Re: [PATCH] generic: Verify if statx() can qurey S_SAX flag on regular file correctly

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Thu, Jul 02, 2020 at 03:08:01PM +0800, Xiao Yang wrote:
> Hi Ira, Darrick
> 
> I have one question about S_DAX flag:
> Current statx() can only query S_DAX flag on regular file,
> why don't we set S_DAX flag for directory in kernel? :-)

This was the kind of confusion I was trying to avoid by having dax.txt
spell out exactly what S_DAX meant (it's the incore flag that means that
*regular file access* is done via direct CPU access and not via
pagecache.

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/filesystems/dax.txt

--D

> 
> Best Regards,
> Xiao Yang
> On 2020/7/2 14:35, Xiao Yang wrote:
> > With new kernel(e.g. v5.8-rc1), statx() can be used to qurey S_SAX flag
> > on regular file, so add a test to verify the feature.
> >
> > Reference:
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=712b2698e4c024b561694cbcc1abba13eb0fd9ce
> >
> > Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
> > ---
> >
> > Note: this patch depends on the following patch set:
> > https://www.spinics.net/lists/fstests/msg14252.html
> >
> >  tests/generic/604     | 100 ++++++++++++++++++++++++++++++++++++++++++
> >  tests/generic/604.out |   2 +
> >  tests/generic/group   |   1 +
> >  3 files changed, 103 insertions(+)
> >  create mode 100644 tests/generic/604
> >  create mode 100644 tests/generic/604.out
> >
> > diff --git a/tests/generic/604 b/tests/generic/604
> > new file mode 100644
> > index 00000000..b0baa781
> > --- /dev/null
> > +++ b/tests/generic/604
> > @@ -0,0 +1,100 @@
> > +#! /bin/bash
> > +# SPDX-License-Identifier: GPL-2.0
> > +# Copyright (c) 2020 Fujitsu.  All Rights Reserved.
> > +#
> > +# FS QA Test 604
> > +#
> > +# By the following cases, verify if statx() can query S_SAX flag
> > +# on regular file correctly.
> > +# 1) With dax=always option, FS_XFLAG_DAX is ignored and S_SAX flag
> > +#    always exists on regular file.
> > +# 2) With dax=inode option, setting/clearing FS_XFLAG_DAX can change
> > +#    S_SAX flag on regular file.
> > +# 3) With dax=never option, FS_XFLAG_DAX is ignored and S_SAX flag
> > +#    never exists on regular file.
> > +#
> > +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 $seqres.full
> > +
> > +_supported_fs generic
> > +_supported_os Linux
> > +_require_scratch_dax_mountopt "dax=always"
> > +_require_scratch_dax_iflag
> > +_require_xfs_io_command "statx" "-r"
> > +
> > +PARENT_DIR=$SCRATCH_MNT/testdir
> > +TEST_FILE=$PARENT_DIR/testfile
> > +
> > +check_s_dax()
> > +{
> > +	local exp_s_dax=$1
> > +
> > +	local attributes=$($XFS_IO_PROG -c 'statx -r' $TEST_FILE | awk '/stat.attributes / { print $3 }')
> > +	if [ $exp_s_dax -eq 0 ]; then
> > +		(( attributes & 0x2000 )) && echo "$TEST_FILE has unexpected S_DAX flag"
> > +	else
> > +		(( attributes & 0x2000 )) || echo "$TEST_FILE doen't have expected S_DAX flag"
> > +	fi
> > +}
> > +
> > +test_s_dax()
> > +{
> > +	local dax_option=$1
> > +	local exp_s_dax1=$2
> > +	local exp_s_dax2=$3
> > +
> > +	# Mount with specified dax option
> > +	_scratch_mount "-o $dax_option"
> > +
> > +	# Prepare directory
> > +	mkdir -p $PARENT_DIR
> > +
> > +	rm -f $TEST_FILE
> > +	$XFS_IO_PROG -c "chattr +x" $PARENT_DIR
> > +	touch $TEST_FILE
> > +	# Check if setting FS_XFLAG_DAX changes S_DAX flag
> > +	check_s_dax $exp_s_dax1
> > +
> > +	rm -f $TEST_FILE
> > +	$XFS_IO_PROG -c "chattr -x" $PARENT_DIR
> > +	touch $TEST_FILE
> > +	# Check if clearing FS_XFLAG_DAX changes S_DAX flag
> > +	check_s_dax $exp_s_dax2
> > +
> > +	_scratch_unmount
> > +}
> > +
> > +do_tests()
> > +{
> > +	test_s_dax "dax=always" 1 1
> > +	test_s_dax "dax=inode" 1 0
> > +	test_s_dax "dax=never" 0 0
> > +}
> > +
> > +_scratch_mkfs >> $seqres.full 2>&1
> > +
> > +do_tests
> > +
> > +# success, all done
> > +echo "Silence is golden"
> > +status=0
> > +exit
> > diff --git a/tests/generic/604.out b/tests/generic/604.out
> > new file mode 100644
> > index 00000000..c06a1c7f
> > --- /dev/null
> > +++ b/tests/generic/604.out
> > @@ -0,0 +1,2 @@
> > +QA output created by 604
> > +Silence is golden
> > diff --git a/tests/generic/group b/tests/generic/group
> > index 1d0d5606..676e0d2e 100644
> > --- a/tests/generic/group
> > +++ b/tests/generic/group
> > @@ -606,3 +606,4 @@
> >  601 auto quick quota
> >  602 auto quick encrypt
> >  603 auto attr quick dax
> > +604 auto attr quick dax
> 
> 
>