Re: [PATCH] io_uring: fix short read/write with linked ops

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

On 10/3/22 10:19, David Stevens wrote:
> From: David Stevens <stevensd@chromium.org>
> 
> When continuing a short read/write, account for any completed bytes when
> calculating the operation's target length. The operation's actual
> accumulated length is fixed up by kiocb_done, and the target and actual
> lengths are then compared by __io_complete_rw_common. That function
> already propagated the actual length to userspace, but the incorrect
> target length was causing it to always cancel linked operations, even
> with a successfully completed read/write.

The issue looks same as fixed with

https://git.kernel.dk/cgit/linux-block/commit/?h=for-6.1/io_uring&id=bf68b5b34311ee57ed40749a1257a30b46127556

Can you check if for-6.1 works for you?

git://git.kernel.dk/linux.git for-6.1/io_uring
https://git.kernel.dk/cgit/linux-block/log/?h=for-6.1/io_uring


> Fixes: 227c0c9673d8 ("io_uring: internally retry short reads")
> Signed-off-by: David Stevens <stevensd@chromium.org>
> ---
>   io_uring/rw.c | 12 ++++++++----
>   1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/io_uring/rw.c b/io_uring/rw.c
> index 76ebcfebc9a6..aa9967a52dfd 100644
> --- a/io_uring/rw.c
> +++ b/io_uring/rw.c
> @@ -706,13 +706,14 @@ int io_read(struct io_kiocb *req, unsigned int issue_flags)
>   	struct kiocb *kiocb = &rw->kiocb;
>   	bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
>   	struct io_async_rw *io;
> -	ssize_t ret, ret2;
> +	ssize_t ret, ret2, target_len;
>   	loff_t *ppos;
>   
>   	if (!req_has_async_data(req)) {
>   		ret = io_import_iovec(READ, req, &iovec, s, issue_flags);
>   		if (unlikely(ret < 0))
>   			return ret;
> +		target_len = iov_iter_count(&s->iter);
>   	} else {
>   		io = req->async_data;
>   		s = &io->s;
> @@ -733,6 +734,7 @@ int io_read(struct io_kiocb *req, unsigned int issue_flags)
>   		 * need to make this conditional.
>   		 */
>   		iov_iter_restore(&s->iter, &s->iter_state);
> +		target_len = iov_iter_count(&s->iter) + io->bytes_done;
>   		iovec = NULL;
>   	}
>   	ret = io_rw_init_file(req, FMODE_READ);
> @@ -740,7 +742,7 @@ int io_read(struct io_kiocb *req, unsigned int issue_flags)
>   		kfree(iovec);
>   		return ret;
>   	}
> -	req->cqe.res = iov_iter_count(&s->iter);
> +	req->cqe.res = target_len;
>   
>   	if (force_nonblock) {
>   		/* If the file doesn't support async, just async punt */
> @@ -850,18 +852,20 @@ int io_write(struct io_kiocb *req, unsigned int issue_flags)
>   	struct iovec *iovec;
>   	struct kiocb *kiocb = &rw->kiocb;
>   	bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
> -	ssize_t ret, ret2;
> +	ssize_t ret, ret2, target_len;
>   	loff_t *ppos;
>   
>   	if (!req_has_async_data(req)) {
>   		ret = io_import_iovec(WRITE, req, &iovec, s, issue_flags);
>   		if (unlikely(ret < 0))
>   			return ret;
> +		target_len = iov_iter_count(&s->iter);
>   	} else {
>   		struct io_async_rw *io = req->async_data;
>   
>   		s = &io->s;
>   		iov_iter_restore(&s->iter, &s->iter_state);
> +		target_len = iov_iter_count(&s->iter) + io->bytes_done;
>   		iovec = NULL;
>   	}
>   	ret = io_rw_init_file(req, FMODE_WRITE);
> @@ -869,7 +873,7 @@ int io_write(struct io_kiocb *req, unsigned int issue_flags)
>   		kfree(iovec);
>   		return ret;
>   	}
> -	req->cqe.res = iov_iter_count(&s->iter);
> +	req->cqe.res = target_len;
>   
>   	if (force_nonblock) {
>   		/* If the file doesn't support async, just async punt */

-- 
Pavel Begunkov