Re: [PATCH v2 6/6] xfs/260: Move xfs/260 to generic

From: Ira Weiny <ira.weiny@intel.com>
To: Xiao Yang <yangx.jy@cn.fujitsu.com>
Cc: Xiao Yang <ice_yangxiao@163.com>,
	fstests@vger.kernel.org, darrick.wong@oracle.com
Subject: Re: [PATCH v2 6/6] xfs/260: Move xfs/260 to generic
Date: Tue, 30 Jun 2020 08:50:58 -0700	[thread overview]
Message-ID: <20200630155058.GT2617015@iweiny-DESK2.sc.intel.com> (raw)
In-Reply-To: <5EFAE502.6060805@cn.fujitsu.com>

On Tue, Jun 30, 2020 at 03:08:50PM +0800, Xiao Yang wrote:
> On 2020/6/24 2:08, Ira Weiny wrote:
> > On Tue, Jun 23, 2020 at 04:51:31PM +0800, Xiao Yang wrote:
> > > On 2020/6/19 23:15, Ira Weiny wrote:
> > > > On Thu, Jun 18, 2020 at 11:35:56PM +0800, Xiao Yang wrote:
> > > > > On 6/18/20 5:48 AM, Ira Weiny wrote:
> > > > > > On Wed, Jun 17, 2020 at 05:32:04PM +0800, Xiao Yang wrote:
> > > > > > > From: Xiao Yang<yangx.jy@cn.fujitsu.com>
> > [snip]
> > 
> > > > > >     }
> > > > > > @@ -124,17 +151,11 @@ do_tests()
> > > > > >     # make xfs aligned for PMD fault testing
> > > > > >     _scratch_mkfs_geom $(_get_hugepagesize) 1>>   $seqres.full 2>&1
> > > > > > -# mount with dax option
> > > > > > -_scratch_mount "-o dax"
> > > > > > -
> > > Hi Ira,
> > > 
> > > Why do you want to remove this combination(i.e. test per-inode DAX flag
> > > under mounting with dax option) ?
> > > Is it because mounting with dax option ignore FS_XFLAG_DAX flag?
> > > I think it is a reasonable combination. :-)
> > Yes running with the DAX mount option really does not test anything IMO.
> Hi Ira,
> 
> Sorry for the late reply because I was busy with other tasks last week. :-)
> 
> After reading related code, setting/clearing FS_XFLAG_DAX have no chance to
> change S_DAX
> flag if mount with dax option, so I will remove this combination in v3
> patch.
> 
> > > > > >     tsize=$((128 * 1024 * 1024))
> > > > > > -do_tests
> > > > > > -_scratch_unmount
> > > > > > -
> > > > > >     # mount again without dax option
> > > > > >     export MOUNT_OPTIONS=""
> > > > > > -_scratch_mount
> > > > > > +_scratch_mount "-o dax=inode"
> > > > > >     do_tests
> > > > > >     # success, all done
> > > Could we keep _scratch_mount without dax so that this test can run on both
> > > old and new kernel?
> > > See the following reasons:
> > > 1) FS_XFLAG_DAX was introduced by commit 58f88ca("xfs: introduce per-inode
> > > DAX enablement") since 2017.
> > > 2) _scratch_mount with dax=inode is equal to _scratch_mount without dax.
> > I suppose that would be ok.  But being generic what happens when this runs on
> > FS's which don't have the FS_XFLAG_DAX flag?  is it ignored?
> 
> Test will report notrun by _require_scratch_dax_iflag() If fs doesn't
> support FS_XFLAG_DAX flag.
> 
> > FWIW I believe that any FS (which includes older kernels) which do not support
> > dax=inode have no need for this test to run.  The use of FS_XFLAG_DAX on older
> > xfs does not do anything and simply does not exist elsewhere.  Only FS's which
> > support dax=inode have behavior which needs to be tested IMO.
> 
> I just want to test FS_XFLAG_DAX on older xfs by keeping _scratch_mount
> without dax because
> the original test(i.e. xfs/260) is designed to test this point. :-)

Sure you can test swapping the flag itself but it really does nothing.

> 
> BTW:  It seems that older xfs can do dax mmap by setting/clearing
> FS_XFLAG_DAX, or do I miss something?

No it can only use DAX with '-o dax' mount option.  Changing FS_XFLAG_DAX on
xfs prior to 5.8 is effectively a no-op as the S_DAX flag would not be set.

See "742d84290739 xfs: disable per-inode DAX flag"

Ira

> 
> Best Regards,
> Xiao Yang
> > Ira
> > 
> > > Best Regards,
> > > Xiao Yang
> > > > .
> > > > 
> > > 
> > .
> > 
> 
> 
> 