From 3c19966d3710dbe5a44658c532052f11d797aecb Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Tue, 15 Jun 2021 16:47:57 +0100 Subject: [PATCH] io_uring: shove more drain bits out of hot path Place all drain_next logic into io_drain_req(), so it's never executed if there was no drained requests before. The only thing we need is to set ->drain_active if we see a request with IOSQE_IO_DRAIN, do that in io_init_req() where flags are definitely in registers. Also, all drain-related code is encapsulated in io_drain_req(), makes it cleaner. Signed-off-by: Pavel Begunkov Link: https://lore.kernel.org/r/68bf4f7395ddaafbf1a26bd97b57d57d45a9f900.1623772051.git.asml.silence@gmail.com Signed-off-by: Jens Axboe --- fs/io_uring.c | 42 ++++++++++++++++++++++-------------------- 1 file changed, 22 insertions(+), 20 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 25106cf..f63fc79 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -5997,11 +5997,31 @@ static u32 io_get_sequence(struct io_kiocb *req) static bool io_drain_req(struct io_kiocb *req) { + struct io_kiocb *pos; struct io_ring_ctx *ctx = req->ctx; struct io_defer_entry *de; int ret; u32 seq; + /* + * If we need to drain a request in the middle of a link, drain the + * head request and the next request/link after the current link. + * Considering sequential execution of links, IOSQE_IO_DRAIN will be + * maintained for every request of our link. + */ + if (ctx->drain_next) { + req->flags |= REQ_F_IO_DRAIN; + ctx->drain_next = false; + } + /* not interested in head, start from the first linked */ + io_for_each_link(pos, req->link) { + if (pos->flags & REQ_F_IO_DRAIN) { + ctx->drain_next = true; + req->flags |= REQ_F_IO_DRAIN; + break; + } + } + /* Still need defer if there is pending req in defer list. */ if (likely(list_empty_careful(&ctx->defer_list) && !(req->flags & REQ_F_IO_DRAIN))) { @@ -6522,6 +6542,8 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req, if ((sqe_flags & IOSQE_BUFFER_SELECT) && !io_op_defs[req->opcode].buffer_select) return -EOPNOTSUPP; + if (unlikely(sqe_flags & IOSQE_IO_DRAIN)) + ctx->drain_active = true; personality = READ_ONCE(sqe->personality); if (personality) { @@ -6573,22 +6595,6 @@ fail_req: return ret; } - if (unlikely(req->flags & REQ_F_IO_DRAIN)) { - ctx->drain_active = true; - - /* - * Taking sequential execution of a link, draining both sides - * of the link also fullfils IOSQE_IO_DRAIN semantics for all - * requests in the link. So, it drains the head and the - * next after the link request. The last one is done via - * drain_next flag to persist the effect across calls. - */ - if (link->head) { - link->head->flags |= REQ_F_IO_DRAIN; - ctx->drain_next = 1; - } - } - ret = io_req_prep(req, sqe); if (unlikely(ret)) goto fail_req; @@ -6620,10 +6626,6 @@ fail_req: io_queue_sqe(head); } } else { - if (unlikely(ctx->drain_next)) { - req->flags |= REQ_F_IO_DRAIN; - ctx->drain_next = 0; - } if (req->flags & (REQ_F_LINK | REQ_F_HARDLINK)) { link->head = req; link->last = req; -- 2.7.4