- folio_remove_rmap_pte(folio, page, vma);
+ folio_remove_rmap_ptes(folio, page, nr, vma);
+
+ /* Only sanity-check the first page in a batch. */
if (unlikely(page_mapcount(page) < 0))
print_bad_pte(vma, addr, ptent, page);
Is there a case for either removing this all together or moving it into
folio_remove_rmap_ptes()? It seems odd to only check some pages.
I really wanted to avoid another nasty loop here.
In my thinking, for 4k folios, or when zapping subpages of large folios, we
still perform the exact same checks. Only when batching we don't. So if there is
some problem, there are ways to get it triggered. And these problems are barely
ever seen.
folio_remove_rmap_ptes() feels like the better place -- especially because the
delayed-rmap handling is effectively unchecked. But in there, we cannot
"print_bad_pte()".
[background: if we had a total mapcount -- iow cheap folio_mapcount(), I'd check
here that the total mapcount does not underflow, instead of checking per-subpage]
All good points... perhaps extend the comment to describe how this could be
solved in future with cheap total_mapcount()? Or in the commit log if you prefer?
I'll add more meat to the cover letter, thanks!
--
Cheers,
David / dhildenb
