Re: [PATCH v5] fstests: btrfs: Add reserved space leak check for rewrite dirty page

[Eryu Guan <eguan@redhat.com>]

On Fri, Aug 21, 2015 at 09:17:14AM +0800, Qu Wenruo wrote:
> Btrfs qgroup reserve codes lacks check for rewrite dirty page, causing
> every write, even rewriting a uncommitted dirty page, to reserve space.
> 
> But only written data will free the reserved space, causing reserved
> space leaking.
> 
> The bug exists almost from the beginning of btrfs qgroup codes, but
> nobody found it.
> 
> For example:
> 
> 1)Write [0, 12K) into file A
>   reserve 12K space
> 
> File A:
> 0	4K	8K	12K
> |<--------dirty-------->|
> reserved: 12K
> 
> 2)Write [0,4K) into file A
> 0	4K	8K	12K
> |<--------dirty-------->|
> reserved: 16K <<< Should be 12K
> 
> 3) Commit transaction
> Dirty pages [0,12) written to disk.
> Free 12K reserved space.
> reserved: 4K <<< Should be 0
> 
> This testcase will test such problem.
> Kernel fix will need some huge change, so won't be soon.
> 
> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
> Reviewed-by: Filipe Manana <fdmanana@suse.com>
> ---
> Changelog:
> v2:
>   Use smaller write size inside loop, in case commit is trigger by dirty
>   page threshold, and ensure following write won't trigger EQUOT
> v3:
>   Add more comments and fix some expression.
> v4:
>   Rebase to latest fstests.
> v5:
>   Use larger number to avoid conflicts with the test from Filipe Manana.
> ---
>  tests/btrfs/099     | 86 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  tests/btrfs/099.out | 13 ++++++++
>  tests/btrfs/group   |  1 +
>  3 files changed, 100 insertions(+)
>  create mode 100755 tests/btrfs/099
>  create mode 100644 tests/btrfs/099.out
> 
> diff --git a/tests/btrfs/099 b/tests/btrfs/099
> new file mode 100755
> index 0000000..ba531e1
> --- /dev/null
> +++ b/tests/btrfs/099
> @@ -0,0 +1,86 @@
> +#! /bin/bash
> +# FS QA Test 099
> +#
> +# Check for qgroup reserved space leaks caused by re-writing dirty ranges
> +# This bug has been present in btrfs qgroup for a long time
> +#
> +#-----------------------------------------------------------------------
> +# Copyright (c) 2015 Fujitsu. All Rights Reserved.
> +#
> +# This program is free software; you can redistribute it and/or
> +# modify it under the terms of the GNU General Public License as
> +# published by the Free Software Foundation.
> +#
> +# This program is distributed in the hope that it would be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program; if not, write the Free Software Foundation,
> +# Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
> +#-----------------------------------------------------------------------
> +#
> +
> +seq=`basename $0`
> +seqres=$RESULT_DIR/$seq
> +echo "QA output created by $seq"
> +
> +here=`pwd`
> +tmp=/tmp/$$
> +status=1	# failure is the default!
> +trap "_cleanup; exit \$status" 0 1 2 3 15
> +
> +_cleanup()
> +{
> +	cd /
> +	rm -f $tmp.*
> +}
> +
> +# get standard environment, filters and checks
> +. ./common/rc
> +. ./common/filter
> +
> +# real QA test starts here
> +
> +_supported_fs btrfs
> +_supported_os Linux
> +_require_scratch
> +_need_to_be_root
> +
> +# Use big blocksize to ensure there is still enough space left for metadata
> +# space reserve.
> +BLOCKSIZE=$(( 2 * 1024 * 1024 )) # 2M block size
> +FILESIZE=$(( 128 * 1024 * 1024 )) # 128M file size
> +
> +_scratch_mkfs >> $seqres.full 2>&1

Just one minor issue here, please remove $seqres.full before test,
otherwise $seqres.full will keep growing.

Thanks,
Eryu