From patchwork Wed Mar 20 11:05:43 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zhang Yi X-Patchwork-Id: 13597778 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [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 6ACC33B2BD; Wed, 20 Mar 2024 11:13:13 +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=1710933195; cv=none; b=p5wtU1t2KzvKLHa+tY+x+lnhjCmXArRTsiTwhNQ3mm2fE9c+hwJsHKAqGgf2z6VhaSOr2gk83n7XqLghMvbpGUG78iJWEWtDDkfHsLBdW9tjTAM5zBVgwOBlCMxu65yp+VPJ52YKvtRQJmyiZd07bKf1+jOiTfUElR8AKawDj+U= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710933195; c=relaxed/simple; bh=V41+AjyTiVyyD6BPEhIp/TsYt0YFHhNHScrXYfWsKP8=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=GGNMnTMP1ZIeAsuU5Qg3r7vZhhIaU6xUeNYfAMaakXrMO8ob4JTnBmXZZoH+k+KNiwL8YrKfanbCPpWpCdEKFwX1M/YcjJXnK1Jrc3Z8D4WWPM2vi64f1ycxVw6BN5T2zHmlnJ31p+Rd7Ai6wOiYl6vdo4Jcg/69pNlwu8mHoUs= 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 [172.19.163.235]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4V05YB2nNPz4f3nTg; Wed, 20 Mar 2024 19:13:02 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.112]) by mail.maildlp.com (Postfix) with ESMTP id 4F1751A06E2; Wed, 20 Mar 2024 19:13:10 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.104.67]) by APP1 (Coremail) with SMTP id cCh0CgBXKBG5xPplGX0fHg--.18516S8; Wed, 20 Mar 2024 19:13:10 +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, tytso@mit.edu, jack@suse.cz, yi.zhang@huawei.com, yi.zhang@huaweicloud.com, chengzhihao1@huawei.com, yukuai3@huawei.com Subject: [PATCH v4 4/9] xfs: convert delayed extents to unwritten when zeroing post eof blocks Date: Wed, 20 Mar 2024 19:05:43 +0800 Message-Id: <20240320110548.2200662-5-yi.zhang@huaweicloud.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240320110548.2200662-1-yi.zhang@huaweicloud.com> References: <20240320110548.2200662-1-yi.zhang@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-CM-TRANSID: cCh0CgBXKBG5xPplGX0fHg--.18516S8 X-Coremail-Antispam: 1UD129KBjvJXoWxWw47Kw4fCw4UJF4DuryDKFg_yoW5CFW8pF Z3Kw15GrsxKw13Zw4fAF9xKw1F93WkCw4UJrySgrn3Z343tr12gr1Iy3Wjq348A393A3W2 qF4jgryI934UZFJanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUPF14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_JF0E3s1l82xGYI kIc2x26xkF7I0E14v26ryj6s0DM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2 z4x0Y4vE2Ix0cI8IcVAFwI0_Ar0_tr1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F 4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq 3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7 IYx2IY67AKxVWUXVWUAwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4U M4x0Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628vn2 kIc2xKxwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E 14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIx kGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAF wI0_Cr0_Gr1UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AKxVWUJV W8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnIWIevJa73UjIFyTuYvjfUoxhL 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 Reviewed-by: Christoph Hellwig Reviewed-by: Darrick J. Wong --- 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 ccf83e72d8ca..334860f780ff 100644 --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -1035,6 +1035,24 @@ xfs_buffered_write_iomap_begin( } if (imap.br_startoff <= offset_fsb) { + /* + * 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) && + 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); + } + } + /* * For reflink files we may need a delalloc reservation when * overwriting shared extents. This includes zeroing of @@ -1158,6 +1176,17 @@ 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) {