linux-kernel - Re: [PATCH v2 1/2] io_uring: Merge io_submit_sqes and io_ring

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Message-ID: <4654948b-caac-3dc8-904c-ceb0c245d7c3@oracle.com>
Date:   Wed, 6 Nov 2019 16:57:12 +0800
From:   Bob Liu <bob.liu@...cle.com>
To:     Pavel Begunkov <asml.silence@...il.com>,
        Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] io_uring: Merge io_submit_sqes and io_ring_submit

On 11/6/19 5:22 AM, Pavel Begunkov wrote:
> io_submit_sqes() and io_ring_submit() are doing the same stuff with
> a little difference. Deduplicate them.
> 
> Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
> ---
>  fs/io_uring.c | 88 +++++++++++----------------------------------------
>  1 file changed, 18 insertions(+), 70 deletions(-)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 7813bc7d5b61..ebe2a4edd644 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -2681,7 +2681,8 @@ static bool io_get_sqring(struct io_ring_ctx *ctx, struct sqe_submit *s)
>  }
>  
>  static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
> -			  struct mm_struct **mm)
> +			  struct file *ring_file, int ring_fd,
> +			  struct mm_struct **mm, bool async)
>  {
>  	struct io_submit_state state, *statep = NULL;
>  	struct io_kiocb *link = NULL;
> @@ -2732,10 +2733,12 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
>  		}
>  
>  out:
> +		s.ring_file = ring_file;
> +		s.ring_fd = ring_fd;
>  		s.has_user = *mm != NULL;
> -		s.in_async = true;
> -		s.needs_fixed_file = true;
> -		trace_io_uring_submit_sqe(ctx, s.sqe->user_data, true, true);
> +		s.in_async = async;
> +		s.needs_fixed_file = async;
> +		trace_io_uring_submit_sqe(ctx, s.sqe->user_data, true, async);
>  		io_submit_sqe(ctx, &s, statep, &link);
>  		submitted++;
>  	}
> @@ -2745,6 +2748,9 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
>  	if (statep)
>  		io_submit_state_end(&state);
>  
> +	 /* Commit SQ ring head once we've consumed and submitted all SQEs */
> +	io_commit_sqring(ctx);
> +

Then don't need io_commit_sqring() in io_sq_thread any more?

Anyway, looks good to me.
Reviewed-by: Bob Liu <bob.liu@...cle.com>

>  	return submitted;
>  }
>  
> @@ -2849,7 +2855,8 @@ static int io_sq_thread(void *data)
>  		}
>  
>  		to_submit = min(to_submit, ctx->sq_entries);
> -		inflight += io_submit_sqes(ctx, to_submit, &cur_mm);
> +		inflight += io_submit_sqes(ctx, to_submit, NULL, -1, &cur_mm,
> +					   true);
>  
>  		/* Commit SQ ring head once we've consumed all SQEs */
>  		io_commit_sqring(ctx);
> @@ -2866,69 +2873,6 @@ static int io_sq_thread(void *data)
>  	return 0;
>  }
>  
> -static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit,
> -			  struct file *ring_file, int ring_fd)
> -{
> -	struct io_submit_state state, *statep = NULL;
> -	struct io_kiocb *link = NULL;
> -	struct io_kiocb *shadow_req = NULL;
> -	bool prev_was_link = false;
> -	int i, submit = 0;
> -
> -	if (to_submit > IO_PLUG_THRESHOLD) {
> -		io_submit_state_start(&state, ctx, to_submit);
> -		statep = &state;
> -	}
> -
> -	for (i = 0; i < to_submit; i++) {
> -		struct sqe_submit s;
> -
> -		if (!io_get_sqring(ctx, &s))
> -			break;
> -
> -		/*
> -		 * If previous wasn't linked and we have a linked command,
> -		 * that's the end of the chain. Submit the previous link.
> -		 */
> -		if (!prev_was_link && link) {
> -			io_queue_link_head(ctx, link, &link->submit, shadow_req);
> -			link = NULL;
> -			shadow_req = NULL;
> -		}
> -		prev_was_link = (s.sqe->flags & IOSQE_IO_LINK) != 0;
> -
> -		if (link && (s.sqe->flags & IOSQE_IO_DRAIN)) {
> -			if (!shadow_req) {
> -				shadow_req = io_get_req(ctx, NULL);
> -				if (unlikely(!shadow_req))
> -					goto out;
> -				shadow_req->flags |= (REQ_F_IO_DRAIN | REQ_F_SHADOW_DRAIN);
> -				refcount_dec(&shadow_req->refs);
> -			}
> -			shadow_req->sequence = s.sequence;
> -		}
> -
> -out:
> -		s.ring_file = ring_file;
> -		s.has_user = true;
> -		s.in_async = false;
> -		s.needs_fixed_file = false;
> -		s.ring_fd = ring_fd;
> -		submit++;
> -		trace_io_uring_submit_sqe(ctx, s.sqe->user_data, true, false);
> -		io_submit_sqe(ctx, &s, statep, &link);
> -	}
> -
> -	if (link)
> -		io_queue_link_head(ctx, link, &link->submit, shadow_req);
> -	if (statep)
> -		io_submit_state_end(statep);
> -
> -	io_commit_sqring(ctx);
> -
> -	return submit;
> -}
> -
>  struct io_wait_queue {
>  	struct wait_queue_entry wq;
>  	struct io_ring_ctx *ctx;
> @@ -4049,10 +3993,14 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
>  			wake_up(&ctx->sqo_wait);
>  		submitted = to_submit;
>  	} else if (to_submit) {
> -		to_submit = min(to_submit, ctx->sq_entries);
> +		struct mm_struct *cur_mm;
>  
> +		to_submit = min(to_submit, ctx->sq_entries);
>  		mutex_lock(&ctx->uring_lock);
> -		submitted = io_ring_submit(ctx, to_submit, f.file, fd);
> +		/* already have mm, so io_submit_sqes() won't try to grab it */
> +		cur_mm = ctx->sqo_mm;
> +		submitted = io_submit_sqes(ctx, to_submit, f.file, fd,
> +					   &cur_mm, false);
>  		mutex_unlock(&ctx->uring_lock);
>  	}
>  	if (flags & IORING_ENTER_GETEVENTS) {
>