dm: don't lock fs when the map is NULL during suspend or resume

[ Upstream commit 2760904d895279f87196f0fa9ec570c79fe6a2e4 ]

As described in commit 38d11da522aa ("dm: don't lock fs when the map is
NULL in process of resume"), a deadlock may be triggered between
do_resume() and do_mount().

This commit preserves the fix from commit 38d11da522aa but moves it to
where it also serves to fix a similar deadlock between do_suspend()
and do_mount().  It does so, if the active map is NULL, by clearing
DM_SUSPEND_LOCKFS_FLAG in dm_suspend() which is called by both
do_suspend() and do_resume().

Fixes: 38d11da522aa ("dm: don't lock fs when the map is NULL in process of resume")
Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 83aecd9..6ae1c19 100644 (file)
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1151,13 +1151,10 @@ static int do_resume(struct dm_ioctl *param)
        /* Do we need to load a new map ? */
        if (new_map) {
                sector_t old_size, new_size;
-               int srcu_idx;
 
                /* Suspend if it isn't already suspended */
-               old_map = dm_get_live_table(md, &srcu_idx);
-               if ((param->flags & DM_SKIP_LOCKFS_FLAG) || !old_map)
+               if (param->flags & DM_SKIP_LOCKFS_FLAG)
                        suspend_flags &= ~DM_SUSPEND_LOCKFS_FLAG;
-               dm_put_live_table(md, srcu_idx);
                if (param->flags & DM_NOFLUSH_FLAG)
                        suspend_flags |= DM_SUSPEND_NOFLUSH_FLAG;
                if (!dm_suspended_md(md))

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 24284d2..acf7e75 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2801,6 +2801,10 @@ retry:
        }
 
        map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));
+       if (!map) {
+               /* avoid deadlock with fs/namespace.c:do_mount() */
+               suspend_flags &= ~DM_SUSPEND_LOCKFS_FLAG;
+       }
 
        r = __dm_suspend(md, map, suspend_flags, TASK_INTERRUPTIBLE, DMF_SUSPENDED);
        if (r)