From patchwork Mon Sep 24 11:53:35 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 10612413 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id EF65314DA for ; Mon, 24 Sep 2018 12:45:22 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id DEEA229C3B for ; Mon, 24 Sep 2018 12:45:22 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id D2C0B29C4B; Mon, 24 Sep 2018 12:45:22 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5A93A29C3B for ; Mon, 24 Sep 2018 12:45:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389312AbeIXSrO (ORCPT ); Mon, 24 Sep 2018 14:47:14 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:59750 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730322AbeIXSrN (ORCPT ); Mon, 24 Sep 2018 14:47:13 -0400 Received: from localhost (ip-213-127-77-73.ip.prioritytelecom.net [213.127.77.73]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 14A1D109E; Mon, 24 Sep 2018 12:45:14 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andrew Jones , Omar Sandoval , Bart Van Assche , linux-scsi@vger.kernel.org, "Martin K. Petersen" , Christoph Hellwig , Ming Lei , Jens Axboe , Sasha Levin Subject: [PATCH 4.18 229/235] blk-mq: avoid to synchronize rcu inside blk_cleanup_queue() Date: Mon, 24 Sep 2018 13:53:35 +0200 Message-Id: <20180924113125.837160833@linuxfoundation.org> X-Mailer: git-send-email 2.19.0 In-Reply-To: <20180924113103.999624566@linuxfoundation.org> References: <20180924113103.999624566@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 4.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ming Lei [ Upstream commit 1311326cf4755c7ffefd20f576144ecf46d9906b ] SCSI probing may synchronously create and destroy a lot of request_queues for non-existent devices. Any synchronize_rcu() in queue creation or destroy path may introduce long latency during booting, see detailed description in comment of blk_register_queue(). This patch removes one synchronize_rcu() inside blk_cleanup_queue() for this case, commit c2856ae2f315d75(blk-mq: quiesce queue before freeing queue) needs synchronize_rcu() for implementing blk_mq_quiesce_queue(), but when queue isn't initialized, it isn't necessary to do that since only pass-through requests are involved, no original issue in scsi_execute() at all. Without this patch and previous one, it may take more 20+ seconds for virtio-scsi to complete disk probe. With the two patches, the time becomes less than 100ms. Fixes: c2856ae2f315d75 ("blk-mq: quiesce queue before freeing queue") Reported-by: Andrew Jones Cc: Omar Sandoval Cc: Bart Van Assche Cc: linux-scsi@vger.kernel.org Cc: "Martin K. Petersen" Cc: Christoph Hellwig Tested-by: Andrew Jones Signed-off-by: Ming Lei Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- block/blk-core.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/block/blk-core.c +++ b/block/blk-core.c @@ -791,9 +791,13 @@ void blk_cleanup_queue(struct request_qu * make sure all in-progress dispatch are completed because * blk_freeze_queue() can only complete all requests, and * dispatch may still be in-progress since we dispatch requests - * from more than one contexts + * from more than one contexts. + * + * No need to quiesce queue if it isn't initialized yet since + * blk_freeze_queue() should be enough for cases of passthrough + * request. */ - if (q->mq_ops) + if (q->mq_ops && blk_queue_init_done(q)) blk_mq_quiesce_queue(q); /* for synchronous bio-based driver finish in-flight integrity i/o */