Re: [PATCH v2] io_uring: Fix reversed nonblock flag

From: Jens Axboe
Date: Fri Oct 04 2019 - 09:05:25 EST


On 10/4/19 4:07 AM, Pavel Begunkov (Silence) wrote:
> From: Pavel Begunkov <asml.silence@xxxxxxxxx>
>
> io_queue_link_head() accepts @force_nonblock flag, but io_ring_submit()
> passes something opposite.
>
> v2: fix build error by test robot: Rebase from custom tree
> Reported-by: kbuild test robot <lkp@xxxxxxxxx>
>
> Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
> ---
> fs/io_uring.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index c934f91c51e9..c909ea2b84e9 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -2703,6 +2703,7 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit,
> struct io_kiocb *shadow_req = NULL;
> bool prev_was_link = false;
> int i, submit = 0;
> + bool force_nonblock = true;
>
> if (to_submit > IO_PLUG_THRESHOLD) {
> io_submit_state_start(&state, ctx, to_submit);
> @@ -2710,9 +2711,9 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit,
> }
>
> for (i = 0; i < to_submit; i++) {
> - bool force_nonblock = true;
> struct sqe_submit s;
>
> + force_nonblock = true;
> if (!io_get_sqring(ctx, &s))
> break;
>
> @@ -2761,7 +2762,7 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit,
>
> if (link)
> io_queue_link_head(ctx, link, &link->submit, shadow_req,
> - block_for_last);
> + force_nonblock);
> if (statep)
> io_submit_state_end(statep);

Shouldn't this just be:

io_queue_link_head(ctx, link, &link->submit, shadow_req,
!block_for_last);

We're outside the loop, so by definition at the end of what we need to
do. We don't need to factor in the fiddling of force_nonblock here,
it'll be false at this point anyway. Only exception is error handling,
if the caller asked for more than what was in the ring. Not a big
deal...

--
Jens Axboe