From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6B5B6C433E3 for ; Tue, 26 May 2020 19:52:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 49984208C3 for ; Tue, 26 May 2020 19:52:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="BAnRbAHj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390179AbgEZTvw (ORCPT ); Tue, 26 May 2020 15:51:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40554 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389933AbgEZTvo (ORCPT ); Tue, 26 May 2020 15:51:44 -0400 Received: from mail-pj1-x1044.google.com (mail-pj1-x1044.google.com [IPv6:2607:f8b0:4864:20::1044]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C8945C03E97D for ; Tue, 26 May 2020 12:51:43 -0700 (PDT) Received: by mail-pj1-x1044.google.com with SMTP id 5so266689pjd.0 for ; Tue, 26 May 2020 12:51:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=Yu5b4WPlNLJ4FShHKrav5N/oC/rLKGyUa0V1npLkROk=; b=BAnRbAHjptEKaSP7aORnMOMvcRRwJYbUJCnBMqSaZ5LExh/WyjZAx0kpm9bGHRNipQ c9xKOXLv3vjiGsiBY1sSp47ys77lF0zegk2Z/RxBhYkJ+oizHWibDzDtaVyKsqqZtscm FwEZma7bB2podeT+bwe2UFoh0El2zE5bb2ykyavUywEuTB1tSqo2t2I71EDQL0x1hfyY EpM1AheRzrX3I6SAVuYiX/AKHnQYJkQtPWkZ9rw2ptTOJVNcB9NTHSHihcMpSOsbvfIi +n+bRE/L+0dLet27JP+fhpHeclePFF8u5DEjtYpBV85c3CaIk2/0DZUoZRk4tv9rWv1y zZ+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=Yu5b4WPlNLJ4FShHKrav5N/oC/rLKGyUa0V1npLkROk=; b=NervzmxgobYBvv7Qd9gaOedTjnk1smaNoPMiZstN15jDjNR2l7ZNc1jshLpyjjQ8fC Mw+LhK/Ql6vdLmKYMcq96EoKLwEl+IV4FqqEAOw40RFCS28tjJUU8QxDv6chmg9hppuG +B0bvWsDlySHPXj1KT2siWki/9ktjiS4erHPe+nKL3nFXs52zil31Kv7ZY7+MgA22hgZ 4IXVntD+beyBcaTJyUVEPcJjqtMy7ZPtGotJX3lXyUmKWMfCjJLqsypYrL9Cn4AZcAki 9JLmv0FEXHkcqWbN/2Is5IfpU5/1AYWbrn9UwLw6FCry6+7N3Ccv7uukMYneiinnk4Lb ERPA== X-Gm-Message-State: AOAM530H7/xF5JjdmGJKhCpM/twNTqjT9l5Z2zMB3keAX1TQycpYkikg OwVM4+j4wZaBMf8+AYSg8NNSoQ== X-Google-Smtp-Source: ABdhPJyp1ndQMqu6aI+tmLSQqXTreoaTLldbZ84COMrIiZ1LVkC/ujNtpmTAZp5Rn4xnmw8iMWAw9Q== X-Received: by 2002:a17:902:228:: with SMTP id 37mr2636599plc.105.1590522703244; Tue, 26 May 2020 12:51:43 -0700 (PDT) Received: from x1.lan ([2605:e000:100e:8c61:94bb:59d2:caf6:70e1]) by smtp.gmail.com with ESMTPSA id c184sm313943pfc.57.2020.05.26.12.51.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 May 2020 12:51:42 -0700 (PDT) From: Jens Axboe To: io-uring@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, Jens Axboe Subject: [PATCH 12/12] io_uring: support true async buffered reads, if file provides it Date: Tue, 26 May 2020 13:51:23 -0600 Message-Id: <20200526195123.29053-13-axboe@kernel.dk> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200526195123.29053-1-axboe@kernel.dk> References: <20200526195123.29053-1-axboe@kernel.dk> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org If the file is flagged with FMODE_BUF_RASYNC, then we don't have to punt the buffered read to an io-wq worker. Instead we can rely on page unlocking callbacks to support retry based async IO. This is a lot more efficient than doing async thread offload. The retry is done similarly to how we handle poll based retry. From the unlock callback, we simply queue the retry to a task_work based handler. Signed-off-by: Jens Axboe --- fs/io_uring.c | 130 ++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 126 insertions(+), 4 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index e6865afa8467..95df63b0b2ce 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -79,6 +79,7 @@ #include #include #include +#include #define CREATE_TRACE_POINTS #include @@ -498,6 +499,8 @@ struct io_async_rw { struct iovec *iov; ssize_t nr_segs; ssize_t size; + struct wait_page_queue wpq; + struct callback_head task_work; }; struct io_async_ctx { @@ -2568,6 +2571,119 @@ static int io_read_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe, return 0; } +static void io_async_buf_cancel(struct