Re: [RFC RFC PATCH] mm: convert VM flags from macros to enum

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

On Mon, Oct 13, 2025 at 03:07:18PM +0200, Vlastimil Babka wrote:
> On 10/13/25 14:57, Lorenzo Stoakes wrote:
> > FOLL_* flags are an anonymous enum, enum fault_flag is not used as a type
> > anywhere, nor is vm_fault_reason. So those are both kinda weird as to why we
> > even name the type (they're in effect anonymous).
> >
> > But also 'we do X in the kernel' doesn't mean doing X is right :)
>
> I think the example to follow could be GFP flags. Nowadays there's an enum
> below it, and a layer that adds (__force gfp_t), so you could do similar
> thing with vm_flags_t.
>
> However I'm not sure how compatible is that with Lorenzo's plans.

That's defining bit values in an anonymous enum so isn't really comparable.

But what it's doing, ultimately, in broad terms (other than the opaque bitmap
type I'll be using for VMA flags) is what my changes will do.

And yeah, trying to do duplicate that is not really a good use of time and will
conflict with my work.

Overall I think this change is generally unnecessary given that I'm about to
radically alter how VMA flags are implemented, and actually will cause me
problems.

But as I said before, I'm happy to prioritise the change that specifies the
flags based on the bit numbers, I actually have it ready more-or-less.

Cheers, Lorenzo