[PATCH v4 06/14] dm-raid: really frozen sync_thread during suspend

[Yu Kuai]

From: Yu Kuai <yukuai3@xxxxxxxxxx>

1) The flag MD_RECOVERY_FROZEN doesn't mean that sync thread is frozen,
   it only prevent new sync_thread to start, and it can't stop the
   running sync thread;
2) The flag MD_RECOVERY_FROZEN doesn't mean that writes are stopped, use
   it as condition for md_stop_writes() in raid_postsuspend() doesn't
   look correct.
3) raid_message can set/clear the flag MD_RECOVERY_FROZEN at anytime,
   and if MD_RECOVERY_FROZEN is cleared while the array is suspended,
   new sync_thread can start unexpected.

Fix above problems by using the new helper to suspend the array during
suspend, also disallow raid_message() to change sync_thread status
during suspend.

Note that after commit f52f5c71f3d4 ("md: fix stopping sync thread"), the
test shell/lvconvert-raid-reshape.sh start to hang in stop_sync_thread(),
and with previous fixes, the test won't hang there anymore, however, the
test will still fail and complain that ext4 is corrupted. And with this
patch, the test won't hang due to stop_sync_thread() or fail due to ext4
is corrupted anymore. However, there is still a deadlock related to
dm-raid456 that will be fixed in following patches.

Reported-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Closes: https://lore.kernel.org/all/e5e8afe2-e9a8-49a2-5ab0-958d4065c55e@xxxxxxxxxx/
Fixes: 1af2048a3e87 ("dm raid: fix deadlock caused by premature md_stop_writes()")
Fixes: 9dbd1aa3a81c ("dm raid: add reshaping support to the target")
Fixes: f52f5c71f3d4 ("md: fix stopping sync thread")
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
 drivers/md/dm-raid.c | 38 +++++++++++++++++++++++++++++---------
 1 file changed, 29 insertions(+), 9 deletions(-)

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index eb009d6bb03a..5ce3c6020b1b 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -3240,11 +3240,12 @@ static int raid_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	rs->md.ro = 1;
 	rs->md.in_sync = 1;
 
-	/* Keep array frozen until resume. */
-	set_bit(MD_RECOVERY_FROZEN, &rs->md.recovery);
-
 	/* Has to be held on running the array */
 	mddev_suspend_and_lock_nointr(&rs->md);
+
+	/* Keep array frozen until resume. */
+	md_frozen_sync_thread(&rs->md);
+
 	r = md_run(&rs->md);
 	rs->md.in_sync = 0; /* Assume already marked dirty */
 	if (r) {
@@ -3722,6 +3723,9 @@ static int raid_message(struct dm_target *ti, unsigned int argc, char **argv,
 	if (!mddev->pers || !mddev->pers->sync_request)
 		return -EINVAL;
 
+	if (test_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags))
+		return -EBUSY;
+
 	if (!strcasecmp(argv[0], "frozen"))
 		set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
 	else
@@ -3791,15 +3795,31 @@ static void raid_io_hints(struct dm_target *ti, struct queue_limits *limits)
 	blk_limits_io_opt(limits, chunk_size_bytes * mddev_data_stripes(rs));
 }
 
+static void raid_presuspend(struct dm_target *ti)
+{
+	struct raid_set *rs = ti->private;
+
+	mddev_lock_nointr(&rs->md);
+	md_frozen_sync_thread(&rs->md);
+	mddev_unlock(&rs->md);
+}
+
+static void raid_presuspend_undo(struct dm_target *ti)
+{
+	struct raid_set *rs = ti->private;
+
+	mddev_lock_nointr(&rs->md);
+	md_unfrozen_sync_thread(&rs->md);
+	mddev_unlock(&rs->md);
+}
+
 static void raid_postsuspend(struct dm_target *ti)
 {
 	struct raid_set *rs = ti->private;
 
 	if (!test_and_set_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags)) {
 		/* Writes have to be stopped before suspending to avoid deadlocks. */
-		if (!test_bit(MD_RECOVERY_FROZEN, &rs->md.recovery))
-			md_stop_writes(&rs->md);
-
+		md_stop_writes(&rs->md);
 		mddev_suspend(&rs->md, false);
 	}
 }
@@ -4012,8 +4032,6 @@ static int raid_preresume(struct dm_target *ti)
 	}
 
 	/* Check for any resize/reshape on @rs and adjust/initiate */
-	/* Be prepared for mddev_resume() in raid_resume() */
-	set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
 	if (mddev->recovery_cp && mddev->recovery_cp < MaxSector) {
 		set_bit(MD_RECOVERY_REQUESTED, &mddev->recovery);
 		mddev->resync_min = mddev->recovery_cp;
@@ -4056,9 +4074,9 @@ static void raid_resume(struct dm_target *ti)
 			rs_set_capacity(rs);
 
 		mddev_lock_nointr(mddev);
-		clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
 		mddev->ro = 0;
 		mddev->in_sync = 0;
+		md_unfrozen_sync_thread(mddev);
 		mddev_unlock_and_resume(mddev);
 	}
 }
@@ -4074,6 +4092,8 @@ static struct target_type raid_target = {
 	.message = raid_message,
 	.iterate_devices = raid_iterate_devices,
 	.io_hints = raid_io_hints,
+	.presuspend = raid_presuspend,
+	.presuspend_undo = raid_presuspend_undo,
 	.postsuspend = raid_postsuspend,
 	.preresume = raid_preresume,
 	.resume = raid_resume,
-- 
2.39.2