[PATCH 5.12 v2] io_uring: fix rw req completion

[PATCH 5.12 v2] io_uring: fix rw req completion

[Pavel Begunkov]

WARNING: at fs/io_uring.c:8578 io_ring_exit_work.cold+0x0/0x18

As reissuing is now passed back by REQ_F_REISSUE, kiocb_done() may just
set the flag and do nothing leaving dangling requests. The handling is a
bit fragile, e.g. can't just complete them because the case of reading
beyond file boundary needs blocking context to return 0, otherwise it
may be -EAGAIN.

Go the easy way for now, just emulate how it was by io_rw_reissue() in
kiocb_done()

Fixes: 230d50d448ac ("io_uring: move reissue into regular IO path")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/f602250d292f8a84cca9a01d747744d1e797be26.1617842918.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

v2: io_rw_reissue() may fail, check return code

 fs/io_uring.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index f1881ac0744b..f2df0569a60a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2762,6 +2762,7 @@ static void kiocb_done(struct kiocb *kiocb, ssize_t ret,
 {
 	struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb);
 	struct io_async_rw *io = req->async_data;
+	bool check_reissue = (kiocb->ki_complete == io_complete_rw);
 
 	/* add previously done IO, if any */
 	if (io && io->bytes_done > 0) {
@@ -2777,6 +2778,18 @@ static void kiocb_done(struct kiocb *kiocb, ssize_t ret,
 		__io_complete_rw(req, ret, 0, issue_flags);
 	else
 		io_rw_done(kiocb, ret);
+
+	if (check_reissue && req->flags & REQ_F_REISSUE) {
+		req->flags &= ~REQ_F_REISSUE;
+		if (!io_rw_reissue(req)) {
+			int cflags = 0;
+
+			req_set_fail_links(req);
+			if (req->flags & REQ_F_BUFFER_SELECTED)
+				cflags = io_put_rw_kbuf(req);
+			__io_req_complete(req, issue_flags, ret, cflags);
+		}
+	}
 }
 
 static int io_import_fixed(struct io_kiocb *req, int rw, struct iov_iter *iter)
-- 
2.24.0

Re: [PATCH 5.12 v2] io_uring: fix rw req completion

[Pavel Begunkov]

On 08/04/2021 18:40, Pavel Begunkov wrote:
> WARNING: at fs/io_uring.c:8578 io_ring_exit_work.cold+0x0/0x18
> 
> As reissuing is now passed back by REQ_F_REISSUE, kiocb_done() may just
> set the flag and do nothing leaving dangling requests. The handling is a
> bit fragile, e.g. can't just complete them because the case of reading
> beyond file boundary needs blocking context to return 0, otherwise it
> may be -EAGAIN.
> 
> Go the easy way for now, just emulate how it was by io_rw_reissue() in
> kiocb_done()

Need to adjust the message a bit, will resend

> 
> Fixes: 230d50d448ac ("io_uring: move reissue into regular IO path")
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> Link: https://lore.kernel.org/r/f602250d292f8a84cca9a01d747744d1e797be26.1617842918.git.asml.silence@gmail.com
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> ---
> 
> v2: io_rw_reissue() may fail, check return code
> 
>  fs/io_uring.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index f1881ac0744b..f2df0569a60a 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -2762,6 +2762,7 @@ static void kiocb_done(struct kiocb *kiocb, ssize_t ret,
>  {
>  	struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb);
>  	struct io_async_rw *io = req->async_data;
> +	bool check_reissue = (kiocb->ki_complete == io_complete_rw);
>  
>  	/* add previously done IO, if any */
>  	if (io && io->bytes_done > 0) {
> @@ -2777,6 +2778,18 @@ static void kiocb_done(struct kiocb *kiocb, ssize_t ret,
>  		__io_complete_rw(req, ret, 0, issue_flags);
>  	else
>  		io_rw_done(kiocb, ret);
> +
> +	if (check_reissue && req->flags & REQ_F_REISSUE) {
> +		req->flags &= ~REQ_F_REISSUE;
> +		if (!io_rw_reissue(req)) {
> +			int cflags = 0;
> +
> +			req_set_fail_links(req);
> +			if (req->flags & REQ_F_BUFFER_SELECTED)
> +				cflags = io_put_rw_kbuf(req);
> +			__io_req_complete(req, issue_flags, ret, cflags);
> +		}
> +	}
>  }
>  
>  static int io_import_fixed(struct io_kiocb *req, int rw, struct iov_iter *iter)
> 

-- 
Pavel Begunkov