>From e8c82d20a9f729cf4b9f73043f7fd4e0872bebfd Mon Sep 17 00:00:00 2001
From: Li Zefan <lizefan@xxxxxxxxxx>
Date: Tue, 18 Jun 2013 18:48:37 +0800
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@xxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
---
Applied to cgroup/for-3.11 with some minor updates.
Thanks.
include/linux/cgroup.h | 6 ----
kernel/cgroup.c | 80 +++++++++++++++++++++++++++-----------------------
2 files changed, 44 insertions(+), 42 deletions(-)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index f975227..b283658 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
@@ -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;
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index e6571ca..0ed7d8d 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)
@@ -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;
}
- mutex_unlock(&cgroup_mutex);
-
/*
- * All new cgroups will see @cfts update on @ss->cftsets. Add/rm
- * files for all cgroups which were created before.
+ * 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.
*/
- list_for_each_entry_safe(cgrp, n, &pending, cft_q_node) {
- struct inode *inode = cgrp->dentry->d_inode;
+ update_upto = atomic64_read(&cgroup_serial_nr_cursor);
+
+ mutex_unlock(&cgroup_mutex);
+
+ /* @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);
--
1.8.2.1
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