In the current jbd code, if a buffer on BJ_SyncData list is dirty and not
locked, the buffer is refiled to BJ_Locked list, submitted to the IO and
waited for IO completion.

But the fsstress test showed the case that when a buffer was already
submitted to the IO just before the buffer_dirty(bh) check, the buffer was
not waited for IO completion.

Following patch solves this problem.  If it is assumed that a buffer is
submitted to the IO before the buffer_dirty(bh) check and still being
written to disk, this buffer is refiled to BJ_Locked list.
Signed-off-by: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
Cc: Jan Kara <jack@ucw.cz>
Cc: "Stephen C. Tweedie" <sct@redhat.com>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>