Re: [PATCH] xfs: test increased overlong directory extent discard threshold

Eryu Guan
2017-09-28T08:55:43Z

On Tue, Sep 26, 2017 at 06:03:48PM -0700, Darrick J. Wong wrote:
> As of 2007, metadump has an interesting "feature" where it discards
> directory extents that are longer than 1000 (originally 20) blocks.
> This ostensibly was to protect metadump from corrupt bmbt records, but
> it also has the effect of omitting from the metadump valid long extents.
> The end result is that we create incomplete metadumps, which is
> exacerbated by the lack of warning unless -w is passed.
>
> So now that we've fixed the default threshold to MAXEXTLEN, check that
> the installed metadump no longer exhibits this behavior.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
> tests/xfs/707 | 101 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> tests/xfs/707.out | 6 +++
> tests/xfs/group | 1 +
> 3 files changed, 108 insertions(+)
> create mode 100755 tests/xfs/707
> create mode 100644 tests/xfs/707.out
>
> diff --git a/tests/xfs/707 b/tests/xfs/707
> new file mode 100755
> index 0000000..f97d029
> --- /dev/null
> +++ b/tests/xfs/707
> @@ -0,0 +1,101 @@
> +#! /bin/bash
> +# FS QA Test No. 707
> +#
> +# Ensure that metadump copies large directory extents
> +#
> +# Metadump helpfully discards directory (and xattr) extents that are
> +# longer than 1000 blocks. This is a little silly since a hardlink farm
> +# can easily create such a monster.
> +#
> +# Now that we've upped metadump's default too-long-extent discard
> +# threshold to 2^21 blocks, make sure we never do that again.
> +#
> +#-----------------------------------------------------------------------
> +# Copyright (c) 2017, Oracle and/or its affiliates. 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 -rf "$tmp".* $metadump_file $metadump_img

'rm -f' to be safe :)

> +}
> +
> +# get standard environment, filters and checks
> +. ./common/rc
> +. ./common/filter
> +
> +# real QA test starts here
> +_supported_os Linux
> +_supported_fs xfs
> +_require_scratch
> +
> +rm -f "$seqres.full"
> +
> +echo "Format and mount"
> +_scratch_mkfs -b size=1k -n size=64k > "$seqres.full" 2>&1

Add some comments about the non-default mkfs options?

> +_scratch_mount >> "$seqres.full" 2>&1
> +
> +metadump_file="$TEST_DIR/meta-$seq"
> +metadump_img="$TEST_DIR/img-$seq"
> +rm -rf $metadump_file $metadump_img

Same here, 'rm -f'

> +testdir="$SCRATCH_MNT/test-$seq"
> +max_fname_len=255
> +blksz=$(_get_block_size $SCRATCH_MNT)
> +
> +# Try to create a directory w/ extents
> +blocks=1050
> +names=$((blocks * (blksz / max_fname_len)))
> +echo "Create huge dir"
> +mkdir -p $testdir
> +touch $SCRATCH_MNT/a
> +seq 0 $names | while read f; do
> + name="$testdir/$(printf "%0${max_fname_len}d" $f)"
> + ln $SCRATCH_MNT/a $name
> +done
> +dir_inum=$(stat -c %i $testdir)
> +
> +echo "Check for > 1000 block extent?"
> +_scratch_unmount
> +check_for_long_extent() {
> + inum=$1
> +
> + _scratch_xfs_db -x -c "inode $dir_inum" -c bmap | \
> + sed -e 's/^.*count \([0-9]*\) flag.*$/\1/g' | \
> + awk '{if ($1 > 1000) { printf("yes, %d\n", $1); } }'
> +}
> +extlen="$(check_for_long_extent $dir_inum)"
> +echo "qualifying extent: $extlen blocks" >> $seqres.full
> +test -n "$extlen" || _fail "could not create dir extent > 1000 blocks"

Is this really a failure? IMHO, _notrun makes more sense here.

Thanks,
Eryu

> +
> +echo "Try to metadump"
> +_scratch_metadump $metadump_file -w
> +xfs_mdrestore $metadump_file $metadump_img
> +
> +echo "Check restored metadump image"
> +$XFS_REPAIR_PROG -n $metadump_img >> $seqres.full 2>&1
> +
> +# success, all done
> +status=0
> +exit
> diff --git a/tests/xfs/707.out b/tests/xfs/707.out
> new file mode 100644
> index 0000000..0d2a222
> --- /dev/null
> +++ b/tests/xfs/707.out
> @@ -0,0 +1,6 @@
> +QA output created by 707
> +Format and mount
> +Create huge dir
> +Check for > 1000 block extent?
> +Try to metadump
> +Check restored metadump image
> diff --git a/tests/xfs/group b/tests/xfs/group
> index 7353b9c..a70c884 100644
> --- a/tests/xfs/group
> +++ b/tests/xfs/group
> @@ -432,3 +432,4 @@
> 703 auto quick clone fsr
> 704 auto quick clone
> 705 auto quick clone fsr
> +707 auto quick dir metadata