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

ruansy.fnst
2022-07-29T03:56:38Z

在 2022/7/22 0:16, Darrick J. Wong 写道:
> On Thu, Jul 21, 2022 at 02:06:10PM +0000, ruansy.fnst@fujitsu.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@fujitsu.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@kernel.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
>>>>
>>>>
>>>>