Re: [PATCH] io_uring/net: use REQ_F_IMPORT_BUFFER for send_zc

[Pavel Begunkov]

On 3/25/25 14:39, Caleb Sander Mateos wrote:
> On Tue, Mar 25, 2025 at 6:30 AM Pavel Begunkov <asml.silence@xxxxxxxxx> wrote:
> > On 3/24/25 15:11, Caleb Sander Mateos wrote:
> > > Instead of a bool field in struct io_sr_msg, use REQ_F_IMPORT_BUFFER to
> > > track whether io_send_zc() has already imported the buffer. This flag
> > > already serves a similar purpose for sendmsg_zc and {read,write}v_fixed.
> > >
> > > Signed-off-by: Caleb Sander Mateos <csander@xxxxxxxxxxxxxxx>
> > > Suggested-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
> > > ---
> > >    include/linux/io_uring_types.h | 5 ++++-
> > >    io_uring/net.c                 | 8 +++-----
> > >    2 files changed, 7 insertions(+), 6 deletions(-)
...
> > > @@ -1305,12 +1304,11 @@ int io_send_zc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
> > >        struct io_ring_ctx *ctx = req->ctx;
> > >        struct io_kiocb *notif;
> > >
> > >        zc->done_io = 0;
> > >        zc->retry = false;
> > > -     zc->imported = false;
> > > -     req->flags |= REQ_F_POLL_NO_LAZY;
> > > +     req->flags |= REQ_F_POLL_NO_LAZY | REQ_F_IMPORT_BUFFER;
> >
> > This function is shared with sendmsg_zc, so if we set it here,
> > it'll trigger io_import_reg_vec() in io_sendmsg_zc() even for
> > non register buffer request.
>
> Good catch. I keep forgetting which prep and issue functions are
> shared between which opcodes.

No worries, can happen. I'd recommend to run liburing tests,
they're very useful for catching such things. I run it out
of curiosity, it crashes on send-zerocopy.c pretty fast.

--
Pavel Begunkov