Commit a1f34ee1 authored by David Hildenbrand's avatar David Hildenbrand Committed by Andrew Morton
Browse files

mm/rmap: warn on new PTE-mapped folios in page_add_anon_rmap() 

If swapin code would ever decide to not use order-0 pages and supply a
PTE-mapped large folio, we will have to change how we call
__folio_set_anon() -- eventually with exclusive=false and an adjusted
address.  For now, let's add a VM_WARN_ON_FOLIO() with a comment about the
situation.

Link: https://lkml.kernel.org/r/20230913125113.313322-5-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent c5c54003

mm/rmap.c

+7 −0
Original line number Diff line number Diff line
@@ -1238,6 +1238,13 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma, 


	if (unlikely(!folio_test_anon(folio))) {

		VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio);

		/*

		 * For a PTE-mapped large folio, we only know that the single

		 * PTE is exclusive. Further, __folio_set_anon() might not get

		 * folio->index right when not given the address of the head

		 * page.

		 */

		VM_WARN_ON_FOLIO(folio_test_large(folio) && !compound, folio);

		__folio_set_anon(folio, vma, address,

				 !!(flags & RMAP_EXCLUSIVE));

	} else if (likely(!folio_test_ksm(folio))) {