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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 314B2C433DF for ; Mon, 29 Jun 2020 20:33:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0C66E206A1 for ; Mon, 29 Jun 2020 20:33:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593462832; bh=OrBffg6MOPJ0XQvccgzc1W1J1qM2pJOx0+JhQ9alzSo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ePXhx/X0t2g7AL7szhGQn4qRjExIqZIq07UWQpKw58K0pEB34pisfBfkYoBfGL0Zc M2yrpBEAmQ99u87iExbvd6gVukiVmnFj9SW2m5iiHWwI5VPWAagwJF7T+lTj8jm46f I/wFq0LPsyYBaLkVEwL0fg6k4YbHjsetcqofNRQM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731916AbgF2Udu (ORCPT ); Mon, 29 Jun 2020 16:33:50 -0400 Received: from mail.kernel.org ([198.145.29.99]:37020 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732287AbgF2TZQ (ORCPT ); Mon, 29 Jun 2020 15:25:16 -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 99374253E6; Mon, 29 Jun 2020 15:42:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593445321; bh=OrBffg6MOPJ0XQvccgzc1W1J1qM2pJOx0+JhQ9alzSo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=InCLuMkSWZfvrcn0ON+B7NyMP/ULDW/lujMDtXCt6SdFpLm3BCgJEmMoyeJmEancq rl3Wc44eRVRq+lmA53GtgfD0c5gN/ZEmZq5B1c8NP2yhUKO3CM/Hpj7VrGybFici6d QdCDEyohiSUnLuZ8E0MQsUQjwbOETleTVTjOGPzA= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Ahmed S. Darwish" , Sebastian Andrzej Siewior , Jens Axboe , Sasha Levin Subject: [PATCH 4.9 088/191] block: nr_sects_write(): Disable preemption on seqcount write Date: Mon, 29 Jun 2020 11:38:24 -0400 Message-Id: <20200629154007.2495120-89-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200629154007.2495120-1-sashal@kernel.org> References: <20200629154007.2495120-1-sashal@kernel.org> MIME-Version: 1.0 X-KernelTest-Patch: http://kernel.org/pub/linux/kernel/v4.x/stable-review/patch-4.9.229-rc1.gz X-KernelTest-Tree: git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git X-KernelTest-Branch: linux-4.9.y X-KernelTest-Patches: git://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git X-KernelTest-Version: 4.9.229-rc1 X-KernelTest-Deadline: 2020-07-01T15:39+00:00 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Ahmed S. Darwish" [ Upstream commit 15b81ce5abdc4b502aa31dff2d415b79d2349d2f ] For optimized block readers not holding a mutex, the "number of sectors" 64-bit value is protected from tearing on 32-bit architectures by a sequence counter. Disable preemption before entering that sequence counter's write side critical section. Otherwise, the read side can preempt the write side section and spin for the entire scheduler tick. If the reader belongs to a real-time scheduling class, it can spin forever and the kernel will livelock. Fixes: c83f6bf98dc1 ("block: add partition resize function to blkpg ioctl") Cc: Signed-off-by: Ahmed S. Darwish Reviewed-by: Sebastian Andrzej Siewior Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- include/linux/genhd.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/include/linux/genhd.h b/include/linux/genhd.h index 3c99fb6727cac..12a2f5ac51c97 100644 --- a/include/linux/genhd.h +++ b/include/linux/genhd.h @@ -716,9 +716,11 @@ static inline sector_t part_nr_sects_read(struct hd_struct *part) static inline void part_nr_sects_write(struct hd_struct *part, sector_t size) { #if BITS_PER_LONG==32 && defined(CONFIG_LBDAF) && defined(CONFIG_SMP) + preempt_disable(); write_seqcount_begin(&part->nr_sects_seq); part->nr_sects = size; write_seqcount_end(&part->nr_sects_seq); + preempt_enable(); #elif BITS_PER_LONG==32 && defined(CONFIG_LBDAF) && defined(CONFIG_PREEMPT) preempt_disable(); part->nr_sects = size; -- 2.25.1