allowed; /* Memory Nodes allowed to tasks */
/*
* Count is atomic so can incr (fork) or decr (exit) without a lock.
*/
atomic_t count; /* count tasks using this cpuset */
/*
* We link our 'sibling' struct into our parents 'children'.
* Our children link their 'sibling' into our 'children'.
*/
struct list_head sibling; /* my parents children */
struct list_head children; /* my children */
struct cpuset *parent; /* my parent */
struct dentry *dentry; /* cpuset fs entry */
/*
* Copy of global cpuset_mems_generation as of the most
* recent time this cpuset changed its mems_allowed.
*/
int mems_generation;
};
/* bits in struct cpuset flags field */
typedef enum {
CS_CPU_EXCLUSIVE,
CS_MEM_EXCLUSIVE,
CS_REMOVED,
CS_NOTIFY_ON_RELEASE
} cpuset_flagbits_t;
/* 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_removed(const struct cpuset *cs)
{
return !!test_bit(CS_REMOVED, &cs->flags);
}
static inline int notify_on_release(const struct cpuset *cs)
{
return !!test_bit(CS_NOTIFY_ON_RELEASE, &cs->flags);
}
/*
* Increment this atomic integer everytime any cpuset changes its
* mems_allowed value. Users of cpusets can track this generation
* number, and avoid having to lock and reload mems_allowed unless
* the cpuset they're using changes generation.
*
* A single, global generation is needed because attach_task() could
* reattach a task to a different cpuset, which must not have its
* generation numbers aliased with those of that tasks previous cpuset.
*
* Generations are needed for mems_allowed because one task cannot
* modify anothers memory placement. So we must enable every task,
* on every visit to __alloc_pages(), to efficiently check whether
* its current->cpuset->mems_allowed has changed, requiring an update
* of its current->mems_allowed.
*/
static atomic_t cpuset_mems_generation = ATOMIC_INIT(1);
static struct cpuset top_cpuset = {
.flags = ((1 << CS_CPU_EXCLUSIVE) | (1 << CS_MEM_EXCLUSIVE)),
.cpus_allowed = CPU_MASK_ALL,
.mems_allowed = NODE_MASK_ALL,
.count = ATOMIC_INIT(0),
.sibling = LIST_HEAD_INIT(top_cpuset.sibling),
.children = LIST_HEAD_INIT(top_cpuset.children),
.parent = NULL,
.dentry = NULL,
.mems_generation = 0,
};
static struct vfsmount *cpuset_mount;
static struct super_block *cpuset_sb = NULL;
/*
* We have two global cpuset semaphores below. They can nest.
* It is ok to first take manage_sem, then nest callback_sem. We also
* require taking task_lock() when dereferencing a tasks cpuset pointer.
* See "The task_lock() exception", at the end of this comment.
*
* A task must hold both semaphores to modify cpusets. If a task
* holds manage_sem, then it blocks others wanting that semaphore,
* ensuring that it is the only task able to also acquire callback_sem
* 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 manage_sem. While it is
* performing these checks, various callback routines can briefly
* acquire callback_sem to query cpusets. Once it is ready to make
* the changes, it takes callback_sem, blocking everyone else.
*
* Calls to the kernel memory allocator can not be made while holding
* callback_sem, as that would risk double tripping on callback_sem
* from one of the callbacks into the cpuset code from within
* __alloc_pages().
*
* If a task is only holding callback_sem, then it has read-only
* access to cpusets.
*
* The task_struct fields mems_allowed and mems_generation may only
* be accessed in the context of that task, so require no locks.
*
* Any task can increment and decrement the count field without lock.
* So in general, code holding manage_sem or callback_sem can't rely
* on the count field not changing. However, if the count goes to
* zero, then only attach_task(), which holds both semaphores, can
* increment it again. Because a count of zero means that no tasks
* are currently attached, therefore there is no way a task attached
* to that cpuset can fork (the other way to increment the count).
* So code holding manage_sem or callback_sem can safely assume that
* if the count is zero, it will stay zero. Similarly, if a task
* holds manage_sem or callback_sem on a cpuset with zero count, it
* knows that the cpuset won't be removed, as cpuset_rmdir() needs
* both of those semaphores.
*
* A possible optimization to improve parallelism would be to make
* callback_sem a R/W semaphore (rwsem), allowing the callback routines
* to proceed in parallel, with read access, until the holder of
* manage_sem needed to take this rwsem for exclusive write access
* and modify some cpusets.
*
* The cpuset_common_file_write handler for operations that modify
* the cpuset hierarchy holds manage_sem across the entire operation,
* single threading all such cpuset modifications across the system.
*
* The cpuset_common_file_read() handlers only hold callback_sem across
* small pieces of code, such as when reading out possibly multi-word
* cpumasks and nodemasks.
*
* The fork and exit callbacks cpuset_fork() and cpuset_exit(), don't
* (usually) take either semaphore. These are the two most performance
* critical pieces of code here. The exception occurs on cpuset_exit(),
* when a task in a notify_on_release cpuset exits. Then manage_sem
* is taken, and if the cpuset count is zero, a usermode call made
* to /sbin/cpuset_release_agent with the name of the cpuset (path
* relative to the root of cpuset file system) as the argument.
*
* A cpuset can only be deleted if both its 'count' of using tasks
* is zero, and its list of 'children' cpusets is empty. Since all
* tasks in the system use _some_ cpuset, and since there is always at
* least one task in the system (init, pid == 1), therefore, top_cpuset
* always has either children cpusets and/or using tasks. So we don't
* need a special hack to ensure that top_cpuset cannot be deleted.
*
* The above "Tale of Two Semaphores" would be complete, but for:
*
* The task_lock() exception
*
* The need for this exception arises from the action of attach_task(),
* which overwrites one tasks cpuset pointer with another. It does
* so using both semaphores, however there are several performance
* critical places that need to reference task->cpuset without the
* expense of grabbing a system global semaphore. Therefore except as
* noted below, when dereferencing or, as in attach_task(), modifying
* a tasks cpuset pointer we use task_lock(), which acts on a spinlock
* (task->alloc_lock) already in the task_struct routinely used for
* such matters.
*/
static DECLARE_MUTEX(manage_sem);
static DECLARE_MUTEX(callback_sem);
/*
* A couple of forward declarations required, due to cyclic reference loop:
* cpuset_mkdir -> cpuset_create -> cpuset_populate_dir -> cpuset_add_file
* -> cpuset_create_file -> cpuset_dir_inode_operations -> cpuset_mkdir.
