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

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Date:   Fri, 6 May 2022 17:22:49 +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 5/6/22 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?

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.


> +		__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