| From | Kamal Mostafa <> | Subject | [PATCH 3.13.y-ckt 21/96] dm: fix AB-BA deadlock in __dm_destroy() | Date | Fri, 13 Nov 2015 13:48:35 -0800 |
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3.13.11-ckt30 -stable review patch. If anyone has any objections, please let me know.
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From: Junichi Nomura <j-nomura@ce.jp.nec.com>
commit 2a708cff93f1845b9239bc7d6310aef54e716c6a upstream.
__dm_destroy() takes io_barrier SRCU lock (dm_get_live_table) and suspend_lock in reverse order. Doing so can cause AB-BA deadlock:
__dm_destroy dm_swap_table --------------------------------------------------- mutex_lock(suspend_lock) dm_get_live_table() srcu_read_lock(io_barrier) dm_sync_table() synchronize_srcu(io_barrier) .. waiting for dm_put_live_table() mutex_lock(suspend_lock) .. waiting for suspend_lock
Fix this by taking the locks in proper order.
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Fixes: ab7c7bb6f4ab ("dm: hold suspend_lock while suspending device during device deletion") Acked-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- drivers/md/dm.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 5489410..071b9ad 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -2490,14 +2490,14 @@ static void __dm_destroy(struct mapped_device *md, bool wait) * do not race with internal suspend. */ mutex_lock(&md->suspend_lock); + map = dm_get_live_table(md, &srcu_idx); if (!dm_suspended_md(md)) { dm_table_presuspend_targets(map); dm_table_postsuspend_targets(map); } - mutex_unlock(&md->suspend_lock); - /* dm_put_live_table must be before msleep, otherwise deadlock is possible */ dm_put_live_table(md, srcu_idx); + mutex_unlock(&md->suspend_lock); /* * Rare, but there may be I/O requests still going to complete, -- 1.9.1
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