[PATCH] quota: Fix WARN_ON in lookup_one_len

[Jan Kara]

We should hold i_mutex when looking up quota files for journaled quotas,
otherwise a WARN_ON in lookup_one_len triggers. The fact that we didn't
hold i_mutex previously probably could not lead to a real bug since the
filesystem is just being mounted / remounted read-write and thus the
root directory cannot change anyway but it's definitely cleaner with
i_mutex.

Reported-by: Bastien ROUCARIES <roucaries.bastien@xxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
 fs/quota/dquot.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 39b49c4..aa97df1 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -2233,7 +2233,9 @@ int vfs_quota_on_mount(struct super_block *sb, char *qf_name,
 	struct dentry *dentry;
 	int error;
 
+	mutex_lock(&sb->s_root->d_inode->i_mutex);
 	dentry = lookup_one_len(qf_name, sb->s_root, strlen(qf_name));
+	mutex_unlock(&sb->s_root->d_inode->i_mutex);
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 
-- 
1.6.0.2


--LQksG6bCIzRHxTLp--
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