From patchwork Wed Jun 23 09:36:33 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 12339361 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 3A865C48BE5 for ; Wed, 23 Jun 2021 09:36:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2280D61220 for ; Wed, 23 Jun 2021 09:36:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230052AbhFWJi7 (ORCPT ); Wed, 23 Jun 2021 05:38:59 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:53718 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230001AbhFWJi6 (ORCPT ); Wed, 23 Jun 2021 05:38:58 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id E4F881FD66; Wed, 23 Jun 2021 09:36:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1624441000; 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=362AqqFYt54Vuml7SJQROHajS0KLTolJ9ZkbHKmgIsU=; b=JA4s+jzecC/vhAck3uaTv9pNGPXXHYeFEBlfYbqlpd4XhBk9n2eE05SmwgvFJghppUIy0z pAorwdSJ9jQKszi+fFalvIzmRCoGsSiHMS0UO9EVRri6jQSZWcR7+Nu+V0Sb5CtZi6Z79t cgLMoaWT9wAvMv8Kb6Gvr3eOa6wZRAs= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1624441000; 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=362AqqFYt54Vuml7SJQROHajS0KLTolJ9ZkbHKmgIsU=; b=/UeOYxh028BXSxz6eAKLHgcNX0NFSgYQm5m7/p4EP0gtZBqWFxanwKpnIQ3qRMq3q7+8/q uMEP+FtUDPXH+2Cw== Received: from quack2.suse.cz (unknown [10.100.224.230]) by relay2.suse.de (Postfix) with ESMTP id 8B8AEA3B8A; Wed, 23 Jun 2021 09:36:40 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id CB6771E0414; Wed, 23 Jun 2021 11:36:38 +0200 (CEST) From: Jan Kara To: Jens Axboe Cc: , Paolo Valente , Jan Kara Subject: [PATCH 1/2] bfq: Remove merged request already in bfq_requests_merged() Date: Wed, 23 Jun 2021 11:36:33 +0200 Message-Id: <20210623093634.27879-2-jack@suse.cz> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210623093634.27879-1-jack@suse.cz> References: <20210623093634.27879-1-jack@suse.cz> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3512; h=from:subject; bh=QdEpWKpi+h8fGc/nQS9oPNguy58aTuoIghWGWfAIIHc=; b=owEBbQGS/pANAwAIAZydqgc/ZEDZAcsmYgBg0wCgf7wF/aAmCR7GnLn311cdBbVX8UYyc1GrqRKr zWjyiz2JATMEAAEIAB0WIQSrWdEr1p4yirVVKBycnaoHP2RA2QUCYNMAoAAKCRCcnaoHP2RA2ZlPCA C7gWAcEmCHMlOAwdYgVh+I0XH3sJ4kTuFc852cYuZ/FHbvpTSsb/3vpURA1gwa3uXfHtLot+ldgc+t yfofFhNCxLfDnSIReTLWQCs9l0zMUP10TqQFYYgP95M7kYLGO3jmPbw1O7vvIc+T//870tDIIyl1L+ MwlKz1tU+6jXexINif8/2YyNa3AEW5T0wOQNbPwzILW9Vjowgwsabo4A3zF+fWJ6mV/OpUifewn1Tu ArFACWc5ogogfemlNraATQbad4wPOLYTOHVqhhQuAnzuvqb23I4EP6wLmT7luvL5OIa/mqc03jZtW2 +p0RINgKXr/fdr1DBUoF6w9bB/mPhk X-Developer-Key: i=jack@suse.cz; a=openpgp; fpr=93C6099A142276A28BBE35D815BC833443038D8C 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 fedb0a8fd388..9433d38e486c 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2433,7 +2433,7 @@ 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 @@ -2456,6 +2456,14 @@ 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 */ @@ -6414,6 +6422,7 @@ 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 @@ -6431,39 +6440,15 @@ 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