From patchwork Mon Apr 14 02:44:08 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qu Wenruo X-Patchwork-Id: 3976111 Return-Path: X-Original-To: patchwork-linux-btrfs@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 60DA5BFF02 for ; Mon, 14 Apr 2014 02:43:46 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 7C41B201BC for ; Mon, 14 Apr 2014 02:43:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7F0962015E for ; Mon, 14 Apr 2014 02:43:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750850AbaDNCnT (ORCPT ); Sun, 13 Apr 2014 22:43:19 -0400 Received: from cn.fujitsu.com ([59.151.112.132]:49019 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750770AbaDNCnT (ORCPT ); Sun, 13 Apr 2014 22:43:19 -0400 X-IronPort-AV: E=Sophos;i="4.97,853,1389715200"; d="scan'208";a="29210497" Received: from unknown (HELO edo.cn.fujitsu.com) ([10.167.33.5]) by heian.cn.fujitsu.com with ESMTP; 14 Apr 2014 10:40:38 +0800 Received: from G08CNEXCHPEKD03.g08.fujitsu.local (localhost.localdomain [127.0.0.1]) by edo.cn.fujitsu.com (8.14.3/8.13.1) with ESMTP id s3E2h2uU018980; Mon, 14 Apr 2014 10:43:02 +0800 Received: from adam-work.lan (10.167.226.24) by G08CNEXCHPEKD03.g08.fujitsu.local (10.167.33.89) with Microsoft SMTP Server (TLS) id 14.3.146.2; Mon, 14 Apr 2014 10:43:07 +0800 From: Qu Wenruo To: CC: Al Viro Subject: [PATCH v2] btrfs: Change the expanding write sequence to fix snapshot related bug. Date: Mon, 14 Apr 2014 10:44:08 +0800 Message-ID: <1397443448-20367-1-git-send-email-quwenruo@cn.fujitsu.com> X-Mailer: git-send-email 1.9.2 MIME-Version: 1.0 X-Originating-IP: [10.167.226.24] Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Spam-Status: No, score=-7.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham 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 When testing fsstress with snapshot making background, some snapshot following problem. Snapshot 270: inode 323: size 0 Snapshot 271: inode 323: size 349145 |-------Hole---|---------Empty gap-------|-------Hole-----| 0 122880 172032 349145 Snapshot 272: inode 323: size 349145 |-------Hole---|------------Data---------|-------Hole-----| 0 122880 172032 349145 The fsstress operation on inode 323 is the following: write: offset 126832 len 43124 truncate: size 349145 Since the write with offset is consist of 2 operations: 1. punch hole 2. write data Hole punching is faster than data write, so hole punching in write and truncate is done first and then buffered write, so the snapshot 271 got empty gap, which will not pass btrfsck. To fix the bug, this patch will change the write sequence which will first punch a hole covering the write end if a hole is needed. Reported-by: Gui Hecheng Signed-off-by: Qu Wenruo Cc: Al Viro Signed-off-by: Chris Mason --- changelog: v2: Use 'pos + count' instead of 'pos + iov->iov_len' to deal with multi-seg iov. --- fs/btrfs/file.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 036f506c..e7e78fa 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -1727,6 +1727,7 @@ static ssize_t btrfs_file_aio_write(struct kiocb *iocb, struct btrfs_root *root = BTRFS_I(inode)->root; loff_t *ppos = &iocb->ki_pos; u64 start_pos; + u64 end_pos; ssize_t num_written = 0; ssize_t err = 0; size_t count, ocount; @@ -1781,7 +1782,9 @@ static ssize_t btrfs_file_aio_write(struct kiocb *iocb, start_pos = round_down(pos, root->sectorsize); if (start_pos > i_size_read(inode)) { - err = btrfs_cont_expand(inode, i_size_read(inode), start_pos); + /* Expand hole size to cover write data, preventing empty gap */ + end_pos = round_up(pos + count, root->sectorsize); + err = btrfs_cont_expand(inode, i_size_read(inode), end_pos); if (err) { mutex_unlock(&inode->i_mutex); goto out;