*/
static int cpuset_mkdir(struct inode *dir, struct dentry *dentry, int mode);
static int cpuset_rmdir(struct inode *unused_dir, struct dentry *dentry);
static struct backing_dev_info cpuset_backing_dev_info = {
.ra_pages = 0, /* No readahead */
.capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
};
static struct inode *cpuset_new_inode(mode_t mode)
{
struct inode *inode = new_inode(cpuset_sb);
if (inode) {
inode->i_mode = mode;
inode->i_uid = current->fsuid;
inode->i_gid = current->fsgid;
inode->i_blksize = PAGE_CACHE_SIZE;
inode->i_blocks = 0;
inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
inode->i_mapping->backing_dev_info = &cpuset_backing_dev_info;
}
return inode;
}
static void cpuset_diput(struct dentry *dentry, struct inode *inode)
{
/* is dentry a directory ? if so, kfree() associated cpuset */
if (S_ISDIR(inode->i_mode)) {
struct cpuset *cs = dentry->d_fsdata;
BUG_ON(!(is_removed(cs)));
kfree(cs);
}
iput(inode);
}
static struct dentry_operations cpuset_dops = {
.d_iput = cpuset_diput,
};
static struct dentry *cpuset_get_dentry(struct dentry *parent, const char *name)
{
struct dentry *d = lookup_one_len(name, parent, strlen(name));
if (!IS_ERR(d))
d->d_op = &cpuset_dops;
return d;
}
static void remove_dir(struct dentry *d)
{
struct dentry *parent = dget(d->d_parent);
d_delete(d);
simple_rmdir(parent->d_inode, d);
dput(parent);
}
/*
* NOTE : the dentry must have been dget()'ed
*/
static void cpuset_d_remove_dir(struct dentry *dentry)
{
struct list_head *node;
spin_lock(&dcache_lock);
node = dentry->d_subdirs.next;
while (node != &dentry->d_subdirs) {
struct dentry *d = list_entry(node, struct dentry, d_child);
list_del_init(node);
if (d->d_inode) {
d = dget_locked(d);
spin_unlock(&dcache_lock);
d_delete(d);
simple_unlink(dentry->d_inode, d);
dput(d);
spin_lock(&dcache_lock);
}
node = dentry->d_subdirs.next;
}
list_del_init(&dentry->d_child);
spin_unlock(&dcache_lock);
remove_dir(dentry);
}
static struct super_operations cpuset_ops = {
.statfs = simple_statfs,
.drop_inode = generic_delete_inode,
};
static int cpuset_fill_super(struct super_block *sb, void *unused_data,
int unused_silent)
{
struct inode *inode;
struct dentry *root;
sb->s_blocksize = PAGE_CACHE_SIZE;
sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
sb->s_magic = CPUSET_SUPER_MAGIC;
sb->s_op = &cpuset_ops;
cpuset_sb = sb;
inode = cpuset_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR);
if (inode) {
inode->i_op = &simple_dir_inode_operations;
inode->i_fop = &simple_dir_operations;
/* directories start off with i_nlink == 2 (for "." entry) */
inode->i_nlink++;
} else {
return -ENOMEM;
}
root = d_alloc_root(inode);
if (!root) {
iput(inode);
return -ENOMEM;
}
sb->s_root = root;
return 0;
}
static struct super_block *cpuset_get_sb(struct file_system_type *fs_type,
int flags, const char *unused_dev_name,
void *data)
{
return get_sb_single(fs_type, flags, data, cpuset_fill_super);
}
static struct file_system_type cpuset_fs_type = {
.name = "cpuset",
.get_sb = cpuset_get_sb,
.kill_sb = kill_litter_super,
};
/* struct cftype:
*
* The files in the cpuset filesystem mostly have a very simple read/write
* handling, some common function will take care of it. Nevertheless some cases
* (read tasks) are special and therefore I define this structure for every
* kind of file.
*
*
* When reading/writing to a file:
* - the cpuset to use in file->f_dentry->d_parent->d_fsdata
* - the 'cftype' of the file is file->f_dentry->d_fsdata
*/
struct cftype {
char *name;
int private;
int (*open) (struct inode *inode, struct file *file);
ssize_t (*read) (struct file *file, char __user *buf, size_t nbytes,
loff_t *ppos);
int (*write) (struct file *file, const char __user *buf, size_t nbytes,
loff_t *ppos);
int (*release) (struct inode *inode, struct file *file);
};
static inline struct cpuset *__d_cs(struct dentry *dentry)
{
return dentry->d_fsdata;
}
static inline struct cftype *__d_cft(struct dentry *dentry)
{
return dentry->d_fsdata;
}
/*
* Call with manage_sem held. Writes path of cpuset into buf.
* Returns 0 on success, -errno on error.
*/
static int cpuset_path(const struct cpuset *cs, char *buf, int buflen)
{
char *start;
start = buf + buflen;
*--start = '\0';
for (;;) {
int len = cs->dentry->d_name.len;
if ((start -= len) < buf)
return -ENAMETOOLONG;
memcpy(start, cs->dentry->d_name.name, len);
cs = cs->parent;
if (!cs)
break;
if (!cs->parent)
continue;
if (--start < buf)
return -ENAMETOOLONG;
*start = '/';
}
memmove(buf, start, buf + buflen - start);
return 0;
}
/*
* Notify userspace when a cpuset is released, by running
* /sbin/cpuset_release_agent with the name of the cpuset (path
* relative to the root of cpuset file system) as the argument.
*
* Most likely, this user command will try to rmdir this cpuset.
*
* This races with the possibility that some other task will be
* attached to this cpuset before it is removed, or that some other
* user task will 'mkdir' a child cpuset of this cpuset. That's ok.
* The presumed 'rmdir' will fail quietly if this cpuset is no longer
* unused, and this cpuset will be reprieved from its death sentence,
* to continue to serve a useful existence. Next time it's released,
* we will get notified again, if it still has 'notify_on_release' set.
*
* The final arg to call_usermodehelper() is 0, which means don't
* wait. The separate /sbin/cpuset_release_agent task is forked by
* call_usermodehelper(), then control in this thread returns here,
* without waiting for the release agent task. We don't bother to
* wait because the caller of this routine has no use for the exit
* status of the /sbin/cpuset_release_agent task, so no sense holding
* our caller up for that.
*
* When we had only one cpuset semaphore, we had to call this
* without holding it, to avoid deadlock when call_usermodehelper()
* allocated memory. With two locks, we could now call this while
* holding manage_sem, but we still don't, so as to minimize
* the time manage_sem is held.
