From 8b48ec23cc51a4e7c8dbaef5f34ebe67e1a80934 Mon Sep 17 00:00:00 2001 From: Guoqing Jiang Date: Sat, 13 Feb 2021 01:49:59 +0100 Subject: md: don't unregister sync_thread with reconfig_mutex held Unregister sync_thread doesn't need to hold reconfig_mutex since it doesn't reconfigure array. And it could cause deadlock problem for raid5 as follows: 1. process A tried to reap sync thread with reconfig_mutex held after echo idle to sync_action. 2. raid5 sync thread was blocked if there were too many active stripes. 3. SB_CHANGE_PENDING was set (because of write IO comes from upper layer) which causes the number of active stripes can't be decreased. 4. SB_CHANGE_PENDING can't be cleared since md_check_recovery was not able to hold reconfig_mutex. More details in the link: https://lore.kernel.org/linux-raid/5ed54ffc-ce82-bf66-4eff-390cb23bc1ac@molgen.mpg.de/T/#t And add one parameter to md_reap_sync_thread since it could be called by dm-raid which doesn't hold reconfig_mutex. Reported-and-tested-by: Donald Buczek Signed-off-by: Guoqing Jiang Signed-off-by: Song Liu --- drivers/md/dm-raid.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/md/dm-raid.c') diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c index 9526ccbedafb..5e41fbae3f6b 100644 --- a/drivers/md/dm-raid.c +++ b/drivers/md/dm-raid.c @@ -3725,7 +3725,7 @@ static int raid_message(struct dm_target *ti, unsigned int argc, char **argv, 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); + md_reap_sync_thread(mddev, false); } } else if (decipher_sync_action(mddev, mddev->recovery) != st_idle) return -EBUSY; -- cgit v1.2.3