[PATCH 0/2] IOSQE_ASYNC patches

[PATCH 0/2] IOSQE_ASYNC patches

[Pavel Begunkov]

There are 2 problems addressed:
1. it never calls *_prep() when going through IOSQE_ASYNC path.
2. non-head linked reqs ignore IOSQE_ASYNC.

Also, there could be yet another problem, when we bypass io_issue_req()
and going straight to async.

Pavel Begunkov (2):
  io_uring: prep req when do IOSQE_ASYNC
  io_uring: honor IOSQE_ASYNC for linked reqs

 fs/io_uring.c | 8 ++++++++
 1 file changed, 8 insertions(+)

-- 
2.24.0

[PATCH 1/2] io_uring: prep req when do IOSQE_ASYNC

[Pavel Begunkov]

Whenever IOSQE_ASYNC is set, requests will be punted to async without
getting into io_issue_req() and without proper preparation done (e.g.
io_req_defer_prep()). Hence they will be left uninitialised.

Prepare them before punting.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 09503d1e9e45..cdbc711ae5fd 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4558,11 +4558,15 @@ static void io_queue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	ret = io_req_defer(req, sqe);
 	if (ret) {
 		if (ret != -EIOCBQUEUED) {
+fail_req:
 			io_cqring_add_event(req, ret);
 			req_set_fail_links(req);
 			io_double_put_req(req);
 		}
 	} else if (req->flags & REQ_F_FORCE_ASYNC) {
+		ret = io_req_defer_prep(req, sqe);
+		if (unlikely(ret < 0))
+			goto fail_req;
 		/*
 		 * Never try inline submit of IOSQE_ASYNC is set, go straight
 		 * to async execution.
-- 
2.24.0

[PATCH 2/2] io_uring: honor IOSQE_ASYNC for linked reqs

[Pavel Begunkov]

REQ_F_FORCE_ASYNC is checked only for the head of a link. Fix it.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index cdbc711ae5fd..9f73586dcfb8 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4512,6 +4512,7 @@ static void __io_queue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	 */
 	if (ret == -EAGAIN && (!(req->flags & REQ_F_NOWAIT) ||
 	    (req->flags & REQ_F_MUST_PUNT))) {
+punt:
 		if (req->work.flags & IO_WQ_WORK_NEEDS_FILES) {
 			ret = io_grab_files(req);
 			if (ret)
@@ -4547,6 +4548,9 @@ static void __io_queue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	if (nxt) {
 		req = nxt;
 		nxt = NULL;
+
+		if (req->flags & REQ_F_FORCE_ASYNC)
+			goto punt;
 		goto again;
 	}
 }
-- 
2.24.0

Re: [PATCH 0/2] IOSQE_ASYNC patches

[Pavel Begunkov]

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On 22/01/2020 23:09, Pavel Begunkov wrote:
> There are 2 problems addressed:
> 1. it never calls *_prep() when going through IOSQE_ASYNC path.
> 2. non-head linked reqs ignore IOSQE_ASYNC.

Those two are intentionally short for quick fix up. I'll prepare something
prettier on top of that a bit later.

> 
> Also, there could be yet another problem, when we bypass io_issue_req()
> and going straight to async.
> 
> Pavel Begunkov (2):
>   io_uring: prep req when do IOSQE_ASYNC
>   io_uring: honor IOSQE_ASYNC for linked reqs
> 
>  fs/io_uring.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 

-- 
Pavel Begunkov


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Re: [PATCH 0/2] IOSQE_ASYNC patches

[Jens Axboe]

On 1/22/20 1:09 PM, Pavel Begunkov wrote:
> There are 2 problems addressed:
> 1. it never calls *_prep() when going through IOSQE_ASYNC path.
> 2. non-head linked reqs ignore IOSQE_ASYNC.
> 
> Also, there could be yet another problem, when we bypass io_issue_req()
> and going straight to async.

Thanks, applied.

-- 
Jens Axboe