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

[Xiao Yang <yangx.jy@cn.fujitsu.com>]

On 2020/7/15 12:15, Ira Weiny wrote:
> 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)
Hi Ira,

dax=inode/dax=never cannot check if underlying device supports dax, so I 
perfer to use dax=always
For example:
XFS:
# mount -o dax=inode /dev/sda8 /mnt/xfstests/test/
# mount | grep sda8
/dev/sda8 on /mnt/xfstests/test type xfs 
(rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,noquota)
...
# mount -o dax=always /dev/sda8 /mnt/xfstests/test/
# mount | grep sda8
/dev/sda8 on /mnt/xfstests/test type xfs 
(rw,relatime,seclabel,attr2,dax=never,inode64,logbufs=8,logbsize=32k,noquota)

EXT4:
# mount -o dax=inode /dev/sda8 /mnt/xfstests/test/
# mount | grep sda8
/dev/sda8 on /mnt/xfstests/test type ext4 (rw,relatime,seclabel,dax=inode)
...
# mount -o dax=always /dev/sda8 /mnt/xfstests/test/
mount: /mnt/xfstests/test: wrong fs type, bad option, bad superblock on 
/dev/sda8, missing codepage or helper program, or other error.
# dmesg | grep DAX
[597988.165120] EXT4-fs (sda8): DAX unsupported by block device.

If we want to test new dax(i.e. dax=inode, dax=always or dax=never), so 
pass "dax=always" to  _require_scratch_dax_mountopt
If we want to test old dax  or new dax=always(either of them), so pass 
"dax" to _require_scratch_dax_mountopt

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