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 4C978C282E1 for ; Wed, 24 Apr 2019 14:42:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1CC03218B0 for ; Wed, 24 Apr 2019 14:42:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556116973; bh=CrsRYr5qipBhxG1imL/VLssU16BOitwzJ/+L3tSk6/E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=mrzKydWSILHmdF8cZv8Yt91cyMScQFVNtbfn8XP3/LPR+KTS8NrEdHLJ7SOVhlBds VTGZGhxsgWPZwZqZZ+rfXubkg3aDOZWA5qJyEO9gZKH2ep4grx2CcXQCcqrN6j0b/W H6hMs9nYbfj67AKdwF5cJuNDDzEQ6Q4qILKJhY0Y= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731953AbfDXOkc (ORCPT ); Wed, 24 Apr 2019 10:40:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:43052 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731951AbfDXOkb (ORCPT ); Wed, 24 Apr 2019 10:40:31 -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 385E721901; Wed, 24 Apr 2019 14:40:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556116830; bh=CrsRYr5qipBhxG1imL/VLssU16BOitwzJ/+L3tSk6/E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=2QwlFTNZRJ/iQCNOnJXyvrjRPVw9UQGwC954wXEhTYw2BuXhyJLEzfUghpIsScNua 98oB6p/XtKh3Qk83tDbB4l25kPgBzxDCOWfXRsI74hqH0fonzBUVhVFqbokKUOsQzn CEVicMpTCEJQWAuwToZQe5CohMaPWgoAJFHKdes8= 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 4.19 34/52] scsi: storvsc: Fix calculation of sub-channel count Date: Wed, 24 Apr 2019 10:38:52 -0400 Message-Id: <20190424143911.28890-34-sashal@kernel.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190424143911.28890-1-sashal@kernel.org> References: <20190424143911.28890-1-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 f03dc03a42c3..0c2ba075bc71 100644 --- a/drivers/scsi/storvsc_drv.c +++ b/drivers/scsi/storvsc_drv.c @@ -664,13 +664,22 @@ 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