Re: [PATCH v2] mm/vma: don't remove VMA from rmap if pgoff unchanged

[Lance Yang]

On 2026/10/2 22:05, Lorenzo Stoakes (ARM) wrote:
> On Thu, Oct 01, 2026 at 11:45:11PM +0800, Lance Yang wrote:
[...]
> > > +static void anon_rmap_tree_update_inplace(struct anon_vma_chain *avc)
> > > +{
> > > +#ifdef CONFIG_DEBUG_VM_RB
> > > +	avc->cached_vma_last = avc_last_pgoff(avc);
> > > +#endif
> > > +	/* Propagate all the way up the tree. */
> >
> > Nit: propagate() can stop early when rb_subtree_last is unchanged ...
> >
> > Maybe:
> >
> > /* Update the subtree maximum and propagate any changes up the tree. */
>
> I think in this case it's ok to be a bit blurry about it :P it deciding not to
> unnecessary work is fine but I don't want to put too much in there.
>
> The point is as a simple sign or pointer to help somebody wondering wtf that's
> for even if it's not quite the full story!
>
> Hopefully that's ok? :)

Fair enough. Let’s leave it as-is ;)

> > > +	__anon_rmap_tree_augment.propagate(&avc->rb, NULL);
> > > +}
> > > +
> > [...]
> >
> > Acked-by: Lance Yang <lance.yang@xxxxxxxxx>
>
> Thanks :)
>
> > Hammered it with VMA churn (split/merge/mremap/madvise/fork) + concurrent
> > rmap walks + hwpoison injection. Nothing complained :D
> >
> > Tested-by: Lance Yang <lance.yang@xxxxxxxxx>
>
> Thanks, very much appreciated! :)

Cheers!