Commit e762d481 authored by Junichi Nomura's avatar Junichi Nomura Committed by Luis Henriques

dm: fix AB-BA deadlock in __dm_destroy()

commit 2a708cff 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: default avatarJun'ichi Nomura <j-nomura@ce.jp.nec.com>
Fixes: ab7c7bb6 ("dm: hold suspend_lock while suspending device during device deletion")
Acked-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent 24d9380d
......@@ -2413,7 +2413,6 @@ static void __dm_destroy(struct mapped_device *md, bool wait)
might_sleep();
spin_lock(&_minor_lock);
map = dm_get_live_table(md, &srcu_idx);
idr_replace(&_minor_idr, MINOR_ALLOCED, MINOR(disk_devt(dm_disk(md))));
set_bit(DMF_FREEING, &md->flags);
spin_unlock(&_minor_lock);
......@@ -2423,14 +2422,14 @@ 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,
......
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