From eeecef0af5ea4efd763c9554cf2bd80fc4a0efd3 Mon Sep 17 00:00:00 2001 From: Eric Sandeen Date: Sat, 18 Aug 2012 22:29:40 -0400 Subject: jbd2: don't write superblock when if its empty This sequence: # truncate --size=1g fsfile # mkfs.ext4 -F fsfile # mount -o loop,ro fsfile /mnt # umount /mnt # dmesg | tail results in an IO error when unmounting the RO filesystem: [ 318.020828] Buffer I/O error on device loop1, logical block 196608 [ 318.027024] lost page write due to I/O error on loop1 [ 318.032088] JBD2: Error -5 detected when updating journal superblock for loop1-8. This was a regression introduced by commit 24bcc89c7e7c: "jbd2: split updating of journal superblock and marking journal empty". Signed-off-by: Eric Sandeen Signed-off-by: "Theodore Ts'o" Cc: stable@vger.kernel.org diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c index bd23f2e..0f16edd 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -1354,6 +1354,11 @@ static void jbd2_mark_journal_empty(journal_t *journal) BUG_ON(!mutex_is_locked(&journal->j_checkpoint_mutex)); read_lock(&journal->j_state_lock); + /* Is it already empty? */ + if (sb->s_start == 0) { + read_unlock(&journal->j_state_lock); + return; + } jbd_debug(1, "JBD2: Marking journal as empty (seq %d)\n", journal->j_tail_sequence); -- cgit v0.10.2