[PATCH] mm: Export PageHeadHuge()

[David Howells]

Export PageHeadHuge() - it's used by folio_test_hugetlb() and thence by
such as folio_file_page() and folio_contains().  Matthew suggested I use
the first of those instead of doing the same calculation manually - but
I can't call it from a module.

Kirill suggested rearranging things to put it in a header, but that
introduces header dependencies because of where constants are defined.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: willy@xxxxxxxxxxxxx
Link: https://lore.kernel.org/r/163707085314.3221130.14783857863702203440.stgit@xxxxxxxxxxxxxxxxxxxxxx/

---
 mm/hugetlb.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 61895cc01d09..5768df43b05c 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1854,6 +1854,7 @@ int PageHeadHuge(struct page *page_head)
 
 	return page_head[1].compound_dtor == HUGETLB_PAGE_DTOR;
 }
+EXPORT_SYMBOL(PageHeadHuge);
 
 /*
  * Find and lock address space (mapping) in write mode.