From: Jens Axboe <axboe@kernel.dk>
Date: Tue, 6 Nov 2012 11:24:26 +0000 (+0100)
Subject: dm: fix deadlock with request based dm and queue request_fn recursion
X-Git-Tag: v3.2.35~11
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=de268a9f92b3b2504e9f87db3b4dd609aafb255f;p=pandora-kernel.git

dm: fix deadlock with request based dm and queue request_fn recursion

commit a8c32a5c98943d370ea606a2e7dc04717eb92206 upstream.

Request based dm attempts to re-run the request queue off the
request completion path. If used with a driver that potentially does
end_io from its request_fn, we could deadlock trying to recurse
back into request dispatch. Fix this by punting the request queue
run to kblockd.

Tested to fix a quickly reproducible deadlock in such a scenario.

Acked-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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