On 12/9/20 4:24 PM, Jason Gunthorpe wrote: > On Wed, Dec 09, 2020 at 04:02:05PM +0000, Joao Martins wrote: > >> Today (without the series) struct pages are not represented the way they >> are expressed in the page tables, which is what I am hoping to fix in this >> series thus initializing these as compound pages of a given order. But me >> introducing PGMAP_COMPOUND was to conservatively keep both old (non-compound) >> and new (compound pages) co-exist. > > Oooh, that I didn't know.. That is kind of horrible to have a PMD > pointing at an order 0 page only in this one special case. > > Still, I think it would be easier to teach record_subpages() that a > PMD doesn't necessarily point to a high order page, eg do something > like I suggested for the SGL where it extracts the page order and > iterates over the contiguous range of pfns. > /me nods > This way it can remain general with no particularly special path for > devmap or a special PGMAP_COMPOUND check here. The less special paths the better, indeed. Joao
