On 2025-02-22 00:54, lizetao wrote:
> Hi,
>
>> -----Original Message-----
>> From: David Wei <dw@xxxxxxxxxxx>
>> Sent: Saturday, February 22, 2025 4:52 AM
>> To: io-uring@xxxxxxxxxxxxxxx
>> Cc: Jens Axboe <axboe@xxxxxxxxx>; Pavel Begunkov <asml.silence@xxxxxxxxx>
>> Subject: [PATCH v2 1/2] io_uring/zcrx: add single shot recvzc
>>
>> Currently only multishot recvzc requests are supported, but sometimes there is
>> a need to do a single recv e.g. peeking at some data in the socket. Add single
>> shot recvzc requests where IORING_RECV_MULTISHOT is _not_ set and the sqe-
>>> len field is set to the number of bytes to read N.
>>
>> There could be multiple completions containing data, like the multishot case,
>> since N bytes could be split across multiple frags. This is followed by a final
>> completion with res and cflags both set to 0 that indicate the completion of the
>> request, or a -res that indicate an error.
>>
>> Signed-off-by: David Wei <dw@xxxxxxxxxxx>
>> ---
>> io_uring/net.c | 19 +++++++++++++++++-- io_uring/zcrx.c | 17 ++++++++++++--
>> --- io_uring/zcrx.h | 2 +-
>> 3 files changed, 30 insertions(+), 8 deletions(-)
>>
>> diff --git a/io_uring/net.c b/io_uring/net.c index 000dc70d08d0..cae34a24266c
>> 100644
>> --- a/io_uring/net.c
>> +++ b/io_uring/net.c
>> @@ -94,6 +94,7 @@ struct io_recvzc {
>> struct file *file;
>> unsigned msg_flags;
>> u16 flags;
>> + u32 len;
>> struct io_zcrx_ifq *ifq;
>> };
>>
>> @@ -1241,7 +1242,7 @@ int io_recvzc_prep(struct io_kiocb *req, const struct
>> io_uring_sqe *sqe)
>> unsigned ifq_idx;
>>
>> if (unlikely(sqe->file_index || sqe->addr2 || sqe->addr ||
>> - sqe->len || sqe->addr3))
>> + sqe->addr3))
>> return -EINVAL;
>>
>> ifq_idx = READ_ONCE(sqe->zcrx_ifq_idx); @@ -1250,6 +1251,12 @@
>> int io_recvzc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>> zc->ifq = req->ctx->ifq;
>> if (!zc->ifq)
>> return -EINVAL;
>> + zc->len = READ_ONCE(sqe->len);
>> + if (zc->len == UINT_MAX)
>> + return -EINVAL;
>> + /* UINT_MAX means no limit on readlen */
>
> What is the difference between unlimited read length and IO_URING_F_MULTISHOT?
> In what specific scenarios would unlimited read length be used?
I will clean up the terminology in the next revision. There isn't a
singleshot vs multishot as such. Rather, it's an unlimited multishot vs
a limited multishot. The unlimited multishot request would be a typical
multishot recv that will keep reading data from the socket. The limited
multishot request will read up to a limit N before completing the
request.
>
>> + if (!zc->len)
>> + zc->len = UINT_MAX;
>>
>> zc->flags = READ_ONCE(sqe->ioprio);
>> zc->msg_flags = READ_ONCE(sqe->msg_flags); @@ -1269,6 +1276,7
>> @@ int io_recvzc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>> int io_recvzc(struct io_kiocb *req, unsigned int issue_flags) {
>> struct io_recvzc *zc = io_kiocb_to_cmd(req, struct io_recvzc);
>> + bool limit = zc->len != UINT_MAX;
>
> It is not used.
