[PATCH v3 3/3] md-cluster: revert local resize and propagate cluster errors

[ghuicao]

From: Cao Guanghui <caoguanghui@xxxxxxxxxx>

In md.c:update_size(), the local array is resized via pers->resize()
before calling the cluster update_size() callback.  If the cluster
operation fails, the local node has the new size while the rest of
the cluster does not, causing a split-brain state.

Propagate the cluster update_size() return value and revert the local
resize on failure.  Also check the return value in the reshape
completion path (md_reap_sync_thread) and log a warning on failure.

Fixes: 818da59f97d6 ("md-cluster: add the support for resize")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Cao Guanghui <caoguanghui@xxxxxxxxxx>
---
 drivers/md/md.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -8022,9 +8022,11 @@ static int update_size(struct mddev *mddev, sector_t num_sectors)
 	}
 	rv = mddev->pers->resize(mddev, num_sectors);
 	if (!rv) {
-		if (mddev_is_clustered(mddev))
-			mddev->cluster_ops->update_size(mddev, old_dev_sectors);
-		else if (!mddev_is_dm(mddev))
+		if (mddev_is_clustered(mddev)) {
+			rv = mddev->cluster_ops->update_size(mddev, old_dev_sectors);
+			if (rv)
+				mddev->pers->resize(mddev, old_dev_sectors);
+		} else if (!mddev_is_dm(mddev))
 			set_capacity_and_notify(mddev->gendisk,
 						mddev->array_sectors);
 	}
@@ -10615,8 +10617,12 @@ void md_reap_sync_thread(struct mddev *mddev)
 	 */
 	if (mddev_is_clustered(mddev) && is_reshaped &&
 	    mddev->pers->finish_reshape &&
-	    !test_bit(MD_CLOSING, &mddev->flags))
-		mddev->cluster_ops->update_size(mddev, old_dev_sectors);
+	    !test_bit(MD_CLOSING, &mddev->flags)) {
+		int ret = mddev->cluster_ops->update_size(mddev, old_dev_sectors);
+
+		if (ret)
+			pr_warn("md: cluster update_size failed after reshape: %d\n", ret);
+	}
 	/* flag recovery needed just to double check */
 	set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
 	sysfs_notify_dirent_safe(mddev->sysfs_completed);
-- 
2.34.1