filemap: Remove thp_contains()

This function is now unused, so delete it.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>

include/linux/pagemap.h

@@ -512,15 +512,6 @@ static inline struct page *grab_cache_page_nowait(struct address_space *mapping,
 			mapping_gfp_mask(mapping));
 }
 
-/* Does this page contain this index? */
-static inline bool thp_contains(struct page *head, pgoff_t index)
-{
-	/* HugeTLBfs indexes the page cache in units of hpage_size */
-	if (PageHuge(head))
-		return head->index == index;
-	return page_index(head) == (index & ~(thp_nr_pages(head) - 1UL));
-}
-
 #define swapcache_index(folio)	__page_file_index(&(folio)->page)
 
 /**