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

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Date:   Sat, 7 May 2022 14:43:01 +0800
From:   Hao Xu <haoxu.linux@...il.com>
To:     Pavel Begunkov <asml.silence@...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

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..
> 
> 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);
>