From: Yu Kuai <yuku...@huawei.com>
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 <mpato...@redhat.com>
Closes:
https://lore.kernel.org/all/9801e40-8ac7-e225-6a71-309dcf9dc...@redhat.com/
Fixes: ecbfb9f118bc ("dm raid: add raid level takeover support")
Fixes: f52f5c71f3d4 ("md: fix stopping sync thread")
Signed-off-by: Yu Kuai <yuku...@huawei.com>
---
drivers/md/md.c | 31 ++++++++++++++++++-------------
1 file changed, 18 insertions(+), 13 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 07b80278eaa5..6906d023f1d6 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -9445,6 +9445,20 @@ static void md_start_sync(struct work_struct *ws)
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.
@@ -9482,7 +9496,8 @@ void md_check_recovery(struct mddev *mddev)
}
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)) ||
@@ -9504,8 +9519,7 @@ void md_check_recovery(struct mddev *mddev)
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;
}
@@ -9568,16 +9582,7 @@ void md_check_recovery(struct mddev *mddev)
* 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;
}
--
2.39.2
