Re: [PATCH v4] overlay: test for whiteout inode sharing

[Chengguang Xu <cgxu519@mykernel.net>]

 ---- 在 星期日, 2020-05-10 23:50:37 Eryu Guan <guan@eryu.me> 撰写 ----
 > On Wed, May 06, 2020 at 06:15:28PM +0800, Chengguang Xu wrote:
 > > This is a test for whiteout inode sharing feature.
 > > 
 > > Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
 > > ---
 > > v1->v2:
 > > - Address Amir's comments in v1
 > > 
 > > v2->v3:
 > > - Address Amir's comments in v2 
 > > 
 > > v3->v4:
 > > - Fix test case based on latest kernel patch(removed module param)
 > > https://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs.git/commit/?h=overlayfs-next&id=4e49695244661568130bfefcb6143dd1eaa3d8e7
 > > 
 > >  tests/overlay/073     | 106 ++++++++++++++++++++++++++++++++++++++++++
 > >  tests/overlay/073.out |   2 +
 > >  tests/overlay/group   |   1 +
 > >  3 files changed, 109 insertions(+)
 > >  create mode 100755 tests/overlay/073
 > >  create mode 100644 tests/overlay/073.out
 > > 
 > > diff --git a/tests/overlay/073 b/tests/overlay/073
 > > new file mode 100755
 > > index 00000000..fc847092
 > > --- /dev/null
 > > +++ b/tests/overlay/073
 > > @@ -0,0 +1,106 @@
 > > +#! /bin/bash
 > > +# SPDX-License-Identifier: GPL-2.0
 > > +# Copyright (c) 2020 Chengguang Xu <cgxu519@mykernel.net>.
 > > +# All Rights Reserved.
 > > +#
 > > +# FS QA Test 073
 > > +#
 > > +# Test whiteout inode sharing functionality.
 > > +#
 > > +# A "whiteout" is an object that has special meaning in overlayfs.
 > > +# A whiteout on an upper layer will effectively hide a matching file
 > > +# in the lower layer, making it appear as if the file didn't exist.
 > > +#
 > > +# Whiteout inode sharing means multiple whiteout objects will share
 > > +# one inode in upper layer, without this feature every whiteout object
 > > +# will consume one inode in upper layer.
 > > +
 > > +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
 > > +
 > > +# remove previous $seqres.full before test
 > > +rm -f $seqres.full
 > > +
 > > +# real QA test starts here
 > > +_supported_fs overlay
 > > +_supported_os Linux
 > > +_require_scratch
 > 
 > I see no feature detection logic, so test just fails on old kernels
 > without this feature? I tried with v5.7-r4 kernel, test fails because
 > each whiteout file has only one hardlink.
 
That's true.

Thanks,
cgxu