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=-20.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 4A80DC07E95 for ; Sun, 4 Jul 2021 23:20:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 359D0613E9 for ; Sun, 4 Jul 2021 23:20:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233189AbhGDXWv (ORCPT ); Sun, 4 Jul 2021 19:22:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:56970 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233804AbhGDXOk (ORCPT ); Sun, 4 Jul 2021 19:14:40 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 2878061982; Sun, 4 Jul 2021 23:10:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1625440234; bh=z3BXUPzwUi9o7tN4WMvZUmXZh/lWJK4IWAuJaZ2qiZw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bgdVUWUmiuJojNVLuTgUrpT+NNRYmaR5R5YWzVmcFFGx/yxixOAvo9Uqr2ov8Td6d xEDJ/p5NzrPTXrf/VE4I7p5N8BrewS5mFgciJ9De8Z9GyZU3WSXPEwDUy2CaeJV1M5 q/a3ITToUTrvVOoLBDNyRF38wECxubSArtuMMb9Gc8XTt0FPE93bm1UKXJAYBnJrXf +EoWCeahPIh9K8OBW3F/E5QktzRchZ2wdF48yg4nejHVEbrKfrIRYaAaMJuM5kPr6a m1x4D2Fpzy2qMZ9QZvH7QoIc0fVksa7o9yxKgsw1CeVFdWqJHFt573Ixlc1eX+oden H6w0YxRzxU6FA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Qu Wenruo , Ritesh Harjani , Anand Jain , David Sterba , Sasha Levin , linux-btrfs@vger.kernel.org Subject: [PATCH AUTOSEL 5.4 43/50] btrfs: fix the filemap_range_has_page() call in btrfs_punch_hole_lock_range() Date: Sun, 4 Jul 2021 19:09:31 -0400 Message-Id: <20210704230938.1490742-43-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210704230938.1490742-1-sashal@kernel.org> References: <20210704230938.1490742-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Qu Wenruo [ Upstream commit 0528476b6ac7832f31e2ed740a57ae31316b124e ] [BUG] With current subpage RW support, the following script can hang the fs with 64K page size. # mkfs.btrfs -f -s 4k $dev # mount $dev -o nospace_cache $mnt # fsstress -w -n 50 -p 1 -s 1607749395 -d $mnt The kernel will do an infinite loop in btrfs_punch_hole_lock_range(). [CAUSE] In btrfs_punch_hole_lock_range() we: - Truncate page cache range - Lock extent io tree - Wait any ordered extents in the range. We exit the loop until we meet all the following conditions: - No ordered extent in the lock range - No page is in the lock range The latter condition has a pitfall, it only works for sector size == PAGE_SIZE case. While can't handle the following subpage case: 0 32K 64K 96K 128K | |///////||//////| || lockstart=32K lockend=96K - 1 In this case, although the range crosses 2 pages, truncate_pagecache_range() will invalidate no page at all, but only zero the [32K, 96K) range of the two pages. Thus filemap_range_has_page(32K, 96K-1) will always return true, thus we will never meet the loop exit condition. [FIX] Fix the problem by doing page alignment for the lock range. Function filemap_range_has_page() has already handled lend < lstart case, we only need to round up @lockstart, and round_down @lockend for truncate_pagecache_range(). This modification should not change any thing for sector size == PAGE_SIZE case, as in that case our range is already page aligned. Tested-by: Ritesh Harjani # [ppc64] Tested-by: Anand Jain # [aarch64] Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/file.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index f6308a7b761d..b678bf7692d5 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -2439,6 +2439,17 @@ static int btrfs_punch_hole_lock_range(struct inode *inode, const u64 lockend, struct extent_state **cached_state) { + /* + * For subpage case, if the range is not at page boundary, we could + * have pages at the leading/tailing part of the range. + * This could lead to dead loop since filemap_range_has_page() + * will always return true. + * So here we need to do extra page alignment for + * filemap_range_has_page(). + */ + const u64 page_lockstart = round_up(lockstart, PAGE_SIZE); + const u64 page_lockend = round_down(lockend + 1, PAGE_SIZE) - 1; + while (1) { struct btrfs_ordered_extent *ordered; int ret; @@ -2458,7 +2469,7 @@ static int btrfs_punch_hole_lock_range(struct inode *inode, (ordered->file_offset + ordered->len <= lockstart || ordered->file_offset > lockend)) && !filemap_range_has_page(inode->i_mapping, - lockstart, lockend)) { + page_lockstart, page_lockend)) { if (ordered) btrfs_put_ordered_extent(ordered); break; -- 2.30.2