*/
static void cpuset_release_agent(const char *pathbuf)
{
char *argv[3], *envp[3];
int i;
if (!pathbuf)
return;
i = 0;
argv[i++] = "/sbin/cpuset_release_agent";
argv[i++] = (char *)pathbuf;
argv[i] = NULL;
i = 0;
/* minimal command environment */
envp[i++] = "HOME=/";
envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
envp[i] = NULL;
call_usermodehelper(argv[0], argv, envp, 0);
kfree(pathbuf);
}
/*
* Either cs->count of using tasks transitioned to zero, or the
* cs->children list of child cpusets just became empty. If this
* cs is notify_on_release() and now both the user count is zero and
* the list of children is empty, prepare cpuset path in a kmalloc'd
* buffer, to be returned via ppathbuf, so that the caller can invoke
* cpuset_release_agent() with it later on, once manage_sem is dropped.
* Call here with manage_sem held.
*
* This check_for_release() routine is responsible for kmalloc'ing
* pathbuf. The above cpuset_release_agent() is responsible for
* kfree'ing pathbuf. The caller of these routines is responsible
* for providing a pathbuf pointer, initialized to NULL, then
* calling check_for_release() with manage_sem held and the address
* of the pathbuf pointer, then dropping manage_sem, then calling
* cpuset_release_agent() with pathbuf, as set by check_for_release().
*/
static void check_for_release(struct cpuset *cs, char **ppathbuf)
{
if (notify_on_release(cs) && atomic_read(&cs->count) == 0 &&
list_empty(&cs->children)) {
char *buf;
buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!buf)
return;
if (cpuset_path(cs, buf, PAGE_SIZE) < 0)
kfree(buf);
else
*ppathbuf = buf;
}
}
/*
* 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_map. Or if passed a NULL cs from an exit'ing
* task, return cpu_online_map.
*
* One way or another, we guarantee to return some non-empty subset
* of cpu_online_map.
*
* Call with callback_sem held.
*/
static void guarantee_online_cpus(const struct cpuset *cs, cpumask_t *pmask)
{
while (cs && !cpus_intersects(cs->cpus_allowed, cpu_online_map))
cs = cs->parent;
if (cs)
cpus_and(*pmask, cs->cpus_allowed, cpu_online_map);
else
*pmask = cpu_online_map;
BUG_ON(!cpus_intersects(*pmask, cpu_online_map));
}
/*
* Return in *pmask the portion of a cpusets's mems_allowed that
* are online. If none are online, 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_online_map.
*
* One way or another, we guarantee to return some non-empty subset
* of node_online_map.
*
* Call with callback_sem held.
*/
static void guarantee_online_mems(const struct cpuset *cs, nodemask_t *pmask)
{
while (cs && !nodes_intersects(cs->mems_allowed, node_online_map))
cs = cs->parent;
if (cs)
nodes_and(*pmask, cs->mems_allowed, node_online_map);
else
*pmask = node_online_map;
BUG_ON(!nodes_intersects(*pmask, node_online_map));
}
/*
* Refresh current tasks mems_allowed and mems_generation from current
* tasks cpuset.
*
* Call without callback_sem or task_lock() held. May be called with
* or without manage_sem held. Will acquire task_lock() and might
* acquire callback_sem during call.
*
* The task_lock() is required to dereference current->cpuset safely.
* Without it, we could pick up the pointer value of current->cpuset
* in one instruction, and then attach_task could give us a different
* cpuset, and then the cpuset we had could be removed and freed,
* and then on our next instruction, we could dereference a no longer
* valid cpuset pointer to get its mems_generation field.
*
* This routine is needed to update the per-task mems_allowed data,
* within the tasks context, when it is trying to allocate memory
* (in various mm/mempolicy.c routines) and notices that some other
* task has been modifying its cpuset.
*/
static void refresh_mems(void)
{
int my_cpusets_mem_gen;
task_lock(current);
my_cpusets_mem_gen = current->cpuset->mems_generation;
task_unlock(current);
if (current->cpuset_mems_generation != my_cpusets_mem_gen) {
struct cpuset *cs;
nodemask_t oldmem = current->mems_allowed;
down(&callback_sem);
task_lock(current);
cs = current->cpuset;
guarantee_online_mems(cs, &current->mems_allowed);
current->cpuset_mems_generation = cs->mems_generation;
task_unlock(current);
up(&callback_sem);
if (!nodes_equal(oldmem, current->mems_allowed))
numa_policy_rebind(&oldmem, &current->mems_allowed);
}
}
/*
* 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 manage_sem.
*/
static int is_cpuset_subset(const struct cpuset *p, const struct cpuset *q)
{
return cpus_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);
}
/*
* 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
* manage_sem 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 cpuset *c, *par;
/* Each of our child cpusets must be a subset of us */
list_for_each_entry(c, &cur->children, sibling) {
if (!is_cpuset_subset(c, trial))
return -EBUSY;
}
/* Remaining checks don't apply to root cpuset */
if ((par = cur->parent) == NULL)
return 0;
/* 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(c, &par->children, sibling) {
if ((is_cpu_exclusive(trial) || is_cpu_exclusive(c)) &&
c != cur &&
cpus_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;
}
return 0;
}
/*
* For a given cpuset cur, partition the system as follows
* a. All cpus in the parent cpuset's cpus_allowed that are not part of any
* exclusive child cpusets
* b. All cpus in the current cpuset's cpus_allowed that are not part of any
* exclusive child cpusets
* Build these two partitions by calling partition_sched_domains
*
* Call with manage_sem held. May nest a call to the
* lock_cpu_hotplug()/unlock_cpu_hotplug() pair.
*/
static void update_cpu_domains(struct cpuset *cur)
{
struct cpuset *c, *par = cur->parent;
cpumask_t pspan, cspan;
if (par == NULL || cpus_empty(cur->cpus_allowed))
return;
/*
* Get all cpus from parent's cpus_allowed not part of exclusive
* children
*/
pspan = par->cpus_allowed;
list_for_each_entry(c, &par->children, sibling) {
if (is_cpu_exclusive(c))
cpus_andnot(pspan, pspan, c->cpus_allowed);
}
if (is_removed(cur) || !is_cpu_exclusive(cur)) {
cpus_or(pspan, pspan, cur->cpus_allowed);
if (cpus_equal(pspan, cur->cpus_allowed))
return;
cspan = CPU_MASK_NONE;
} else {
if (cpus_empty(pspan))
return;
cspan = cur->cpus_allowed;
/*
* Get all cpus from current cpuset's cpus_allowed not part
* of exclusive children
*/
list_for_each_entry(c, &cur->children, sibling) {
if (is_cpu_exclusive(c))
cpus_andnot(cspan, cspan, c->cpus_allowed);
}
}
lock_cpu_hotplug();
partition_sched_domains(&pspan, &cspan);
unlock_cpu_hotplug();
}
/*
* Call with manage_sem held. May take callback_sem during call.
