From: Josef Bacik <josef@redhat.com>
Date: Fri, 7 Aug 2009 15:46:34 -0400
Subject: [ext3] fix online resize bug
Message-id: 20090807194634.GA5824@localhost.localdomain
O-Subject: [RHEL 5.5][PATCH] ext3: fix online resize bug
Bugzilla: 515759
RH-Acked-by: Eric Sandeen <sandeen@redhat.com>
RH-Acked-by: Stefan Assmann <sassmann@redhat.com>

Hello,

This is in reference to bz 515759.  I'm a moron and fixed this problem for a
different bug, but I posted the wrong patch, and we just figured it out last
week that this happened.  So lets try this again, here is the patch that
actually fixes the problem and has been tested with the testcase, it is a
backport of the following upstream commit

commit 9bb91784de6618c955994b2d5be332fb68c87ef1
Author: Josef Bacik <jbacik@redhat.com>
Date:   Thu Jun 5 22:46:47 2008 -0700

    ext3: fix online resize bug

    There is a bug when we are trying to verify that the reserve inode's
    double indirect blocks point back to the primary gdt blocks.  The fix is
    obvious, we need to mod the gdb count by the addr's per block.  You can
    verify this with the following test case

    dd if=/dev/zero of=disk1 seek=1024 count=1 bs=100M
    losetup /dev/loop1 disk1
    pvcreate /dev/loop1
    vgcreate loopvg1 /dev/loop1
    lvcreate -l 100%VG loopvg1 -n looplv1
    mkfs.ext3 -J size=64 -b 1024 /dev/loopvg1/looplv1
    mount /dev/loopvg1/looplv1 /mnt/loop
    dd if=/dev/zero of=disk2 seek=1024 count=1 bs=50M
    losetup /dev/loop2 disk2
    pvcreate /dev/loop2
    vgextend loopvg1 /dev/loop2
    lvextend -l 100%VG /dev/loopvg1/looplv1
    resize2fs /dev/loopvg1/looplv1

    without this patch the resize2fs fails, with it the resize2fs succeeds.

    Signed-off-by: Josef Bacik <jbacik@redhat.com>
    Acked-by: Andreas Dilger <adilger@sun.com>
    Cc: <linux-ext4@vger.kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/ext3/resize.c b/fs/ext3/resize.c
index f2354d2..e9a7a54 100644
--- a/fs/ext3/resize.c
+++ b/fs/ext3/resize.c
@@ -583,7 +583,8 @@ static int reserve_backup_gdb(handle_t *handle, struct inode *inode,
 	}
 
 	blk = EXT3_SB(sb)->s_sbh->b_blocknr + 1 + EXT3_SB(sb)->s_gdb_count;
-	data = (__u32 *)dind->b_data + EXT3_SB(sb)->s_gdb_count;
+	data = (__u32 *)dind->b_data + EXT3_SB(sb)->s_gdb_count %
+		EXT3_ADDR_PER_BLOCK(sb);
 	end = (__u32 *)dind->b_data + EXT3_ADDR_PER_BLOCK(sb);
 
 	/* Get each reserved primary GDT block and verify it holds backups */