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Date: Tue, 28 Jun 2022 09:17:35 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Dylan Yudaken <dylany@...com>,
Pavel Begunkov <asml.silence@...il.com>,
io-uring@...r.kernel.org
Cc: Kernel-team@...com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH for-next 8/8] io_uring: multishot recv
On 6/28/22 9:02 AM, Dylan Yudaken wrote:
> @@ -399,13 +401,22 @@ int io_recvmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
> sr->umsg = u64_to_user_ptr(READ_ONCE(sqe->addr));
> sr->len = READ_ONCE(sqe->len);
> sr->flags = READ_ONCE(sqe->addr2);
> - if (sr->flags & ~IORING_RECVSEND_POLL_FIRST)
> + if (sr->flags & ~(RECVMSG_FLAGS))
> return -EINVAL;
> sr->msg_flags = READ_ONCE(sqe->msg_flags) | MSG_NOSIGNAL;
> if (sr->msg_flags & MSG_DONTWAIT)
> req->flags |= REQ_F_NOWAIT;
> if (sr->msg_flags & MSG_ERRQUEUE)
> req->flags |= REQ_F_CLEAR_POLLIN;
> + if (sr->flags & IORING_RECV_MULTISHOT) {
> + if (!(req->flags & REQ_F_BUFFER_SELECT))
> + return -EINVAL;
> + if (sr->msg_flags & MSG_WAITALL)
> + return -EINVAL;
> + if (req->opcode == IORING_OP_RECV && sr->len)
> + return -EINVAL;
> + req->flags |= REQ_F_APOLL_MULTISHOT;
> + }
Do we want to forbid not using provided buffers? If you have a ping-pong
type setup, eg you know you'll have to send something before you receive
anything again, seems like it'd be feasible to use this with a normal
buffer?
I strongly suspect that most use cases will use provided buffers for
this, just wondering if there are any particular reasons for forbidding
it explicitly.
>
> #ifdef CONFIG_COMPAT
> if (req->ctx->compat)
> @@ -415,6 +426,14 @@ int io_recvmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
> return 0;
> }
>
> +static inline void io_recv_prep_retry(struct io_kiocb *req)
> +{
> + struct io_sr_msg *sr = io_kiocb_to_cmd(req);
> +
> + sr->done_io = 0;
> + sr->len = 0; /* get from the provided buffer */
> +}
> +
> int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
> {
> struct io_sr_msg *sr = io_kiocb_to_cmd(req);
> @@ -424,6 +443,7 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
> unsigned flags;
> int ret, min_ret = 0;
> bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
> + size_t len = sr->len;
>
> sock = sock_from_file(req->file);
> if (unlikely(!sock))
> @@ -442,16 +462,17 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
> (sr->flags & IORING_RECVSEND_POLL_FIRST))
> return io_setup_async_msg(req, kmsg);
>
> +retry_multishot:
> if (io_do_buffer_select(req)) {
> void __user *buf;
>
> - buf = io_buffer_select(req, &sr->len, issue_flags);
> + buf = io_buffer_select(req, &len, issue_flags);
> if (!buf)
> return -ENOBUFS;
> kmsg->fast_iov[0].iov_base = buf;
> - kmsg->fast_iov[0].iov_len = sr->len;
> + kmsg->fast_iov[0].iov_len = len;
> iov_iter_init(&kmsg->msg.msg_iter, READ, kmsg->fast_iov, 1,
> - sr->len);
> + len);
> }
>
> flags = sr->msg_flags;
> @@ -463,8 +484,15 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
> kmsg->msg.msg_get_inq = 1;
> ret = __sys_recvmsg_sock(sock, &kmsg->msg, sr->umsg, kmsg->uaddr, flags);
> if (ret < min_ret) {
> - if (ret == -EAGAIN && force_nonblock)
> - return io_setup_async_msg(req, kmsg);
> + if (ret == -EAGAIN && force_nonblock) {
> + ret = io_setup_async_msg(req, kmsg);
> + if (ret == -EAGAIN && (req->flags & IO_APOLL_MULTI_POLLED) ==
