[PATCH 3.8 27/81] ext4: fix online resize with a non-standard blocks per group setting

[Kamal Mostafa]

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

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

From: Theodore Ts'o <tytso at mit.edu>

commit 3d2660d0c9c2f296837078c189b68a47f6b2e3b5 upstream.

The set_flexbg_block_bitmap() function assumed that the number of
blocks in a blockgroup was sb->blocksize * 8, which is normally true,
but not always!  Use EXT4_BLOCKS_PER_GROUP(sb) instead, to fix block
bitmap corruption after:

mke2fs -t ext4 -g 3072 -i 4096 /dev/vdd 1G
mount -t ext4 /dev/vdd /vdd
resize2fs /dev/vdd 8G

Signed-off-by: "Theodore Ts'o" <tytso at mit.edu>
Reported-by: Jon Bernard <jbernard at tuxion.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/ext4/resize.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index d2c12df..d7f6b63 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -404,7 +404,7 @@ static int set_flexbg_block_bitmap(struct super_block *sb, handle_t *handle,
 		start = ext4_group_first_block_no(sb, group);
 		group -= flex_gd->groups[0].group;
 
-		count2 = sb->s_blocksize * 8 - (block - start);
+		count2 = EXT4_BLOCKS_PER_GROUP(sb) - (block - start);
 		if (count2 > count)
 			count2 = count;
 
-- 
1.8.3.2