Re: [PATCHES][RFC] packing struct block_device flags

Al Viro
2024-04-29T18:30:44Z

On Mon, Apr 29, 2024 at 07:13:00PM +0100, Al Viro wrote:
> On Mon, Apr 29, 2024 at 06:02:09PM +0100, Al Viro wrote:
> > On Mon, Apr 29, 2024 at 08:31:07AM +0100, Al Viro wrote:
> >
> > > FWIW, we could go for atomic_t there and use
> > > atomic_read() & 0xff
> > > for partno, with atomic_or()/atomic_and() for set/clear and
> > > atomic_read() & constant for test. That might slightly optimize
> > > set/clear on some architectures, but setting/clearing flags is
> > > nowhere near hot enough for that to make a difference.
> >
> > Incremental for that (would be folded into 3/8 if we went that way)
> > is below; again, I'm not at all sure it's idiomatic enough to bother
> > with, but that should at least show what's going on:
>
> Or this, for that matter:

See #work.bd_flags-2 for carve-up of that variant.