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=-9.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 ECB38C282CE for ; Wed, 24 Apr 2019 14:55:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BBE0E2084F for ; Wed, 24 Apr 2019 14:55:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556117730; bh=FGZvCJGbG6E/IS3ogkjcyAnSzLfc5s2taeM+T6G2neI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Dz9SbCymA/tm5pFy/rv+KfI95bi3zuiUPaMmSteheb2qf5qBpudizQR5enu3sFmat KB6ejeUnJFmLRIqK3BhxZAJiJS+FfZNZlTDc5NGoGEH877/SSR+1hzvYOeiZwRXVFr CIX26l4Ca1Ai8Ee3MBhhAIAlrdCzjRjkwjdzPbeU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732724AbfDXOvF (ORCPT ); Wed, 24 Apr 2019 10:51:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:50174 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732731AbfDXOvB (ORCPT ); Wed, 24 Apr 2019 10:51:01 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A68AA218FC; Wed, 24 Apr 2019 14:50:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556117460; bh=FGZvCJGbG6E/IS3ogkjcyAnSzLfc5s2taeM+T6G2neI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sBn2zx/kqnaCkPN2NxmXGwcUqCGquBkkdThX7JSeJFApTz1joQYHM+tqm+HivhWHZ REIBnnSx2lp8hSeGsFjT9J3Xqpjs9uiq8irtQArq7tpw7Pt0Dc+TsArkLBwytjxfoC EYohNc6PAZKy4AXGqLtizNzlkJfqfLKiMiqFbeAs= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Michael Kelley , "Martin K . Petersen" , Sasha Levin , linux-hyperv@vger.kernel.org, linux-scsi@vger.kernel.org Subject: [PATCH AUTOSEL 4.9 19/28] scsi: storvsc: Fix calculation of sub-channel count Date: Wed, 24 Apr 2019 10:50:03 -0400 Message-Id: <20190424145012.30886-19-sashal@kernel.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190424145012.30886-1-sashal@kernel.org> References: <20190424145012.30886-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Michael Kelley [ 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 d92b2808d191..6df34d68737f 100644 --- a/drivers/scsi/storvsc_drv.c +++ b/drivers/scsi/storvsc_drv.c @@ -641,13 +641,22 @@ 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; -- 2.19.1