Re: [PATCH 1/3] io_uring: add hash_index and its logic to track req in cancel_hash

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

On 6/6/22 07:57, Hao Xu wrote:
> From: Hao Xu <howeyxu@tencent.com>
> 
> Add a new member hash_index in struct io_kiocb to track the req index
> in cancel_hash array. This is needed in later patches.
> 
> Signed-off-by: Hao Xu <howeyxu@tencent.com>
> ---
>   io_uring/io_uring_types.h | 1 +
>   io_uring/poll.c           | 4 +++-
>   2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/io_uring/io_uring_types.h b/io_uring/io_uring_types.h
> index 7c22cf35a7e2..2041ee83467d 100644
> --- a/io_uring/io_uring_types.h
> +++ b/io_uring/io_uring_types.h
> @@ -474,6 +474,7 @@ struct io_kiocb {
>   			u64		extra2;
>   		};
>   	};
> +	unsigned int			hash_index;

Didn't take a closer look, but can we make rid of it?
E.g. computing it again when ejecting a request from
the hash? or keep it in struct io_poll?

>   	/* internal polling, see IORING_FEAT_FAST_POLL */
>   	struct async_poll		*apoll;
>   	/* opcode allocated if it needs to store data for async defer */
> diff --git a/io_uring/poll.c b/io_uring/poll.c
> index 0df5eca93b16..95e28f32b49c 100644
> --- a/io_uring/poll.c
> +++ b/io_uring/poll.c
> @@ -74,8 +74,10 @@ static void io_poll_req_insert(struct io_kiocb *req)
>   {
>   	struct io_ring_ctx *ctx = req->ctx;
>   	struct hlist_head *list;
> +	u32 index = hash_long(req->cqe.user_data, ctx->cancel_hash_bits);
>   
> -	list = &ctx->cancel_hash[hash_long(req->cqe.user_data, ctx->cancel_hash_bits)];
> +	req->hash_index = index;
> +	list = &ctx->cancel_hash[index];
>   	hlist_add_head(&req->hash_node, list);
>   }
>   

-- 
Pavel Begunkov