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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 812B2C433DB for ; Mon, 4 Jan 2021 23:31:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4A28E22286 for ; Mon, 4 Jan 2021 23:31:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727220AbhADXbP (ORCPT ); Mon, 4 Jan 2021 18:31:15 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58708 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726930AbhADXbO (ORCPT ); Mon, 4 Jan 2021 18:31:14 -0500 Received: from mail-wm1-x32e.google.com (mail-wm1-x32e.google.com [IPv6:2a00:1450:4864:20::32e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2E52DC061793; Mon, 4 Jan 2021 15:30:34 -0800 (PST) Received: by mail-wm1-x32e.google.com with SMTP id a6so738602wmc.2; Mon, 04 Jan 2021 15:30:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=AT0KaanAHQpX/yi7u0zSE1SQN69yvyDd46YRWgQ6kQs=; b=gsd0c/UlNljEANw7TjEIu4gwDWDenqLgI1VUVGfaDuJf5c2CW2TIJIlZAJy+1Hgzhg h+ttPqZY8WdsZI2Iz9R3lA4AE7oytyLRXZF5t0lsb8j2UbXUMrWxt4nuq3gJtcdNohZc lXI6mJ4wd7uxPkfoKXSYBODV9vuSgR+yAhLrTAjIdVnpKTEIkoHMW9YEWA7KHKoqAiEo O+sAfPN/pu5UR1MctNSniPcu+0PWvQ7tcbjarCbC8btiWvahMCamiNz6IRX53VB5kR+D 4JvFl8C4hOhLJgQigeP0TSFWWvEmdFu/b6o0YUhEKjFJu4rq4TibaUyxjQMNUHBGXb/G bEBA== 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=AT0KaanAHQpX/yi7u0zSE1SQN69yvyDd46YRWgQ6kQs=; b=ggAVzX59LFG0+HuHY6hWqOLfisAev1nBHleFZjJ0sVF2WGiBy2DRUJPPaBOyQ/Hjdh bU9Flg/xaZ3aHqewVV2lKf3q6SdoSSaYeobmFuNXwE1y1gBcT449Ces21WFfoNb19ZQI aUJypx5SbwLaSrKyJhLvBKhupoy9Pf+vU9U8BPTR7U0scI7QqKIOwZb6UrcdO7PX5/E2 6Z6olxtbqMiDQtaF1+ktMDqB5qFY16du46LrL1H9cy+/sJRs1zM/hLbOP6iW0eqmo9fT 7YNtuuK7BWdk8Av9OmJ7W86Dl3QwwkKv0GfongqMqnGiSyBF1d5bjLnqRB/5cI+od0dF icYA== X-Gm-Message-State: AOAM531xuro02XtWQMDhmzFHKCsM3/abULQAXGJKvs2HDtra1BmvusFT nqMybBJHFsn7r7kcsSxV6WwxfSvn0kGFKQ== X-Google-Smtp-Source: ABdhPJw0Md6WprYfcBGMCMVJ86M0wOizibVI8Ao//VpdFaKAwgfDqvcqBbAkb6gMdqEPyo4fNq8m5g== X-Received: by 2002:a1c:5406:: with SMTP id i6mr527234wmb.137.1609792814179; Mon, 04 Jan 2021 12:40:14 -0800 (PST) Received: from localhost.localdomain ([85.255.233.205]) by smtp.gmail.com with ESMTPSA id w21sm734483wmi.45.2021.01.04.12.40.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Jan 2021 12:40:13 -0800 (PST) From: Pavel Begunkov To: Jens Axboe , io-uring@vger.kernel.org Cc: stable@vger.kernel.org Subject: [PATCH v3 2/2] io_uring: patch up IOPOLL overflow_flush sync Date: Mon, 4 Jan 2021 20:36:36 +0000 Message-Id: X-Mailer: git-send-email 2.24.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org IOPOLL skips completion locking but keeps it under uring_lock, thus io_cqring_overflow_flush() and so io_cqring_events() need additional locking with uring_lock in some cases for IOPOLL. Remove __io_cqring_overflow_flush() from io_cqring_events(), introduce a wrapper around flush doing needed synchronisation and call it by hand. Cc: stable@vger.kernel.org # 5.5+ Signed-off-by: Pavel Begunkov --- fs/io_uring.c | 78 +++++++++++++++++++++++++++------------------------ 1 file changed, 41 insertions(+), 37 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 5be33fd8b6bc..445035b24a50 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1713,9 +1713,9 @@ static void io_cqring_ev_posted(struct io_ring_ctx *ctx) } /* Returns true if there are no backlogged entries after the flush */ -static bool io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force, - struct task_struct *tsk, - struct files_struct *files) +static bool __io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force, + struct task_struct *tsk, + struct files_struct *files) { struct io_rings *rings = ctx->rings; struct io_kiocb *req, *tmp; @@ -1768,6 +1768,20 @@ static bool io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force, return all_flushed; } +static void io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force, + struct task_struct *tsk, + struct files_struct *files) +{ + if (test_bit(0, &ctx->cq_check_overflow)) { + /* iopoll syncs against uring_lock, not completion_lock */ + if (ctx->flags & IORING_SETUP_IOPOLL) + mutex_lock(&ctx->uring_lock); + __io_cqring_overflow_flush(ctx, force, tsk, files); + if (ctx->flags & IORING_SETUP_IOPOLL) + mutex_unlock(&ctx->uring_lock); + } +} + static void __io_cqring_fill_event(struct io_kiocb *req, long res, long cflags) { struct io_ring_ctx *ctx = req->ctx; @@ -2314,20 +2328,8 @@ static void io_double_put_req(struct io_kiocb *req) io_free_req(req); } -static unsigned io_cqring_events(struct io_ring_ctx *ctx, bool noflush) +static unsigned io_cqring_events(struct io_ring_ctx *ctx) { - if (test_bit(0, &ctx->cq_check_overflow)) { - /* - * noflush == true is from the waitqueue handler, just ensure - * we wake up the task, and the next invocation will flush the - * entries. We cannot safely to it from here. - */ - if (noflush) - return -1U; - - io_cqring_overflow_flush(ctx, false, NULL, NULL); - } - /* See comment at the top of this file */ smp_rmb(); return __io_cqring_events(ctx); @@ -2552,7 +2554,9 @@ static int io_iopoll_check(struct io_ring_ctx *ctx, long min) * If we do, we can potentially be spinning for commands that * already triggered a CQE (eg in error). */ - if (io_cqring_events(ctx, false)) + if (test_bit(0, &ctx->cq_check_overflow)) + __io_cqring_overflow_flush(ctx, false, NULL, NULL); + if (io_cqring_events(ctx)) break; /* @@ -6827,7 +6831,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr) /* if we have a backlog and couldn't flush it all, return BUSY */ if (test_bit(0, &ctx->sq_check_overflow)) { - if (!io_cqring_overflow_flush(ctx, false, NULL, NULL)) + if (!__io_cqring_overflow_flush(ctx, false, NULL, NULL)) return -EBUSY; } @@ -7090,7 +7094,7 @@ struct io_wait_queue { unsigned nr_timeouts; }; -static inline bool io_should_wake(struct io_wait_queue *iowq, bool noflush) +static inline bool io_should_wake(struct io_wait_queue *iowq) { struct io_ring_ctx *ctx = iowq->ctx; @@ -7099,7 +7103,7 @@ static inline bool io_should_wake(struct io_wait_queue *iowq, bool noflush) * started waiting. For timeouts, we always want to return to userspace, * regardless of event count. */ - return io_cqring_events(ctx, noflush) >= iowq->to_wait || + return io_cqring_events(ctx) >= iowq->to_wait || atomic_read(&ctx->cq_timeouts) != iowq->nr_timeouts; } @@ -7109,11 +7113,13 @@ static int io_wake_function(struct