[PATCH 053/145] ext4: fix corruption when online resizing a fs with 1K block size

[Kamal Mostafa]

3.8.13.5 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Maarten ter Huurne <maarten at treewalker.org>

commit 6ca792edc13c409e8d4eb9001e048264c6a2eb64 upstream.

Subtracting the number of the first data block places the superblock
backups one block too early, corrupting the file system. When the block
size is larger than 1K, the first data block is 0, so the subtraction
has no effect and no corruption occurs.

Signed-off-by: Maarten ter Huurne <maarten at treewalker.org>
Signed-off-by: "Theodore Ts'o" <tytso at mit.edu>
Reviewed-by: Jan Kara <jack at suse.cz>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/ext4/resize.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 0cfa2f4..28d5f2c 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1654,12 +1654,10 @@ errout:
 		err = err2;
 
 	if (!err) {
-		ext4_fsblk_t first_block;
-		first_block = ext4_group_first_block_no(sb, 0);
 		if (test_opt(sb, DEBUG))
 			printk(KERN_DEBUG "EXT4-fs: extended group to %llu "
 			       "blocks\n", ext4_blocks_count(es));
-		update_backups(sb, EXT4_SB(sb)->s_sbh->b_blocknr - first_block,
+		update_backups(sb, EXT4_SB(sb)->s_sbh->b_blocknr,
 			       (char *)es, sizeof(struct ext4_super_block), 0);
 	}
 	return err;
-- 
1.8.1.2