From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from dggsgout11.his.huawei.com (unknown [45.249.212.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9058E149DEC; Thu, 25 Apr 2024 13:23:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.51 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714051390; cv=none; b=ONUt71U66ueNE7InoQztV4v+Usmgy58ehid6fJFSJkDSuF7Ro17agzyvGgf+K5qYowrQHDnMEm3yxXW2MgO1V1Jt61+5LMTw8n+F8H+Qbltgvy/p/Lox4uIjbO6dGd46sXLb6OLZ8ryOjHV/dkDqvSS3pnae2n/+ecDHZFW8Mgc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714051390; c=relaxed/simple; bh=zIeSjJNQpUGix72xtxA5Vo0qvD65js2yiyhGJyfzuLk=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=IDpOg7fggqTi6UJL9U05VxgHf473xcpDIwmNrj+QMjugz6913Wt9JwXyyJV9Bsj/Zs+XijsU7zwphBEPeGELJ2k+bX80dHMNEEgqD2chEwxIEvqg3i0SRLQiEbSIIyRhTrb5uu7dXFc7FuumYd9LUiWtqHPz96YhxHZxKlENFds= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.216]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4VQGkS0tj1z4f3nJV; Thu, 25 Apr 2024 21:22:56 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.112]) by mail.maildlp.com (Postfix) with ESMTP id 5EEFC1A1129; Thu, 25 Apr 2024 21:23:05 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.104.67]) by APP1 (Coremail) with SMTP id cCh0CgCXaBEqWSpmHu+2Kw--.61462S8; Thu, 25 Apr 2024 21:23:05 +0800 (CST) From: Zhang Yi To: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, djwong@kernel.org, hch@infradead.org, brauner@kernel.org, david@fromorbit.com, chandanbabu@kernel.org, tytso@mit.edu, jack@suse.cz, yi.zhang@huawei.com, yi.zhang@huaweicloud.com, chengzhihao1@huawei.com, yukuai3@huawei.com Subject: [PATCH v5 4/9] xfs: convert delayed extents to unwritten when zeroing post eof blocks Date: Thu, 25 Apr 2024 21:13:30 +0800 Message-Id: <20240425131335.878454-5-yi.zhang@huaweicloud.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240425131335.878454-1-yi.zhang@huaweicloud.com> References: <20240425131335.878454-1-yi.zhang@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID:cCh0CgCXaBEqWSpmHu+2Kw--.61462S8 X-Coremail-Antispam: 1UD129KBjvJXoWxWw47Kw4fCw4UJF4DuryDKFg_yoWrGrWrpF Zagw13GrsrGw13Zw4fAF15Wr1F93Z5Cr4UJry5Xws3Z34aqr4IgryIy3Wjqry8Cws3A3Wj vF4jgas2934qvaDanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUPF14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_JF0E3s1l82xGYI kIc2x26xkF7I0E14v26ryj6s0DM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2 z4x0Y4vE2Ix0cI8IcVAFwI0_Ar0_tr1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F 4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq 3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7 IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4U M4x0Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628vn2 kIc2xKxwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E 14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIx kGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAF wI0_Cr0_Gr1UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AKxVWUJV W8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnIWIevJa73UjIFyTuYvjfUOBTY UUUUU X-CM-SenderInfo: d1lo6xhdqjqx5xdzvxpfor3voofrz/ From: Zhang Yi Current clone operation could be non-atomic if the destination of a file is beyond EOF, user could get a file with corrupted (zeroed) data on crash. The problem is about preallocations. If you write some data into a file: [A...B) and XFS decides to preallocate some post-eof blocks, then it can create a delayed allocation reservation: [A.........D) The writeback path tries to convert delayed extents to real ones by allocating blocks. If there aren't enough contiguous free space, we can end up with two extents, the first real and the second still delalloc: [A....C)[C.D) After that, both the in-memory and the on-disk file sizes are still B. If we clone into the range [E...F) from another file: [A....C)[C.D) [E...F) then xfs_reflink_zero_posteof() calls iomap_zero_range() to zero out the range [B, E) beyond EOF and flush it. Since [C, D) is still a delalloc extent, its pagecache will be zeroed and both the in-memory and on-disk size will be updated to D after flushing but before cloning. This is wrong, because the user can see the size change and read the zeroes while the clone operation is ongoing. We need to keep the in-memory and on-disk size before the clone operation starts, so instead of writing zeroes through the page cache for delayed ranges beyond EOF, we convert these ranges to unwritten and invalidate any cached data over that range beyond EOF. Suggested-by: Dave Chinner Signed-off-by: Zhang Yi --- Changes since v4: Move the delalloc converting hunk before searching the COW fork. Because if the file has been reflinked and copied on write, xfs_bmap_extsize_align() aligned the range of COW delalloc extent, after the writeback, there might be some unwritten extents left over in the COW fork that overlaps the delalloc extent we found in data fork. data fork ...wwww|dddddddddd... cow fork |uuuuuuuuuu... ^ i_size In my v4, we search the COW fork before checking the delalloc extent, goto found_cow tag and return unconverted delalloc srcmap in the above case, so the delayed extent in the data fork will have no chance to convert to unwritten, it will lead to delalloc extent residue and break generic/522 after merging patch 6. fs/xfs/xfs_iomap.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c index 236ee78aa75b..2857ef1b0272 100644 --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -1022,6 +1022,24 @@ xfs_buffered_write_iomap_begin( goto out_unlock; } + /* + * For zeroing, trim a delalloc extent that extends beyond the EOF + * block. If it starts beyond the EOF block, convert it to an + * unwritten extent. + */ + if ((flags & IOMAP_ZERO) && imap.br_startoff <= offset_fsb && + isnullstartblock(imap.br_startblock)) { + xfs_fileoff_t eof_fsb = XFS_B_TO_FSB(mp, XFS_ISIZE(ip)); + + if (offset_fsb >= eof_fsb) + goto convert_delay; + if (end_fsb > eof_fsb) { + end_fsb = eof_fsb; + xfs_trim_extent(&imap, offset_fsb, + end_fsb - offset_fsb); + } + } + /* * Search the COW fork extent list even if we did not find a data fork * extent. This serves two purposes: first this implements the @@ -1167,6 +1185,17 @@ xfs_buffered_write_iomap_begin( xfs_iunlock(ip, lockmode); return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, 0, seq); +convert_delay: + xfs_iunlock(ip, lockmode); + truncate_pagecache(inode, offset); + error = xfs_bmapi_convert_delalloc(ip, XFS_DATA_FORK, offset, + iomap, NULL); + if (error) + return error; + + trace_xfs_iomap_alloc(ip, offset, count, XFS_DATA_FORK, &imap); + return 0; + found_cow: seq = xfs_iomap_inode_sequence(ip, 0); if (imap.br_startoff <= offset_fsb) { -- 2.39.2