The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

Thanks, Sasha

------------------ original commit in Linus's tree ------------------

From cd32b27a66db8776d8b8e82ec7d7dde97a8693b0 Mon Sep 17 00:00:00 2001 From: Yu Kuai yukuai3@huawei.com Date: Tue, 5 Mar 2024 15:23:03 +0800 Subject: [PATCH] md/dm-raid: don't call md_reap_sync_thread() directly

Currently md_reap_sync_thread() is called from raid_message() directly without holding 'reconfig_mutex', this is definitely unsafe because md_reap_sync_thread() can change many fields that is protected by 'reconfig_mutex'.

However, hold 'reconfig_mutex' here is still problematic because this will cause deadlock, for example, commit 130443d60b1b ("md: refactor idle/frozen_sync_thread() to fix deadlock").

Fix this problem by using stop_sync_thread() to unregister sync_thread, like md/raid did.

Fixes: be83651f0050 ("DM RAID: Add message/status support for changing sync action") Cc: stable@vger.kernel.org # v6.7+ Signed-off-by: Yu Kuai yukuai3@huawei.com Signed-off-by: Xiao Ni xni@redhat.com Acked-by: Mike Snitzer snitzer@kernel.org Signed-off-by: Song Liu song@kernel.org Link: https://lore.kernel.org/r/20240305072306.2562024-7-yukuai1@huaweicloud.com --- drivers/md/dm-raid.c | 28 ++++++++++++++++++---------- 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c index e2d7a73c0f874..47c4b1b6e532a 100644 --- a/drivers/md/dm-raid.c +++ b/drivers/md/dm-raid.c @@ -3719,6 +3719,7 @@ static int raid_message(struct dm_target *ti, unsigned int argc, char **argv, { struct raid_set *rs = ti->private; struct mddev *mddev = &rs->md; + int ret = 0;

if (!mddev->pers || !mddev->pers->sync_request) return -EINVAL; @@ -3726,17 +3727,24 @@ static int raid_message(struct dm_target *ti, unsigned int argc, char **argv, if (test_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags)) return -EBUSY;

- if (!strcasecmp(argv[0], "frozen")) - set_bit(MD_RECOVERY_FROZEN, &mddev->recovery); - else - clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); + if (!strcasecmp(argv[0], "frozen")) { + ret = mddev_lock(mddev); + if (ret) + return ret;

- if (!strcasecmp(argv[0], "idle") || !strcasecmp(argv[0], "frozen")) { - if (mddev->sync_thread) { - set_bit(MD_RECOVERY_INTR, &mddev->recovery); - md_reap_sync_thread(mddev); - } - } else if (decipher_sync_action(mddev, mddev->recovery) != st_idle) + md_frozen_sync_thread(mddev); + mddev_unlock(mddev); + } else if (!strcasecmp(argv[0], "idle")) { + ret = mddev_lock(mddev); + if (ret) + return ret; + + md_idle_sync_thread(mddev); + mddev_unlock(mddev); + } + + clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); + if (decipher_sync_action(mddev, mddev->recovery) != st_idle) return -EBUSY; else if (!strcasecmp(argv[0], "resync")) ; /* MD_RECOVERY_NEEDED set below */