From b06075a98d595b761881fb2d7b8a557ea2f8b7ac Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@redhat.com>
Date: Fri, 10 Jul 2015 17:21:43 -0400
Subject: [PATCH] dm: fix use after free crash due to incorrect cleanup
 sequence

Linux 4.2-rc1 Commit 0f20972f7bf6 ("dm: factor out a common
cleanup_mapped_device()") moved a common cleanup code to a separate
function.  Unfortunately, that commit incorrectly changed the order of
cleanup, so that it destroys the mapped_device's srcu structure
'io_barrier' before destroying its workqueue.

The function that is executed on the workqueue (dm_wq_work) uses the srcu
structure, thus it may use it after being freed.  That results in a
crash in the LVM test suite's mirror-vgreduce-removemissing.sh test.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: 0f20972f7bf6 ("dm: factor out a common cleanup_mapped_device()")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
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