[PATCH 15/16] mm: switch gup_hugepte to use try_get_compound_head

[Christoph Hellwig]

This applies the overflow fixes from 8fde12ca79aff
("mm: prevent get_user_pages() from overflowing page refcount")
to the powerpc hugepd code and brings it back in sync with the
other GUP cases.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 mm/gup.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/gup.c b/mm/gup.c
index e03c7e6b1422..6090044227f1 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2006,7 +2006,8 @@ static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
 		refs++;
 	} while (addr += PAGE_SIZE, addr != end);
 
-	if (!page_cache_add_speculative(head, refs)) {
+	head = try_get_compound_head(head, refs);
+	if (!head) {
 		*nr -= refs;
 		return 0;
 	}
-- 
2.20.1