6.7-stable review patch. If anyone has any objections, please let me know.
------------------
From: Yu Kuai yukuai3@huawei.com
commit 55a48ad2db64737f7ffc0407634218cc6e4c513b upstream.
Usually if the array is not read-write, md_check_recovery() won't register new sync_thread in the first place. And if the array is read-write and sync_thread is registered, md_set_readonly() will unregister sync_thread before setting the array read-only. md/raid follow this behavior hence there is no problem.
After commit f52f5c71f3d4 ("md: fix stopping sync thread"), following hang can be triggered by test shell/integrity-caching.sh:
1) array is read-only. dm-raid update super block: rs_update_sbs ro = mddev->ro mddev->ro = 0 -> set array read-write md_update_sb
2) register new sync thread concurrently.
3) dm-raid set array back to read-only: rs_update_sbs mddev->ro = ro
4) stop the array: raid_dtr md_stop stop_sync_thread set_bit(MD_RECOVERY_INTR, &mddev->recovery); md_wakeup_thread_directly(mddev->sync_thread); wait_event(..., !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
5) sync thread done: md_do_sync set_bit(MD_RECOVERY_DONE, &mddev->recovery); md_wakeup_thread(mddev->thread);
6) daemon thread can't unregister sync thread: md_check_recovery if (!md_is_rdwr(mddev) && !test_bit(MD_RECOVERY_NEEDED, &mddev->recovery)) return; -> -> MD_RECOVERY_RUNNING can't be cleared, hence step 4 hang;
The root cause is that dm-raid manipulate 'mddev->ro' by itself, however, dm-raid really should stop sync thread before setting the array read-only. Unfortunately, I need to read more code before I can refacter the handler of 'mddev->ro' in dm-raid, hence let's fix the problem the easy way for now to prevent dm-raid regression.
Reported-by: Mikulas Patocka mpatocka@redhat.com Closes: https://lore.kernel.org/all/9801e40-8ac7-e225-6a71-309dcf9dc9aa@redhat.com/ Fixes: ecbfb9f118bc ("dm raid: add raid level takeover support") Fixes: f52f5c71f3d4 ("md: fix stopping sync thread") Cc: stable@vger.kernel.org # v6.7+ Signed-off-by: Yu Kuai yukuai3@huawei.com Signed-off-by: Song Liu song@kernel.org Link: https://lore.kernel.org/r/20240201092559.910982-3-yukuai1@huaweicloud.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/md/md.c | 31 ++++++++++++++++++------------- 1 file changed, 18 insertions(+), 13 deletions(-)
--- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -9495,6 +9495,20 @@ not_running: sysfs_notify_dirent_safe(mddev->sysfs_action); }
+static void unregister_sync_thread(struct mddev *mddev) +{ + if (!test_bit(MD_RECOVERY_DONE, &mddev->recovery)) { + /* resync/recovery still happening */ + clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery); + return; + } + + if (WARN_ON_ONCE(!mddev->sync_thread)) + return; + + md_reap_sync_thread(mddev); +} + /* * This routine is regularly called by all per-raid-array threads to * deal with generic issues like resync and super-block update. @@ -9532,7 +9546,8 @@ void md_check_recovery(struct mddev *mdd }
if (!md_is_rdwr(mddev) && - !test_bit(MD_RECOVERY_NEEDED, &mddev->recovery)) + !test_bit(MD_RECOVERY_NEEDED, &mddev->recovery) && + !test_bit(MD_RECOVERY_DONE, &mddev->recovery)) return; if ( ! ( (mddev->sb_flags & ~ (1<<MD_SB_CHANGE_PENDING)) || @@ -9554,8 +9569,7 @@ void md_check_recovery(struct mddev *mdd struct md_rdev *rdev;
if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) { - /* sync_work already queued. */ - clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery); + unregister_sync_thread(mddev); goto unlock; }
@@ -9618,16 +9632,7 @@ void md_check_recovery(struct mddev *mdd * still set. */ if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) { - if (!test_bit(MD_RECOVERY_DONE, &mddev->recovery)) { - /* resync/recovery still happening */ - clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery); - goto unlock; - } - - if (WARN_ON_ONCE(!mddev->sync_thread)) - goto unlock; - - md_reap_sync_thread(mddev); + unregister_sync_thread(mddev); goto unlock; }