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

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[ Upstream commit 2760904d89 ]

As described in commit 38d11da522 ("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 38d11da522 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: 38d11da522 ("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>
This commit is contained in:
Li Lingfeng 2023-06-01 14:14:23 +08:00 • committed by Justin Hammond
parent a9d27dd08b
commit b908f98d3a
2 changed files with 5 additions and 4 deletions
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5
drivers/md/dm-ioctl.c
View file

@ -1145,13 +1145,10 @@ static int do_resume(struct dm_ioctl *param)
/* Do we need to load a new map ? */ /* Do we need to load a new map ? */
if (new_map) { if (new_map) {
sector_t old_size, new_size; sector_t old_size, new_size;
int srcu_idx;
/* Suspend if it isn't already suspended */ /* Suspend if it isn't already suspended */
old_map = dm_get_live_table(md, &srcu_idx); if (param->flags & DM_SKIP_LOCKFS_FLAG)
if ((param->flags & DM_SKIP_LOCKFS_FLAG) || !old_map)
suspend_flags &= ~DM_SUSPEND_LOCKFS_FLAG; suspend_flags &= ~DM_SUSPEND_LOCKFS_FLAG;
dm_put_live_table(md, srcu_idx);
if (param->flags & DM_NOFLUSH_FLAG) if (param->flags & DM_NOFLUSH_FLAG)
suspend_flags |= DM_SUSPEND_NOFLUSH_FLAG; suspend_flags |= DM_SUSPEND_NOFLUSH_FLAG;
if (!dm_suspended_md(md)) if (!dm_suspended_md(md))

4
drivers/md/dm.c
View file

@ -2526,6 +2526,10 @@ retry:
} }
map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock)); 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); r = __dm_suspend(md, map, suspend_flags, TASK_INTERRUPTIBLE, DMF_SUSPENDED);
if (r) if (r)