*/
static int update_cpumask(struct cpuset *cs, char *buf)
{
struct cpuset trialcs;
int retval, cpus_unchanged;
trialcs = *cs;
retval = cpulist_parse(buf, trialcs.cpus_allowed);
if (retval < 0)
return retval;
cpus_and(trialcs.cpus_allowed, trialcs.cpus_allowed, cpu_online_map);
if (cpus_empty(trialcs.cpus_allowed))
return -ENOSPC;
retval = validate_change(cs, &trialcs);
if (retval < 0)
return retval;
cpus_unchanged = cpus_equal(cs->cpus_allowed, trialcs.cpus_allowed);
down(&callback_sem);
cs->cpus_allowed = trialcs.cpus_allowed;
up(&callback_sem);
if (is_cpu_exclusive(cs) && !cpus_unchanged)
update_cpu_domains(cs);
return 0;
}
/*
* Call with manage_sem held. May take callback_sem during call.
*/
static int update_nodemask(struct cpuset *cs, char *buf)
{
struct cpuset trialcs;
int retval;
trialcs = *cs;
retval = nodelist_parse(buf, trialcs.mems_allowed);
if (retval < 0)
return retval;
nodes_and(trialcs.mems_allowed, trialcs.mems_allowed, node_online_map);
if (nodes_empty(trialcs.mems_allowed))
return -ENOSPC;
retval = validate_change(cs, &trialcs);
if (retval == 0) {
down(&callback_sem);
cs->mems_allowed = trialcs.mems_allowed;
atomic_inc(&cpuset_mems_generation);
cs->mems_generation = atomic_read(&cpuset_mems_generation);
up(&callback_sem);
}
return retval;
}
/*
* update_flag - read a 0 or a 1 in a file and update associated flag
* bit: the bit to update (CS_CPU_EXCLUSIVE, CS_MEM_EXCLUSIVE,
* CS_NOTIFY_ON_RELEASE)
* cs: the cpuset to update
* buf: the buffer where we read the 0 or 1
*
* Call with manage_sem held.
*/
static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs, char *buf)
{
int turning_on;
struct cpuset trialcs;
int err, cpu_exclusive_changed;
turning_on = (simple_strtoul(buf, NULL, 10) != 0);
trialcs = *cs;
if (turning_on)
set_bit(bit, &trialcs.flags);
else
clear_bit(bit, &trialcs.flags);
err = validate_change(cs, &trialcs);
if (err < 0)
return err;
cpu_exclusive_changed =
(is_cpu_exclusive(cs) != is_cpu_exclusive(&trialcs));
down(&callback_sem);
if (turning_on)
set_bit(bit, &cs->flags);
else
clear_bit(bit, &cs->flags);
up(&callback_sem);
if (cpu_exclusive_changed)
update_cpu_domains(cs);
return 0;
}
/*
* Attack task specified by pid in 'pidbuf' to cpuset 'cs', possibly
* writing the path of the old cpuset in 'ppathbuf' if it needs to be
* notified on release.
*
* Call holding manage_sem. May take callback_sem and task_lock of
* the task 'pid' during call.
*/
static int attach_task(struct cpuset *cs, char *pidbuf, char **ppathbuf)
{
pid_t pid;
struct task_struct *tsk;
struct cpuset *oldcs;
cpumask_t cpus;
if (sscanf(pidbuf, "%d", &pid) != 1)
return -EIO;
if (cpus_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
return -ENOSPC;
if (pid) {
read_lock(&tasklist_lock);
tsk = find_task_by_pid(pid);
if (!tsk || tsk->flags & PF_EXITING) {
read_unlock(&tasklist_lock);
return -ESRCH;
}
get_task_struct(tsk);
read_unlock(&tasklist_lock);
if ((current->euid) && (current->euid != tsk->uid)
&& (current->euid != tsk->suid)) {
put_task_struct(tsk);
return -EACCES;
}
} else {
tsk = current;
get_task_struct(tsk);
}
down(&callback_sem);
task_lock(tsk);
oldcs = tsk->cpuset;
if (!oldcs) {
task_unlock(tsk);
up(&callback_sem);
put_task_struct(tsk);
return -ESRCH;
}
atomic_inc(&cs->count);
tsk->cpuset = cs;
task_unlock(tsk);
guarantee_online_cpus(cs, &cpus);
set_cpus_allowed(tsk, cpus);
up(&callback_sem);
put_task_struct(tsk);
if (atomic_dec_and_test(&oldcs->count))
check_for_release(oldcs, ppathbuf);
return 0;
}
/* The various types of files and directories in a cpuset file system */
typedef enum {
FILE_ROOT,
FILE_DIR,
FILE_CPULIST,
FILE_MEMLIST,
FILE_CPU_EXCLUSIVE,
FILE_MEM_EXCLUSIVE,
FILE_NOTIFY_ON_RELEASE,
FILE_TASKLIST,
} cpuset_filetype_t;
static ssize_t cpuset_common_file_write(struct file *file, const char __user *userbuf,
size_t nbytes, loff_t *unused_ppos)
{
struct cpuset *cs = __d_cs(file->f_dentry->d_parent);
struct cftype *cft = __d_cft(file->f_dentry);
cpuset_filetype_t type = cft->private;
char *buffer;
char *pathbuf = NULL;
int retval = 0;
/* Crude upper limit on largest legitimate cpulist user might write. */
if (nbytes > 100 + 6 * NR_CPUS)
return -E2BIG;
/* +1 for nul-terminator */
if ((buffer = kmalloc(nbytes + 1, GFP_KERNEL)) == 0)
return -ENOMEM;
if (copy_from_user(buffer, userbuf, nbytes)) {
retval = -EFAULT;
goto out1;
}
buffer[nbytes] = 0; /* nul-terminate */
down(&manage_sem);
if (is_removed(cs)) {
retval = -ENODEV;
goto out2;
}
switch (type) {
case FILE_CPULIST:
retval = update_cpumask(cs, buffer);
break;
case FILE_MEMLIST:
retval = update_nodemask(cs, buffer);
break;
case FILE_CPU_EXCLUSIVE:
retval = update_flag(CS_CPU_EXCLUSIVE, cs, buffer);
break;
case FILE_MEM_EXCLUSIVE:
retval = update_flag(CS_MEM_EXCLUSIVE, cs, buffer);
break;
case FILE_NOTIFY_ON_RELEASE:
retval = update_flag(CS_NOTIFY_ON_RELEASE, cs, buffer);
break;
case FILE_TASKLIST:
retval = attach_task(cs, buffer, &pathbuf);
break;
default:
retval = -EINVAL;
goto out2;
}
if (retval == 0)
retval = nbytes;
out2:
up(&manage_sem);
cpuset_release_agent(pathbuf);
out1:
kfree(buffer);
return retval;
}
static ssize_t cpuset_file_write(struct file *file, const char __user *buf,
size_t nbytes, loff_t *ppos)
{
ssize_t retval = 0;
struct cftype *cft = __d_cft(file->f_dentry);
if (!cft)
return -ENODEV;
/* special function ? */
if (cft->write)
retval = cft->write(file, buf, nbytes, ppos);
else
