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Date: Tue, 18 Jun 2013 18:48:37 +0800
From: Li Zefan <lizefan@...wei.com>
To: Tejun Heo <tj@...nel.org>
CC: LKML <linux-kernel@...r.kernel.org>,
cgroups <cgroups@...r.kernel.org>
Subject: [PATCH 2/2] cgroup: convert cgroup_cft_commit() to use cgroup_for_each_descendant_pre()
We used root->allcg_list to iterate cgroup hierarchy because at that time
cgroup_for_each_descendant_pre() hasn't been invented.
Signed-off-by: Li Zefan <lizefan@...wei.com>
---
include/linux/cgroup.h | 6 -----
kernel/cgroup.c | 62 +++++++++++++++++++++++++++-----------------------
2 files changed, 33 insertions(+), 35 deletions(-)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 835918c..f70b116 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -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
@@ -317,9 +314,6 @@ 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;
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index b1d98f2..bc46c28 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -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)
@@ -2775,65 +2772,74 @@ 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 inode *inode;
+ struct dentry *prev = NULL;
+ u64 serial_nr = atomic64_read(&cgroup_serial_nr_cursor);
/* %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;
}
+ mutex_unlock(&cgroup_mutex);
+ 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);
/*
* 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;
+ 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 <= serial_nr && !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();
}
+ rcu_read_unlock();
+ dput(prev);
if (sb)
deactivate_super(sb);
-
- mutex_unlock(&cgroup_cft_mutex);
}
/**
@@ -4316,7 +4322,6 @@ 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++;
@@ -4555,7 +4560,6 @@ 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);
--
1.8.0.2
--
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