[ 3.8.y.z extended stable ] Patch "ext4: fix corruption when online resizing a fs with 1K block" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

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

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 2a5944c0e698fb813f439dd99a6c9b3ed12c1fd4 Mon Sep 17 00:00:00 2001
From: Maarten ter Huurne <maarten at treewalker.org>
Date: Mon, 1 Jul 2013 08:12:08 -0400
Subject: [PATCH] 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 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