md: Handle growth of v1.x metadata correctly.

The v1.x metadata does not have a fixed size and can grow
when devices are added.
If it grows enough to require an extra sector of storage,
we need to update the 'sb_size' to match.

Without this, md can write out an incomplete superblock with a
bad checksum, which will be rejected when trying to re-assemble
the array.

Cc: stable@kernel.org
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 7 insertions, 1 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 249b2896d4ea..52c988b072d0 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1399,8 +1399,14 @@ static void super_1_sync(mddev_t *mddev, mdk_rdev_t *rdev)
                 if (rdev2->desc_nr+1 > max_dev)
                         max_dev = rdev2->desc_nr+1;
 
-        if (max_dev > le32_to_cpu(sb->max_dev))
+        if (max_dev > le32_to_cpu(sb->max_dev)) {
+                int bmask;
                 sb->max_dev = cpu_to_le32(max_dev);
+                rdev->sb_size = max_dev * 2 + 256;
+                bmask = queue_logical_block_size(rdev->bdev->bd_disk->queue)-1;
+                if (rdev->sb_size & bmask)
+                        rdev->sb_size = (rdev->sb_size | bmask) + 1;
+        }
         for (i=0; i<max_dev;i++)
                 sb->dev_roles[i] = cpu_to_le16(0xfffe);