Re: [PATCH 1/2] io_uring/uring_cmd: cleanup struct io_uring_cmd_data layout

[Pavel Begunkov <asml.silence@gmail.com>]

On 1/23/25 14:54, Jens Axboe wrote:
> On 1/23/25 7:38 AM, Pavel Begunkov wrote:
>> On 1/23/25 14:21, Jens Axboe wrote:
>>> A few spots in uring_cmd assume that the SQEs copied are always at the
>>> start of the structure, and hence mix req->async_data and the struct
>>> itself.
>>>
>>> Clean that up and use the proper indices.
>>>
>>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>>> ---
>>>    io_uring/uring_cmd.c | 6 +++---
>>>    1 file changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
>>> index 3993c9339ac7..6a63ec4b5445 100644
>>> --- a/io_uring/uring_cmd.c
>>> +++ b/io_uring/uring_cmd.c
>>> @@ -192,8 +192,8 @@ static int io_uring_cmd_prep_setup(struct io_kiocb *req,
>>>            return 0;
>>>        }
>>>    -    memcpy(req->async_data, sqe, uring_sqe_size(req->ctx));
>>> -    ioucmd->sqe = req->async_data;
>>> +    memcpy(cache->sqes, sqe, uring_sqe_size(req->ctx));
>>> +    ioucmd->sqe = cache->sqes;
>>>        return 0;
>>>    }
>>>    @@ -260,7 +260,7 @@ int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags)
>>>            struct io_uring_cmd_data *cache = req->async_data;
>>>              if (ioucmd->sqe != (void *) cache)
>>> -            memcpy(cache, ioucmd->sqe, uring_sqe_size(req->ctx));
>>> +            memcpy(cache->sqes, ioucmd->sqe, uring_sqe_size(req->ctx));
>>
>> 3347fa658a1b ("io_uring/cmd: add per-op data to struct io_uring_cmd_data")
>>
>> IIUC the patch above is queued for 6.14, and with that this patch
>> looks like a fix? At least it feels pretty dangerous without.
> 
> It's not a fix, the sqes are first in the struct even with that patch.

Ah yes

> So I'd consider it a cleanup. In any case, targeting 6.14 for these
> alloc cache cleanups as it got introduced there as well.

That's good, makes it not that brittle

-- 
Pavel Begunkov