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[PATCH] md: fix deadlock due to md thread processing delayed requests.

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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>
This commit is contained in:
NeilBrown
2005-06-21 17:17:26 -07:00
committed by Linus Torvalds
parent 41158c7eb2
commit 3d310eb7b3
7 changed files with 23 additions and 39 deletions
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4
drivers/md/raid1.c
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@@ -561,8 +561,8 @@ static int make_request(request_queue_t *q, struct bio * bio)
* 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++;