[PATCH] nvme-apple: Use acquire/release for queue enabled state

[Gui-Dong Han]

On Wed, Jun 3, 2026 at 5:54 PM Keith Busch <kbusch at kernel.org> wrote:
>
> On Wed, Jun 03, 2026 at 03:22:05PM +0800, Gui-Dong Han wrote:
> > apple_nvme_init_queue() initializes queue state and then marks the queue
> > enabled. The interrupt and request paths check enabled before using that
> > queue state.
> >
> > The existing wmb() after WRITE_ONCE(enabled, true) orders the enabled
> > store before later queue use, but it does not publish the earlier
> > initialization before enabled becomes visible.
> >
> > Use a release store when enabling the queue and acquire loads when
> > testing it. Keep the existing wmb() in place for the
> > store-before-later-use ordering.
>
> Doesn't smp_store_release() already get you those semantics?

Yes, smp_store_release() is enough for the ordering intended by that
comment.

The old wmb() after the store does not really provide that ordering.  I
kept it only because it is not identical to a release store, and I was
worried it might have some other ordering effect with later queue-start
operations.

If you prefer, I can drop the wmb() in v2.

>
> Also, there are a few other places doing the READ/WRITE_ONCE() calls in
> apple_nvme_disable. Do you want to update those too for consistency?

For apple_nvme_disable(), I left those READ_ONCE()/WRITE_ONCE() users
unchanged because they are used for the shutdown path rather than for
publishing queue initialization.

The READ_ONCE(anv->ioq.enabled) only decides whether to issue delete
SQ/CQ commands.  It does not consume the queue state initialized before
enabled is set.

The WRITE_ONCE(false) users are followed by mb(), which orders the
shutdown/quiesce path.  A release store would not replace that.

If you prefer the consistency, I can update them in v2 too.

Thanks.