Re: [PATCH 5.12 v3] io_uring: fix rw req completion

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

On 08/04/2021 19:28, 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 and kiocb_done()
> internally uses __io_complete_rw(), it may stop after setting the flag
> so leaving a dangling request.

Jens, this one is instead of taken v1, it handles io_rw_reissue() errors.
The handling code is partially hand coded __io_complete_rw(). Obviously,
needs cleaning in the nearest future.

> 
> There are tricky edge cases, e.g. reading beyound file, boundary, so
> the easiest way is to hand code reissue in kiocb_done() as
> __io_complete_rw() was doing for us before.
> 
> 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
> v3: adjust commit message
> 
>  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