From: NeilBrown <neilb@suse.com>
Date: Thu, 24 Sep 2015 04:00:51 +0000 (+1000)
Subject: md: wait for pending superblock updates before switching to read-only
X-Git-Tag: firefly_0821_release~176^2~934^2~8
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=88724bfa68be792c1487d759e87568c36ac1a1cc;p=firefly-linux-kernel-4.4.55.git

md: wait for pending superblock updates before switching to read-only

If a superblock update is pending, wait for it to complete before
letting md_set_readonly() switch to readonly.
Otherwise we might lose important information about a device having
failed.

For external arrays, waiting for superblock updates can wait on
user-space, so in that case, just return an error.

Reported-and-tested-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
---

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 4f5ecbe94ccb..b8247bc32cf6 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5409,9 +5409,13 @@ static int md_set_readonly(struct mddev *mddev, struct block_device *bdev)
 		 * which will now never happen */
 		wake_up_process(mddev->sync_thread->tsk);
 
+	if (mddev->external && test_bit(MD_CHANGE_PENDING, &mddev->flags))
+		return -EBUSY;
 	mddev_unlock(mddev);
 	wait_event(resync_wait, !test_bit(MD_RECOVERY_RUNNING,
 					  &mddev->recovery));
+	wait_event(mddev->sb_wait,
+		   !test_bit(MD_CHANGE_PENDING, &mddev->flags));
 	mddev_lock_nointr(mddev);
 
 	mutex_lock(&mddev->open_mutex);