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

[Theodore Ts'o]

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?

How common do we think broken atomics implementations; is this
something that we could solve using a blacklist of broken devices?

It used to be the case that broken flash devices would get bricked
when trim commands would get sent racing with write requests.  But
over time, the broken devices died out (in some cases, when the
companies selling the broken SSD's died out :-).  It would have been
annoying if we had to explicitly enable trim support in 2025 just
because there were some broken SSD's existed a decade or more ago.

	       	  	      	      - Ted