Re: [PATCH v3 07/25] io_uring/kbuf: add recycling for kernel managed buffer rings

[Gabriel Krisman Bertazi <krisman@suse.de>]

Joanne Koong <joannelkoong@gmail.com> writes:

>> But now I see this is never exposed to userspace as an io_uring_cmd
>> command itself, it is only used internally by other fuse operations.
>> Nevertheless, it's implemented as an io_uring_cmd by
>> io_uring_cmd_kmbuffer_recycle.
>>
>> Is it eventually going to be exposed as operations to userspace? If not,
>> I'd suggest to stay out of the io_uring_cmd namespace (perhaps call
>> io_kmbuf_recycle directly from fs/fuse).  Do we need to have this
>> io_uring_cmd abstraction for some reason I'm missing?
>
> Hi Gabriel,
>
> Thanks for taking a look at the patchset.
>
> This is not going to be exposed as an operation to userspace. Only the
> kernel will be able to recycle kmbufs.
>
> I was under the impression the io_uring_cmd_* abstraction was
> preferred as the API for interfacing with io_uring from another
> subsystem.

Hello,

I don't think that's the case, no. io_uring_cmd are used to expose
backend-specific file operations to userspace, similar to an
asynchronous ioctl.  Moreover, it would just add an extra layer, without
bringing any benefits, IMO.

> In that case then, I'll get rid of the io_uring_cmd layers
> for the calls then, that will make things simpler.

-- 
Gabriel Krisman Bertazi