[PATCH] md: only unlock mddev from action_store

[Guoqing Jiang <guoqing.jiang@xxxxxxxxx>]

The 07reshape5intr test is broke because of below path.

    md_reap_sync_thread
            -> mddev_unlock
            -> md_unregister_thread(&mddev->sync_thread)

And md_check_recovery is triggered by,

mddev_unlock -> md_wakeup_thread(mddev->thread)

then mddev->reshape_position is set to MaxSector in raid5_finish_reshape
since MD_RECOVERY_INTR is cleared in md_check_recovery, which means
feature_map is not set with MD_FEATURE_RESHAPE_ACTIVE and superblock's
reshape_position can't be updated accordingly.

Since the bug which commit 8b48ec23cc51a ("md: don't unregister sync_thread
with reconfig_mutex held") fixed is related with action_store path, other
callers which reap sync_thread didn't need to be changed, let's

1. only unlock mddev in md_reap_sync_thread if caller is action_store,
   so the parameter is renamed to reflect the change.
2. save some contexts (MD_RECOVERY_INTR and reshape_position) since they
   could be changed by other processes, then restore them after get lock
   again.

Fixes: 8b48ec23cc51a ("md: don't unregister sync_thread with reconfig_mutex held")
Reported-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Signed-off-by: Guoqing Jiang <guoqing.jiang@xxxxxxxxx>
---
I suppose the previous bug still can be fixed with the change, but it is
better to verify it. Donald, could you help to test the new code?

Thanks,
Guoqing

 drivers/md/md.c | 24 ++++++++++++++++++------
 drivers/md/md.h |  2 +-
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 5c8efef13881..3387260dd55b 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -6197,7 +6197,7 @@ 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, true);
+		md_reap_sync_thread(mddev, false);
 	}
 
 	del_timer_sync(&mddev->safemode_timer);
@@ -9303,7 +9303,7 @@ 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, true);
+			md_reap_sync_thread(mddev, false);
 			clear_bit(MD_RECOVERY_RECOVER, &mddev->recovery);
 			clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
 			clear_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags);
@@ -9338,7 +9338,7 @@ void md_check_recovery(struct mddev *mddev)
 			goto unlock;
 		}
 		if (mddev->sync_thread) {
-			md_reap_sync_thread(mddev, true);
+			md_reap_sync_thread(mddev, false);
 			goto unlock;
 		}
 		/* Set RUNNING before clearing NEEDED to avoid
@@ -9411,18 +9411,30 @@ void md_check_recovery(struct mddev *mddev)
 }
 EXPORT_SYMBOL(md_check_recovery);
 
-void md_reap_sync_thread(struct mddev *mddev, bool reconfig_mutex_held)
+void md_reap_sync_thread(struct mddev *mddev, bool unlock_mddev)
 {
 	struct md_rdev *rdev;
 	sector_t old_dev_sectors = mddev->dev_sectors;
+	sector_t old_reshape_position;
 	bool is_reshaped = false;
+	bool is_interrupted = false;
 
-	if (reconfig_mutex_held)
+	if (unlock_mddev) {
+		old_reshape_position = mddev->reshape_position;
+		if (test_bit(MD_RECOVERY_INTR, &mddev->recovery))
+			is_interrupted = true;
 		mddev_unlock(mddev);
+	}
 	/* resync has finished, collect result */
 	md_unregister_thread(&mddev->sync_thread);
-	if (reconfig_mutex_held)
+	if (unlock_mddev) {
 		mddev_lock_nointr(mddev);
+		/* restore the previous flag and position */
+		mddev->reshape_position = old_reshape_position;
+		if (is_interrupted)
+			set_bit(MD_RECOVERY_INTR, &mddev->recovery);
+	}
+
 	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 82465a4b1588..3e3ff3b20e81 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -719,7 +719,7 @@ 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, bool reconfig_mutex_held);
+extern void md_reap_sync_thread(struct mddev *mddev, bool unlock_mddev);
 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);
-- 
2.31.1