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=-9.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 204D8C04E53 for ; Wed, 15 May 2019 12:20:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E79BE20578 for ; Wed, 15 May 2019 12:20:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557922838; bh=Rigk2BP1vhzhrGcwtIj8zm7+kw/wq++uhMPtlRGgHN4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=lQ4vE2+LiTRU0pKgmzN7A3juz41z17O4oFxCZi+iHAjAOnWXEAvf6UthxWxrnuLfp +E3/FNSpTk3cuKd0tSdaDew965RaTJ6QZsOj+weZUnKRROLJvgwv83zeeTXJroKJX4 uwRrcLMNikFsYCz9DqPo3jqLdukPXgjRwLmnE0wM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726124AbfEOK71 (ORCPT ); Wed, 15 May 2019 06:59:27 -0400 Received: from mail.kernel.org ([198.145.29.99]:55954 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727153AbfEOK7Z (ORCPT ); Wed, 15 May 2019 06:59:25 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id AD0662166E; Wed, 15 May 2019 10:59:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557917965; bh=Rigk2BP1vhzhrGcwtIj8zm7+kw/wq++uhMPtlRGgHN4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JWEa4yJAU+x8hHsPqhP2FyuYZ72mDyTLm3DS6abLuy1ZySc0nxAJDgdIO2a/yODU0 v1/+CoSeGYv6RH9A4zJqfoLkMNViO2yVSX1qiUASbviWST8jYebvjjhia1y60IeVQ7 ec7Au3o4cq4XopBTv166en+eYBeVG6nqoTBKqJzQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Michael Kelley , Vitaly Kuznetsov , Long Li , "Martin K. Petersen" , Sasha Levin Subject: [PATCH 3.18 42/86] scsi: storvsc: Fix calculation of sub-channel count Date: Wed, 15 May 2019 12:55:19 +0200 Message-Id: <20190515090650.899536539@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190515090642.339346723@linuxfoundation.org> References: <20190515090642.339346723@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org [ Upstream commit 382e06d11e075a40b4094b6ef809f8d4bcc7ab2a ] When the number of sub-channels offered by Hyper-V is >= the number of CPUs in the VM, calculate the correct number of sub-channels. The current code produces one too many. This scenario arises only when the number of CPUs is artificially restricted (for example, with maxcpus= on the kernel boot line), because Hyper-V normally offers a sub-channel count < number of CPUs. While the current code doesn't break, the extra sub-channel is unbalanced across the CPUs (for example, a total of 5 channels on a VM with 4 CPUs). Signed-off-by: Michael Kelley Reviewed-by: Vitaly Kuznetsov Reviewed-by: Long Li Signed-off-by: Martin K. Petersen Signed-off-by: Sasha Levin --- drivers/scsi/storvsc_drv.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c index 96c6e75bbfe6..bc29b571e3fb 100644 --- a/drivers/scsi/storvsc_drv.c +++ b/drivers/scsi/storvsc_drv.c @@ -788,13 +788,22 @@ static void handle_sc_creation(struct vmbus_channel *new_sc) static void handle_multichannel_storage(struct hv_device *device, int max_chns) { struct storvsc_device *stor_device; - int num_cpus = num_online_cpus(); int num_sc; struct storvsc_cmd_request *request; struct vstor_packet *vstor_packet; int ret, t; - num_sc = ((max_chns > num_cpus) ? num_cpus : max_chns); + /* + * If the number of CPUs is artificially restricted, such as + * with maxcpus=1 on the kernel boot line, Hyper-V could offer + * sub-channels >= the number of CPUs. These sub-channels + * should not be created. The primary channel is already created + * and assigned to one CPU, so check against # CPUs - 1. + */ + num_sc = min((int)(num_online_cpus() - 1), max_chns); + if (!num_sc) + return; + stor_device = get_out_stor_device(device); if (!stor_device) return; -- 2.20.1