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

[Darrick J. Wong]

On Mon, Jul 14, 2025 at 03:30:14PM +0200, Christoph Hellwig wrote:
> On Mon, Jul 14, 2025 at 09:24:07AM -0400, Theodore Ts'o wrote:
> > > 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?
> 
> I don't know.  But cheap consumer SSDs can basically exhibit any
> brokenness you can imagine.  And claiming to support atomics basically
> just means filling out a single field in identify with a non-zero
> value.  So my hopes of only seeing it in a few devices is low,
> moreover we will only notice it was broken when people lost data.

Do you want to handle it the same way as we do discard-zeroes-data and
have a quirks list of devices we trust?  Though I can hardly talk,
knowing the severe limitations of allowlists vs. product managers trying
to win benchmarks with custom firmware. :(

--D