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cgroup: refactor hierarchy_id handling

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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@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2013-04-14 11:36:56 -07:00
parent f722406faa
commit fa3ca07e96
1 changed files with 35 additions and 21 deletions
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56
kernel/cgroup.c
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@ -1426,13 +1426,13 @@ 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,
@ -1448,7 +1448,18 @@ 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)
@ -1482,10 +1493,6 @@ 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;
@ -1500,17 +1507,15 @@ 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)
@ -1597,7 +1602,7 @@ 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;
}
@ -1641,6 +1646,10 @@ 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);
@ -1684,7 +1693,7 @@ 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);
if (((root->flags | opts.flags) & CGRP_ROOT_SANE_BEHAVIOR) &&
root->flags != opts.flags) {
@ -1702,6 +1711,7 @@ 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);
@ -1754,13 +1764,15 @@ 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) {