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

From: Christoph Hellwig
Date: Sat Jun 01 2019 - 03:55:01 EST


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