From patchwork Fri May 22 20:23:11 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jens Axboe X-Patchwork-Id: 11566151 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B9D66912 for ; Fri, 22 May 2020 20:23:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9D09120759 for ; Fri, 22 May 2020 20:23:40 +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="Qy+W6tsC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731125AbgEVUXh (ORCPT ); Fri, 22 May 2020 16:23:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52544 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731113AbgEVUXd (ORCPT ); Fri, 22 May 2020 16:23:33 -0400 Received: from mail-pj1-x1041.google.com (mail-pj1-x1041.google.com [IPv6:2607:f8b0:4864:20::1041]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CE211C05BD43 for ; Fri, 22 May 2020 13:23:32 -0700 (PDT) Received: by mail-pj1-x1041.google.com with SMTP id n15so5457425pjt.4 for ; Fri, 22 May 2020 13:23:32 -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=1VFf/UOKNgDVHZUKx45LznEg0u8N2FCy/awErcAtR0g=; b=Qy+W6tsCL3NH8Bq3rG6/UjcK93NBssdcv0jZGDBJKxqpc8Af5iRRlidXvE4LvcTbjQ VswLrbHzrKsuwOrz8VLGnv4GIz9ELw0+Ck61xKY0Cn/sicxCkPfwlPILus5BsdR4XbHd FivBuJiFW4rFu1pVMTyYm5FNYETtOu+OOK1rt/4nQryYpkvnhwXM0A8XWOflc3woQ/sR 5DVb+1ZIdrXK55MofhVLQcNwXyEsdQ/96R6uxVzL1zl1RP6pM7dRbw7qO6+uESrtdbTm TkK2TDXxpzbuWMaamdVVkjq2ku206Y+RpE6CKRjgQcmzRKlbx4iykHwOt3uPGN411ew9 Vgxw== 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=1VFf/UOKNgDVHZUKx45LznEg0u8N2FCy/awErcAtR0g=; b=gUwzLscT+7WwW2awNQD5+9MzwSWC8YoakLg+Fsm8RxrSpxDbmFJFm2lY2SH/SUiR8+ rEnTehMPlRcfGD0QDU+tJN000j+fsOaSZ/LrsWdcUdVJWod4sTNYWCZRQKHbfrBzlhsS ck+3B/D9Y33z/h/efgvUhOLHpoTx67Lm/PcxulciDDIwBLAXcefph9nKiYUqk2CG4wlb p6+Su2RSWoSR+aFa10q31jNcp8mr51tuFkA0a1raHucv81rB05TZltqpVNC4F8t7JRx4 XTFTgJrD8aIGs6NXr7mnFLntwqVwwMjZrMpkhi7rtHdH0ZgJLD7EeSsseCmQhn7tG2PY VN9w== X-Gm-Message-State: AOAM533etMmchW34NCs/SXlHBosgLKXn/+D7UzkUhV+OgGq+E2Hv8b6E Bv5dl/y+5w7za1T9xUS5NS5HYA== X-Google-Smtp-Source: ABdhPJyT3Ms2U6ScNVRxn8m3K+qYSXq6NTkzTCRzpeAAa7saFGGrDfVA2J0tFqYg01QCmFSbHYGH+w== X-Received: by 2002:a17:902:228:: with SMTP id 37mr16857591plc.105.1590179012288; Fri, 22 May 2020 13:23:32 -0700 (PDT) Received: from x1.lan ([2605:e000:100e:8c61:e0db:da55:b0a4:601]) by smtp.gmail.com with ESMTPSA id e19sm7295561pfn.17.2020.05.22.13.23.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 22 May 2020 13:23:31 -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, Jens Axboe Subject: [PATCH 11/11] io_uring: support true async buffered reads, if file provides it Date: Fri, 22 May 2020 14:23:11 -0600 Message-Id: <20200522202311.10959-12-axboe@kernel.dk> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200522202311.10959-1-axboe@kernel.dk> References: <20200522202311.10959-1-axboe@kernel.dk> MIME-Version: 1.0 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 | 101 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 101 insertions(+) diff --git a/fs/io_uring.c b/fs/io_uring.c index e95481c552ff..f0ca98bb688f 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -498,6 +498,8 @@ struct io_async_rw { struct iovec *iov; ssize_t nr_segs; ssize_t size; + struct wait_page_async wait; + struct callback_head task_work; }; struct io_async_ctx { @@ -2568,6 +2570,101 @@ 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->wait.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->wait.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_async *wp; + 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; + + wp = container_of(wait, struct wait_page_async, wait); + if (wp->key.page != key->page) + return 0; + if (wp->key.bit_nr != key->bit_nr) + return 0; + if (test_bit(PG_locked, &key->page->flags)) + return -1; + + 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; + + /* 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; + + ret = kiocb_wait_page_async_init(kiocb, &req->io->rw.wait, + io_async_buf_func, req); + if (ret) + return false; + get_task_struct(current); + req->task = current; + return true; +} + static int io_read(struct io_kiocb *req, bool force_nonblock) { struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs; @@ -2601,6 +2698,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock) if (!ret) { ssize_t ret2; +retry: if (req->file->f_op->read_iter) ret2 = call_read_iter(req->file, kiocb, &iter); else @@ -2619,6 +2717,9 @@ 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 (io_rw_should_retry(req)) + goto retry; + kiocb->ki_flags &= ~IOCB_WAITQ; return -EAGAIN; } }