[PATCH] ext4: queue conversion after adding to inode's completed IO list

[Eric Sandeen <sandeen@redhat.com>]

By queuing the io end on the unwritten workqueue before adding it
to our inode's list of completed IOs, I think we run the risk
of the work getting completed, and the IO freed, before we try
to add it to the inode's i_completed_io_list.

It should be safe to add it to the inode's list of completed
IOs, and -then- queue it for completion, I think.

Thanks to Dave Chinner for pointing out the race.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

(At least I think this is right; I haven't actually demonstrated a race...)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 0afc8c1..7f56c48 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3804,14 +3804,14 @@ static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
 	io_end->flag = EXT4_IO_UNWRITTEN;
 	wq = EXT4_SB(io_end->inode->i_sb)->dio_unwritten_wq;
 
-	/* queue the work to convert unwritten extents to written */
-	queue_work(wq, &io_end->work);