[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>

1 files changed, 1 insertions, 2 deletions

diff --git a/drivers/md/raid6main.c b/drivers/md/raid6main.c
index d9c385496dc..f62ea1a73d0 100644
--- a/drivers/md/raid6main.c
+++ b/drivers/md/raid6main.c
@@ -1570,8 +1570,7 @@ static int make_request (request_queue_t *q, struct bio * bi)
         sector_t logical_sector, last_sector;
         struct stripe_head *sh;
 
-        if (md_write_start(mddev, bi)==0)
-                return 0;
+        md_write_start(mddev, bi);
 
         if (bio_data_dir(bi)==WRITE) {
                 disk_stat_inc(mddev->gendisk, writes);