mm: add is_huge_zero_folio()

This is the folio equivalent of is_huge_zero_page().  It doesn't add any
efficiency, but it does prevent the caller from passing a tail page and
getting confused when the predicate returns false.

Link: https://lkml.kernel.org/r/20240326202833.523759-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 1540a1481daf..600c6008262b 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -356,6 +356,11 @@ static inline bool is_huge_zero_page(const struct page *page)
 	return READ_ONCE(huge_zero_page) == page;
 }
 
+static inline bool is_huge_zero_folio(const struct folio *folio)
+{
+	return READ_ONCE(huge_zero_page) == &folio->page;
+}
+
 static inline bool is_huge_zero_pmd(pmd_t pmd)
 {
 	return pmd_present(pmd) && READ_ONCE(huge_zero_pfn) == pmd_pfn(pmd);
@@ -485,6 +490,11 @@ static inline bool is_huge_zero_page(const struct page *page)
 	return false;
 }
 
+static inline bool is_huge_zero_folio(const struct folio *folio)
+{
+	return false;
+}
+
 static inline bool is_huge_zero_pmd(pmd_t pmd)
 {
 	return false;