retval = cpuset_common_file_write(file, buf, nbytes, ppos);
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 int cpuset_sprintf_cpulist(char *page, struct cpuset *cs)
{
cpumask_t mask;
down(&callback_sem);
mask = cs->cpus_allowed;
up(&callback_sem);
return cpulist_scnprintf(page, PAGE_SIZE, mask);
}
static int cpuset_sprintf_memlist(char *page, struct cpuset *cs)
{
nodemask_t mask;
down(&callback_sem);
mask = cs->mems_allowed;
up(&callback_sem);
return nodelist_scnprintf(page, PAGE_SIZE, mask);
}
static ssize_t cpuset_common_file_read(struct file *file, char __user *buf,
size_t nbytes, loff_t *ppos)
{
struct cftype *cft = __d_cft(file->f_dentry);
struct cpuset *cs = __d_cs(file->f_dentry->d_parent);
cpuset_filetype_t type = cft->private;
char *page;
ssize_t retval = 0;
char *s;
if (!(page = (char *)__get_free_page(GFP_KERNEL)))
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;
case FILE_CPU_EXCLUSIVE:
*s++ = is_cpu_exclusive(cs) ? '1' : '0';
break;
case FILE_MEM_EXCLUSIVE:
*s++ = is_mem_exclusive(cs) ? '1' : '0';
break;
case FILE_NOTIFY_ON_RELEASE:
*s++ = notify_on_release(cs) ? '1' : '0';
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 ssize_t cpuset_file_read(struct file *file, char __user *buf, size_t nbytes,
loff_t *ppos)
{
ssize_t retval = 0;
struct cftype *cft = __d_cft(file->f_dentry);
if (!cft)
return -ENODEV;
/* special function ? */
if (cft->read)
retval = cft->read(file, buf, nbytes, ppos);
else
retval = cpuset_common_file_read(file, buf, nbytes, ppos);
return retval;
}
static int cpuset_file_open(struct inode *inode, struct file *file)
{
int err;
struct cftype *cft;
err = generic_file_open(inode, file);
if (err)
return err;
cft = __d_cft(file->f_dentry);
if (!cft)
return -ENODEV;
if (cft->open)
err = cft->open(inode, file);
else
err = 0;
return err;
}
static int cpuset_file_release(struct inode *inode, struct file *file)
{
struct cftype *cft = __d_cft(file->f_dentry);
if (cft->release)
return cft->release(inode, file);
return 0;
}
/*
* cpuset_rename - Only allow simple rename of directories in place.
*/
static int cpuset_rename(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry)
{
if (!S_ISDIR(old_dentry->d_inode->i_mode))
return -ENOTDIR;
if (new_dentry->d_inode)
return -EEXIST;
if (old_dir != new_dir)
return -EIO;
return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
}
static struct file_operations cpuset_file_operations = {
.read = cpuset_file_read,
.write = cpuset_file_write,
.llseek = generic_file_llseek,
.open = cpuset_file_open,
.release = cpuset_file_release,
};
static struct inode_operations cpuset_dir_inode_operations = {
.lookup = simple_lookup,
.mkdir = cpuset_mkdir,
.rmdir = cpuset_rmdir,
.rename = cpuset_rename,
};
static int cpuset_create_file(struct dentry *dentry, int mode)
{
struct inode *inode;
if (!dentry)
return -ENOENT;
if (dentry->d_inode)
return -EEXIST;
inode = cpuset_new_inode(mode);
if (!inode)
return -ENOMEM;
if (S_ISDIR(mode)) {
inode->i_op = &cpuset_dir_inode_operations;
inode->i_fop = &simple_dir_operations;
/* start off with i_nlink == 2 (for "." entry) */
inode->i_nlink++;
} else if (S_ISREG(mode)) {
inode->i_size = 0;
inode->i_fop = &cpuset_file_operations;
}
d_instantiate(dentry, inode);
dget(dentry); /* Extra count - pin the dentry in core */
return 0;
}
/*
* cpuset_create_dir - create a directory for an object.
* cs: the cpuset we create the directory for.
* It must have a valid ->parent field
* And we are going to fill its ->dentry field.
* name: The name to give to the cpuset directory. Will be copied.
* mode: mode to set on new directory.
*/
static int cpuset_create_dir(struct cpuset *cs, const char *name, int mode)
{
struct dentry *dentry = NULL;
struct dentry *parent;
int error = 0;
parent = cs->parent->dentry;
dentry = cpuset_get_dentry(parent, name);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
error = cpuset_create_file(dentry, S_IFDIR | mode);
if (!error) {
dentry->d_fsdata = cs;
parent->d_inode->i_nlink++;
cs->dentry = dentry;
}
dput(dentry);
return error;
}
static int cpuset_add_file(struct dentry *dir, const struct cftype *cft)
{
struct dentry *dentry;
int error;
down(&dir->d_inode->i_sem);
dentry = cpuset_get_dentry(dir, cft->name);
if (!IS_ERR(dentry)) {
error = cpuset_create_file(dentry, 0644 | S_IFREG);
if (!error)
dentry->d_fsdata = (void *)cft;
dput(dentry);
} else
error = PTR_ERR(dentry);
up(&dir->d_inode->i_sem);
return error;
}
/*
* Stuff for reading the 'tasks' file.
*
* Reading this file can return large amounts of data if a cpuset has
* *lots* of attached tasks. So it may need several calls to read(),
* but we cannot guarantee that the information we produce is correct
* unless we produce it entirely atomically.
*
* Upon tasks file open(), a struct ctr_struct is allocated, that
* will have a pointer to an array (also allocated here). The struct
* ctr_struct * is stored in file->private_data. Its resources will
* be freed by release() when the file is closed. The array is used
* to sprintf the PIDs and then used by read().
*/
/* cpusets_tasks_read array */
struct ctr_struct {
char *buf;
int bufsz;
};
/*
* Load into 'pidarray' up to 'npids' of the tasks using cpuset 'cs'.
* Return actual number of pids loaded. No need to task_lock(p)
* when reading out p->cpuset, as we don't really care if it changes
* on the next cycle, and we are not going to try to dereference it.
