From: Theodore Ts'o <tytso@mit.edu>
Subject: Re: Weird resize2fs failures when mounting ext3 as ext4
Date: Sun, 21 Apr 2013 19:30:57 -0400
Message-ID: <20130421233057.GA5625@thunk.org>
References: <51229FF7.7090003@redhat.com>
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Cc: ext4 development <linux-ext4@vger.kernel.org>
To: Eric Sandeen <sandeen@redhat.com>
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In-Reply-To: <51229FF7.7090003@redhat.com>
Sender: linux-ext4-owner@vger.kernel.org

On Mon, Feb 18, 2013 at 03:41:11PM -0600, Eric Sandeen wrote:
> Can't remember how I stumbled on this testcase, but mounting
> an ext3 filesystem with "-t ext4" and then resizing leads to trouble.

Is there a bugzilla entry for this?  I found the problem and a fix;
patch follows in a moment.

Also, here's a simplified repro that doesn't require LVM.  The bug was
introduced in commit fb0a387dcdc, so it goes back to 2.6.32.  It only
affects block allocations for files that aren't extent mapped, and is
caused by the fact that the online resizer wasn't updating
s_blockfile_groups (which was introduced in commit fb0a387dcdc).

						- Ted

#!/bin/bash

COUNT=15
SIZE_1=15G
SIZE_2=16G
DEVICE=/dev/vdc
XFS_IO=/root/xfstests/bin/xfs_io

mkdir -p mnt
umount mnt &>/dev/null
mkfs.ext3  $DEVICE $SIZE_1
mount -t ext4 -o nodelalloc $DEVICE mnt/

for I in `seq 1 $COUNT`; do mkdir mnt/dir$I; dd if=/dev/zero of=mnt/dir$I/file$I bs=1M count=1024; done
echo "before growing:"
df mnt/

umount mnt
mount -t ext4 -o nodelalloc $DEVICE mnt/

echo "growing:"
#export RESIZE2FS_KERNEL_VERSION=3.2.0
strace -o /tmp/resize2fs.strace resize2fs $DEVICE $SIZE_2

echo "done growing:"
df mnt/

# This gets ENOSPC for all of them
echo "try extending files:"
for I in `seq 1 $COUNT`; do $XFS_IO -f -F -c "pwrite -b 4m 1G 50m" mnt/dir$I/file$I; done 
df mnt/

umount mnt