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 C1F68C3A59F for ; Thu, 29 Aug 2019 18:14:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 991EE23404 for ; Thu, 29 Aug 2019 18:14:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567102483; bh=FL8bHyiyQZxqHEAAaSx3IsT3DTGpqyV0KzVXHvH5kpo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=woHJWoX4SNP/GqQ05X8s5JKUMan5gjlMF/egpL5VIzi1WPNcZ/MhU38NGXae5NBNe kekJOHS5yTM+GZx2mz+wWtjN7UyivS6Fmh1oP9yzBoavTNUsnCEdt78jwyJlFUu5IK Sq+ZbNNq1P3x+NITxcGjxcyMr6vk5aex6Ac2KyVk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728960AbfH2SOm (ORCPT ); Thu, 29 Aug 2019 14:14:42 -0400 Received: from mail.kernel.org ([198.145.29.99]:56236 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728919AbfH2SOi (ORCPT ); Thu, 29 Aug 2019 14:14:38 -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 F05DB233FF; Thu, 29 Aug 2019 18:14:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567102476; bh=FL8bHyiyQZxqHEAAaSx3IsT3DTGpqyV0KzVXHvH5kpo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=l92DR7+FdrrN+6t51yCPr5YDJXVh9e5cGEcKr4oDWn8KNOm3cVY2OZq1Lp7p+V4qe r1Ugsirr7Fq6l7E8xtIWsQjpiUNekhfKfcN8ftkahN4jibWfFdGQmdLq6QJP2YWP2h Ioig2zmKcWw/6Zu5yyGDP1DJ7ZvzZUYSDFOBvcfM= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Darrick J. Wong" , Bill O'Donnell , Matthew Wilcox , Sasha Levin , linux-fsdevel@vger.kernel.org Subject: [PATCH AUTOSEL 5.2 40/76] vfs: fix page locking deadlocks when deduping files Date: Thu, 29 Aug 2019 14:12:35 -0400 Message-Id: <20190829181311.7562-40-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190829181311.7562-1-sashal@kernel.org> References: <20190829181311.7562-1-sashal@kernel.org> MIME-Version: 1.0 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: "Darrick J. Wong" [ Upstream commit edc58dd0123b552453a74369bd0c8d890b497b4b ] When dedupe wants to use the page cache to compare parts of two files for dedupe, we must be very careful to handle locking correctly. The current code doesn't do this. It must lock and unlock the page only once if the two pages are the same, since the overlapping range check doesn't catch this when blocksize < pagesize. If the pages are distinct but from the same file, we must observe page locking order and lock them in order of increasing offset to avoid clashing with writeback locking. Fixes: 876bec6f9bbfcb3 ("vfs: refactor clone/dedupe_file_range common functions") Signed-off-by: Darrick J. Wong Reviewed-by: Bill O'Donnell Reviewed-by: Matthew Wilcox (Oracle) Signed-off-by: Sasha Levin --- fs/read_write.c | 49 +++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 41 insertions(+), 8 deletions(-) diff --git a/fs/read_write.c b/fs/read_write.c index c543d965e2880..e8b0f1192a3a4 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -1776,10 +1776,7 @@ static int generic_remap_check_len(struct inode *inode_in, return (remap_flags & REMAP_FILE_DEDUP) ? -EBADE : -EINVAL; } -/* - * Read a page's worth of file data into the page cache. Return the page - * locked. - */ +/* Read a page's worth of file data into the page cache. */ static struct page *vfs_dedupe_get_page(struct inode *inode, loff_t offset) { struct page *page; @@ -1791,10 +1788,32 @@ static struct page *vfs_dedupe_get_page(struct inode *inode, loff_t offset) put_page(page); return ERR_PTR(-EIO); } - lock_page(page); return page; } +/* + * Lock two pages, ensuring that we lock in offset order if the pages are from + * the same file. + */ +static void vfs_lock_two_pages(struct page *page1, struct page *page2) +{ + /* Always lock in order of increasing index. */ + if (page1->index > page2->index) + swap(page1, page2); + + lock_page(page1); + if (page1 != page2) + lock_page(page2); +} + +/* Unlock two pages, being careful not to unlock the same page twice. */ +static void vfs_unlock_two_pages(struct page *page1, struct page *page2) +{ + unlock_page(page1); + if (page1 != page2) + unlock_page(page2); +} + /* * Compare extents of two files to see if they are the same. * Caller must have locked both inodes to prevent write races. @@ -1832,10 +1851,24 @@ static int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff, dest_page = vfs_dedupe_get_page(dest, destoff); if (IS_ERR(dest_page)) { error = PTR_ERR(dest_page); - unlock_page(src_page); put_page(src_page); goto out_error; } + + vfs_lock_two_pages(src_page, dest_page); + + /* + * Now that we've locked both pages, make sure they're still + * mapped to the file data we're interested in. If not, + * someone is invalidating pages on us and we lose. + */ + if (!PageUptodate(src_page) || !PageUptodate(dest_page) || + src_page->mapping != src->i_mapping || + dest_page->mapping != dest->i_mapping) { + same = false; + goto unlock; + } + src_addr = kmap_atomic(src_page); dest_addr = kmap_atomic(dest_page); @@ -1847,8 +1880,8 @@ static int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff, kunmap_atomic(dest_addr); kunmap_atomic(src_addr); - unlock_page(dest_page); - unlock_page(src_page); +unlock: + vfs_unlock_two_pages(src_page, dest_page); put_page(dest_page); put_page(src_page); -- 2.20.1