From patchwork Fri Jun 2 16:38:45 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Martin Wilck X-Patchwork-Id: 13265679 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E65A2C7EE2A for ; Fri, 2 Jun 2023 16:39:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235908AbjFBQj2 (ORCPT ); Fri, 2 Jun 2023 12:39:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57936 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235888AbjFBQjY (ORCPT ); Fri, 2 Jun 2023 12:39:24 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BE9B61A2; Fri, 2 Jun 2023 09:39:23 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 7845C21A41; Fri, 2 Jun 2023 16:39:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1685723962; 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=W9OEDtirDdPxMdKXugNer/vMTQpbJcSihzhcFKHZfe4=; b=azUE1btUpaczu20RjTRAtrnutqHE2OTIvs8RB3wJ33isstVqrA/CznmPI126nKykTYxl89 KJkw1Ljt8G/75Tm2oYT2/nsKlfD3AuIUXyvJKvCqDiP2qqwxEFO0J6lS1ZGG4mgjc0dwE2 Kx0H+Rv1fQxQ6C05qkM5JmSk6uhwDdM= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 2A52D133E6; Fri, 2 Jun 2023 16:39:22 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id YKWXCDobemSEDwAAMHmgww (envelope-from ); Fri, 02 Jun 2023 16:39:22 +0000 From: mwilck@suse.com To: "Martin K. Petersen" , Christoph Hellwig , Ming Lei Cc: James Bottomley , Bart Van Assche , linux-scsi@vger.kernel.org, linux-block@vger.kernel.org, Hannes Reinecke Subject: [PATCH 3/3] scsi: simplify scsi_stop_queue() Date: Fri, 2 Jun 2023 18:38:45 +0200 Message-Id: <20230602163845.32108-4-mwilck@suse.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230602163845.32108-1-mwilck@suse.com> References: <20230602163845.32108-1-mwilck@suse.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org From: Hannes Reinecke scsi_target_block() calls scsi_stop_queue() for each scsi_device and scsi_stop_queue() calls blk_mq_wait_quiesce_done() for each LUN. As blk_mq_wait_quiesce_done() comes down to synchronize_rcu() for SCSI queues, this can cause substantial delay for scsi_target_block() on a target with a lot of logical units (we measured more than 100s delay for blocking a FC rport with 2048 LUNs). Simplify scsi_stop_queue(), which is only called in this code path, to never wait for the quiescing to finish. Rather call synchronize_rcu() from scsi_target_block() after iterating over all devices. Also, move the call to scsi_stop_queue() in scsi_internal_device_block() out of the code section where the state_mutex is held. This patch uses the same basic idea as commit f983622ae605 ("scsi: core: Avoid calling synchronize_rcu() for each device in scsi_host_block()"). Signed-off-by: Hannes Reinecke Signed-off-by: Martin Wilck --- drivers/scsi/scsi_lib.c | 29 +++++++++++++++-------------- 1 file changed, 15 insertions(+), 14 deletions(-) diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index b7c569a42aa4..ed5bc9e1dbed 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -2725,24 +2725,18 @@ void scsi_start_queue(struct scsi_device *sdev) blk_mq_unquiesce_queue(sdev->request_queue); } -static void scsi_stop_queue(struct scsi_device *sdev, bool nowait) +static void scsi_stop_queue(struct scsi_device *sdev) { /* * The atomic variable of ->queue_stopped covers that * blk_mq_quiesce_queue* is balanced with blk_mq_unquiesce_queue. * * However, we still need to wait until quiesce is done - * in case that queue has been stopped. + * in case that queue has been stopped. This is done in + * scsi_target_block() for all devices of the target. */ - if (!cmpxchg(&sdev->queue_stopped, 0, 1)) { - if (nowait) - blk_mq_quiesce_queue_nowait(sdev->request_queue); - else - blk_mq_quiesce_queue(sdev->request_queue); - } else { - if (!nowait) - blk_mq_wait_quiesce_done(sdev->request_queue->tag_set); - } + if (!cmpxchg(&sdev->queue_stopped, 0, 1)) + blk_mq_quiesce_queue_nowait(sdev->request_queue); } /** @@ -2769,7 +2763,7 @@ int scsi_internal_device_block_nowait(struct scsi_device *sdev) * request queue. */ if (!ret) - scsi_stop_queue(sdev, true); + scsi_stop_queue(sdev); return ret; } EXPORT_SYMBOL_GPL(scsi_internal_device_block_nowait); @@ -2795,9 +2789,9 @@ static int scsi_internal_device_block(struct scsi_device *sdev) mutex_lock(&sdev->state_mutex); err = __scsi_internal_device_block_nowait(sdev); - if (err == 0) - scsi_stop_queue(sdev, false); mutex_unlock(&sdev->state_mutex); + if (err == 0) + scsi_stop_queue(sdev); return err; } @@ -2910,6 +2904,13 @@ scsi_target_block(struct device *dev) device_block); else device_for_each_child(dev, NULL, target_block); + + /* + * SCSI never enables blk-mq's BLK_MQ_F_BLOCKING flag, + * so blk_mq_wait_quiesce_done() comes down to just synchronize_rcu(). + * Just calling it once is enough. + */ + synchronize_rcu(); } EXPORT_SYMBOL_GPL(scsi_target_block);