| From | Greg Kroah-Hartman <> | Subject | [ 16/37] dm: fix deadlock with request based dm and queue request_fn recursion | Date | Fri, 30 Nov 2012 10:46:03 -0800 |
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3.0-stable review patch. If anyone has any objections, please let me know.
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From: Jens Axboe <axboe@kernel.dk>
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/md/dm.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
--- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -745,8 +745,14 @@ static void rq_completed(struct mapped_d if (!md_in_flight(md)) wake_up(&md->wait); + /* + * Run this off this callpath, as drivers could invoke end_io while + * inside their request_fn (and holding the queue lock). Calling + * back into ->request_fn() could deadlock attempting to grab the + * queue lock again. + */ if (run_queue) - blk_run_queue(md->queue); + blk_run_queue_async(md->queue); /* * dm_put() must be at the end of this function. See the comment above
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