From 38d11da522aacaa05898c734a1cec86f1e611129 Mon Sep 17 00:00:00 2001
From: Li Lingfeng <lilingfeng3@huawei.com>
Date: Tue, 18 Apr 2023 16:38:04 +0800
Subject: [PATCH] dm: don't lock fs when the map is NULL in process of resume
Git-commit: 38d11da522aacaa05898c734a1cec86f1e611129
Patch-mainline: v6.4-rc1
References: git-fixes
Commit fa247089de99 ("dm: requeue IO if mapping table not yet available")
added a detection of whether the mapping table is available in the IO
submission process. If the mapping table is unavailable, it returns
BLK_STS_RESOURCE and requeues the IO.
This can lead to the following deadlock problem:
dm create mount
ioctl(DM_DEV_CREATE_CMD)
ioctl(DM_TABLE_LOAD_CMD)
do_mount
vfs_get_tree
ext4_get_tree
get_tree_bdev
sget_fc
alloc_super
// got &s->s_umount
down_write_nested(&s->s_umount, ...);
ext4_fill_super
ext4_load_super
ext4_read_bh
submit_bio
// submit and wait io end
ioctl(DM_DEV_SUSPEND_CMD)
dev_suspend
do_resume
dm_suspend
__dm_suspend
lock_fs
freeze_bdev
get_active_super
grab_super
// wait for &s->s_umount
down_write(&s->s_umount);
dm_swap_table
__bind
// set md->map(can't get here)
IO will be continuously requeued while holding the lock since mapping
table is NULL. At the same time, mapping table won't be set since the
lock is not available.
Like request-based DM, bio-based DM also has the same problem.
It's not proper to just abort IO if the mapping table not available.
So clear DM_SKIP_LOCKFS_FLAG when the mapping table is NULL, this
allows the DM table to be loaded and the IO submitted upon resume.
Fixes: fa247089de99 ("dm: requeue IO if mapping table not yet available")
Cc: stable@vger.kernel.org
Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Coly Li <colyli@suse.de>
---
drivers/md/dm-ioctl.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 7d5c9c582ed2..cc77cf3d4109 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1168,10 +1168,13 @@ 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 */
- if (param->flags & DM_SKIP_LOCKFS_FLAG)
+ old_map = dm_get_live_table(md, &srcu_idx);
+ if ((param->flags & DM_SKIP_LOCKFS_FLAG) || !old_map)
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))
--
2.35.3