Bart reported a case where dm would crash with use-after-free
poison. This is due to dm_softirq_done() accessing memory
associated with a request after calling end_request on it.
This is most visible on !blk-mq, since we free the memory
immediately for that case.
Reported-by: NBart Van Assche <bart.vanassche@sandisk.com>
Suggested-by: NLinus Torvalds <torvalds@linux-foundation.org>
Fixes: eb8db831 ("dm: always defer request allocation to the owner of the request_queue")
Signed-off-by: NJens Axboe <axboe@fb.com>