Re: [PATCH v8 1/7] common/rc: Introduce helpers for new dax mount options and FS_XFLAG_DAX

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

On Mon, Aug 03, 2020 at 12:49:19PM -0700, Ira Weiny wrote:
> On Mon, Aug 03, 2020 at 04:38:32PM +0800, Xiao Yang wrote:
> > 1) _check_scratch_dax_mountopt() checks old/new dax mount option and
> >    returns a value.
> > 2) _require_scratch_dax_mountopt() throws notrun if _check_scratch_dax_mountopt()
> >    returns a non-zero value.
> > 3) _require_dax_iflag() checks FS_XFLAG_DAX.
> > 
> > Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
> > ---
> >  common/rc | 42 ++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 42 insertions(+)
> > 
> > diff --git a/common/rc b/common/rc
> > index 1b7b2575..d7926bc5 100644
> > --- a/common/rc
> > +++ b/common/rc
> > @@ -3188,6 +3188,48 @@ _require_scratch_dax()
> >  	_scratch_unmount
> >  }
> >  
> > +# Only accept dax/dax=always mount option becasue dax=always, dax=inode
> > +# and dax=never are always introduced together.
> > +# Return 0 if filesystem/device supports the specified dax option.
> > +# Return 1 if mount fails with the specified dax option.
> > +# Return 2 if /proc/mounts shows wrong dax option.
> > +# Check new dax=inode, dax=always or dax=never option by passing "dax=always".
> > +# Check old dax or new dax=always by passing "dax".
> > +_check_scratch_dax_mountopt()
> 
> So I think I see what you are trying to say here but I'm not sure the
> comment/doc is clear.  How about:
> 
> # Check if dax mount options are supported
> #
> # $1 can be either 'dax=always' or 'dax'
> #
> # dax=always
> #      Check for the new dax options (dax=inode, dax=always or dax=never) by
> #      passing "dax=always".
> # dax
> #      Check for the old dax or new dax=always by passing "dax".
> #
> # This only accepts 'dax=always' because dax=always, dax=inode
> # and dax=never are always supported together.  So if the other options are
> # required checking for 'dax=always' indicates support for the other 2.
> #
> # Return 0 if filesystem/device supports the specified dax option.
> # Return 1 if mount fails with the specified dax option.
> # Return 2 if /proc/mounts shows wrong dax option.

/me likes this better.

--D

> Ira
> 
> > +{
> > +	local option=$1
> > +
> > +	_require_scratch
> > +	_scratch_mkfs > /dev/null 2>&1
> > +
> > +	_try_scratch_mount "-o $option" > /dev/null 2>&1 || return 1
> > +
> > +	if _fs_options $SCRATCH_DEV | egrep -q "dax(=always|,|$)"; then
> > +		_scratch_unmount
> > +		return 0
> > +	else
> > +		_scratch_unmount
> > +		return 2
> > +	fi
> > +}
> > +
> > +# Throw notrun if _check_scratch_dax_mountopt() returns a non-zero value.
> > +_require_scratch_dax_mountopt()
> > +{
> > +	local mountopt=$1
> > +
> > +	_check_scratch_dax_mountopt "$mountopt"
> > +	local res=$?
> > +
> > +	[ $res -eq 1 ] && _notrun "mount $SCRATCH_DEV with $mountopt failed"
> > +	[ $res -eq 2 ] && _notrun "$SCRATCH_DEV $FSTYP does not support -o $mountopt"
> > +}
> > +
> > +_require_dax_iflag()
> > +{
> > +	_require_xfs_io_command "chattr" "x"
> > +}
> > +
> >  # Does norecovery support by this fs?
> >  _require_norecovery()
> >  {
> > -- 
> > 2.21.0
> > 
> > 
> >