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 194BA19882F; Tue, 25 Feb 2025 17:50:15 +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=1740505818; cv=none; b=pYmsLmnhR4bDCek45v0tcTGflQ5sGuQfZAJJkSjmv5Qn9HTJ1eVhNvTybNChKBdCsXyFadBduBMezmsnl/ug97eOU2VwzKHOv/AxBMF80m0SLNhOBwOJ3hNg4Ml7aHQAJ+yukD2tXeEEGKo7Hla2zhJWRu+yKSmyLzMPsfOq9YA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740505818; c=relaxed/simple; bh=pseHv10suOnTrBMeDPRE21TEpcumthLSZ89PrafeTmA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=FBShzLXD2a7Xb0sZF2l7p0QF4qcfSeKNde7n2R7BBw+JXMU7gG7G1aWdJ6ATXl1ug9gmTx27PbQ0fiBHnEYzDc7EXc1cXpxYT+aPlPk8JR+mJ59RivknWyK2LahW6Hd3Io7WCfWbRbD6qdOlt6DggFTpS11NwNFfS2/51gRbs4g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FA2HYpU7; 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="FA2HYpU7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6609EC4CEDD; Tue, 25 Feb 2025 17:50:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1740505815; bh=pseHv10suOnTrBMeDPRE21TEpcumthLSZ89PrafeTmA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FA2HYpU7sxl9DbGvZS2VrTSZkTRi0NbggriHvkAoRNsLSClEhqvmlLRf0WKvLtKn6 nsmfJnfzqFpDz+JsDT4zYL3AHGMKjWy89TgRyjPtRsKGvsIGfEyvXoMsp0bP1GGGc2 J3MPOWvmuwX7nhoBVYD6e+1R9ZikLZXD4cp2sMSaV8/wVLKUZepFhWNAm+0Ny0v+M/ 6qc5PJ5Ik0O2W3+IeRnL0869QbeBToUMz85xSn20NcC9W65V5+JiYRz0gkaa4o4JsR lWluW5luUuayby5720qFTotpcZMAmv+zn2/JA8BO1zAuJObKL4WVibt24mv1DljorM 5jpObOLzOR9mA== Date: Tue, 25 Feb 2025 09:50:14 -0800 From: "Darrick J. Wong" To: John Garry Cc: brauner@kernel.org, cem@kernel.org, dchinner@redhat.com, hch@lst.de, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, ojaswin@linux.ibm.com, ritesh.list@gmail.com, martin.petersen@oracle.com, tytso@mit.edu, linux-ext4@vger.kernel.org Subject: Re: [PATCH v2 09/11] xfs: Commit CoW-based atomic writes atomically Message-ID: <20250225175014.GG6242@frogsfrogsfrogs> References: <20250213135619.1148432-1-john.g.garry@oracle.com> <20250213135619.1148432-10-john.g.garry@oracle.com> <20250224202034.GE21808@frogsfrogsfrogs> Precedence: bulk X-Mailing-List: linux-ext4@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: On Tue, Feb 25, 2025 at 11:11:45AM +0000, John Garry wrote: > On 24/02/2025 20:20, Darrick J. Wong wrote: > > On Thu, Feb 13, 2025 at 01:56:17PM +0000, John Garry wrote: > > > When completing a CoW-based write, each extent range mapping update is > > > covered by a separate transaction. > > > > > > For a CoW-based atomic write, all mappings must be changed at once, so > > > change to use a single transaction. > > > > > > Signed-off-by: John Garry > > > --- > > > fs/xfs/xfs_file.c | 5 ++++- > > > fs/xfs/xfs_reflink.c | 45 ++++++++++++++++++++++++++++++++++++++++++++ > > > fs/xfs/xfs_reflink.h | 3 +++ > > > 3 files changed, 52 insertions(+), 1 deletion(-) > > > > > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > > > index 9762fa503a41..243640fe4874 100644 > > > --- a/fs/xfs/xfs_file.c > > > +++ b/fs/xfs/xfs_file.c > > > @@ -527,7 +527,10 @@ xfs_dio_write_end_io( > > > nofs_flag = memalloc_nofs_save(); > > > if (flags & IOMAP_DIO_COW) { > > > - error = xfs_reflink_end_cow(ip, offset, size); > > > + if (iocb->ki_flags & IOCB_ATOMIC) > > > + error = xfs_reflink_end_atomic_cow(ip, offset, size); > > > + else > > > + error = xfs_reflink_end_cow(ip, offset, size); > > > if (error) > > > goto out; > > > } > > > diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c > > > index 3dab3ba900a3..d097d33dc000 100644 > > > --- a/fs/xfs/xfs_reflink.c > > > +++ b/fs/xfs/xfs_reflink.c > > > @@ -986,6 +986,51 @@ xfs_reflink_end_cow( > > > trace_xfs_reflink_end_cow_error(ip, error, _RET_IP_); > > > return error; > > > } > > > +int > > > +xfs_reflink_end_atomic_cow( > > > + struct xfs_inode *ip, > > > + xfs_off_t offset, > > > + xfs_off_t count) > > > +{ > > > + xfs_fileoff_t offset_fsb; > > > + xfs_fileoff_t end_fsb; > > > + int error = 0; > > > + struct xfs_mount *mp = ip->i_mount; > > > + struct xfs_trans *tp; > > > + unsigned int resblks; > > > + > > > + trace_xfs_reflink_end_cow(ip, offset, count); > > > + > > > + offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset); > > > + end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count); > > > > Use @mp here instead of walking the pointer. > > Yes > > > > > > + > > > + resblks = (end_fsb - offset_fsb) * > > > + XFS_NEXTENTADD_SPACE_RES(mp, 1, XFS_DATA_FORK); > > > > How did you arrive at this computation? > > hmmm... you suggested this, but maybe I picked it up incorrectly :) > > > The "b" parameter to > > XFS_NEXTENTADD_SPACE_RES is usually the worst case number of mappings > > that you're going to change on this file. I think that quantity is > > (end_fsb - offset_fsb)? > > Can you please check this versus what you suggested in > https://lore.kernel.org/linux-xfs/20250206215014.GX21808@frogsfrogsfrogs/#t Ah, yeah, that ^^ is correct. This needs a better comment then: /* * Each remapping operation could cause a btree split, so in * the worst case that's one for each block. */ resblks = (end_fsb - offset_fsb) * XFS_NEXTENTADD_SPACE_RES(mp, 1, XFS_DATA_FORK); --D > > > > > + > > > + error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, > > > + XFS_TRANS_RESERVE, &tp); > > > + if (error) > > > + return error; > > > + > > > + xfs_ilock(ip, XFS_ILOCK_EXCL); > > > + xfs_trans_ijoin(tp, ip, 0); > > > + > > > + while (end_fsb > offset_fsb && !error) > > > + error = xfs_reflink_end_cow_extent_locked(tp, ip, &offset_fsb, > > > + end_fsb); > > > > Overly long line, and the continuation line only needs to be indented > > two more tabs. > > ok > > > > > > + > > > + if (error) { > > > + trace_xfs_reflink_end_cow_error(ip, error, _RET_IP_); > > > + goto out_cancel; > > > + } > > > + error = xfs_trans_commit(tp); > > > + xfs_iunlock(ip, XFS_ILOCK_EXCL); > > > + return 0; > > > > Why is it ok to drop @error here? Shouldn't a transaction commit error > > should be reported to the writer thread? > > > > I can fix that, as I should not ignore errors from xfs_trans_commit() > > Thanks, > John >