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cgroup: convert cgroup_cft_commit() to use cgroup_for_each_descendant_pre()

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We used root->allcg_list to iterate cgroup hierarchy because at that time
cgroup_for_each_descendant_pre() hasn't been invented.

tj: In cgroup_cfts_commit(), s/@serial_nr/@update_upto/, move the
    assignment right above releasing cgroup_mutex and explain what's
    going on there.

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Li Zefan 2013-06-18 18:48:37 +08:00 committed by Tejun Heo
parent 794611a1df
commit e8c82d20a9
2 changed files with 44 additions and 42 deletions
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6
include/linux/cgroup.h
View file

@ -206,9 +206,6 @@ struct cgroup {
*/
struct list_head cset_links;
struct list_head allcg_node; /* cgroupfs_root->allcg_list */
struct list_head cft_q_node; /* used during cftype add/rm */
/*
* Linked list running through all cgroups that can
* potentially be reaped by the release agent. Protected by
@ -313,9 +310,6 @@ struct cgroupfs_root {
/* A list running through the active hierarchies */
struct list_head root_list;
/* All cgroups on this root, cgroup_mutex protected */
struct list_head allcg_list;
/* Hierarchy-specific flags */
unsigned long flags;

80
kernel/cgroup.c
View file

@ -1399,7 +1399,6 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp)
INIT_LIST_HEAD(&cgrp->children);
INIT_LIST_HEAD(&cgrp->files);
INIT_LIST_HEAD(&cgrp->cset_links);
INIT_LIST_HEAD(&cgrp->allcg_node);
INIT_LIST_HEAD(&cgrp->release_list);
INIT_LIST_HEAD(&cgrp->pidlists);
mutex_init(&cgrp->pidlist_mutex);
@ -1414,12 +1413,10 @@ static void init_cgroup_root(struct cgroupfs_root *root)
INIT_LIST_HEAD(&root->subsys_list);
INIT_LIST_HEAD(&root->root_list);
INIT_LIST_HEAD(&root->allcg_list);
root->number_of_cgroups = 1;
cgrp->root = root;
cgrp->name = &root_cgroup_name;
init_cgroup_housekeeping(cgrp);
list_add_tail(&cgrp->allcg_node, &root->allcg_list);
}
static int cgroup_init_root_id(struct cgroupfs_root *root)
@ -2785,65 +2782,78 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
return ret;
}
static DEFINE_MUTEX(cgroup_cft_mutex);
static void cgroup_cfts_prepare(void)
__acquires(&cgroup_cft_mutex) __acquires(&cgroup_mutex)
__acquires(&cgroup_mutex)
{
/*
* Thanks to the entanglement with vfs inode locking, we can't walk
* the existing cgroups under cgroup_mutex and create files.
* Instead, we increment reference on all cgroups and build list of
* them using @cgrp->cft_q_node. Grab cgroup_cft_mutex to ensure
* exclusive access to the field.
* Instead, we use cgroup_for_each_descendant_pre() and drop RCU
* read lock before calling cgroup_addrm_files().
*/
mutex_lock(&cgroup_cft_mutex);
mutex_lock(&cgroup_mutex);
}
static void cgroup_cfts_commit(struct cgroup_subsys *ss,
struct cftype *cfts, bool is_add)
__releases(&cgroup_mutex) __releases(&cgroup_cft_mutex)
__releases(&cgroup_mutex)
{
LIST_HEAD(pending);
struct cgroup *cgrp, *n;
struct cgroup *cgrp, *root = &ss->root->top_cgroup;
struct super_block *sb = ss->root->sb;
struct dentry *prev = NULL;
struct inode *inode;
u64 update_upto;
/* %NULL @cfts indicates abort and don't bother if @ss isn't attached */
if (cfts && ss->root != &rootnode &&
atomic_inc_not_zero(sb->s_active)) {
list_for_each_entry(cgrp, &ss->root->allcg_list, allcg_node) {
dget(cgrp->dentry);
list_add_tail(&cgrp->cft_q_node, &pending);
}
} else {
sb = NULL;
if (!cfts || ss->root == &rootnode ||
!atomic_inc_not_zero(&sb->s_active)) {
mutex_unlock(&cgroup_mutex);
return;
}
/*
* All cgroups which are created after we drop cgroup_mutex will
* have the updated set of files, so we only need to update the
* cgroups created before the current @cgroup_serial_nr_cursor.
*/
update_upto = atomic64_read(&cgroup_serial_nr_cursor);
mutex_unlock(&cgroup_mutex);
/*
* All new cgroups will see @cfts update on @ss->cftsets. Add/rm
* files for all cgroups which were created before.
*/
list_for_each_entry_safe(cgrp, n, &pending, cft_q_node) {
struct inode *inode = cgrp->dentry->d_inode;
/* @root always needs to be updated */
inode = root->dentry->d_inode;
mutex_lock(&inode->i_mutex);
mutex_lock(&cgroup_mutex);
cgroup_addrm_files(root, ss, cfts, is_add);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&inode->i_mutex);
/* add/rm files for all cgroups created before */
rcu_read_lock();
cgroup_for_each_descendant_pre(cgrp, root) {
if (cgroup_is_dead(cgrp))
continue;
inode = cgrp->dentry->d_inode;
dget(cgrp->dentry);
rcu_read_unlock();
dput(prev);
prev = cgrp->dentry;
mutex_lock(&inode->i_mutex);
mutex_lock(&cgroup_mutex);
if (!cgroup_is_dead(cgrp))
if (cgrp->serial_nr <= update_upto && !cgroup_is_dead(cgrp))
cgroup_addrm_files(cgrp, ss, cfts, is_add);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&inode->i_mutex);
list_del_init(&cgrp->cft_q_node);
dput(cgrp->dentry);
rcu_read_lock();
}
if (sb)
deactivate_super(sb);
mutex_unlock(&cgroup_cft_mutex);
rcu_read_unlock();
dput(prev);
deactivate_super(sb);
}
/**
@ -4320,7 +4330,6 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
cgrp->serial_nr = atomic64_inc_return(&cgroup_serial_nr_cursor);
/* allocation complete, commit to creation */
list_add_tail(&cgrp->allcg_node, &root->allcg_list);
list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
root->number_of_cgroups++;
@ -4559,7 +4568,6 @@ static void cgroup_offline_fn(struct work_struct *work)
/* delete this cgroup from parent->children */
list_del_rcu(&cgrp->sibling);
list_del_init(&cgrp->allcg_node);
dput(d);