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

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

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.

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
> 
> 
>