Re: [PATCH v3 0/3] io_uring getdents

[Hao Xu <hao.xu@linux.dev>]

Hi,

On 7/12/23 08:56, Jens Axboe wrote:
> On 7/11/23 6:53 PM, Dominique Martinet wrote:
>> Jens Axboe wrote on Tue, Jul 11, 2023 at 05:51:46PM -0600:
>>>> So what filesystem actually uses this new NOWAIT functionality?
>>>> Unless I'm blind (quite possibly) I don't see any filesystem
>>>> implementation of this functionality in the patch series.
>>
>> I had implemented this for kernfs and libfs (so sysfs, debugfs, possibly
>> tmpfs/proc?) in v2
>>
>> The patch as of v2's mail has a bug, but my branch has it fixed as of
>> https://github.com/martinetd/linux/commits/io_uring_getdents
>>
>> (I guess these aren't "real" enough though)
> 
> No, I definitely think those are real and valid. But would be nice with
> a "real" file system as well.
> 
>>>> I know I posted a prototype for XFS to use it, and I expected that
>>>> it would become part of this patch series to avoid the "we don't add
>>>> unused code to the kernel" problem. i.e. the authors would take the
>>>> XFS prototype, make it work, add support into for the new io_uring
>>>> operation to fsstress in fstests and then use that to stress test
>>>> the new infrastructure before it gets merged....
>>>>
>>>> But I don't see any of this?
>>>
>>> That would indeed be great if we could get NOWAIT, that might finally
>>> convince me that it's worth plumbing up! Do you have a link to that
>>> prototype? That seems like what should be the base for this, and be an
>>> inspiration for other file systems to get efficient getdents via this
>>> (rather than io-wq punt, which I'm not a huge fan of...).
>>
>> the xfs poc was in this mail:
>> https://lore.kernel.org/all/20230501071603.GE2155823@dread.disaster.area/
>>
>> I never spent time debugging it, but it should definitely be workable
> 
> If either you or Hao wants to take a stab at it and see how it goes,
> I think that would be hugely beneficial for this patchset.
> 


I can take the xfs and kernfs part if Dominique doesn't mind.

Regards,
Hao