mm/hugetlb: Use try_grab_folio() instead of try_grab_compound_head()

follow_hugetlb_page() only cares about success or failure, so it doesn't
need to know the type of the returned pointer, only whether it's NULL
or not.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>

include/linux/mm.h

@@ -1124,9 +1124,6 @@ static inline void get_page(struct page *page)
 }
 
 bool __must_check try_grab_page(struct page *page, unsigned int flags);
-struct page *try_grab_compound_head(struct page *page, int refs,
-				    unsigned int flags);
-
 
 static inline __must_check bool try_get_page(struct page *page)
 {

mm/gup.c

@@ -133,7 +133,7 @@ struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags)
 	return NULL;
 }
 
-struct page *try_grab_compound_head(struct page *page,
+static inline struct page *try_grab_compound_head(struct page *page,
 		int refs, unsigned int flags)
 {
 	return &try_grab_folio(page, refs, flags)->page;

mm/hugetlb.c

@@ -6076,7 +6076,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 
 		if (pages) {
 			/*
-			 * try_grab_compound_head() should always succeed here,
+			 * try_grab_folio() should always succeed here,
 			 * because: a) we hold the ptl lock, and b) we've just
 			 * checked that the huge page is present in the page
 			 * tables. If the huge page is present, then the tail
@@ -6085,9 +6085,8 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
 			 * any way. So this page must be available at this
 			 * point, unless the page refcount overflowed:
 			 */
-			if (WARN_ON_ONCE(!try_grab_compound_head(pages[i],
-								 refs,
-								 flags))) {
+			if (WARN_ON_ONCE(!try_grab_folio(pages[i], refs,
+							 flags))) {
 				spin_unlock(ptl);
 				remainder = 0;
 				err = -ENOMEM;