From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from dggsgout12.his.huawei.com (unknown [45.249.212.56]) (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 035A9BE4E; Tue, 12 Mar 2024 12:32:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710246733; cv=none; b=XBICoIVGRklg5JpsQQfxm3nuI9LWgltO7FrCFw8rlKkcuvbCf01CiRtdwabv5xW3nkDbuuiMIytRFjJCZRdo4ys6sg58XYaOfeAUniU6F34Fn+cjdxSR51XMGRVs0IPAGINVhKW5L05uQxg71/j35QJ3C5A+eutekpBCNgzXrMk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710246733; c=relaxed/simple; bh=/g7B/ioTRVrLBJ0KUmDdgTSPZPbItDsNOgmeSr4A6T4=; h=Subject:To:Cc:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=EKDqm4M36S4SR3mC5KbQhjI8tVbCX5rDr1qncIs8Uw+nwNxYXV27S1+J0sx6F2mNuwRkyb9Eu06W6fNTA53J00X3q+CbZKSMK5ue/EBQtPys7GUI9dPDgBo/Pb6GSVQC9XiIdhUe6UU5qMRcRs7j+EgKUSWZpuwVYTyjNic8Yho= 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=45.249.212.56 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 dggsgout12.his.huawei.com (SkyGuard) with ESMTP id 4TvCgv00xrz4f3jcx; Tue, 12 Mar 2024 20:31:54 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.112]) by mail.maildlp.com (Postfix) with ESMTP id A63171A0199; Tue, 12 Mar 2024 20:32:00 +0800 (CST) Received: from [10.174.176.34] (unknown [10.174.176.34]) by APP1 (Coremail) with SMTP id cCh0CgCXaBE+S_BlweXlGg--.27994S3; Tue, 12 Mar 2024 20:32:00 +0800 (CST) Subject: Re: [PATCH 2/4] xfs: convert delayed extents to unwritten when zeroing post eof blocks To: "Darrick J. Wong" Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, hch@infradead.org, brauner@kernel.org, david@fromorbit.com, tytso@mit.edu, jack@suse.cz, yi.zhang@huawei.com, chengzhihao1@huawei.com, yukuai3@huawei.com References: <20240311122255.2637311-1-yi.zhang@huaweicloud.com> <20240311122255.2637311-3-yi.zhang@huaweicloud.com> <20240311153737.GT1927156@frogsfrogsfrogs> From: Zhang Yi Message-ID: Date: Tue, 12 Mar 2024 20:31:58 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20240311153737.GT1927156@frogsfrogsfrogs> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-CM-TRANSID:cCh0CgCXaBE+S_BlweXlGg--.27994S3 X-Coremail-Antispam: 1UD129KBjvJXoWxWF4fZw4ruFW3trWrZFykGrg_yoWrur4UpF Z3K3W5GF43tw12vwn7AFn8Ww1Fvas7Cr48Ar13Wwn5Z3sIyr1IgFykC3WY9w18C39Iy3W2 vF4UWFyI9w4YvFDanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvIb4IE77IF4wAFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Xr0_Ar1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x 0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG 6I80ewAv7VC0I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFV Cjc4AY6r1j6r4UM4x0Y48IcVAKI48JM4IIrI8v6xkF7I0E8cxan2IY04v7Mxk0xIA0c2IE e2xFo4CEbIxvr21l42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxV Aqx4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r1q 6r43MIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6x kF7I0E14v26r4j6F4UMIIF0xvE42xK8VAvwI8IcIk0rVWrZr1j6s0DMIIF0xvEx4A2jsIE 14v26r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf 9x07UWE__UUUUU= X-CM-SenderInfo: d1lo6xhdqjqx5xdzvxpfor3voofrz/ On 2024/3/11 23:37, Darrick J. Wong wrote: > On Mon, Mar 11, 2024 at 08:22:53PM +0800, Zhang Yi wrote: >> 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 to pre-alloctions. If you write some data into a >> file [A, B) (the position letters are increased one by one), and xfs >> could pre-allocate some blocks, then we get a delayed extent [A, D). >> Then the writeback path