jbd2: fix potential memory leak on transaction commit

There is potential memory leak of journal head in function
jbd2_journal_commit_transaction. The problem is that JBD2 will not
reclaim the journal head of commit record if error occurs or journal
is abotred.

I use the following script to reproduce this issue, on a RHEL6
system. I found it very easy to reproduce with async commit enabled.

mount /dev/sdb /mnt -o journal_checksum,journal_async_commit
touch /mnt/xxx
echo offline > /sys/block/sdb/device/state
sync
umount /mnt
rmmod ext4
rmmod jbd2

Removal of the jbd2 module will make slab complaining that
"cache `jbd2_journal_head': can't free all objects".

Signed-off-by: Zhang Huan <zhhuan@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 3 insertions, 1 deletions

diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index fa36d7662b21..b98e4c1eecff 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -105,6 +105,8 @@ static int journal_submit_commit_record(journal_t *journal,
         int ret;
         struct timespec now = current_kernel_time();
 
+        *cbh = NULL;
+
         if (is_journal_aborted(journal))
                 return 0;
 
@@ -806,7 +808,7 @@ wait_for_iobuf:
                 if (err)
                         __jbd2_journal_abort_hard(journal);
         }
-        if (!err && !is_journal_aborted(journal))
+        if (cbh)
                 err = journal_wait_on_commit_record(journal, cbh);
         if (JBD2_HAS_INCOMPAT_FEATURE(journal,
                                       JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT) &&