[RFC,v1,10/12] powerpc/mm: Prepare maybe_pte_to_page() for PG_reserved changes

Commit Message

David Hildenbrand Oct. 22, 2019, 5:12 p.m. UTC

Right now, ZONE_DEVICE memory is always set PG_reserved. We want to
change that.

We could explicitly check for is_zone_device_page(page). But looking at
the pfn_valid() check, it seems safer to just use pfn_to_online_page()
here, that will skip all ZONE_DEVICE pages right away.

Cc: Benjamin Herrenschmidt <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Michael Ellerman <[e-mail]>
Cc: Christophe Leroy <[e-mail]>
Cc: "Aneesh Kumar K.V" <[e-mail]>
Cc: Allison Randal <[e-mail]>
Cc: Nicholas Piggin <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Signed-off-by: David Hildenbrand <[e-mail]>
---
 arch/powerpc/mm/pgtable.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

Patch

diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index e3759b69f81b..613c98fa7dc0 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -55,10 +55,12 @@  static struct page *maybe_pte_to_page(pte_t pte)
 	unsigned long pfn = pte_pfn(pte);
 	struct page *page;
 
-	if (unlikely(!pfn_valid(pfn)))
-		return NULL;
-	page = pfn_to_page(pfn);
-	if (PageReserved(page))
+	/*
+	 * We reject any pages that are not online (not managed by the buddy).
+	 * This includes ZONE_DEVICE pages.
+	 */
+	page = pfn_to_online_page(pfn);
+	if (unlikely(!page || PageReserved(page)))
 		return NULL;
 	return page;
 }