allocate blocks and convert this delayed extent >> [A, C) since lack of enough contiguous physical blocks, so the extent >> [C, D) is still delayed. After that, both the in-memory and the on-disk >> file size are B. If we clone file range into [E, F) from another file, >> xfs_reflink_zero_posteof() would call iomap_zero_range() to zero out the >> range [B, E) beyond EOF and flush range. Since [C, D) is still a delayed >> extent, it will be zeroed and the file's in-memory && on-disk size will >> be updated to D after flushing and before doing the clone operation. >> This is wrong, because user can user can see the size change and read >> zeros in the middle of the clone operation. >> >> 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 >> invalidating any cached data over that range beyond EOF. >> >> Suggested-by: Dave Chinner >> Signed-off-by: Zhang Yi >> --- >> 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..2b2aace25355 100644 >> --- a/fs/xfs/xfs_iomap.c >> +++ b/fs/xfs/xfs_iomap.c >> @@ -957,6 +957,7 @@ xfs_buffered_write_iomap_begin( >> struct xfs_mount *mp = ip->i_mount; >> xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset); >> xfs_fileoff_t end_fsb = xfs_iomap_end_fsb(mp, offset, count); >> + xfs_fileoff_t eof_fsb = XFS_B_TO_FSBT(mp, XFS_ISIZE(ip)); >> struct xfs_bmbt_irec imap, cmap; >> struct xfs_iext_cursor icur, ccur; >> xfs_fsblock_t prealloc_blocks = 0; >> @@ -1035,6 +1036,22 @@ xfs_buffered_write_iomap_begin( >> } >> >> if (imap.br_startoff <= offset_fsb) { >> + /* >> + * For zeroing out delayed allocation extent, we trim it if >> + * it's partial beyonds EOF block, or convert it to unwritten >> + * extent if it's all beyonds EOF block. >> + */ >> + if ((flags & IOMAP_ZERO) && >> + isnullstartblock(imap.br_startblock)) { >> + if (offset_fsb > eof_fsb) >> + goto convert_delay; >> + if (end_fsb > eof_fsb) { >> + end_fsb = eof_fsb + 1; >> + 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 +1175,18 @@ xfs_buffered_write_iomap_begin( >> xfs_iunlock(ip, lockmode); >> return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, 0, seq); >> >> +convert_delay: >> + end_fsb = min(end_fsb, imap.br_startoff + imap.br_blockcount); >> + xfs_iunlock(ip, lockmode); >> + truncate_pagecache_range(inode, offset, XFS_FSB_TO_B(mp, end_fsb)); >> + error = xfs_iomap_write_direct(ip, offset_fsb, end_fsb - offset_fsb, >> + flags, &imap, &seq); > > I expected this to be a direct call to xfs_bmapi_convert_delalloc. > What was the reason not for using that? > It's because xfs_bmapi_convert_delalloc() isn't guarantee to convert enough blocks once a time, it may convert insufficient blocks since lack of enough contiguous free physical blocks. If we are going to use it, I suppose we need to introduce a new helper something like xfs_convert_blocks(), add a loop to do the conversion. xfs_iomap_write_direct() has done all the work of converting, but the name of this function is non-obviousness than xfs_bmapi_convert_delalloc(), I can change to use it if you think xfs_bmapi_convert_delalloc() is better. :) Thanks, Yi. > --D > >> + if (error) >> + return error; >> + >> + trace_xfs_iomap_alloc(ip, offset, count, XFS_DATA_FORK, &imap); >> + return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, IOMAP_F_NEW, seq); >> + >> found_cow: >> seq = xfs_iomap_inode_sequence(ip, 0); >> if (imap.br_startoff <= offset_fsb) { >> -- >> 2.39.2 >> >>