[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/include/linux/raid/md_k.h b/include/linux/raid/md_k.h
index 6cdcb44..3e97702 100644
--- a/include/linux/raid/md_k.h
+++ b/include/linux/raid/md_k.h
@@ -261,7 +261,7 @@
sector_t recovery_cp;
spinlock_t write_lock;
- struct bio_list write_list;
+ wait_queue_head_t sb_wait; /* for waiting on superblock updates */
unsigned int safemode; /* if set, update "clean" superblock
* when no writes pending.