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,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 D4B24C433E3 for ; Mon, 29 Jun 2020 19:02:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A891B20663 for ; Mon, 29 Jun 2020 19:02:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593457359; bh=akbiHMLtrh9zquQkY+XHTWnClXAmVlxeMPT7R0tvfBo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=fP0CAoZxBtFQDqr2rxsRkps0lGlEAdc4Tf9Xf23/Pec1wQr/fk7QpYT3OBYE+WQca sdtqyP+Q/AXqdsvWUn8XmCoIJA4n4RiWFi+TdiKlLEX4r7XSn7FPrQcohD58RPsb5I 6n94ZihRlXJOf/8Za/tv7sh0NOrPbShqLk4IfaPc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729927AbgF2TCi (ORCPT ); Mon, 29 Jun 2020 15:02:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:45478 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730311AbgF2TAU (ORCPT ); Mon, 29 Jun 2020 15:00:20 -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 86A4B2550C; Mon, 29 Jun 2020 15:54:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593446069; bh=akbiHMLtrh9zquQkY+XHTWnClXAmVlxeMPT7R0tvfBo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jKXP+UBckU059fX8dk4fbaSJ+VDzYa1UA3qqpfmGuP6jQ4OzGE2lmimKuzUGeBRlo trsz2blUeAT04aanPxNmesqgrItJELpuoFxdCjjLZLn9EsforoECRWgq6+Sil60IyA 3TiykO1pyEREf41n/Be5+PIijOQfF8qsP4hxF7vg= 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 4.4 068/135] block: nr_sects_write(): Disable preemption on seqcount write Date: Mon, 29 Jun 2020 11:52:02 -0400 Message-Id: <20200629155309.2495516-69-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200629155309.2495516-1-sashal@kernel.org> References: <20200629155309.2495516-1-sashal@kernel.org> MIME-Version: 1.0 X-KernelTest-Patch: http://kernel.org/pub/linux/kernel/v4.x/stable-review/patch-4.4.229-rc1.gz X-KernelTest-Tree: git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git X-KernelTest-Branch: linux-4.4.y X-KernelTest-Patches: git://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git X-KernelTest-Version: 4.4.229-rc1 X-KernelTest-Deadline: 2020-07-01T15:53+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 5012fcdb4c9ed..a27d0aef07f66 100644 --- a/include/linux/genhd.h +++ b/include/linux/genhd.h @@ -727,9 +727,11 @@ 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