wait_queue_entry *curr, unsigned int mode, struct io_wait_queue *iowq = container_of(curr, struct io_wait_queue, wq); - /* use noflush == true, as we can't safely rely on locking context */ - if (!io_should_wake(iowq, true)) - return -1; - - return autoremove_wake_function(curr, mode, wake_flags, key); + /* + * Cannot safely flush overflowed CQEs from here, ensure we wake up + * the task, and the next invocation will do it. + */ + if (io_should_wake(iowq) || test_bit(0, &iowq->ctx->cq_check_overflow)) + return autoremove_wake_function(curr, mode, wake_flags, key); + return -1; } static int io_run_task_work_sig(void) @@ -7150,7 +7156,8 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, int ret = 0; do { - if (io_cqring_events(ctx, false) >= min_events) + io_cqring_overflow_flush(ctx, false, NULL, NULL); + if (io_cqring_events(ctx) >= min_events) return 0; if (!io_run_task_work()) break; @@ -7178,6 +7185,7 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, iowq.nr_timeouts = atomic_read(&ctx->cq_timeouts); trace_io_uring_cqring_wait(ctx, min_events); do { + io_cqring_overflow_flush(ctx, false, NULL, NULL); prepare_to_wait_exclusive(&ctx->wait, &iowq.wq, TASK_INTERRUPTIBLE); /* make sure we run task_work before checking for signals */ @@ -7186,8 +7194,10 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, continue; else if (ret < 0) break; - if (io_should_wake(&iowq, false)) + if (io_should_wake(&iowq)) break; + if (test_bit(0, &ctx->cq_check_overflow)) + continue; if (uts) { timeout = schedule_timeout(timeout); if (timeout == 0) { @@ -8625,7 +8635,8 @@ static __poll_t io_uring_poll(struct file *file, poll_table *wait) smp_rmb(); if (!io_sqring_full(ctx)) mask |= EPOLLOUT | EPOLLWRNORM; - if (io_cqring_events(ctx, false)) + io_cqring_overflow_flush(ctx, false, NULL, NULL); + if (io_cqring_events(ctx)) mask |= EPOLLIN | EPOLLRDNORM; return mask; @@ -8683,7 +8694,7 @@ static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx) /* if force is set, the ring is going away. always drop after that */ ctx->cq_overflow_flushed = 1; if (ctx->rings) - io_cqring_overflow_flush(ctx, true, NULL, NULL); + __io_cqring_overflow_flush(ctx, true, NULL, NULL); mutex_unlock(&ctx->uring_lock); io_kill_timeouts(ctx, NULL, NULL); @@ -8857,9 +8868,7 @@ static void io_uring_cancel_task_requests(struct io_ring_ctx *ctx, } io_cancel_defer_files(ctx, task, files); - io_ring_submit_lock(ctx, (ctx->flags & IORING_SETUP_IOPOLL)); io_cqring_overflow_flush(ctx, true, task, files); - io_ring_submit_unlock(ctx, (ctx->flags & IORING_SETUP_IOPOLL)); if (!files) __io_uring_cancel_task_requests(ctx, task); @@ -9195,13 +9204,8 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit, */ ret = 0; if (ctx->flags & IORING_SETUP_SQPOLL) { - if (!list_empty_careful(&ctx->cq_overflow_list)) { - bool needs_lock = ctx->flags & IORING_SETUP_IOPOLL; + io_cqring_overflow_flush(ctx, false, NULL, NULL); - io_ring_submit_lock(ctx, needs_lock); - io_cqring_overflow_flush(ctx, false, NULL, NULL); - io_ring_submit_unlock(ctx, needs_lock); - } if (flags & IORING_ENTER_SQ_WAKEUP) wake_up(&ctx->sq_data->wait); if (flags & IORING_ENTER_SQ_WAIT) -- 2.24.0