From: Guoqing Jiang guoqing.jiang@cloud.ionos.com
[ Upstream commit 8b48ec23cc51a4e7c8dbaef5f34ebe67e1a80934 ]
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@molg...
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 buczek@molgen.mpg.de Signed-off-by: Guoqing Jiang guoqing.jiang@cloud.ionos.com Signed-off-by: Song Liu song@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/md/dm-raid.c | 2 +- drivers/md/md.c | 14 +++++++++----- drivers/md/md.h | 2 +- 3 files changed, 11 insertions(+), 7 deletions(-)
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c index b16332917220..0be03123d6a2 100644 --- a/drivers/md/dm-raid.c +++ b/drivers/md/dm-raid.c @@ -3710,7 +3710,7 @@ 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; diff --git a/drivers/md/md.c b/drivers/md/md.c index 7e0477e883c7..da7954eff4d7 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -4611,7 +4611,7 @@ action_store(struct mddev *mddev, const char *page, size_t len) flush_workqueue(md_misc_wq); if (mddev->sync_thread) { set_bit(MD_RECOVERY_INTR, &mddev->recovery); - md_reap_sync_thread(mddev); + md_reap_sync_thread(mddev, true); } mddev_unlock(mddev); } @@ -5871,7 +5871,7 @@ static void __md_stop_writes(struct mddev *mddev) flush_workqueue(md_misc_wq); if (mddev->sync_thread) { set_bit(MD_RECOVERY_INTR, &mddev->recovery); - md_reap_sync_thread(mddev); + md_reap_sync_thread(mddev, true); }
del_timer_sync(&mddev->safemode_timer); @@ -8893,7 +8893,7 @@ void md_check_recovery(struct mddev *mddev) * ->spare_active and clear saved_raid_disk */ set_bit(MD_RECOVERY_INTR, &mddev->recovery); - md_reap_sync_thread(mddev); + md_reap_sync_thread(mddev, true); clear_bit(MD_RECOVERY_RECOVER, &mddev->recovery); clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery); clear_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags); @@ -8928,7 +8928,7 @@ void md_check_recovery(struct mddev *mddev) goto unlock; } if (mddev->sync_thread) { - md_reap_sync_thread(mddev); + md_reap_sync_thread(mddev, true); goto unlock; } /* Set RUNNING before clearing NEEDED to avoid @@ -9001,12 +9001,16 @@ void md_check_recovery(struct mddev *mddev) } EXPORT_SYMBOL(md_check_recovery);
-void md_reap_sync_thread(struct mddev *mddev) +void md_reap_sync_thread(struct mddev *mddev, bool reconfig_mutex_held) { struct md_rdev *rdev;
+ if (reconfig_mutex_held) + mddev_unlock(mddev); /* resync has finished, collect result */ md_unregister_thread(&mddev->sync_thread); + if (reconfig_mutex_held) + mddev_lock_nointr(mddev); if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery) && !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) && mddev->degraded != mddev->raid_disks) { diff --git a/drivers/md/md.h b/drivers/md/md.h index cce62bbc2bcb..027b220dec14 100644 --- a/drivers/md/md.h +++ b/drivers/md/md.h @@ -674,7 +674,7 @@ extern struct md_thread *md_register_thread( extern void md_unregister_thread(struct md_thread **threadp); extern void md_wakeup_thread(struct md_thread *thread); extern void md_check_recovery(struct mddev *mddev); -extern void md_reap_sync_thread(struct mddev *mddev); +extern void md_reap_sync_thread(struct mddev *mddev, bool reconfig_mutex_held); extern int mddev_init_writes_pending(struct mddev *mddev); extern bool md_write_start(struct mddev *mddev, struct bio *bi); extern void md_write_inc(struct mddev *mddev, struct bio *bi);