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Re: [PATCH v2] xfstests: add regression test for btrfs incremental send

To: Filipe David Borba Manana <fdmanana@xxxxxxxxx>
Subject: Re: [PATCH v2] xfstests: add regression test for btrfs incremental send
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Mon, 17 Feb 2014 10:08:52 +1100
Cc: xfs@xxxxxxxxxxx, linux-btrfs@xxxxxxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1392478573-4513-1-git-send-email-fdmanana@xxxxxxxxx>
References: <1392408522-764-1-git-send-email-fdmanana@xxxxxxxxx> <1392478573-4513-1-git-send-email-fdmanana@xxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Sat, Feb 15, 2014 at 03:36:13PM +0000, Filipe David Borba Manana wrote:
> Test for a btrfs incremental send issue where we end up sending a
> wrong section of data from a file extent if the corresponding file
> extent is compressed and the respective file extent item has a non
> zero data offset.
> 
> Fixed by the following linux kernel btrfs patch:
> 
>    Btrfs: use right clone root offset for compressed extents
> 
> Signed-off-by: Filipe David Borba Manana <fdmanana@xxxxxxxxx>
> ---
> 
> V2: Made the test more reliable. Now it doesn't depend anymore of btrfs'
>     hole punch implementation leaving hole file extent items when we punch
>     beyond the file's current size.
> 
>  tests/btrfs/040     |  115 
> +++++++++++++++++++++++++++++++++++++++++++++++++++
>  tests/btrfs/040.out |    1 +
>  tests/btrfs/group   |    1 +
>  3 files changed, 117 insertions(+)
>  create mode 100755 tests/btrfs/040
>  create mode 100644 tests/btrfs/040.out
> 
> diff --git a/tests/btrfs/040 b/tests/btrfs/040
> new file mode 100755
> index 0000000..d6b37bf
> --- /dev/null
> +++ b/tests/btrfs/040
> @@ -0,0 +1,115 @@
> +#! /bin/bash
> +# FS QA Test No. btrfs/040
> +#
> +# Test for a btrfs incremental send issue where we end up sending a
> +# wrong section of data from a file extent if the corresponding file
> +# extent is compressed and the respective file extent item has a non
> +# zero data offset.
> +#
> +# Fixed by the following linux kernel btrfs patch:
> +#
> +#   Btrfs: use right clone root offset for compressed extents
> +#
> +#-----------------------------------------------------------------------
> +# Copyright (c) 2014 Filipe Manana.  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=`mktemp -d`
> +status=1     # failure is the default!
> +trap "_cleanup; exit \$status" 0 1 2 3 15
> +
> +_cleanup()
> +{
> +    rm -fr $tmp
> +}
> +
> +# get standard environment, filters and checks
> +. ./common/rc
> +. ./common/filter
> +
> +# real QA test starts here
> +_supported_fs btrfs
> +_supported_os Linux
> +_require_scratch
> +_need_to_be_root
> +
> +FSSUM_PROG=$here/src/fssum
> +[ -x $FSSUM_PROG ] || _notrun "fssum not built"
> +
> +rm -f $seqres.full
> +
> +_scratch_mkfs >/dev/null 2>&1
> +_scratch_mount "-o compress-force=lzo"
> +
> +run_check $XFS_IO_PROG -f -c "truncate 118811" $SCRATCH_MNT/foo
> +run_check $XFS_IO_PROG -c "pwrite -S 0x0d -b 39987 92267 39987" \
> +     $SCRATCH_MNT/foo

Ugh. filter the output, don't use run_check.

$XFS_IO_PROG -f -c "truncate 118811" $SCRATCH_MNT/foo
$XFS_IO_PROG -c "pwrite -S 0x0d -b 39987 92267 39987" \
        $SCRATCH_MNT/foo | _filter_xfs_io

If something fails, we still want the test to continue running, even
if all it does is exercise error handling paths. run_check simply
terminates the test at the first failure.

> +run_check $BTRFS_UTIL_PROG subvolume snapshot -r $SCRATCH_MNT \
> +     $SCRATCH_MNT/mysnap1
> +
> +run_check $XFS_IO_PROG -c "pwrite -S 0x3e -b 80000 200000 80000" \
> +     $SCRATCH_MNT/foo
> +run_check $BTRFS_UTIL_PROG filesystem sync $SCRATCH_MNT

Why a special btrfs sync here? Why isn't "sync" sufficient, or even
a synchronous write or write plus fsync like:

$XFS_IO_PROG -c "pwrite -S 0x3e -b 80000 200000 80000" -c "fsync" \
        $SCRATCH_MNT/foo | _filter_xfs_io

Tests need to be documented the same way code is documented....

> +run_check $XFS_IO_PROG -c "pwrite -S 0xdc -b 10000 250000 10000" \
> +     $SCRATCH_MNT/foo
> +run_check $XFS_IO_PROG -c "pwrite -S 0xff -b 10000 300000 10000" \
> +     $SCRATCH_MNT/foo

I'm getting to the point where I'm starting to consider "run_check"
as being harmful....

I know you are trying to work around the fact that the btrfs
progs commands have inconsistent output and so are difficult to
match. However, given that this is leading to bad habits like using
run_check for everything.

I'd suggest that we need a set of $BTRFS_UTIL_PROG specific handlers
to deal with these differences rather than continuing to pollute the
tests with run_check. e.g.

_run_btrfs_util_prog()
{
        run_check $BTRFS_UTIL_PROG $*
}

would be a good start because it gets that run_check pattern out of
the main test scripts and hence out of the heads of test writers.

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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