From patchwork Wed Jan 27 19:29:40 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Filipe Manana X-Patchwork-Id: 8139241 Return-Path: X-Original-To: patchwork-linux-btrfs@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 3043F9F38B for ; Wed, 27 Jan 2016 19:29:57 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 37F97201FA for ; Wed, 27 Jan 2016 19:29:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 43A7F20123 for ; Wed, 27 Jan 2016 19:29:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935635AbcA0T3v (ORCPT ); Wed, 27 Jan 2016 14:29:51 -0500 Received: from mail.kernel.org ([198.145.29.136]:52755 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934408AbcA0T3s (ORCPT ); Wed, 27 Jan 2016 14:29:48 -0500 Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 705A9201ED for ; Wed, 27 Jan 2016 19:29:47 +0000 (UTC) Received: from debian3.lan (bl8-199-62.dsl.telepac.pt [85.241.199.62]) (using TLSv1.2 with cipher AES128-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 16B1520251 for ; Wed, 27 Jan 2016 19:29:45 +0000 (UTC) From: fdmanana@kernel.org To: linux-btrfs@vger.kernel.org Subject: [PATCH 1/2] Btrfs: fix page reading in extent_same ioctl leading to csum errors Date: Wed, 27 Jan 2016 19:29:40 +0000 Message-Id: <1453922980-2253-1-git-send-email-fdmanana@kernel.org> X-Mailer: git-send-email 2.7.0.rc3 X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Filipe Manana In the extent_same ioctl, we were grabbing the pages (locked) and attempting to read them without bothering about any concurrent IO against them. That is, we were not checking for any ongoing ordered extents nor waiting for them to complete, which leads to a race where the extent_same() code gets a checksum verification error when it reads the pages, producing a message like the following in dmesg and making the operation fail to user space with -ENOMEM: [18990.161265] BTRFS warning (device sdc): csum failed ino 259 off 495616 csum 685204116 expected csum 1515870868 Fix this by using btrfs_readpage() for reading the pages instead of extent_read_full_page_nolock(), which waits for any concurrent ordered extents to complete and locks the io range. Also do better error handling and don't treat all failures as -ENOMEM, as that's clearly misleasing, becoming identical to the checks and operation of prepare_uptodate_page(). The use of extent_read_full_page_nolock() was required before commit f441460202cb ("btrfs: fix deadlock with extent-same and readpage"), as we had the range locked in an inode's io tree before attempting to read the pages. Fixes: f441460202cb ("btrfs: fix deadlock with extent-same and readpage") Cc: stable@vger.kernel.org # 4.2+ Signed-off-by: Filipe Manana --- fs/btrfs/ioctl.c | 29 +++++++++++++++++++++-------- 1 file changed, 21 insertions(+), 8 deletions(-) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index dd39546..d3784e9 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -2790,21 +2790,27 @@ out: static struct page *extent_same_get_page(struct inode *inode, pgoff_t index) { struct page *page; - struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree; page = grab_cache_page(inode->i_mapping, index); if (!page) - return NULL; + return ERR_PTR(-ENOMEM); if (!PageUptodate(page)) { - if (extent_read_full_page_nolock(tree, page, btrfs_get_extent, - 0)) - return NULL; + int ret; + + ret = btrfs_readpage(NULL, page); + if (ret) + return ERR_PTR(ret); lock_page(page); if (!PageUptodate(page)) { unlock_page(page); page_cache_release(page); - return NULL; + return ERR_PTR(-EIO); + } + if (page->mapping != inode->i_mapping) { + unlock_page(page); + page_cache_release(page); + return ERR_PTR(-EAGAIN); } } @@ -2818,9 +2824,16 @@ static int gather_extent_pages(struct inode *inode, struct page **pages, pgoff_t index = off >> PAGE_CACHE_SHIFT; for (i = 0; i < num_pages; i++) { +again: pages[i] = extent_same_get_page(inode, index + i); - if (!pages[i]) - return -ENOMEM; + if (IS_ERR(pages[i])) { + int err = PTR_ERR(pages[i]); + + if (err == -EAGAIN) + goto again; + pages[i] = NULL; + return err; + } } return 0; }