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Tue, 04 Feb 2025 11:48:31 -0800 (PST) Received: from localhost.localdomain ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id 8926c6da1cb9f-4ec746c95c4sm2841466173.127.2025.02.04.11.48.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Feb 2025 11:48:30 -0800 (PST) From: Jens Axboe To: io-uring@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, brauner@kernel.org, Jens Axboe Subject: [PATCH 11/11] io_uring/epoll: add multishot support for IORING_OP_EPOLL_WAIT Date: Tue, 4 Feb 2025 12:46:45 -0700 Message-ID: <20250204194814.393112-12-axboe@kernel.dk> X-Mailer: git-send-email 2.47.2 In-Reply-To: <20250204194814.393112-1-axboe@kernel.dk> References: <20250204194814.393112-1-axboe@kernel.dk> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 As with other multishot requests, submitting a multishot epoll wait request will keep it re-armed post the initial trigger. This allows multiple epoll wait completions per request submitted, every time events are available. If more completions are expected for this epoll wait request, then IORING_CQE_F_MORE will be set in the posted cqe->flags. For multishot, the request remains on the epoll callback waitqueue head. This means that epoll doesn't need to juggle the ep->lock writelock (and disable/enable IRQs) for each invocation of the reaping loop. That should translate into nice efficiency gains. Use by setting IORING_EPOLL_WAIT_MULTISHOT in the sqe->epoll_flags member. Must be used with provided buffers. Signed-off-by: Jens Axboe --- include/uapi/linux/io_uring.h | 6 +++++ io_uring/epoll.c | 46 ++++++++++++++++++++++++++++------- 2 files changed, 43 insertions(+), 9 deletions(-) diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index a559e1e1544a..93f504b6d4ec 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -73,6 +73,7 @@ struct io_uring_sqe { __u32 futex_flags; __u32 install_fd_flags; __u32 nop_flags; + __u32 epoll_flags; }; __u64 user_data; /* data to be passed back at completion time */ /* pack this to avoid bogus arm OABI complaints */ @@ -405,6 +406,11 @@ enum io_uring_op { #define IORING_ACCEPT_DONTWAIT (1U << 1) #define IORING_ACCEPT_POLL_FIRST (1U << 2) +/* + * epoll_wait flags, stored in sqe->epoll_flags + */ +#define IORING_EPOLL_WAIT_MULTISHOT (1U << 0) + /* * IORING_OP_MSG_RING command types, stored in sqe->addr */ diff --git a/io_uring/epoll.c b/io_uring/epoll.c index 134112e7a505..2474f2e069ef 100644 --- a/io_uring/epoll.c +++ b/io_uring/epoll.c @@ -25,6 +25,7 @@ struct io_epoll { struct io_epoll_wait { struct file *file; int maxevents; + int flags; struct epoll_event __user *events; struct wait_queue_entry wait; }; @@ -151,11 +152,12 @@ static void io_epoll_retry(struct io_kiocb *req, struct io_tw_state *ts) io_req_task_submit(req, ts); } -static int io_epoll_execute(struct io_kiocb *req) +static int io_epoll_execute(struct io_kiocb *req, __poll_t mask) { struct io_epoll_wait *iew = io_kiocb_to_cmd(req, struct io_epoll_wait); - list_del_init_careful(&iew->wait.entry); + if (mask & EPOLL_URING_WAKE || !(req->flags & REQ_F_APOLL_MULTISHOT)) + list_del_init_careful(&iew->wait.entry); if (io_poll_get_ownership(req)) { req->io_task_work.func = io_epoll_retry; io_req_task_work_add(req); @@ -164,13 +166,13 @@ static int io_epoll_execute(struct io_kiocb *req) return 1; } -static __cold int io_epoll_pollfree_wake(struct io_kiocb *req) +static __cold int io_epoll_pollfree_wake(struct io_kiocb *req, __poll_t mask) { struct io_epoll_wait *iew = io_kiocb_to_cmd(req, struct io_epoll_wait); io_poll_mark_cancelled(req); list_del_init_careful(&iew->wait.entry); - io_epoll_execute(req); + io_epoll_execute(req, mask); return 1; } @@ -181,20 +183,28 @@ static int io_epoll_wait_fn(struct wait_queue_entry *wait, unsigned mode, __poll_t mask = key_to_poll(key); if (unlikely(mask & POLLFREE)) - return io_epoll_pollfree_wake(req); + return io_epoll_pollfree_wake(req, mask); - return io_epoll_execute(req); + return io_epoll_execute(req, mask); } int io_epoll_wait_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) { struct io_epoll_wait *iew = io_kiocb_to_cmd(req, struct io_epoll_wait); - if (sqe->off || sqe->rw_flags || sqe->splice_fd_in) + if (sqe->off || sqe->splice_fd_in) return -EINVAL; iew->maxevents = READ_ONCE(sqe->len); iew->events = u64_to_user_ptr(READ_ONCE(sqe->addr)); + iew->flags = READ_ONCE(sqe->epoll_flags); + if (iew->flags & ~IORING_EPOLL_WAIT_MULTISHOT) { + return -EINVAL; + } else if (iew->flags & IORING_EPOLL_WAIT_MULTISHOT) { + if (!(req->flags & REQ_F_BUFFER_SELECT)) + return -EINVAL; + req->flags |= REQ_F_APOLL_MULTISHOT; + } if (req->flags & REQ_F_BUFFER_SELECT && iew->events) return -EINVAL; @@ -217,7 +227,7 @@ int io_epoll_wait(struct io_kiocb *req, unsigned int issue_flags) int ret; io_ring_submit_lock(ctx, issue_flags); - +retry: if (io_do_buffer_select(req)) { size_t len = iew->maxevents * sizeof(*evs); @@ -238,14 +248,32 @@ int io_epoll_wait(struct io_kiocb *req, unsigned int issue_flags) return IOU_ISSUE_SKIP_COMPLETE; } else if (ret > 0) { cflags = io_put_kbuf(req, ret * sizeof(*evs), 0); + if (req->flags & REQ_F_BL_EMPTY) + goto stop_multi; + if (req->flags & REQ_F_APOLL_MULTISHOT) { + if (io_req_post_cqe(req, ret, cflags | IORING_CQE_F_MORE)) + goto retry; + goto stop_multi; + } } else if (!ret) { io_kbuf_recycle(req, 0); } else { err: req_set_fail(req); + if (req->flags & REQ_F_APOLL_MULTISHOT) { +stop_multi: + atomic_or(IO_POLL_FINISH_FLAG, &req->poll_refs); + io_poll_multishot_retry(req); + if (!list_empty_careful(&iew->wait.entry)) + epoll_wait_remove(req->file, &iew->wait); + req->flags &= ~REQ_F_APOLL_MULTISHOT; + } } - hlist_del_init(&req->hash_node); + if (!(req->flags & REQ_F_APOLL_MULTISHOT)) + hlist_del_init(&req->hash_node); io_ring_submit_unlock(ctx, issue_flags); io_req_set_res(req, ret, cflags); + if (issue_flags & IO_URING_F_MULTISHOT) + return IOU_STOP_MULTISHOT; return IOU_OK; }