ext4: Fix hang on umount with quotas when journal is aborted

Call dquot_drop() from ext4_dquot_drop() even if we fail to start a
transaction. Otherwise we never get to dropping references to quota structures
from the inode and umount will hang indefinitely.  Thanks to Payphone LIOU for
spotting the problem.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
CC: Payphone LIOU <lioupayphone@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 7 insertions, 1 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 93a7e746f425..e3b3483b600d 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3040,8 +3040,14 @@ static int ext4_dquot_drop(struct inode *inode)
 
         /* We may delete quota structure so we need to reserve enough blocks */
         handle = ext4_journal_start(inode, 2*EXT4_QUOTA_DEL_BLOCKS(inode->i_sb));
-        if (IS_ERR(handle))
+        if (IS_ERR(handle)) {
+                /*
+                 * We call dquot_drop() anyway to at least release references
+                 * to quota structures so that umount does not hang.
+                 */
+                dquot_drop(inode);
                 return PTR_ERR(handle);
+        }
         ret = dquot_drop(inode);
         err = ext4_journal_stop(handle);
         if (!ret)