From 8031c3ddc70ab93099e7d1814382dba39f57b43e Mon Sep 17 00:00:00 2001
From: Shaohua Li <shli@fb.com>
Date: Thu, 17 Aug 2017 10:35:11 -0700
Subject: [PATCH] md/bitmap: copy correct data for bitmap super
Git-commit: 8031c3ddc70ab93099e7d1814382dba39f57b43e
Patch-mainline: v4.14-rc1
References: bsc#1093023

raid5 cache could write bitmap superblock before bitmap superblock is
initialized. The bitmap superblock is less than 512B. The current code will
only copy the superblock to a new page and write the whole 512B, which will
zero the the data after the superblock. Unfortunately the data could include
bitmap, which we should preserve. The patch will make superblock read do 4k
chunk and we always copy the 4k data to new page, so the superblock write will
old data to disk and we don't change the bitmap.

Reported-by: Song Liu <songliubraving@fb.com>
Reviewed-by: Song Liu <songliubraving@fb.com>
Cc: stable@vger.kernel.org (4.10+)
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Coly Li <colyli@suse.de>

---
 drivers/md/bitmap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 40f3cd7eab0f..67e992185a24 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -625,7 +625,7 @@ static int bitmap_read_sb(struct bitmap *bitmap)
 		err = read_sb_page(bitmap->mddev,
 				   offset,
 				   sb_page,
-				   0, sizeof(bitmap_super_t));
+				   0, PAGE_SIZE);
 	}
 	if (err)
 		return err;
@@ -2118,7 +2118,7 @@ int bitmap_resize(struct bitmap *bitmap, sector_t blocks,
 	if (store.sb_page && bitmap->storage.sb_page)
 		memcpy(page_address(store.sb_page),
 		       page_address(bitmap->storage.sb_page),
-		       sizeof(bitmap_super_t));
+		       PAGE_SIZE);
 	bitmap_file_unmap(&bitmap->storage);
 	bitmap->storage = store;
 
-- 
2.16.3