From patchwork Mon Feb 8 15:04:21 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jinpu Wang X-Patchwork-Id: 379263 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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham 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 06747C433E0 for ; Mon, 8 Feb 2021 15:07:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B9F8264EDB for ; Mon, 8 Feb 2021 15:07:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232132AbhBHPHI (ORCPT ); Mon, 8 Feb 2021 10:07:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50432 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232733AbhBHPFL (ORCPT ); Mon, 8 Feb 2021 10:05:11 -0500 Received: from mail-ed1-x534.google.com (mail-ed1-x534.google.com [IPv6:2a00:1450:4864:20::534]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9175AC06178C for ; Mon, 8 Feb 2021 07:04:31 -0800 (PST) Received: by mail-ed1-x534.google.com with SMTP id c6so18527704ede.0 for ; Mon, 08 Feb 2021 07:04:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloud.ionos.com; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=BfO/909mdUaRpv6ekeQ5pLoyeo6G7O5g5UYJLsEOL80=; b=MmGtK51mZ/nb4m6J+tegtGj9dEOWyEsw4IM6ibVo9nz/IxSChfLMDRAudfCxGzPbym z/m21H2HxzTt7EV42jQnB0JS0Xz9D2a2frYh6lxYb0R8nEo1G8eEtGdslD0PFWNx4ilS MgqnnxC+/zuUgv5U2iI63iPTzW1la1s5KyqWuAB63nQIJ3gA94SKgR7zmOSAQvmXJfqx 3N9vYqQlXqschblGlUvYIlJIpL4HFOxB1Eh2pyxuw7imB2rrC86UAOFeS/UZFhmrFPMd cEbYPMY28VwyIjikW9mCuDCB8EdLScD/XVzRP1P8G19218/lqOxbYfzms1TuOOQmVc2D i2sw== 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=BfO/909mdUaRpv6ekeQ5pLoyeo6G7O5g5UYJLsEOL80=; b=NJI1UB5Rwzjwo41RQNthmeZ5MkVCQF2j0H4CTEJS8alfQL09Hlh4IznIxjBIOmSDnd 3kHfjfbDb6Hpw+UR+l01O79pfWL+FUC2VJQ2vA/OhzNMwoku3Zgibw9qJKZwcaYnUMLZ xhGKxzaP0ILvC/Ld1R/EJsGBMO2gGUfux4yHH6aCf/ZCc1tYLhJC7IIju1xRxErBVzym NCyC4m8nlXJcVdoA5vp/SaGLSfMrwwCRPCwiPnCon/1B/5cy2NzPovRVlH2IqYR6dXkJ WPHv0OAtqaHeqxZOGBrxnuRt5jjpshcbMYT5XGeLUgXHOGtKNY0H5iiMhcqUzxbcp5vM xSxg== X-Gm-Message-State: AOAM531KuFnUxHi54r+WIXPqPUoke6myJ0PCIWW4Uj/hVPX4rREDKflk iyAPLwLWewcCVBKh/vLPJzMTAw== X-Google-Smtp-Source: ABdhPJySqwps4jJIuSEUwGbgLGSxUHSe/fFXecOuSpzJWz5pxtiUcs15gqWQxwl4+QnF1eLfkHcEWw== X-Received: by 2002:a05:6402:2690:: with SMTP id w16mr17703671edd.304.1612796669170; Mon, 08 Feb 2021 07:04:29 -0800 (PST) Received: from jwang-Latitude-5491.fkb.profitbricks.net ([2001:16b8:4980:d900:bc0f:acd:c20a:c261]) by smtp.gmail.com with ESMTPSA id kb25sm4359106ejc.19.2021.02.08.07.04.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Feb 2021 07:04:28 -0800 (PST) From: Jack Wang To: gregkh@linuxfoundation.org, sashal@kernel.org, axboe@kernel.dk, stable@vger.kernel.org Cc: Ming Lei , Christoph Hellwig , Hannes Reinecke , Mike Snitzer , Bart Van Assche , Damien Le Moal Subject: [stable-4.19 Resend 2/7] block: don't hold q->sysfs_lock in elevator_init_mq Date: Mon, 8 Feb 2021 16:04:21 +0100 Message-Id: <20210208150426.62755-3-jinpu.wang@cloud.ionos.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210208150426.62755-1-jinpu.wang@cloud.ionos.com> References: <20210208150426.62755-1-jinpu.wang@cloud.ionos.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Ming Lei The original comment says: q->sysfs_lock must be held to provide mutual exclusion between elevator_switch() and here. Which is simply wrong. elevator_init_mq() is only called from blk_mq_init_allocated_queue, which is always called before the request queue is registered via blk_register_queue(), for dm-rq or normal rq based driver. However, queue's kobject is only exposed and added to sysfs in blk_register_queue(). So there isn't such race between elevator_switch() and elevator_init_mq(). So avoid to hold q->sysfs_lock in elevator_init_mq(). Cc: Christoph Hellwig Cc: Hannes Reinecke Cc: Greg KH Cc: Mike Snitzer Cc: Bart Van Assche Cc: Damien Le Moal Reviewed-by: Bart Van Assche Signed-off-by: Ming Lei Signed-off-by: Jens Axboe (cherry picked from commit c48dac137a62a5d6fa1ef3fa445cbd9c43655a76) Signed-off-by: Jack Wang --- block/elevator.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) diff --git a/block/elevator.c b/block/elevator.c index fae58b2f906f..ddbcd36616a8 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -980,23 +980,19 @@ int elevator_init_mq(struct request_queue *q) if (q->nr_hw_queues != 1) return 0; - /* - * q->sysfs_lock must be held to provide mutual exclusion between - * elevator_switch() and here. - */ - mutex_lock(&q->sysfs_lock); + WARN_ON_ONCE(test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags)); + if (unlikely(q->elevator)) - goto out_unlock; + goto out; e = elevator_get(q, "mq-deadline", false); if (!e) - goto out_unlock; + goto out; err = blk_mq_init_sched(q, e); if (err) elevator_put(e); -out_unlock: - mutex_unlock(&q->sysfs_lock); +out: return err; }