Re: [PATCH v6 1/7] common/rc: Introduce new helpers for DAX mount options and FS_XFLAG_DAX

[Ira Weiny <ira.weiny@intel.com>]

On Wed, Jul 15, 2020 at 11:19:58AM +0800, Xiao Yang wrote:
> On 2020/7/15 9:59, Ira Weiny wrote:
> > On Tue, Jul 14, 2020 at 05:40:03PM +0800, Xiao Yang wrote:
> > > 1) _require_scratch_dax_mountopt() checks both old and new DAX mount option
> > > 2) _require_dax_iflag() checks FS_XFLAG_DAX
> > > 
> > > Signed-off-by: Xiao Yang<yangx.jy@cn.fujitsu.com>
> > Reviewed-by: Ira Weiny<ira.weiny@intel.com>
> Hi Ira,
> 
> Do you want to check if invalid parameter is passed to
> _require_scratch_dax_mountopt? Thought
> I think it is not necessary(user should pass correct parament).
> Like this:
> [ "$mountopt" != "dax" ] && [ "$mountopt" != "dax=always" ] && _notrun
> "$mountopt is invalid"

I thought this patch was just checking if the filesystem/device supported DAX
such that DAX tests could run using either old _or_ new dax support...

But after thinking about it I think we need something more complicated.

Something like:

if ('-o dax=inode')
	// FS is DAX with per file support (ie ext4 || XFS kernel >= 5.8)
else if ('-o dax')
	// FS is DAX (ie ext4 || XFS on kernel < 5.8)
else
	// FS has no dax support.

Do we do that with 2 functions?

	_require_scratch_dax_mountopt()
	_require_scratch_new_dax_mountopt()

If both fail we are in the else clause above?

We can use the dax=inode because it is a new option and is not necessarily the
option used while running the tests.  (I think.  as I said my xfstests skills
are not great so I'm not always sure of the correct patterns)

Ira

> 
> Best Regards,
> Xiao Yang
> > > ---
> > > 
> > > V5->V6:
> > > Simplify _require_scratch_dax_mountopt because it is enough to only check
> > > dax/dax=always mount option.  See the following reasons:
> > > 1) we cannot detect if underlying device supports dax by mounting dax=inode
> > >     or dax=never.
> > > 2) dax=always, dax=inode, dax=never are always introduced together.
> > > 
> > >   common/rc | 22 ++++++++++++++++++++++
> > >   1 file changed, 22 insertions(+)
> > > 
> > > diff --git a/common/rc b/common/rc
> > > index f17b19f2..aeec1f11 100644
> > > --- a/common/rc
> > > +++ b/common/rc
> > > @@ -3188,6 +3188,28 @@ _require_scratch_dax()
> > >   	_scratch_unmount
> > >   }
> > > 
> > > +# Only accept dax/dax=always mount option becasue dax=always, dax=inode
> > > +# and dax=never are always introduced together.
> > > +_require_scratch_dax_mountopt()
> > > +{
> > > +	local mountopt=$1
> > > +
> > > +	_require_scratch
> > > +	_scratch_mkfs>  /dev/null 2>&1
> > > +	_try_scratch_mount "-o $mountopt">  /dev/null 2>&1 || \
> > > +		_notrun "mount $SCRATCH_DEV with $mountopt failed"
> > > +
> > > +	_fs_options $SCRATCH_DEV | egrep -q "dax(=always|,|$)" || \
> > > +		_notrun "$SCRATCH_DEV $FSTYP does not support -o $mountopt"
> > > +
> > > +	_scratch_unmount
> > > +}
> > > +
> > > +_require_dax_iflag()
> > > +{
> > > +	_require_xfs_io_command "chattr" "x"
> > > +}
> > > +
> > >   # Does norecovery support by this fs?
> > >   _require_norecovery()
> > >   {
> > > -- 
> > > 2.21.0
> > > 
> > > 
> > > 
> > 
> > .
> > 
> 
> 
>