From 0c7bf3e8cab7900e17ce7f97104c39927d835469 Mon Sep 17 00:00:00 2001 From: Zefan Li Date: Sat, 20 Sep 2014 14:49:10 +0800 Subject: [PATCH] cgroup: remove redundant variable in cgroup_mount() 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 Signed-off-by: Zefan Li Signed-off-by: Tejun Heo --- kernel/cgroup.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index f873c4681316..5eb20cd1709c 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -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; }