3.5.7.17 -stable review patch. If anyone has any objections, please let me know.
------------------ From: Li Zefan <[email protected]> commit 084457f284abf6789d90509ee11dae383842b23b upstream. cgroup_cfts_commit() uses dget() to keep cgroup alive after cgroup_mutex is dropped, but dget() won't prevent cgroupfs from being umounted. When the race happens, vfs will see some dentries with non-zero refcnt while umount is in process. Keep running this: mount -t cgroup -o blkio xxx /cgroup umount /cgroup And this: modprobe cfq-iosched rmmod cfs-iosched After a while, the BUG() in shrink_dcache_for_umount_subtree() may be triggered: BUG: Dentry xxx{i=0,n=blkio.yyy} still in use (1) [umount of cgroup cgroup] Signed-off-by: Li Zefan <[email protected]> Signed-off-by: Tejun Heo <[email protected]> [ luis: backported to 3.5: - fixed build error: added '&' to atomic_inc_not_zero parameter; this was fixed upstream by commit e8c82d20a9f729cf4b9f73043f7fd4e0872bebfd ] Signed-off-by: Luis Henriques <[email protected]> --- kernel/cgroup.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 07ba52a..3b3fa5b 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2771,13 +2771,17 @@ static void cgroup_cfts_commit(struct cgroup_subsys *ss, { LIST_HEAD(pending); struct cgroup *cgrp, *n; + struct super_block *sb = ss->root->sb; /* %NULL @cfts indicates abort and don't bother if @ss isn't attached */ - if (cfts && ss->root != &rootnode) { + if (cfts && ss->root != &rootnode && + atomic_inc_not_zero(&sb->s_active)) { list_for_each_entry(cgrp, &ss->root->allcg_list, allcg_node) { dget(cgrp->dentry); list_add_tail(&cgrp->cft_q_node, &pending); } + } else { + sb = NULL; } mutex_unlock(&cgroup_mutex); @@ -2800,6 +2804,9 @@ static void cgroup_cfts_commit(struct cgroup_subsys *ss, dput(cgrp->dentry); } + if (sb) + deactivate_super(sb); + mutex_unlock(&cgroup_cft_mutex); } -- 1.8.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
