Re: [PATCH V2] fstests: _require_dm_target should not always skip DAX capable devices

[Zorro Lang <zlang@redhat.com>]

On Wed, Oct 27, 2021 at 12:38:42PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> Recent changes have turned off all dm-error, dm-thin and dm-flakey
> tests on pmem devices even when we are not explicitly testing DAX.
> This is a regression resulting in a large number of log recovery
> tests no longer running on my pmem-based test VMs. I added the "-o
> dax=never" mount options to these test configs, only to find it
> still would not run the dm tests even though the filesystem will
> never use DAX.
> 
> Fix this so that the dm target DAX test explicitly ignores the
> the block device DAX capability when the filesystem is mounted with
> dax=never and hence we can use all the dm targets when the tests are
> being run with FSDAX disabled.
> 
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---

Make sense.

Reviewed-by: Zorro Lang <zlang@redhat.com>

> Version 2:
> -use -w for grep command to do exact word matching for options.
> 
>  common/rc | 21 +++++++++++++++------
>  1 file changed, 15 insertions(+), 6 deletions(-)
> 
> diff --git a/common/rc b/common/rc
> index 7f693d39..75197453 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -1965,12 +1965,19 @@ _require_sane_bdev_flush()
>  }
>  
>  # Decide if the scratch filesystem is likely to be mounted in fsdax mode.
> -# If there's a dax clause in the mount options we assume the test runner
> -# wants us to test DAX; or if the scratch device itself advertises dax mode
> -# in sysfs.
> -__detect_scratch_fsdax()
> +# It goes 3 ways based on mount options::
> +#	1. "dax" or "dax=always" means always test using DAX
> +#	2. "dax=never" means we'll never use DAX
> +#	3. "dax=inode" or nothing means "use scratch dev capability" to
> +#	    determine whether DAX is going to be used.
> +#
> +# Returns 0 if DAX will be used, 1 if DAX is not going to be used.
> +__scratch_uses_fsdax()
>  {
> -	_normalize_mount_options | egrep -q "dax(=always| |$)" && return 0
> +	local ops=$(_normalize_mount_options)
> +
> +	echo $ops | egrep -qw "dax(=always| |$)" && return 0
> +	echo $ops | grep -qw "dax=never" && return 1
>  
>  	local sysfs="/sys/block/$(_short_dev $SCRATCH_DEV)"
>  	test -e "${sysfs}/dax" && return 0
> @@ -1982,6 +1989,8 @@ __detect_scratch_fsdax()
>  _require_dm_target()
>  {
>  	local target=$1
> +	local fsdax
> +	local bdevdax
>  
>  	# require SCRATCH_DEV to be a valid block device with sane BLKFLSBUF
>  	# behaviour
> @@ -1989,7 +1998,7 @@ _require_dm_target()
>  	_require_sane_bdev_flush $SCRATCH_DEV
>  	_require_command "$DMSETUP_PROG" dmsetup
>  
> -	if __detect_scratch_fsdax; then
> +	if __scratch_uses_fsdax; then
>  		case $target in
>  		stripe|linear|log-writes)
>  			;;
>