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dm: fix AB-BA deadlock in __dm_destroy()

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__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>
Cc: stable@vger.kernel.org
This commit is contained in:
Junichi Nomura 2015-10-01 08:31:51 +00:00 committed by Mike Snitzer
parent 9ffecb1028
commit 2a708cff93
1 changed files with 2 additions and 4 deletions
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6
drivers/md/dm.c
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@ -2837,8 +2837,6 @@ static void __dm_destroy(struct mapped_device *md, bool wait)
might_sleep(); might_sleep();
map = dm_get_live_table(md, &srcu_idx);
spin_lock(&_minor_lock); spin_lock(&_minor_lock);
idr_replace(&_minor_idr, MINOR_ALLOCED, MINOR(disk_devt(dm_disk(md)))); idr_replace(&_minor_idr, MINOR_ALLOCED, MINOR(disk_devt(dm_disk(md))));
set_bit(DMF_FREEING, &md->flags); set_bit(DMF_FREEING, &md->flags);
@ -2852,14 +2850,14 @@ static void __dm_destroy(struct mapped_device *md, bool wait)
* do not race with internal suspend. * do not race with internal suspend.
*/ */
mutex_lock(&md->suspend_lock); mutex_lock(&md->suspend_lock);
map = dm_get_live_table(md, &srcu_idx);
if (!dm_suspended_md(md)) { if (!dm_suspended_md(md)) {
dm_table_presuspend_targets(map); dm_table_presuspend_targets(map);
dm_table_postsuspend_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 must be before msleep, otherwise deadlock is possible */
dm_put_live_table(md, srcu_idx); dm_put_live_table(md, srcu_idx);
mutex_unlock(&md->suspend_lock);
/* /*
* Rare, but there may be I/O requests still going to complete, * Rare, but there may be I/O requests still going to complete,