mm: remove page_rmapping()

After converting the last user to folio_raw_mapping(), we can safely
remove the function.

Link: https://lkml.kernel.org/r/20230701032853.258697-3-zhangpeng362@huawei.comSigned-off-by: ZhangPeng <zhangpeng362@huawei.com>
Reviewed-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/mm.h

@@ -2170,7 +2170,6 @@ static inline void *folio_address(const struct folio *folio)
 	return page_address(&folio->page);
 }
 
-extern void *page_rmapping(struct page *page);
 extern pgoff_t __page_file_index(struct page *page);
 
 /*

mm/util.c

@@ -734,12 +734,6 @@ void *vcalloc(size_t n, size_t size)
 }
 EXPORT_SYMBOL(vcalloc);
 
-/* Neutral page->mapping pointer to address_space or anon_vma or other */
-void *page_rmapping(struct page *page)
-{
-	return folio_raw_mapping(page_folio(page));
-}
-
 struct anon_vma *folio_anon_vma(struct folio *folio)
 {
 	unsigned long mapping = (unsigned long)folio->mapping;