mm: remove page_rmapping()

JIRA: https://issues.redhat.com/browse/RHEL-27743

This patch is a backport of the following upstream commit:
commit fc1878e
Author: ZhangPeng <[email protected]>
Date:   Sat Jul 1 11:28:53 2023 +0800

    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/[email protected]
    Signed-off-by: ZhangPeng <[email protected]>
    Reviewed-by: Sidhartha Kumar <[email protected]>
    Reviewed-by: Matthew Wilcox (Oracle) <[email protected]>
    Cc: Kefeng Wang <[email protected]>
    Cc: Nanyong Sun <[email protected]>
    Signed-off-by: Andrew Morton <[email protected]>

Signed-off-by: Rafael Aquini <[email protected]>

Author: Rafael Aquini

include/linux/mm.h

@@ -2278,7 +2278,6 @@ 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

@@ -738,12 +738,6 @@ 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;