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Message-Id: <1365964619-14762-2-git-send-email-tj@kernel.org>
Date: Sun, 14 Apr 2013 11:36:56 -0700
From: Tejun Heo <tj@...nel.org>
To: lizefan@...wei.com
Cc: containers@...ts.linux-foundation.org, cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org, kay@...y.org, greg@...ah.com,
lennart@...ttering.net, daniel@...que.org,
Tejun Heo <tj@...nel.org>
Subject: [PATCH 1/4] cgroup: refactor hierarchy_id handling
We're planning to converting hierarchy_ida to an idr and use it to
look up hierarchy from its id. As we want the mapping to happen
atomically with cgroupfs_root registration, this patch refactors
hierarchy_id init / exit so that ida operations happen inside
cgroup_[root_]mutex.
* s/init_root_id()/cgroup_init_root_id()/ and make it return 0 or
-errno like a normal function.
* Move hierarchy_id initialization from cgroup_root_from_opts() into
cgroup_mount() block where the root is confirmed to be used and
being registered while holding both mutexes.
* Split cgroup_drop_id() into cgroup_exit_root_id() and
cgroup_free_root(), so that ID release can happen before dropping
the mutexes in cgroup_kill_sb(). The latter expects hierarchy_id to
be exited before being invoked.
Signed-off-by: Tejun Heo <tj@...nel.org>
---
kernel/cgroup.c | 56 +++++++++++++++++++++++++++++++++++---------------------
1 file changed, 35 insertions(+), 21 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a790409..823cb56 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1452,13 +1452,13 @@ static void init_cgroup_root(struct cgroupfs_root *root)
list_add_tail(&cgrp->allcg_node, &root->allcg_list);
}
-static bool init_root_id(struct cgroupfs_root *root)
+static int cgroup_init_root_id(struct cgroupfs_root *root)
{
- int ret = 0;
+ int ret;
do {
if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL))
- return false;
+ return -ENOMEM;
spin_lock(&hierarchy_id_lock);
/* Try to allocate the next unused ID */
ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id,
@@ -1474,7 +1474,18 @@ static bool init_root_id(struct cgroupfs_root *root)
}
spin_unlock(&hierarchy_id_lock);
} while (ret);
- return true;
+ return 0;
+}
+
+static void cgroup_exit_root_id(struct cgroupfs_root *root)
+{
+ if (root->hierarchy_id) {
+ spin_lock(&hierarchy_id_lock);
+ ida_remove(&hierarchy_ida, root->hierarchy_id);
+ spin_unlock(&hierarchy_id_lock);
+
+ root->hierarchy_id = 0;
+ }
}
static int cgroup_test_super(struct super_block *sb, void *data)
@@ -1508,10 +1519,6 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
if (!root)
return ERR_PTR(-ENOMEM);
- if (!init_root_id(root)) {
- kfree(root);
- return ERR_PTR(-ENOMEM);
- }
init_cgroup_root(root);
root->subsys_mask = opts->subsys_mask;
@@ -1526,17 +1533,15 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
return root;
}
-static void cgroup_drop_root(struct cgroupfs_root *root)
+static void cgroup_free_root(struct cgroupfs_root *root)
{
- if (!root)
- return;
+ if (root) {
+ /* hierarhcy ID shoulid already have been released */
+ WARN_ON_ONCE(root->hierarchy_id);
- BUG_ON(!root->hierarchy_id);
- spin_lock(&hierarchy_id_lock);
- ida_remove(&hierarchy_ida, root->hierarchy_id);
- spin_unlock(&hierarchy_id_lock);
- ida_destroy(&root->cgroup_ida);
- kfree(root);
+ ida_destroy(&root->cgroup_ida);
+ kfree(root);
+ }
}
static int cgroup_set_super(struct super_block *sb, void *data)
@@ -1623,7 +1628,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts);
if (IS_ERR(sb)) {
ret = PTR_ERR(sb);
- cgroup_drop_root(opts.new_root);
+ cgroup_free_root(opts.new_root);
goto drop_modules;
}
@@ -1667,6 +1672,10 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
if (ret)
goto unlock_drop;
+ ret = cgroup_init_root_id(root);
+ if (ret)
+ goto unlock_drop;
+
ret = rebind_subsystems(root, root->subsys_mask);
if (ret == -EBUSY) {
free_cg_links(&tmp_cg_links);
@@ -1710,7 +1719,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
* We re-used an existing hierarchy - the new root (if
* any) is not needed
*/
- cgroup_drop_root(opts.new_root);
+ cgroup_free_root(opts.new_root);
/* no subsys rebinding, so refcounts don't change */
drop_parsed_module_refcounts(opts.subsys_mask);
}
@@ -1720,6 +1729,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
return dget(sb->s_root);
unlock_drop:
+ cgroup_exit_root_id(root);
mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&inode->i_mutex);
@@ -1772,13 +1782,15 @@ static void cgroup_kill_sb(struct super_block *sb) {
root_count--;
}
+ cgroup_exit_root_id(root);
+
mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
simple_xattrs_free(&cgrp->xattrs);
kill_litter_super(sb);
- cgroup_drop_root(root);
+ cgroup_free_root(root);
}
static struct file_system_type cgroup_fs_type = {
@@ -4642,7 +4654,9 @@ int __init cgroup_init(void)
/* Add init_css_set to the hash table */
key = css_set_hash(init_css_set.subsys);
hash_add(css_set_table, &init_css_set.hlist, key);
- BUG_ON(!init_root_id(&rootnode));
+
+ /* allocate id for the dummy hierarchy */
+ BUG_ON(cgroup_init_root_id(&rootnode));
cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
if (!cgroup_kobj) {
--
1.8.1.4
--
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