Re: Do we need an opt-in for file systems use of hw atomic writes?

[Dave Chinner <david@fromorbit.com>]

On Mon, Jul 14, 2025 at 03:17:13PM +0200, Christoph Hellwig wrote:
> Hi all,
> 
> I'm currently trying to sort out the nvme atomics limits mess, and
> between that, the lack of a atomic write command in nvme, and the
> overall degrading quality of cheap consumer nvme devices I'm starting
> to free really uneasy about XFS using hardware atomics by default without
> an explicit opt-in, as broken atomics implementations will lead to
> really subtle data corruption.
> 
> Is is just me, or would it be a good idea to require an explicit
> opt-in to user hardware atomics?

This isn't a filesystem question - this is a question about what
features the block device should expose by default to the
user/filesystem by default.

Block device feature configuration is typically done at hotplug time
with udev rules.  Require the user to add a custom udev rule for the
block device to enable hardware atomics if you are concerned that
hardware atomic writes are problematic.

Once the user has opted in to having their bdev feature activated,
then the filesystem should be able to detect and use it
automatically.

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