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Miller" , Eric Dumazet , Jesper Dangaard Brouer , David Ahern , Mina Almasry References: <20240312214430.2923019-1-dw@davidwei.uk> <20240312214430.2923019-14-dw@davidwei.uk> <7752a08c-f55c-48d5-87f2-70f248381e48@kernel.dk> Content-Language: en-US From: Pavel Begunkov In-Reply-To: <7752a08c-f55c-48d5-87f2-70f248381e48@kernel.dk> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/13/24 20:25, Jens Axboe wrote: > On 3/12/24 3:44 PM, David Wei wrote: >> Add an io_uring opcode OP_RECV_ZC for doing ZC reads from a socket that >> is set up for ZC Rx. The request reads skbs from a socket. Completions >> are posted into the main CQ for each page frag read. >> >> Big CQEs (CQE32) is required as the OP_RECV_ZC specific metadata (ZC >> region, offset, len) are stored in the extended 16 bytes as a >> struct io_uring_rbuf_cqe. >> >> For now there is no limit as to how much work each OP_RECV_ZC request >> does. It will attempt to drain a socket of all available data. >> >> Multishot requests are also supported. The first time an io_recvzc >> request completes, EAGAIN is returned which arms an async poll. Then, in >> subsequent runs in task work, IOU_ISSUE_SKIP_COMPLETE is returned to >> continue async polling. > > I'd probably drop that last paragraph, this is how all multishot > requests work and is implementation detail that need not go in the > commit message. Probably suffices just to say it supports multishot. > >> @@ -695,7 +701,7 @@ static inline bool io_recv_finish(struct io_kiocb *req, int *ret, >> unsigned int cflags; >> >> cflags = io_put_kbuf(req, issue_flags); >> - if (msg->msg_inq && msg->msg_inq != -1) >> + if (msg && msg->msg_inq && msg->msg_inq != -1) >> cflags |= IORING_CQE_F_SOCK_NONEMPTY; >> >> if (!(req->flags & REQ_F_APOLL_MULTISHOT)) { >> @@ -723,7 +729,7 @@ static inline bool io_recv_finish(struct io_kiocb *req, int *ret, >> goto enobufs; >> >> /* Known not-empty or unknown state, retry */ >> - if (cflags & IORING_CQE_F_SOCK_NONEMPTY || msg->msg_inq == -1) { >> + if (cflags & IORING_CQE_F_SOCK_NONEMPTY || (msg && msg->msg_inq == -1)) { >> if (sr->nr_multishot_loops++ < MULTISHOT_MAX_RETRY) >> return false; >> /* mshot retries exceeded, force a requeue */ > > Maybe refactor this a bit so that you don't need to add these NULL > checks? That seems pretty fragile, hard to read, and should be doable > without extra checks. That chunk can be completely thrown away, we're not using io_recv_finish() here anymore >> @@ -1053,6 +1058,85 @@ struct io_zc_rx_ifq *io_zc_verify_sock(struct io_kiocb *req, >> return ifq; >> } >> >> +int io_recvzc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) >> +{ >> + struct io_recvzc *zc = io_kiocb_to_cmd(req, struct io_recvzc); >> + >> + /* non-iopoll defer_taskrun only */ >> + if (!req->ctx->task_complete) >> + return -EINVAL; > > What's the reasoning behind this? CQ locking, see the comment a couple lines below >> + struct io_recvzc *zc = io_kiocb_to_cmd(req, struct io_recvzc); >> + struct io_zc_rx_ifq *ifq; >> + struct socket *sock; >> + int ret; >> + >> + /* >> + * We're posting CQEs deeper in the stack, and to avoid taking CQ locks >> + * we serialise by having only the master thread modifying the CQ with >> + * DEFER_TASkRUN checked earlier and forbidding executing it from io-wq. >> + * That's similar to io_check_multishot() for multishot CQEs. >> + */ This one ^^, though it doesn't read well, I should reword it for next time. >> + if (issue_flags & IO_URING_F_IOWQ) >> + return -EAGAIN; >> + if (WARN_ON_ONCE(!(issue_flags & IO_URING_F_NONBLOCK))) >> + return -EAGAIN; > > If rebased on the current tree, does this go away? It's just a little behind not to have that change -- Pavel Begunkov