*/
static inline int pid_array_load(pid_t *pidarray, int npids, struct cpuset *cs)
{
int n = 0;
struct task_struct *g, *p;
read_lock(&tasklist_lock);
do_each_thread(g, p) {
if (p->cpuset == cs) {
pidarray[n++] = p->pid;
if (unlikely(n == npids))
goto array_full;
}
} while_each_thread(g, p);
array_full:
read_unlock(&tasklist_lock);
return n;
}
static int cmppid(const void *a, const void *b)
{
return *(pid_t *)a - *(pid_t *)b;
}
/*
* Convert array 'a' of 'npids' pid_t's to a string of newline separated
* decimal pids in 'buf'. Don't write more than 'sz' chars, but return
* count 'cnt' of how many chars would be written if buf were large enough.
*/
static int pid_array_to_buf(char *buf, int sz, pid_t *a, int npids)
{
int cnt = 0;
int i;
for (i = 0; i < npids; i++)
cnt += snprintf(buf + cnt, max(sz - cnt, 0), "%d\n", a[i]);
return cnt;
}
/*
* Handle an open on 'tasks' file. Prepare a buffer listing the
* process id's of tasks currently attached to the cpuset being opened.
*
* Does not require any specific cpuset semaphores, and does not take any.
*/
static int cpuset_tasks_open(struct inode *unused, struct file *file)
{
struct cpuset *cs = __d_cs(file->f_dentry->d_parent);
struct ctr_struct *ctr;
pid_t *pidarray;
int npids;
char c;
if (!(file->f_mode & FMODE_READ))
return 0;
ctr = kmalloc(sizeof(*ctr), GFP_KERNEL);
if (!ctr)
goto err0;
/*
* If cpuset gets more users after we read count, we won't have
* enough space - tough. This race is indistinguishable to the
* caller from the case that the additional cpuset users didn't
* show up until sometime later on.
*/
npids = atomic_read(&cs->count);
pidarray = kmalloc(npids * sizeof(pid_t), GFP_KERNEL);
if (!pidarray)
goto err1;
npids = pid_array_load(pidarray, npids, cs);
sort(pidarray, npids, sizeof(pid_t), cmppid, NULL);
/* Call pid_array_to_buf() twice, first just to get bufsz */
ctr->bufsz = pid_array_to_buf(&c, sizeof(c), pidarray, npids) + 1;
ctr->buf = kmalloc(ctr->bufsz, GFP_KERNEL);
if (!ctr->buf)
goto err2;
ctr->bufsz = pid_array_to_buf(ctr->buf, ctr->bufsz, pidarray, npids);
kfree(pidarray);
file->private_data = ctr;
return 0;
err2:
kfree(pidarray);
err1:
kfree(ctr);
err0:
return -ENOMEM;
}
static ssize_t cpuset_tasks_read(struct file *file, char __user *buf,
size_t nbytes, loff_t *ppos)
{
struct ctr_struct *ctr = file->private_data;
if (*ppos + nbytes > ctr->bufsz)
nbytes = ctr->bufsz - *ppos;
if (copy_to_user(buf, ctr->buf + *ppos, nbytes))
return -EFAULT;
*ppos += nbytes;
return nbytes;
}
static int cpuset_tasks_release(struct inode *unused_inode, struct file *file)
{
struct ctr_struct *ctr;
if (file->f_mode & FMODE_READ) {
ctr = file->private_data;
kfree(ctr->buf);
kfree(ctr);
}
return 0;
}
/*
* for the common functions, 'private' gives the type of file
*/
static struct cftype cft_tasks = {
.name = "tasks",
.open = cpuset_tasks_open,
.read = cpuset_tasks_read,
.release = cpuset_tasks_release,
.private = FILE_TASKLIST,
};
static struct cftype cft_cpus = {
.name = "cpus",
.private = FILE_CPULIST,
};
static struct cftype cft_mems = {
.name = "mems",
.private = FILE_MEMLIST,
};
static struct cftype cft_cpu_exclusive = {
.name = "cpu_exclusive",
.private = FILE_CPU_EXCLUSIVE,
};
static struct cftype cft_mem_exclusive = {
.name = "mem_exclusive",
.private = FILE_MEM_EXCLUSIVE,
};
static struct cftype cft_notify_on_release = {
.name = "notify_on_release",
.private = FILE_NOTIFY_ON_RELEASE,
};
static int cpuset_populate_dir(struct dentry *cs_dentry)
{
int err;
if ((err = cpuset_add_file(cs_dentry, &cft_cpus)) < 0)
return err;
if ((err = cpuset_add_file(cs_dentry, &cft_mems)) < 0)
return err;
if ((err = cpuset_add_file(cs_dentry, &cft_cpu_exclusive)) < 0)
return err;
if ((err = cpuset_add_file(cs_dentry, &cft_mem_exclusive)) < 0)
return err;
if ((err = cpuset_add_file(cs_dentry, &cft_notify_on_release)) < 0)
return err;
if ((err = cpuset_add_file(cs_dentry, &cft_tasks)) < 0)
return err;
return 0;
}
/*
* cpuset_create - create a cpuset
* parent: cpuset that will be parent of the new cpuset.
* name: name of the new cpuset. Will be strcpy'ed.
* mode: mode to set on new inode
*
* Must be called with the semaphore on the parent inode held
*/
static long cpuset_create(struct cpuset *parent, const char *name, int mode)
{
struct cpuset *cs;
int err;
cs = kmalloc(sizeof(*cs), GFP_KERNEL);
if (!cs)
return -ENOMEM;
down(&manage_sem);
refresh_mems();
cs->flags = 0;
if (notify_on_release(parent))
set_bit(CS_NOTIFY_ON_RELEASE, &cs->flags);
cs->cpus_allowed = CPU_MASK_NONE;
cs->mems_allowed = NODE_MASK_NONE;
atomic_set(&cs->count, 0);
INIT_LIST_HEAD(&cs->sibling);
INIT_LIST_HEAD(&cs->children);
atomic_inc(&cpuset_mems_generation);
cs->mems_generation = atomic_read(&cpuset_mems_generation);
cs->parent = parent;
down(&callback_sem);
list_add(&cs->sibling, &cs->parent->children);
up(&callback_sem);
err = cpuset_create_dir(cs, name, mode);
if (err < 0)
goto err;
/*
* Release manage_sem before cpuset_populate_dir() because it
* will down() this new directory's i_sem and if we race with
* another mkdir, we might deadlock.