callback_head *cb) +{ + struct io_async_rw *rw; + struct io_ring_ctx *ctx; + struct io_kiocb *req; + + rw = container_of(cb, struct io_async_rw, task_work); + req = rw->wpq.wait.private; + ctx = req->ctx; + + spin_lock_irq(&ctx->completion_lock); + io_cqring_fill_event(req, -ECANCELED); + io_commit_cqring(ctx); + spin_unlock_irq(&ctx->completion_lock); + + io_cqring_ev_posted(ctx); + req_set_fail_links(req); + io_double_put_req(req); +} + +static void io_async_buf_retry(struct callback_head *cb) +{ + struct io_async_rw *rw; + struct io_ring_ctx *ctx; + struct io_kiocb *req; + + rw = container_of(cb, struct io_async_rw, task_work); + req = rw->wpq.wait.private; + ctx = req->ctx; + + __set_current_state(TASK_RUNNING); + mutex_lock(&ctx->uring_lock); + __io_queue_sqe(req, NULL); + mutex_unlock(&ctx->uring_lock); +} + +static int io_async_buf_func(struct wait_queue_entry *wait, unsigned mode, + int sync, void *arg) +{ + struct wait_page_queue *wpq; + struct io_kiocb *req = wait->private; + struct io_async_rw *rw = &req->io->rw; + struct wait_page_key *key = arg; + struct task_struct *tsk; + int ret; + + wpq = container_of(wait, struct wait_page_queue, wait); + + ret = wake_page_match(wpq, key); + if (ret != 1) + return ret; + + list_del_init(&wait->entry); + + init_task_work(&rw->task_work, io_async_buf_retry); + /* submit ref gets dropped, acquire a new one */ + refcount_inc(&req->refs); + tsk = req->task; + ret = task_work_add(tsk, &rw->task_work, true); + if (unlikely(ret)) { + /* queue just for cancelation */ + init_task_work(&rw->task_work, io_async_buf_cancel); + tsk = io_wq_get_task(req->ctx->io_wq); + task_work_add(tsk, &rw->task_work, true); + } + wake_up_process(tsk); + return 1; +} + +static bool io_rw_should_retry(struct io_kiocb *req) +{ + struct kiocb *kiocb = &req->rw.kiocb; + int ret; + + /* never retry for NOWAIT, we just complete with -EAGAIN */ + if (req->flags & REQ_F_NOWAIT) + return false; + + /* already tried, or we're doing O_DIRECT */ + if (kiocb->ki_flags & (IOCB_DIRECT | IOCB_WAITQ)) + return false; + /* + * just use poll if we can, and don't attempt if the fs doesn't + * support callback based unlocks + */ + if (file_can_poll(req->file) || !(req->file->f_mode & FMODE_BUF_RASYNC)) + return false; + + /* + * If request type doesn't require req->io to defer in general, + * we need to allocate it here + */ + if (!req->io && __io_alloc_async_ctx(req)) + return false; + + ret = kiocb_wait_page_queue_init(kiocb, &req->io->rw.wpq, + io_async_buf_func, req); + if (!ret) { + get_task_struct(current); + req->task = current; + return true; + } + + return false; +} + +static int io_iter_do_read(struct io_kiocb *req, struct iov_iter *iter) +{ + if (req->file->f_op->read_iter) + return call_read_iter(req->file, &req->rw.kiocb, iter); + return loop_rw_iter(READ, req->file, &req->rw.kiocb, iter); +} + static int io_read(struct io_kiocb *req, bool force_nonblock) { struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs; @@ -2601,10 +2717,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock) if (!ret) { ssize_t ret2; - if (req->file->f_op->read_iter) - ret2 = call_read_iter(req->file, kiocb, &iter); - else - ret2 = loop_rw_iter(READ, req->file, kiocb, &iter); + ret2 = io_iter_do_read(req, &iter); /* Catch -EAGAIN return for forced non-blocking submission */ if (!force_nonblock || ret2 != -EAGAIN) { @@ -2619,6 +2732,15 @@ static int io_read(struct io_kiocb *req, bool force_nonblock) if (!(req->flags & REQ_F_NOWAIT) && !file_can_poll(req->file)) req->flags |= REQ_F_MUST_PUNT; + /* if we can retry, do so with the callbacks armed */ + if (io_rw_should_retry(req)) { + ret2 = io_iter_do_read(req, &iter); + if (ret2 != -EAGAIN) { + kiocb_done(kiocb, ret2); + goto out_free; + } + } + kiocb->ki_flags &= ~IOCB_WAITQ; return -EAGAIN; } } -- 2.26.2