David Hildenbrand wrote: > Marking PMDs that map a "normal" refcounted folios as special is > against our rules documented for vm_normal_page(). > > Fortunately, there are not that many pmd_special() check that can be > mislead, and most vm_normal_page_pmd()/vm_normal_folio_pmd() users that > would get this wrong right now are rather harmless: e.g., none so far > bases decisions whether to grab a folio reference on that decision. > > Well, and GUP-fast will fallback to GUP-slow. All in all, so far no big > implications as it seems. > > Getting this right will get more important as we use > folio_normal_page_pmd() in more places. > > Fix it by teaching insert_pfn_pmd() to properly handle folios and > pfns -- moving refcount/mapcount/etc handling in there, renaming it to > insert_pmd(), and distinguishing between both cases using a new simple > "struct folio_or_pfn" structure. > > Use folio_mk_pmd() to create a pmd for a folio cleanly.
Looks good, I like copying the sockptr_t approach for this, and agree that this seems to not cause any problems in practice today, but definitely will be a trip hazard going forward. Reviewed-by: Dan Williams <dan.j.willi...@intel.com>
