Re: [PATCH 0/5] io_uring: add opcodes for current working directory

[Jens Axboe <axboe@kernel.dk>]

On 5/31/22 3:35 PM, Usama Arif wrote:
> 
> 
> On 31/05/2022 20:22, Jens Axboe wrote:
>> On 5/31/22 1:18 PM, Usama Arif wrote:
>>>
>>>
>>> On 31/05/2022 19:58, Jens Axboe wrote:
>>>> On 5/31/22 12:41 PM, Usama Arif wrote:
>>>>> This provides consistency between io_uring and the respective I/O syscall
>>>>> and avoids having the user of liburing specify the cwd in sqe when working
>>>>> with current working directory, for e.g. the user can directly call with
>>>>> IORING_OP_RENAME instead of IORING_OP_RENAMEAT and providing AT_FDCWD in
>>>>> sqe->fd and sqe->len, similar to syscall interface.
>>>>>
>>>>> This is done for rename, unlink, mkdir, symlink and link in this
>>>>> patch-series.
>>>>>
>>>>> The tests for these opcodes in liburing are present at
>>>>> https://github.com/uarif1/liburing/tree/cwd_opcodes. If the patches are
>>>>> acceptable, I am happy to create a PR in above for the tests.
>>>>
>>>> Can't we just provide prep helpers for them in liburing?
>>>>
>>>
>>> We could add a io_uring_prep_unlink with IORING_OP_UNLINKAT and
>>> AT_FDCWD in liburing. But i guess adding in kernel adds a more
>>> consistent interface? and allows to make calls bypassing liburing
>>> (although i guess people probably don't bypass liburing that much :))
>>
>> I'm not really aware of much that doesn't use the library, and even
>> those would most likely use the liburing man pages as that's all we
>> have. The kernel API is raw. If you use that, I would expect you to know
>> that you can just use AT_FDCWD!
>>
>>> Making the changes in both kernel and liburing provides more of a
>>> standard interface in my opinion so maybe it looks better. But happy
>>> to just create a PR in liburing only with prep helpers as you
>>> suggested if you think that is better?
>>
>> I don't disagree with that, but it seems silly to waste 5 opcodes on
>> something that is a strict subset of something that is already there.
>> Hence my suggestion would be to just add io_uring_prep_link() etc
>> helpers to make it simpler to use, without having to add 5 extra
>> opcodes.
>>
> 
> Thanks, I have created a PR for it on
> https://github.com/axboe/liburing/pull/588. We can review it there if
> it makes sense!

Sounds good, we'll move it there.

-- 
Jens Axboe