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Date: Wed, 14 Feb 2024 10:50:22 +1100
From: Dave Chinner <david@fromorbit.com>
To: Christoph Hellwig <hch@lst.de>
Cc: John Garry <john.g.garry@oracle.com>, djwong@kernel.org,
	viro@zeniv.linux.org.uk, brauner@kernel.org, dchinner@redhat.com,
	jack@suse.cz, chandan.babu@oracle.com, martin.petersen@oracle.com,
	linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, tytso@mit.edu, jbongio@google.com,
	ojaswin@linux.ibm.com
Subject: Re: [PATCH 0/6] block atomic writes for XFS
Message-ID: <ZcwAPq8e/ZpAwhYf@dread.disaster.area>
References: <20240124142645.9334-1-john.g.garry@oracle.com>
 <20240213072237.GA24218@lst.de>
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On Tue, Feb 13, 2024 at 08:22:37AM +0100, Christoph Hellwig wrote:
> From reading the series and the discussions with Darrick and Dave
> I'm coming more and more back to my initial position that tying this
> user visible feature to hardware limits is wrong and will just keep
> on creating ever more painpoints in the future.

Yes, that's pretty much what I've been trying to say from the start.

The functionality atomic writes need from the filesystem is for
extent alignment constraints to be applied to all extent
manipulations, not just allocation.  This is the same functionality
that DAX based XFS filesystems need to guarantee PMD aligned
extents.

IOWs, the required filesystem extent alignment functionality is not
specific to atomic writes and it is not specific to a particular
type of storage hardware.

If we implement the generic extent alignment constraints properly,
everything else from there is just a matter of configuring the
filesystem geometry to match the underlying hardware capability.
mkfs can do that for us, like it already does for RAID storage...

-Dave.
-- 
Dave Chinner
david@fromorbit.com