[PATCH] md/raid5: reject llbitmap chunk shrink during reshape

llbitmap reshape keeps one live bitmap and only supports growing the
tracked chunk geometry. Reject RAID5 reshape attempts that would shrink
the llbitmap chunk size.

Signed-off-by: Yu Kuai <[email protected]>
---
 drivers/md/raid5.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 0c58c175bad9..178283aa91a4 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -8459,6 +8459,9 @@ static int check_reshape(struct mddev *mddev)
 	if (!check_stripe_cache(mddev))
 		return -ENOSPC;
 
+	if (mddev->bitmap_id == ID_LLBITMAP &&
+	    mddev->new_chunk_sectors < mddev->chunk_sectors)
+		return -EOPNOTSUPP;
 	if (mddev->new_chunk_sectors > mddev->chunk_sectors ||
 	    mddev->delta_disks > 0)
 		if (resize_chunks(conf,
-- 
2.51.0