linux-kernel - Re: [PATCH 4/5] io_uring: add a helper for poll clean

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Date:   Sat, 7 May 2022 10:29:58 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Hao Xu <haoxu.linux@...il.com>, io-uring@...r.kernel.org
Cc:     Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] io_uring: add a helper for poll clean

On 5/7/22 07:43, Hao Xu wrote:
> 在 2022/5/7 上午12:22, Pavel Begunkov 写道:
>> On 5/6/22 08:01, Hao Xu wrote:
>>> From: Hao Xu <howeyxu@...cent.com>
>>>
>>> Add a helper for poll clean, it will be used in the multishot accept in
>>> the later patches.
>>>
>>> Signed-off-by: Hao Xu <howeyxu@...cent.com>
>>> ---
>>>   fs/io_uring.c | 23 ++++++++++++++++++-----
>>>   1 file changed, 18 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>>> index d33777575faf..0a83ecc457d1 100644
>>> --- a/fs/io_uring.c
>>> +++ b/fs/io_uring.c
>>> @@ -5711,6 +5711,23 @@ static int io_accept_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>>>       return 0;
>>>   }
>>> +static inline void __io_poll_clean(struct io_kiocb *req)
>>> +{
>>> +    struct io_ring_ctx *ctx = req->ctx;
>>> +
>>> +    io_poll_remove_entries(req);
>>> +    spin_lock(&ctx->completion_lock);
>>> +    hash_del(&req->hash_node);
>>> +    spin_unlock(&ctx->completion_lock);
>>> +}
>>> +
>>> +#define REQ_F_APOLL_MULTI_POLLED (REQ_F_APOLL_MULTISHOT | REQ_F_POLLED)
>>> +static inline void io_poll_clean(struct io_kiocb *req)
>>> +{
>>> +    if ((req->flags & REQ_F_APOLL_MULTI_POLLED) == REQ_F_APOLL_MULTI_POLLED)
>>
>> So it triggers for apoll multishot only when REQ_F_POLLED is _not_ set,
>> but if it's not set it did never go through arm_poll / etc. and there is
>> nothing to clean up. What is the catch?
> 
> No, it is triggered for apoll multishot only when REQ_F_POLLED is set..

Ok, see it now, probably confused REQ_F_APOLL_MULTI_POLLED on the right
hand side with something else


>> btw, don't see the function used in this patch, better to add it later
>> or at least mark with attribute unused, or some may get build failures.
> Gotcha.
>>
>>
>>> +        __io_poll_clean(req);
>>> +}
>>> +
>>>   static int io_accept(struct io_kiocb *req, unsigned int issue_flags)
>>>   {
>>>       struct io_accept *accept = &req->accept;
>>> @@ -6041,17 +6058,13 @@ static void io_poll_task_func(struct io_kiocb *req, bool *locked)
>>>   static void io_apoll_task_func(struct io_kiocb *req, bool *locked)
>>>   {
>>> -    struct io_ring_ctx *ctx = req->ctx;
>>>       int ret;
>>>       ret = io_poll_check_events(req, locked);
>>>       if (ret > 0)
>>>           return;
>>> -    io_poll_remove_entries(req);
>>> -    spin_lock(&ctx->completion_lock);
>>> -    hash_del(&req->hash_node);
>>> -    spin_unlock(&ctx->completion_lock);
>>> +    __io_poll_clean(req);
>>>       if (!ret)
>>>           io_req_task_submit(req, locked);
>>
> 

-- 
Pavel Begunkov