linux-kernel - Re: [PATCH] io_uring/rsrc: use rq_data

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Message-ID: <a4001bbf-5782-47ee-9ea1-ea2020ed121d@gmail.com>
Date: Sat, 1 Mar 2025 02:01:45 +0000
From: Pavel Begunkov <asml.silence@...il.com>
To: Caleb Sander Mateos <csander@...estorage.com>
Cc: Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] io_uring/rsrc: use rq_data_dir() to compute bvec dir

On 3/1/25 01:42, Caleb Sander Mateos wrote:
> On Fri, Feb 28, 2025 at 5:23 PM Pavel Begunkov <asml.silence@...il.com> wrote:
>>
>> On 2/28/25 22:30, Caleb Sander Mateos wrote:
>>> The macro rq_data_dir() already computes a request's data direction.
>>> Use it in place of the if-else to set imu->dir.
>>>
>>> Signed-off-by: Caleb Sander Mateos <csander@...estorage.com>
>>> ---
>>>    io_uring/rsrc.c | 6 +-----
>>>    1 file changed, 1 insertion(+), 5 deletions(-)
>>>
>>> diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
>>> index 45bfb37bca1e..3107a03d56b8 100644
>>> --- a/io_uring/rsrc.c
>>> +++ b/io_uring/rsrc.c
>>> @@ -957,15 +957,11 @@ int io_buffer_register_bvec(struct io_uring_cmd *cmd, struct request *rq,
>>>        imu->nr_bvecs = nr_bvecs;
>>>        refcount_set(&imu->refs, 1);
>>>        imu->release = release;
>>>        imu->priv = rq;
>>>        imu->is_kbuf = true;
>>> -
>>> -     if (op_is_write(req_op(rq)))
>>> -             imu->dir = IO_IMU_SOURCE;
>>> -     else
>>> -             imu->dir = IO_IMU_DEST;
>>> +     imu->dir = 1 << rq_data_dir(rq);
>>
>> rq_data_dir returns READ/WRITE, which should be fine, but it'd
>> be nicer to be more explicit unless it's already enforced
>> somewhere else
>>
>> BUILD_BUG_ON(WRITE ==  ITER_SOURCE);
>> ditto for READ
> 
> The definitions of ITER_SOURCE and ITER_DEST seem pretty clear that
> they are aliases for WRITE/READ:
> #define ITER_SOURCE 1 // == WRITE
> #define ITER_DEST 0 // == READ
> 
> So I assume other code is already relying on this equivalence.

And it'll be left a mystery they weren't defined through
WRITE/READ in the first place. but the patch should be fine
then.

-- 
Pavel Begunkov