Re: [PATCH v1 4/4] mm/mmu_gather: Store and process pages in contig ranges

[Matthew Wilcox]

On Tue, Aug 29, 2023 at 03:02:22PM +0100, Ryan Roberts wrote:
> >> +			if (put_devmap_managed_page(&folio->page))
> >> +				continue;
> >> +			if (folio_put_testzero(folio))
> > 
> > We're only putting one ref for the zone_device folios?  Surely
> > this should be ref_sub_and_test like below?
> 
> Good point. This function is originally a copy/paste of release_pages(), and I
> obviously missed this. In fact, looking at it again today, I think I'll factor
> out the vast majority into a common helper, since I'm currently duplicating a
> whole bunch here.
> 
> In practice I think all devmap folios will be small today though? So while I
> agree I need to fix this, I think in practice it will currently do the right thing?

I think the devdax code uses 2MB folios.

> > You'll be glad to know I've factored out a nice little helper for that.
> 
> OK, what's it called? This is just copied from release_pages() at the moment.
> Happy to use your helper in the refactored common helper.

I'll send out those patches today.