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cgroup: remove redundant variable in cgroup_mount()

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Both pinned_sb and new_sb indicate if a new superblock is needed,
so we can just remove new_sb.

Note now we must check if kernfs_tryget_sb() returns NULL, because
when it returns NULL, kernfs_mount() may still re-use an existing
superblock, which is just allocated by another concurent mount.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Zefan Li 2014-09-20 14:49:10 +08:00 committed by Tejun Heo
parent 3e2cd91ab9
commit 0c7bf3e8ca
1 changed files with 4 additions and 7 deletions
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11
kernel/cgroup.c
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@ -1694,7 +1694,6 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
struct dentry *dentry;
int ret;
int i;
bool new_sb;
/*
* The first time anyone tries to mount a cgroup, enable the list
@ -1785,7 +1784,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
* path is super cold. Let's just sleep a bit and retry.
*/
pinned_sb = kernfs_pin_sb(root->kf_root, NULL);
if (IS_ERR(pinned_sb) ||
if (IS_ERR_OR_NULL(pinned_sb) ||
!percpu_ref_tryget_live(&root->cgrp.self.refcnt)) {
mutex_unlock(&cgroup_mutex);
if (!IS_ERR_OR_NULL(pinned_sb))
@ -1831,18 +1830,16 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
return ERR_PTR(ret);
dentry = kernfs_mount(fs_type, flags, root->kf_root,
CGROUP_SUPER_MAGIC, &new_sb);
if (IS_ERR(dentry) || !new_sb)
CGROUP_SUPER_MAGIC, NULL);
if (IS_ERR(dentry) || pinned_sb)
cgroup_put(&root->cgrp);
/*
* If @pinned_sb, we're reusing an existing root and holding an
* extra ref on its sb. Mount is complete. Put the extra ref.
*/
if (pinned_sb) {
WARN_ON(new_sb);
if (pinned_sb)
deactivate_super(pinned_sb);
}
return dentry;
}