From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 22B6E41C92; Mon, 11 Mar 2024 15:37:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710171458; cv=none; b=IxTod+S5Ji/vWpMDKCHT6amz7WW8RT7ov/slBPshI2wHVjE7Xp8MH1OC5XXn/UXdMBkNzO95QSk1srQzKXQKjZtXsly4X0oGkLQxOU3nqvGMMqzpwyg98RU0O9nvipRLkZtKtjqBSe3o0uH2OMC85643uP+P2V+fnJgzSctuqQ4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710171458; c=relaxed/simple; bh=LQcdiCTC36GrmbF/Aarge8Ouhfrl/F5lC6nrPd2ehTY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=cMjbBLA9uh4sXihbF34hmgt9oM8N//aOL0LXoHPvqdLuKS58pn7pwtfUbkBLdT7tSI7odc+xD9A0TWx7U/CqdTVkYToR6Cdqx/diHijDFrPO/fLyLy8DnenpGj8D1jz0Kg38Mbo9vshF0UcxrQVay4cHljPNm+56E1s+oohzTJo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FWf70wnQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="FWf70wnQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9E606C433C7; Mon, 11 Mar 2024 15:37:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1710171457; bh=LQcdiCTC36GrmbF/Aarge8Ouhfrl/F5lC6nrPd2ehTY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FWf70wnQqKd+K1pxiLfkPG0sbOlhXmEzmJ0z8v8wEyYVuA76tac5necE1DxVR56dy Lp4Npvi+RFCU0VgvPs91dnREsOhdPppGInqNSEPLZLyiKhpMc1y4eXgkjGvQe/2SbX jTPM98xuKL1Wq3/yPckZJCJSQq79uH+TQueILc/Jeq75X0S3N9hwAQB5qnZFEZW455 gjgqdecOSLH3GT2GhoX4IKyI+pxQ4D2G7sxO1U9HP9sCaV4O3l4go5dlrOAT66ZRMO 0QvXuN4zFaBg1D8c0OXgbO/SANReWsIQu2QOGsONvQNLVWwDzpOlDFIpaEcmUyk3Xp QLEylOEm2FCcg== Date: Mon, 11 Mar 2024 08:37:37 -0700 From: "Darrick J. Wong" To: Zhang Yi 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 Subject: Re: [PATCH 2/4] xfs: convert delayed extents to unwritten when zeroing post eof blocks Message-ID: <20240311153737.GT1927156@frogsfrogsfrogs> References: <20240311122255.2637311-1-yi.zhang@huaweicloud.com> <20240311122255.2637311-3-yi.zhang@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240311122255.2637311-3-yi.zhang@huaweicloud.com> 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? --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 > >