linux-kernel - Re: [PATCH] xfs: fail dax mount if reflink is enabled on a partition

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Date:   Fri, 29 Jul 2022 03:55:24 +0000
From:   "ruansy.fnst@...itsu.com" <ruansy.fnst@...itsu.com>
To:     "Darrick J. Wong" <djwong@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
        "nvdimm@...ts.linux.dev" <nvdimm@...ts.linux.dev>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "david@...morbit.com" <david@...morbit.com>,
        "hch@...radead.org" <hch@...radead.org>
Subject: Re: [PATCH] xfs: fail dax mount if reflink is enabled on a partition



在 2022/7/22 0:16, Darrick J. Wong 写道:
> On Thu, Jul 21, 2022 at 02:06:10PM +0000, ruansy.fnst@...itsu.com wrote:
>> 在 2022/7/1 8:31, Darrick J. Wong 写道:
>>> On Thu, Jun 09, 2022 at 10:34:35PM +0800, Shiyang Ruan wrote:
>>>> Failure notification is not supported on partitions.  So, when we mount
>>>> a reflink enabled xfs on a partition with dax option, let it fail with
>>>> -EINVAL code.
>>>>
>>>> Signed-off-by: Shiyang Ruan <ruansy.fnst@...itsu.com>
>>>
>>> Looks good to me, though I think this patch applies to ... wherever all
>>> those rmap+reflink+dax patches went.  I think that's akpm's tree, right?
>>>
>>> Ideally this would go in through there to keep the pieces together, but
>>> I don't mind tossing this in at the end of the 5.20 merge window if akpm
>>> is unwilling.
>>
>> BTW, since these patches (dax&reflink&rmap + THIS + pmem-unbind) are
>> waiting to be merged, is it time to think about "removing the
>> experimental tag" again?  :)
> 
> It's probably time to take up that question again.
> 
> Yesterday I tried running generic/470 (aka the MAP_SYNC test) and it
> didn't succeed because it sets up dmlogwrites atop dmthinp atop pmem,
> and at least one of those dm layers no longer allows fsdax pass-through,
> so XFS silently turned mount -o dax into -o dax=never. :(

Hi Darrick,

I tried generic/470 but it didn't run:
   [not run] Cannot use thin-pool devices on DAX capable block devices.

Did you modify the _require_dm_target() in common/rc?  I added thin-pool 
to not to check dax capability:

         case $target in
         stripe|linear|log-writes|thin-pool)  # add thin-pool here
                 ;;

then the case finally ran and it silently turned off dax as you said.

Are the steps for reproduction correct? If so, I will continue to 
investigate this problem.


--
Thanks,
Ruan.



> 
> I'm not sure how to fix that...
> 
> --D
> 
>>
>> --
>> Thanks,
>> Ruan.
>>
>>>
>>> Reviewed-by: Darrick J. Wong <djwong@...nel.org>
>>>
>>> --D
>>>
>>>> ---
>>>>    fs/xfs/xfs_super.c | 6 ++++--
>>>>    1 file changed, 4 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
>>>> index 8495ef076ffc..a3c221841fa6 100644
>>>> --- a/fs/xfs/xfs_super.c
>>>> +++ b/fs/xfs/xfs_super.c
>>>> @@ -348,8 +348,10 @@ xfs_setup_dax_always(
>>>>    		goto disable_dax;
>>>>    	}
>>>>    
>>>> -	if (xfs_has_reflink(mp)) {
>>>> -		xfs_alert(mp, "DAX and reflink cannot be used together!");
>>>> +	if (xfs_has_reflink(mp) &&
>>>> +	    bdev_is_partition(mp->m_ddev_targp->bt_bdev)) {
>>>> +		xfs_alert(mp,
>>>> +			"DAX and reflink cannot work with multi-partitions!");
>>>>    		return -EINVAL;
>>>>    	}
>>>>    
>>>> -- 
>>>> 2.36.1
>>>>
>>>>
>>>>