This is a note to let you know that I've just added the patch titled
dm: fix AB-BA deadlock in __dm_destroy()
to the 4.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
dm-fix-ab-ba-deadlock-in-__dm_destroy.patch
and it can be found in the queue-4.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 2a708cff93f1845b9239bc7d6310aef54e716c6a Mon Sep 17 00:00:00 2001
From: Junichi Nomura <j-nomura@xxxxxxxxxxxxx>
Date: Thu, 1 Oct 2015 08:31:51 +0000
Subject: dm: fix AB-BA deadlock in __dm_destroy()
From: Junichi Nomura <j-nomura@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Fixes: ab7c7bb6f4ab ("dm: hold suspend_lock while suspending device during device deletion")
Acked-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/dm.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2952,8 +2952,6 @@ static void __dm_destroy(struct mapped_d
might_sleep();
- map = dm_get_live_table(md, &srcu_idx);
-
spin_lock(&_minor_lock);
idr_replace(&_minor_idr, MINOR_ALLOCED, MINOR(disk_devt(dm_disk(md))));
set_bit(DMF_FREEING, &md->flags);
@@ -2967,14 +2965,14 @@ static void __dm_destroy(struct mapped_d
* 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,
Patches currently in stable-queue which might be from j-nomura@xxxxxxxxxxxxx are
queue-4.2/dm-fix-ab-ba-deadlock-in-__dm_destroy.patch
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