cgroup: fix root_count when mount fails due to busy subsystem
authorPaul Menage <menage@google.com>
Thu, 29 Jan 2009 22:25:22 +0000 (14:25 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 30 Jan 2009 02:04:45 +0000 (18:04 -0800)
root_count was being incremented in cgroup_get_sb() after all error
checking was complete, but decremented in cgroup_kill_sb(), which can be
called on a superblock that we gave up on due to an error.  This patch
changes cgroup_kill_sb() to only decrement root_count if the root was
previously linked into the list of roots.

Signed-off-by: Paul Menage <menage@google.com>
Tested-by: Serge Hallyn <serue@us.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kernel/cgroup.c

index 492215d67fa5c3f153f6b1de42416ec4a1653298..5a54ff42874ee916997139c859b8cfda725b9a33 100644 (file)
@@ -1115,8 +1115,10 @@ static void cgroup_kill_sb(struct super_block *sb) {
        }
        write_unlock(&css_set_lock);
 
-       list_del(&root->root_list);
-       root_count--;
+       if (!list_empty(&root->root_list)) {
+               list_del(&root->root_list);
+               root_count--;
+       }
 
        mutex_unlock(&cgroup_mutex);