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=-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,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 CB8E0C4708D for ; Fri, 28 May 2021 12:30:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A831A613C9 for ; Fri, 28 May 2021 12:30:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230056AbhE1Mc2 (ORCPT ); Fri, 28 May 2021 08:32:28 -0400 Received: from mx2.suse.de ([195.135.220.15]:54886 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234845AbhE1McY (ORCPT ); Fri, 28 May 2021 08:32:24 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1622205049; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=h3rSQRu3T4RRxVJcqF/TJ6k5VtR27iELBJgcDdBJsa0=; b=2sSNEeeEBShtuW0ZGrNKp3+Yb8jxlC0J+IWYLfIT3cVaFihZnkqCo75lQbJkv4CFsh/mhC g6JSg2bevmCfw+ma1Zb6WZE1jH8fW0ggjm95TP2DmpxvSNu3eXB00zPA6Okz3ostDfAyDO ZPxW12NMgKjg9I1XgAzoVhnmt/dl9Kc= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1622205049; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=h3rSQRu3T4RRxVJcqF/TJ6k5VtR27iELBJgcDdBJsa0=; b=0SPgiJ8nVu71NOurB8V3nbK0izD6DUbg+odJB1dQTtjVLQe12/q1x4xQdute8cs217mBrI p6/Dp/gIvA7kgLDw== Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 0DE4DAB6D; Fri, 28 May 2021 12:30:49 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id CEEBE1E0CB7; Fri, 28 May 2021 14:30:48 +0200 (CEST) From: Jan Kara To: Jens Axboe Cc: , Khazhy Kumykov , Ming Lei , Paolo Valente , Jan Kara Subject: [PATCH 1/2] bfq: Remove merged request already in bfq_requests_merged() Date: Fri, 28 May 2021 14:30:40 +0200 Message-Id: <20210528123041.29914-2-jack@suse.cz> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210528123041.29914-1-jack@suse.cz> References: <20210528123041.29914-1-jack@suse.cz> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3512; h=from:subject; bh=5IElGV66Jwz1zQCX+WGSCHRJi87Kjj9GNqKfebNvnR8=; b=owEBbQGS/pANAwAIAZydqgc/ZEDZAcsmYgBgsOJgDWQnQTpt9NUCOr4aDYip+ISXHF4GMulDvPZU 1cNsfvWJATMEAAEIAB0WIQSrWdEr1p4yirVVKBycnaoHP2RA2QUCYLDiYAAKCRCcnaoHP2RA2Q1vB/ 0T80dzpkvYZ+grrBU9onu/uUnJm8Rj41eX/yFPr457UImFz9iQRG7gw49SLo7Lpk5J3hQFkRnYFXd4 uHiEh33iO6npm0X8f6ohjx0/miX0hm+HdgMss2KzCI3VfwM+euAWcE4dD36fGMbCLf5Od1KriG7c2q D3642wN5chi7LwzvyQsyW6kDRM3X+A9M0O5O5P4Zax5bMUbrJr9lOLUJWCpeqzqlWRK75cBjVueqEE bd6wDd8lC0y5ir0Kn96e9CbR0z3JSlnBqIBHCsFQFyI9Y8YAkwi81TULTbxpHDcBxrFZPD86GUi3NY naDoqwnOTteFCBYJQsM2JAboZPSpug X-Developer-Key: i=jack@suse.cz; a=openpgp; fpr=93C6099A142276A28BBE35D815BC833443038D8C Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Currently, bfq does very little in bfq_requests_merged() and handles all the request cleanup in bfq_finish_requeue_request() called from blk_mq_free_request(). That is currently safe only because blk_mq_free_request() is called shortly after bfq_requests_merged() while bfqd->lock is still held. However to fix a lock inversion between bfqd->lock and ioc->lock, we need to call blk_mq_free_request() after dropping bfqd->lock. That would mean that already merged request could be seen by other processes inside bfq queues and possibly dispatched to the device which is wrong. So move cleanup of the request from bfq_finish_requeue_request() to bfq_requests_merged(). Acked-by: Paolo Valente Signed-off-by: Jan Kara --- block/bfq-iosched.c | 41 +++++++++++++---------------------------- 1 file changed, 13 insertions(+), 28 deletions(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index acd1f881273e..50a29fdf51da 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2405,7 +2405,7 @@ static void bfq_requests_merged(struct request_queue *q, struct request *rq, *next_bfqq = bfq_init_rq(next); if (!bfqq) - return; + goto remove; /* * If next and rq belong to the same bfq_queue and next is older @@ -2428,6 +2428,14 @@ static void bfq_requests_merged(struct request_queue *q, struct request *rq, bfqq->next_rq = rq; bfqg_stats_update_io_merged(bfqq_group(bfqq), next->cmd_flags); +remove: + /* Merged request may be in the IO scheduler. Remove it. */ + if (!RB_EMPTY_NODE(&next->rb_node)) { + bfq_remove_request(next->q, next); + if (next_bfqq) + bfqg_stats_update_io_remove(bfqq_group(next_bfqq), + next->cmd_flags); + } } /* Must be called with bfqq != NULL */ @@ -6376,6 +6384,7 @@ static void bfq_finish_requeue_request(struct request *rq) { struct bfq_queue *bfqq = RQ_BFQQ(rq); struct bfq_data *bfqd; + unsigned long flags; /* * rq either is not associated with any icq, or is an already @@ -6393,39 +6402,15 @@ static void bfq_finish_requeue_request(struct request *rq) rq->io_start_time_ns, rq->cmd_flags); + spin_lock_irqsave(&bfqd->lock, flags); if (likely(rq->rq_flags & RQF_STARTED)) { - unsigned long flags; - - spin_lock_irqsave(&bfqd->lock, flags); - if (rq == bfqd->waited_rq) bfq_update_inject_limit(bfqd, bfqq); bfq_completed_request(bfqq, bfqd); - bfq_finish_requeue_request_body(bfqq); - - spin_unlock_irqrestore(&bfqd->lock, flags); - } else { - /* - * Request rq may be still/already in the scheduler, - * in which case we need to remove it (this should - * never happen in case of requeue). And we cannot - * defer such a check and removal, to avoid - * inconsistencies in the time interval from the end - * of this function to the start of the deferred work. - * This situation seems to occur only in process - * context, as a consequence of a merge. In the - * current version of the code, this implies that the - * lock is held. - */ - - if (!RB_EMPTY_NODE(&rq->rb_node)) { - bfq_remove_request(rq->q, rq); - bfqg_stats_update_io_remove(bfqq_group(bfqq), - rq->cmd_flags); - } - bfq_finish_requeue_request_body(bfqq); } + bfq_finish_requeue_request_body(bfqq); + spin_unlock_irqrestore(&bfqd->lock, flags); /* * Reset private fields. In case of a requeue, this allows -- 2.26.2