> + IO_APOLL_MULTI_POLLED) {
> + io_kbuf_recycle(req, issue_flags);
> + ret = IOU_ISSUE_SKIP_COMPLETE;
> + }
> + return ret;
> + }
> if (ret == -ERESTARTSYS)
> ret = -EINTR;
> if (ret > 0 && io_net_retry(sock, flags)) {
> @@ -491,8 +519,24 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
> cflags = io_put_kbuf(req, issue_flags);
> if (kmsg->msg.msg_inq)
> cflags |= IORING_CQE_F_SOCK_NONEMPTY;
> +
> + if (!(req->flags & REQ_F_APOLL_MULTISHOT)) {
> + io_req_set_res(req, ret, cflags);
> + return IOU_OK;
> + }
> +
> + if (ret > 0) {
> + if (io_post_aux_cqe(req->ctx, req->cqe.user_data, ret,
> + cflags | IORING_CQE_F_MORE)) {
> + io_recv_prep_retry(req);
> + goto retry_multishot;
> + } else {
> + ret = -ECANCELED;
> + }
> + }
> +
> io_req_set_res(req, ret, cflags);
> - return IOU_OK;
> + return req->flags & REQ_F_POLLED ? IOU_STOP_MULTISHOT : ret;
> }
Minor style, but I prefer avoiding ternaries if possible. This is much
easier to read for me:
if (req->flags & REQ_F_POLLED)
return IOU_STOP_MULTISHOT;
return ret;
> @@ -505,6 +549,7 @@ int io_recv(struct io_kiocb *req, unsigned int issue_flags)
> unsigned flags;
> int ret, min_ret = 0;
> bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
> + size_t len = sr->len;
>
> if (!(req->flags & REQ_F_POLLED) &&
> (sr->flags & IORING_RECVSEND_POLL_FIRST))
> @@ -514,16 +559,17 @@ int io_recv(struct io_kiocb *req, unsigned int issue_flags)
> if (unlikely(!sock))
> return -ENOTSOCK;
>
> +retry_multishot:
> if (io_do_buffer_select(req)) {
> void __user *buf;
>
> - buf = io_buffer_select(req, &sr->len, issue_flags);
> + buf = io_buffer_select(req, &len, issue_flags);
> if (!buf)
> return -ENOBUFS;
> sr->buf = buf;
> }
>
> - ret = import_single_range(READ, sr->buf, sr->len, &iov, &msg.msg_iter);
> + ret = import_single_range(READ, sr->buf, len, &iov, &msg.msg_iter);
> if (unlikely(ret))
> goto out_free;
>
> @@ -543,8 +589,14 @@ int io_recv(struct io_kiocb *req, unsigned int issue_flags)
>
> ret = sock_recvmsg(sock, &msg, flags);
> if (ret < min_ret) {
> - if (ret == -EAGAIN && force_nonblock)
> - return -EAGAIN;
> + if (ret == -EAGAIN && force_nonblock) {
> + if ((req->flags & IO_APOLL_MULTI_POLLED) == IO_APOLL_MULTI_POLLED) {
> + io_kbuf_recycle(req, issue_flags);
> + ret = IOU_ISSUE_SKIP_COMPLETE;
> + }
> +
> + return ret;
> + }
Maybe:
if ((req->flags & IO_APOLL_MULTI_POLLED) == IO_APOLL_MULTI_POLLED) {
io_kbuf_recycle(req, issue_flags);
return IOU_ISSUE_SKIP_COMPLETE;
}
return ret;
> @@ -570,8 +622,25 @@ int io_recv(struct io_kiocb *req, unsigned int issue_flags)
> cflags = io_put_kbuf(req, issue_flags);
> if (msg.msg_inq)
> cflags |= IORING_CQE_F_SOCK_NONEMPTY;
> +
> +
> + if (!(req->flags & REQ_F_APOLL_MULTISHOT)) {
> + io_req_set_res(req, ret, cflags);
> + return IOU_OK;
> + }
> +
> + if (ret > 0) {
> + if (io_post_aux_cqe(req->ctx, req->cqe.user_data, ret,
> + cflags | IORING_CQE_F_MORE)) {
> + io_recv_prep_retry(req);
> + goto retry_multishot;
> + } else {
> + ret = -ECANCELED;
> + }
> + }
> +
> io_req_set_res(req, ret, cflags);
> - return IOU_OK;
> + return req->flags & REQ_F_POLLED ? IOU_STOP_MULTISHOT : ret;
> }
Same here, and maybe this needs to be a helper so you could just do
return io_recv_finish(req, ret, cflags);
or something like that? It's non-trivial duplicated code.
--
Jens Axboe
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