*/
up(&manage_sem);
err = cpuset_populate_dir(cs->dentry);
/* If err < 0, we have a half-filled directory - oh well ;) */
return 0;
err:
list_del(&cs->sibling);
up(&manage_sem);
kfree(cs);
return err;
}
static int cpuset_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
struct cpuset *c_parent = dentry->d_parent->d_fsdata;
/* the vfs holds inode->i_sem already */
return cpuset_create(c_parent, dentry->d_name.name, mode | S_IFDIR);
}
static int cpuset_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
struct cpuset *cs = dentry->d_fsdata;
struct dentry *d;
struct cpuset *parent;
char *pathbuf = NULL;
/* the vfs holds both inode->i_sem already */
down(&manage_sem);
refresh_mems();
if (atomic_read(&cs->count) > 0) {
up(&manage_sem);
return -EBUSY;
}
if (!list_empty(&cs->children)) {
up(&manage_sem);
return -EBUSY;
}
parent = cs->parent;
down(&callback_sem);
set_bit(CS_REMOVED, &cs->flags);
if (is_cpu_exclusive(cs))
update_cpu_domains(cs);
list_del(&cs->sibling); /* delete my sibling from parent->children */
spin_lock(&cs->dentry->d_lock);
d = dget(cs->dentry);
cs->dentry = NULL;
spin_unlock(&d->d_lock);
cpuset_d_remove_dir(d);
dput(d);
up(&callback_sem);
if (list_empty(&parent->children))
check_for_release(parent, &pathbuf);
up(&manage_sem);
cpuset_release_agent(pathbuf);
return 0;
}
/**
* cpuset_init - initialize cpusets at system boot
*
* Description: Initialize top_cpuset and the cpuset internal file system,
**/
int __init cpuset_init(void)
{
struct dentry *root;
int err;
top_cpuset.cpus_allowed = CPU_MASK_ALL;
top_cpuset.mems_allowed = NODE_MASK_ALL;
atomic_inc(&cpuset_mems_generation);
top_cpuset.mems_generation = atomic_read(&cpuset_mems_generation);
init_task.cpuset = &top_cpuset;
err = register_filesystem(&cpuset_fs_type);
if (err < 0)
goto out;
cpuset_mount = kern_mount(&cpuset_fs_type);
if (IS_ERR(cpuset_mount)) {
printk(KERN_ERR "cpuset: could not mount!\n");
err = PTR_ERR(cpuset_mount);
cpuset_mount = NULL;
goto out;
}
root = cpuset_mount->mnt_sb->s_root;
root->d_fsdata = &top_cpuset;
root->d_inode->i_nlink++;
top_cpuset.dentry = root;
root->d_inode->i_op = &cpuset_dir_inode_operations;
err = cpuset_populate_dir(root);
out:
return err;
}
/**
* cpuset_init_smp - initialize cpus_allowed
*
* Description: Finish top cpuset after cpu, node maps are initialized
**/
void __init cpuset_init_smp(void)
{
top_cpuset.cpus_allowed = cpu_online_map;
top_cpuset.mems_allowed = node_online_map;
}
/**
* cpuset_fork - attach newly forked task to its parents cpuset.
* @tsk: pointer to task_struct of forking parent process.
*
* Description: A task inherits its parent's cpuset at fork().
*
* A pointer to the shared cpuset was automatically copied in fork.c
* by dup_task_struct(). However, we ignore that copy, since it was
* not made under the protection of task_lock(), so might no longer be
* a valid cpuset pointer. attach_task() might have already changed
* current->cpuset, allowing the previously referenced cpuset to
* be removed and freed. Instead, we task_lock(current) and copy
* its present value of current->cpuset for our freshly forked child.
*
* At the point that cpuset_fork() is called, 'current' is the parent
* task, and the passed argument 'child' points to the child task.
**/
void cpuset_fork(struct task_struct *child)
{
task_lock(current);
child->cpuset = current->cpuset;
atomic_inc(&child->cpuset->count);
task_unlock(current);
}
/**
* cpuset_exit - detach cpuset from exiting task
* @tsk: pointer to task_struct of exiting process
*
* Description: Detach cpuset from @tsk and release it.
*
* Note that cpusets marked notify_on_release force every task in
* them to take the global manage_sem semaphore when exiting.
* This could impact scaling on very large systems. Be reluctant to
* use notify_on_release cpusets where very high task exit scaling
* is required on large systems.
*
* Don't even think about derefencing 'cs' after the cpuset use count
* goes to zero, except inside a critical section guarded by manage_sem
* or callback_sem. Otherwise a zero cpuset use count is a license to
* any other task to nuke the cpuset immediately, via cpuset_rmdir().
*
* This routine has to take manage_sem, not callback_sem, because
* it is holding that semaphore while calling check_for_release(),
* which calls kmalloc(), so can't be called holding callback__sem().
*
* We don't need to task_lock() this reference to tsk->cpuset,
* because tsk is already marked PF_EXITING, so attach_task() won't
* mess with it.
**/
void cpuset_exit(struct task_struct *tsk)
{
struct cpuset *cs;
BUG_ON(!(tsk->flags & PF_EXITING));
cs = tsk->cpuset;
tsk->cpuset = NULL;
if (notify_on_release(cs)) {
char *pathbuf = NULL;
down(&manage_sem);
if (atomic_dec_and_test(&cs->count))
check_for_release(cs, &pathbuf);
up(&manage_sem);
cpuset_release_agent(pathbuf);
} else {
atomic_dec(&cs->count);
}
}
/**
* cpuset_cpus_allowed - return cpus_allowed mask from a tasks cpuset.
* @tsk: pointer to task_struct from which to obtain cpuset->cpus_allowed.
*
* Description: Returns the cpumask_t cpus_allowed of the cpuset
* attached to the specified @tsk. Guaranteed to return some non-empty
* subset of cpu_online_map, even if this means going outside the
* tasks cpuset.
**/
cpumask_t cpuset_cpus_allowed(const struct task_struct *tsk)
{
cpumask_t mask;
down(&callback_sem);
task_lock((struct task_struct *)tsk);
guarantee_online_cpus(tsk->cpuset, &mask);
task_unlock((struct task_struct *)tsk);
up(&callback_sem);
return mask;
}
void cpuset_init_current_mems_allowed(void)
{
current->mems_allowed = NODE_MASK_ALL;
}
/**
* cpuset_update_current_mems_allowed - update mems parameters to new values
*
* If the current tasks cpusets mems_allowed changed behind our backs,
* update current->mems_allowed and mems_generation to the new value.
* Do not call this routine if in_interrupt().
*
* Call without callback_sem or task_lock() held. May be called
* with or without manage_sem held. Unless exiting, it will acquire
* task_lock(). Also might acquire callback_sem during call to
* refresh_mems().
*/
void cpuset_update_current_mems_allowed(void)
{
struct cpuset *cs;
int need_to_refresh = 0;
task_lock(current);
cs = current->cpuset;
if (!cs)
goto done;
if (current->cpuset_mems_generation != cs->mems_generation)
need_to_refresh = 1;
done:
task_unlock(current);
if (need_to_refresh)
refresh_mems();
}
/**
* cpuset_restrict_to_mems_allowed - limit nodes to current mems_allowed
* @nodes: pointer to a node bitmap that is and-ed with mems_allowed
*/
void cpuset_restrict_to_mems_allowed(unsigned long *nodes)
{
bitmap_and(nodes, nodes, nodes_addr(current->mems_allowed),
MAX_NUMNODES);
}
/**
* cpuset_zonelist_valid_mems_allowed - check zonelist vs. curremt mems_allowed
* @zl: the zonelist to be checked
*
* Are any of the nodes on zonelist zl allowed in current->mems_allowed?
