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

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>

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 707095b924d9869d1105dc459df009ef968e96b0..c5adbb318a90c8c612c97dab1a47c0143b19ef77 100644 (file)
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1660,12 +1660,10 @@ 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;