Up to this point the code assumed old refcounting for hugepages
(pre-thp). This updates the code directly to the thp mapcount tail
page refcounting.
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
---
arch/sparc/mm/gup.c | 13 +++++++++++++
1 files changed, 13 insertions(+), 0 deletions(-)
diff --git a/arch/sparc/mm/gup.c b/arch/sparc/mm/gup.c
index a986b5d..afcebac 100644
--- a/arch/sparc/mm/gup.c
+++ b/arch/sparc/mm/gup.c
@@ -12,6 +12,17 @@
#include <linux/rwsem.h>
#include <asm/pgtable.h>
+static inline void get_huge_page_tail(struct page *page)
+{
+ /*
+ * __split_huge_page_refcount() cannot run
+ * from under us.
+ */
+ VM_BUG_ON(page_mapcount(page) < 0);
+ VM_BUG_ON(atomic_read(&page->_count) != 0);
+ atomic_inc(&page->_mapcount);
+}
+
/*
* The performance critical leaf functions are made noinline otherwise gcc
* inlines everything into a single function which results in too much
@@ -56,6 +67,8 @@ static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
put_page(head);
return 0;
}
+ if (head != page)
+ get_huge_page_tail(page);
pages[*nr] = page;
(*nr)++;
--
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