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Diffstat (limited to 'mm')
-rw-r--r--mm/hugetlb.c16
1 files changed, 15 insertions, 1 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 691f2264a6ce..0b7656e804d1 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -696,8 +696,22 @@ static void prep_compound_gigantic_page(struct page *page, unsigned long order)
/* we rely on prep_new_huge_page to set the destructor */
set_compound_order(page, order);
__SetPageHead(page);
+ __ClearPageReserved(page);
for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
__SetPageTail(p);
+ /*
+ * For gigantic hugepages allocated through bootmem at
+ * boot, it's safer to be consistent with the not-gigantic
+ * hugepages and clear the PG_reserved bit from all tail pages
+ * too. Otherwse drivers using get_user_pages() to access tail
+ * pages may get the reference counting wrong if they see
+ * PG_reserved set on a tail page (despite the head page not
+ * having PG_reserved set). Enforcing this consistency between
+ * head and tail pages allows drivers to optimize away a check
+ * on the head page when they need know if put_page() is needed
+ * after get_user_pages().
+ */
+ __ClearPageReserved(p);
set_page_count(p, 0);
p->first_page = page;
}
@@ -1330,9 +1344,9 @@ static void __init gather_bootmem_prealloc(void)
#else
page = virt_to_page(m);
#endif
- __ClearPageReserved(page);
WARN_ON(page_count(page) != 1);
prep_compound_huge_page(page, h->order);
+ WARN_ON(PageReserved(page));
prep_new_huge_page(h, page, page_to_nid(page));
/*
* If we had gigantic hugepages allocated at boot time, we need