[PATCH] md: fix deadlock due to md thread processing delayed requests.
Before completing a 'write' the md superblock might need to be updated.
This is best done by the md_thread.
The current code schedules this up and queues the write request for later
handling by the md_thread.
However some personalities (Raid5/raid6) will deadlock if the md_thread
tries to submit requests to its own array.
So this patch changes things so the processes submitting the request waits
for the superblock to be written and then submits the request itself.
This fixes a recently-created deadlock in raid5/raid6
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 3f5234f..98b0977 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -561,8 +561,8 @@
* thread has put up a bar for new requests.
* Continue immediately if no resync is active currently.
*/
- if (md_write_start(mddev, bio)==0)
- return 0;
+ md_write_start(mddev, bio); /* wait on superblock update early */
+
spin_lock_irq(&conf->resync_lock);
wait_event_lock_irq(conf->wait_resume, !conf->barrier, conf->resync_lock, );
conf->nr_pending++;