*/
int cpuset_zonelist_valid_mems_allowed(struct zonelist *zl)
{
int i;
for (i = 0; zl->zones[i]; i++) {
int nid = zl->zones[i]->zone_pgdat->node_id;
if (node_isset(nid, current->mems_allowed))
return 1;
}
return 0;
}
/*
* nearest_exclusive_ancestor() - Returns the nearest mem_exclusive
* ancestor to the specified cpuset. Call holding callback_sem.
* If no ancestor is mem_exclusive (an unusual configuration), then
* returns the root cpuset.
*/
static const struct cpuset *nearest_exclusive_ancestor(const struct cpuset *cs)
{
while (!is_mem_exclusive(cs) && cs->parent)
cs = cs->parent;
return cs;
}
/**
* cpuset_zone_allowed - Can we allocate memory on zone z's memory node?
* @z: is this zone on an allowed node?
* @gfp_mask: memory allocation flags (we use __GFP_HARDWALL)
*
* If we're in interrupt, yes, we can always allocate. If zone
* z's node is in our tasks mems_allowed, yes. If it's not a
* __GFP_HARDWALL request and this zone's nodes is in the nearest
* mem_exclusive cpuset ancestor to this tasks cpuset, yes.
* Otherwise, no.
*
* GFP_USER allocations are marked with the __GFP_HARDWALL bit,
* and do not allow allocations outside the current tasks cpuset.
* GFP_KERNEL allocations are not so marked, so can escape to the
* nearest mem_exclusive ancestor cpuset.
*
* Scanning up parent cpusets requires callback_sem. The __alloc_pages()
* routine only calls here with __GFP_HARDWALL bit _not_ set if
* it's a GFP_KERNEL allocation, and all nodes in the current tasks
* mems_allowed came up empty on the first pass over the zonelist.
* So only GFP_KERNEL allocations, if all nodes in the cpuset are
* short of memory, might require taking the callback_sem semaphore.
*
* The first loop over the zonelist in mm/page_alloc.c:__alloc_pages()
* calls here with __GFP_HARDWALL always set in gfp_mask, enforcing
* hardwall cpusets - no allocation on a node outside the cpuset is
* allowed (unless in interrupt, of course).
*
* The second loop doesn't even call here for GFP_ATOMIC requests
* (if the __alloc_pages() local variable 'wait' is set). That check
* and the checks below have the combined affect in the second loop of
* the __alloc_pages() routine that:
* in_interrupt - any node ok (current task context irrelevant)
* GFP_ATOMIC - any node ok
* GFP_KERNEL - any node in enclosing mem_exclusive cpuset ok
* GFP_USER - only nodes in current tasks mems allowed ok.
**/
int cpuset_zone_allowed(struct zone *z, gfp_t gfp_mask)
{
int node; /* node that zone z is on */
const struct cpuset *cs; /* current cpuset ancestors */
int allowed = 1; /* is allocation in zone z allowed? */
if (in_interrupt())
return 1;
node = z->zone_pgdat->node_id;
if (node_isset(node, current->mems_allowed))
return 1;
if (gfp_mask & __GFP_HARDWALL) /* If hardwall request, stop here */
return 0;
/* Not hardwall and node outside mems_allowed: scan up cpusets */
down(&callback_sem);
if (current->flags & PF_EXITING) /* Let dying task have memory */
return 1;
task_lock(current);
cs = nearest_exclusive_ancestor(current->cpuset);
task_unlock(current);
allowed = node_isset(node, cs->mems_allowed);
up(&callback_sem);
return allowed;
}
/**
* cpuset_excl_nodes_overlap - Do we overlap @p's mem_exclusive ancestors?
* @p: pointer to task_struct of some other task.
*
* Description: Return true if the nearest mem_exclusive ancestor
* cpusets of tasks @p and current overlap. Used by oom killer to
* determine if task @p's memory usage might impact the memory
* available to the current task.
*
* Acquires callback_sem - not suitable for calling from a fast path.
**/
int cpuset_excl_nodes_overlap(const struct task_struct *p)
{
const struct cpuset *cs1, *cs2; /* my and p's cpuset ancestors */
int overlap = 0; /* do cpusets overlap? */
down(&callback_sem);
task_lock(current);
if (current->flags & PF_EXITING) {
task_unlock(current);
goto done;
}
cs1 = nearest_exclusive_ancestor(current->cpuset);
task_unlock(current);
task_lock((struct task_struct *)p);
if (p->flags & PF_EXITING) {
task_unlock((struct task_struct *)p);
goto done;
}
cs2 = nearest_exclusive_ancestor(p->cpuset);
task_unlock((struct task_struct *)p);
overlap = nodes_intersects(cs1->mems_allowed, cs2->mems_allowed);
done:
up(&callback_sem);
return overlap;
}
/*
* 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 manage_sem, keeping attach_task() from changing it
* anyway.
*/
static int proc_cpuset_show(struct seq_file *m, void *v)
{
struct cpuset *cs;
struct task_struct *tsk;
char *buf;
int retval = 0;
buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!buf)
return -ENOMEM;
tsk = m->private;
down(&manage_sem);
cs = tsk->cpuset;
if (!cs) {
retval = -EINVAL;
goto out;
}
retval = cpuset_path(cs, buf, PAGE_SIZE);
if (retval < 0)
goto out;
seq_puts(m, buf);
seq_putc(m, '\n');
out:
up(&manage_sem);
kfree(buf);
return retval;
}
static int cpuset_open(struct inode *inode, struct file *file)
{
struct task_struct *tsk = PROC_I(inode)->task;
return single_open(file, proc_cpuset_show, tsk);
}
struct file_operations proc_cpuset_operations = {
.open = cpuset_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
/* Display task cpus_allowed, mems_allowed in /proc/<pid>/status file. */
char *cpuset_task_status_allowed(struct task_struct *task, char *buffer)
{
buffer += sprintf(buffer, "Cpus_allowed:\t");
buffer += cpumask_scnprintf(buffer, PAGE_SIZE, task->cpus_allowed);
buffer += sprintf(buffer, "\n");
buffer += sprintf(buffer, "Mems_allowed:\t");
buffer += nodemask_scnprintf(buffer, PAGE_SIZE, task->mems_allowed);
buffer += sprintf(buffer, "\n");
return buffer;
}