Re: [PATCH 4/4] io_uring: mark opcodes that always need io-wq punt

Jens Axboe
2023-04-25T02:08:14Z

On 4/24/23 6:57?PM, Ming Lei wrote:
> On Mon, Apr 24, 2023 at 09:24:33AM -0600, Jens Axboe wrote:
>> On 4/24/23 1:30?AM, Ming Lei wrote:
>>> On Thu, Apr 20, 2023 at 12:31:35PM -0600, Jens Axboe wrote:
>>>> Add an opdef bit for them, and set it for the opcodes where we always
>>>> need io-wq punt. With that done, exclude them from the file_can_poll()
>>>> check in terms of whether or not we need to punt them if any of the
>>>> NO_OFFLOAD flags are set.
>>>>
>>>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>>>> ---
>>>> io_uring/io_uring.c | 2 +-
>>>> io_uring/opdef.c | 22 ++++++++++++++++++++--
>>>> io_uring/opdef.h | 2 ++
>>>> 3 files changed, 23 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
>>>> index fee3e461e149..420cfd35ebc6 100644
>>>> --- a/io_uring/io_uring.c
>>>> +++ b/io_uring/io_uring.c
>>>> @@ -1948,7 +1948,7 @@ static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
>>>> return -EBADF;
>>>>
>>>> if (issue_flags & IO_URING_F_NO_OFFLOAD &&
>>>> - (!req->file || !file_can_poll(req->file)))
>>>> + (!req->file || !file_can_poll(req->file) || def->always_iowq))
>>>> issue_flags &= ~IO_URING_F_NONBLOCK;
>>>
>>> I guess the check should be !def->always_iowq?
>>
>> How so? Nobody that takes pollable files should/is setting
>> ->always_iowq. If we can poll the file, we should not force inline
>> submission. Basically the ones setting ->always_iowq always do -EAGAIN
>> returns if nonblock == true.
>
> I meant IO_URING_F_NONBLOCK is cleared here for ->always_iowq, and
> these OPs won't return -EAGAIN, then run in the current task context
> directly.

Right, of IO_URING_F_NO_OFFLOAD is set, which is entirely the point of
it :-)

--
Jens Axboe