Re: [PATCH v2 7/7] overlay: test dropping nlink below zero

[Eryu Guan <eguan@redhat.com>]

On Tue, Jul 04, 2017 at 02:40:34PM +0300, Amir Goldstein wrote:
> nlink of overlay inode could be dropped indefinety by adding
> un-accounted lower hardlinks underneath a mounted overlay and
> trying to remove them.

Sorry, I didn't quite follow the hardlink patches, could you please
describe what is "accounted/un-accounted" hardlinks and the expected
behavior in commit log? And what does "indefinety" mean? I couldn't find
it in dictionary.

> 
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>  tests/overlay/034     | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  tests/overlay/034.out |  2 ++
>  tests/overlay/group   |  1 +
>  3 files changed, 94 insertions(+)
>  create mode 100755 tests/overlay/034
>  create mode 100644 tests/overlay/034.out
> 
> diff --git a/tests/overlay/034 b/tests/overlay/034
> new file mode 100755
> index 0000000..cb023bf
> --- /dev/null
> +++ b/tests/overlay/034
> @@ -0,0 +1,91 @@
> +#! /bin/bash
> +# FS QA Test 034
> +#
> +# Test overlay nlink when adding lower hardlinks.
> +#
> +# nlink of overlay inode could be dropped indefinety by adding
> +# unaccounted lower hardlinks underneath a mounted overlay and
> +# trying to remove them.
> +#
> +#-----------------------------------------------------------------------
> +# Copyright (C) 2017 CTERA Networks. All Rights Reserved.
> +# Author: Amir Goldstein <amir73il@gmail.com>
> +#
> +# 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"
> +
> +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
> +
> +# remove previous $seqres.full before test
> +rm -f $seqres.full
> +
> +# real QA test starts here
> +_supported_fs overlay
> +_supported_os Linux
> +_require_scratch
> +
> +# Remove all files from previous tests
> +_scratch_mkfs
> +
> +# Create lower hardlink
> +lowerdir=$OVL_BASE_SCRATCH_MNT/$OVL_LOWER
> +mkdir -p $lowerdir
> +touch $lowerdir/0
> +ln $lowerdir/0 $lowerdir/1
> +
> +_scratch_mount
> +
> +# Copy up lower hardlink - nlink should be 2
> +touch $SCRATCH_MNT/0
> +
> +# Add lower hardlinks while overlay is mounted

Why "while overlay is mounted" is needed?

> +ln $lowerdir/0 $lowerdir/2
> +ln $lowerdir/0 $lowerdir/3
> +
> +# Unlink un-accounted lowers to drive nlink to 0
> +rm $SCRATCH_MNT/2
> +rm $SCRATCH_MNT/3

drive nlink of which file to 0? Sorry, I'm a bit lost on overlay
hardlink behaviors..

> +
> +# Check for getting ENOENT for trying to link !I_LINKABLE with nlink 0
> +ln $SCRATCH_MNT/0 $SCRATCH_MNT/4

Shouldn't we expect an error message from this ln, if "check for getting
ENOEND"? BTW, this test passed on 4.12-rc7 kernel, I'm not sure if
that's expected result.

Thanks,
Eryu

> +
> +# Unlink all hardlink to drive nlink below 0
> +rm $SCRATCH_MNT/0
> +rm $SCRATCH_MNT/1
> +rm $SCRATCH_MNT/4
> +
> +# Verify that orphan index is cleaned on mount
> +_scratch_cycle_mount
> +ls $OVL_BASE_SCRATCH_MNT/$OVL_WORK/index 2>/dev/null
> +
> +echo "Silence is golden"
> +status=0
> +exit
> diff --git a/tests/overlay/034.out b/tests/overlay/034.out
> new file mode 100644
> index 0000000..4c8873c
> --- /dev/null
> +++ b/tests/overlay/034.out
> @@ -0,0 +1,2 @@
> +QA output created by 034
> +Silence is golden
> diff --git a/tests/overlay/group b/tests/overlay/group
> index 35cd5a5..b55ed0c 100644
> --- a/tests/overlay/group
> +++ b/tests/overlay/group
> @@ -36,3 +36,4 @@
>  031 auto quick whiteout
>  032 auto quick copyup hardlink
>  033 auto quick copyup hardlink
> +034 auto quick copyup hardlink
> -- 
> 2.7.4
>