[PATCH v2 1/3] md-cluster: fix error handling and superblock update in update_size revert

[ghuicao@163.com]

From: Cao Guanghui <caoguanghui@kylinos.cn>

In update_size(), when cluster_check_sync_size() detects that not all
nodes have updated their sync_size, the initiator reverts the array
size via pers->resize().  Two issues exist in this revert path:

1. The return value of resize() is immediately overwritten by
   __sendmsg(), so a resize failure is silently lost.  The array
   remains at the new size while other nodes have not confirmed the
   change, with no error logged.

2. The on-disk superblock still retains the new size written by the
   earlier md_update_sb() call.  Other nodes that receive the
   METADATA_UPDATED message will re-read the on-disk superblock and
   adopt the new size, while the initiator runs with the reverted old
   size, causing a cluster-wide metadata inconsistency.

Fix by checking the resize() return value and logging an error, then
calling md_update_sb() so the on-disk superblock matches the in-memory
array size before broadcasting the message.

Fixes: 818da59f97d6 ("md-cluster: add the support for resize")
Cc: stable@vger.kernel.org
Signed-off-by: Cao Guanghui <caoguanghui@kylinos.cn>
---

Changes in v2:
  - Fold in the md_update_sb() fix (was a separate patch in v1)
  - Combine error check and superblock update into one coherent fix

 drivers/md/md-cluster.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/md/md-cluster.c b/drivers/md/md-cluster.c
--- a/drivers/md/md-cluster.c
+++ b/drivers/md/md-cluster.c
@@ -1349,7 +1349,11 @@ static void update_size(struct mddev *mddev, sector_t old_dev_sectors)
 	} else {
 		/* revert to previous sectors */
 		ret = mddev->pers->resize(mddev, old_dev_sectors);
+		if (ret)
+			pr_err("%s:%d: failed to revert array size\n",
+			       __func__, __LINE__);
+		md_update_sb(mddev, 1);
 		ret = __sendmsg(cinfo, &cmsg);
 		if (ret)
 			pr_err("%s:%d: failed to send METADATA_UPDATED msg\n",
 			       __func__, __LINE__);
 	}
-- 
2.34.1