From patchwork Wed Feb 3 13:20:16 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jinpu Wang X-Patchwork-Id: 376871 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 A0B48C43381 for ; Wed, 3 Feb 2021 13:21:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 76DCB64F4C for ; Wed, 3 Feb 2021 13:21:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231488AbhBCNVI (ORCPT ); Wed, 3 Feb 2021 08:21:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40414 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231535AbhBCNVH (ORCPT ); Wed, 3 Feb 2021 08:21:07 -0500 Received: from mail-wr1-x42e.google.com (mail-wr1-x42e.google.com [IPv6:2a00:1450:4864:20::42e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 96BDFC0613ED for ; Wed, 3 Feb 2021 05:20:26 -0800 (PST) Received: by mail-wr1-x42e.google.com with SMTP id c12so24266105wrc.7 for ; Wed, 03 Feb 2021 05:20:26 -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=gsVKCsbnjeaznli0xpdvVmzAqPGuh4XLY8ewqDtW9H0ByfqTqUzh94eZc1D8KKY1hq nX1zLzSXvYGlO1euxs91gXIFAyrpG82Ng+uSgqKKYeAMyrb65lk/IhHq4fMt2N5BOUiH La9YTIjrJEUf0dG0qVXKD2SzSdJ+h+PYZhlciS0a0yhc27Vko3fmOY3HFHrfoa90khPG qgvyraEXz7tJwlOD2sDOTQHl9VldLPQkNWwE1wbaiDLNRAsHFWBN6xKSnek5OZDtew/N b+QlcNTvcAU1sGbwt4jx5aovfvSMQ54yUgTAGO6dbbkEHlxFilUcFEU60Jns5irp2IMB DxwQ== 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=T/l+rzA7CA4sP1dU9KPPGwnB828kRQAJetYYwNk32kcO1Sq/aYwD5CRN+tiQ24iAKg tCJhkHOdEbOoujHZFtc1usYihzTkRhen4QxwjNVlWVfTexvq9Sx7T24/z5SK13+k0FE/ FsAg/QwVd8zJ5jQVDjDHGDzpIjsOr4IT4YToeLPx7MT5pNfUTnTO18ltHjaqJW7iipbu Rpwlst3/TAFS3SFWnaiI7IUNeqCe6CTwi+yT1E/BXlFbbkcy52JP9r1XeemBuoVzfWSG wb6D9yy9SZKLwj7Te4CDOIWPQrT+qoNFOcytn0y6FA7biecUXRlJKX4x3INy9AGuTxuZ Sqqw== X-Gm-Message-State: AOAM5303WZpn6nZ6JAI71h/XwGYK7dB/1RKR0ixRuTZOPW5XaRqGevwZ I4Fn6bhMN7o0IUjEvZ5GDmdYYQ== X-Google-Smtp-Source: ABdhPJy0UOU3brOw2FrfNueaOntHlnbvuoV2ZynvOsSmdEWrTFHUMK2jqRW0vTVx8x4J4DzY39nPuQ== X-Received: by 2002:adf:c64f:: with SMTP id u15mr3391897wrg.270.1612358425343; Wed, 03 Feb 2021 05:20:25 -0800 (PST) Received: from jwang-Latitude-5491.fritz.box ([2001:16b8:4947:3c00:7cf4:7472:391:9d0d]) by smtp.gmail.com with ESMTPSA id d10sm3738430wrn.88.2021.02.03.05.20.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Feb 2021 05:20:24 -0800 (PST) From: Jack Wang To: gregkh@linuxfoundation.org, sashal@kernel.org, stable@vger.kernel.org Cc: Ming Lei , Christoph Hellwig , Hannes Reinecke , Mike Snitzer , Bart Van Assche , Damien Le Moal , Jens Axboe Subject: [stable-4.19 2/8] block: don't hold q->sysfs_lock in elevator_init_mq Date: Wed, 3 Feb 2021 14:20:16 +0100 Message-Id: <20210203132022.92406-3-jinpu.wang@cloud.ionos.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210203132022.92406-1-jinpu.wang@cloud.ionos.com> References: <20210203132022.92406-1-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; }