Re: [PATCH 4/4] io_uring: mark opcodes that always need io-wq punt

Ming Lei
2023-04-25T00:58:38Z

On Mon, Apr 24, 2023 at 09:24:33AM -0600, Jens Axboe wrote:
> On 4/24/23 1:30?AM, Ming Lei wrote:
> > On Thu, Apr 20, 2023 at 12:31:35PM -0600, Jens Axboe wrote:
> >> Add an opdef bit for them, and set it for the opcodes where we always
> >> need io-wq punt. With that done, exclude them from the file_can_poll()
> >> check in terms of whether or not we need to punt them if any of the
> >> NO_OFFLOAD flags are set.
> >>
> >> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> >> ---
> >> io_uring/io_uring.c | 2 +-
> >> io_uring/opdef.c | 22 ++++++++++++++++++++--
> >> io_uring/opdef.h | 2 ++
> >> 3 files changed, 23 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> >> index fee3e461e149..420cfd35ebc6 100644
> >> --- a/io_uring/io_uring.c
> >> +++ b/io_uring/io_uring.c
> >> @@ -1948,7 +1948,7 @@ static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
> >> return -EBADF;
> >>
> >> if (issue_flags & IO_URING_F_NO_OFFLOAD &&
> >> - (!req->file || !file_can_poll(req->file)))
> >> + (!req->file || !file_can_poll(req->file) || def->always_iowq))
> >> issue_flags &= ~IO_URING_F_NONBLOCK;
> >
> > I guess the check should be !def->always_iowq?
>
> How so? Nobody that takes pollable files should/is setting
> ->always_iowq. If we can poll the file, we should not force inline
> submission. Basically the ones setting ->always_iowq always do -EAGAIN
> returns if nonblock == true.

I meant IO_URING_F_NONBLOCK is cleared here for ->always_iowq, and
these OPs won't return -EAGAIN, then run in the current task context
directly.

Thanks,
Ming