>
>> struct socket *sock;
>> int ret;
>>
>> @@ -1281,7 +1289,7 @@ int io_recvzc(struct io_kiocb *req, unsigned int
>> issue_flags)
>> return -ENOTSOCK;
>>
>> ret = io_zcrx_recv(req, zc->ifq, sock, zc->msg_flags | MSG_DONTWAIT,
>> - issue_flags);
>> + issue_flags, &zc->len);
>> if (unlikely(ret <= 0) && ret != -EAGAIN) {
>> if (ret == -ERESTARTSYS)
>> ret = -EINTR;
>> @@ -1296,6 +1304,13 @@ int io_recvzc(struct io_kiocb *req, unsigned int
>> issue_flags)
>> return IOU_OK;
>> }
>>
>> + if (zc->len == 0) {
>> + io_req_set_res(req, 0, 0);
>> +
>> + if (issue_flags & IO_URING_F_MULTISHOT)
>> + return IOU_STOP_MULTISHOT;
>> + return IOU_OK;
>> + }
>> if (issue_flags & IO_URING_F_MULTISHOT)
>> return IOU_ISSUE_SKIP_COMPLETE;
>> return -EAGAIN;
>> diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c index
>> f2d326e18e67..74bca4e471bc 100644
>> --- a/io_uring/zcrx.c
>> +++ b/io_uring/zcrx.c
>> @@ -817,6 +817,7 @@ io_zcrx_recv_skb(read_descriptor_t *desc, struct
>> sk_buff *skb,
>> int i, copy, end, off;
>> int ret = 0;
>>
>> + len = min_t(size_t, len, desc->count);
>> if (unlikely(args->nr_skbs++ > IO_SKBS_PER_CALL_LIMIT))
>> return -EAGAIN;
>>
>> @@ -894,26 +895,32 @@ io_zcrx_recv_skb(read_descriptor_t *desc, struct
>> sk_buff *skb,
>> out:
>> if (offset == start_off)
>> return ret;
>> + if (desc->count != UINT_MAX)
>> + desc->count -= (offset - start_off);
>> return offset - start_off;
>> }
>>
>> static int io_zcrx_tcp_recvmsg(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
>> struct sock *sk, int flags,
>> - unsigned issue_flags)
>> + unsigned issue_flags, unsigned int *outlen)
>> {
>> + unsigned int len = *outlen;
>> + bool limit = len != UINT_MAX;
>> struct io_zcrx_args args = {
>> .req = req,
>> .ifq = ifq,
>> .sock = sk->sk_socket,
>> };
>> read_descriptor_t rd_desc = {
>> - .count = 1,
>> + .count = len,
>> .arg.data = &args,
>> };
>> int ret;
>>
>> lock_sock(sk);
>> ret = tcp_read_sock(sk, &rd_desc, io_zcrx_recv_skb);
>> + if (limit && ret)
>> + *outlen = len - ret;
>> if (ret <= 0) {
>> if (ret < 0 || sock_flag(sk, SOCK_DONE))
>> goto out;
>> @@ -930,7 +937,7 @@ static int io_zcrx_tcp_recvmsg(struct io_kiocb *req,
>> struct io_zcrx_ifq *ifq,
>> ret = IOU_REQUEUE;
>> } else if (sock_flag(sk, SOCK_DONE)) {
>> /* Make it to retry until it finally gets 0. */
>> - if (issue_flags & IO_URING_F_MULTISHOT)
>> + if (!limit && (issue_flags & IO_URING_F_MULTISHOT))
>> ret = IOU_REQUEUE;
>> else
>> ret = -EAGAIN;
>> @@ -942,7 +949,7 @@ static int io_zcrx_tcp_recvmsg(struct io_kiocb *req,
>> struct io_zcrx_ifq *ifq,
>>
>> int io_zcrx_recv(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
>> struct socket *sock, unsigned int flags,
>> - unsigned issue_flags)
>> + unsigned issue_flags, unsigned int *len)
>> {
>> struct sock *sk = sock->sk;
>> const struct proto *prot = READ_ONCE(sk->sk_prot); @@ -951,5
>> +958,5 @@ int io_zcrx_recv(struct io_kiocb *req, struct io_zcrx_ifq *ifq,
>> return -EPROTONOSUPPORT;
>>
>> sock_rps_record_flow(sk);
>> - return io_zcrx_tcp_recvmsg(req, ifq, sk, flags, issue_flags);
>> + return io_zcrx_tcp_recvmsg(req, ifq, sk, flags, issue_flags, len);
>> }
>> diff --git a/io_uring/zcrx.h b/io_uring/zcrx.h index
>> a16bdd921f03..1b4042dc48e2 100644
>> --- a/io_uring/zcrx.h
>> +++ b/io_uring/zcrx.h
>> @@ -46,7 +46,7 @@ void io_unregister_zcrx_ifqs(struct io_ring_ctx *ctx); void
>> io_shutdown_zcrx_ifqs(struct io_ring_ctx *ctx); int io_zcrx_recv(struct io_kiocb
>> *req, struct io_zcrx_ifq *ifq,
>> struct socket *sock, unsigned int flags,
>> - unsigned issue_flags);
>> + unsigned issue_flags, unsigned int *len);
>> #else
>> static inline int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
>> struct io_uring_zcrx_ifq_reg __user
>> *arg)
>> --
>> 2.43.5
>>
>>
>
> ---
> Li Zetao
