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Date: Tue, 13 Feb 2024 08:22:37 +0100
From: Christoph Hellwig <hch@lst.de>
To: John Garry <john.g.garry@oracle.com>
Cc: hch@lst.de, 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: <20240213072237.GA24218@lst.de>
References: <20240124142645.9334-1-john.g.garry@oracle.com>
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User-Agent: Mutt/1.5.17 (2007-11-01)

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.

Based on that I suspect that doing proper software only atomic writes
using the swapext log item and selective always COW mode and making that
work should be the first step.  We can then avoid that overhead for
properly aligned writs if the hardware supports it.  For your Oracle
DB loads you'll set the alignment hints and maybe even check with
fiemap that everything is fine and will get the offload, but we also
provide a nice and useful API for less performance critical applications
that don't have to care about all these details.