mm: add folio_is_pci_p2pdma()

Reimplement is_pci_p2pdma_page() in terms of folio_is_pci_p2pdma().  Moves
the page_folio() call from inside page_pgmap() to is_pci_p2pdma_page(). 
This removes a page_folio() call from try_grab_folio() which already has a
folio and can pass it in.

Link: https://lkml.kernel.org/r/20250805172307.1302730-12-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

2 files changed, 9 insertions, 3 deletions

diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 450d4bb6835c..aa1b6aa877a0 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -170,11 +170,17 @@ static inline bool is_device_private_page(const struct page *page)
 		folio_is_device_private(page_folio(page));
 }
 
+static inline bool folio_is_pci_p2pdma(const struct folio *folio)
+{
+	return IS_ENABLED(CONFIG_PCI_P2PDMA) &&
+		folio_is_zone_device(folio) &&
+		folio->pgmap->type == MEMORY_DEVICE_PCI_P2PDMA;
+}
+
 static inline bool is_pci_p2pdma_page(const struct page *page)
 {
 	return IS_ENABLED(CONFIG_PCI_P2PDMA) &&
-		is_zone_device_page(page) &&
-		page_pgmap(page)->type == MEMORY_DEVICE_PCI_P2PDMA;
+		folio_is_pci_p2pdma(page_folio(page));
 }
 
 static inline bool folio_is_device_coherent(const struct folio *folio)
diff --git a/mm/gup.c b/mm/gup.c
index 331d22bf7b2d..b2a78f029127 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -148,7 +148,7 @@ int __must_check try_grab_folio(struct folio *folio, int refs,
 	if (WARN_ON_ONCE(folio_ref_count(folio) <= 0))
 		return -ENOMEM;
 
-	if (unlikely(!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(&folio->page)))
+	if (unlikely(!(flags & FOLL_PCI_P2PDMA) && folio_is_pci_p2pdma(folio)))
 		return -EREMOTEIO;
 
 	if (flags & FOLL_GET)