ext4: fix corruption when online resizing a fs with 1K block size

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@treewalker.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 1 insertions, 3 deletions

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index b27c96d01965..49d3c01eabf8 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1656,12 +1656,10 @@ 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;