[PATCH 1/3] mm: Correct page_mapped_in_vma() for large folios

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

If 'page' is the first page of a large folio then vma_address() will scan
for any page in the entire folio.  This can lead to page_mapped_in_vma()
returning true if some of the tail pages are mapped and the head page
is not.  This could lead to memory failure choosing to kill a task
unnecessarily.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/page_vma_mapped.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 74d2de15fb5e..ac48d6284bad 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -325,6 +325,8 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
  */
 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
 {
+	struct folio *folio = page_folio(page);
+	pgoff_t pgoff = folio->index + folio_page_idx(folio, page);
 	struct page_vma_mapped_walk pvmw = {
 		.pfn = page_to_pfn(page),
 		.nr_pages = 1,
@@ -332,7 +334,7 @@ int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
 		.flags = PVMW_SYNC,
 	};
 
-	pvmw.address = vma_address(page, vma);
+	pvmw.address = vma_pgoff_address(pgoff, 1, vma);
 	if (pvmw.address == -EFAULT)
 		return 0;
 	if (!page_vma_mapped_walk(&pvmw))
-- 
2.43.0