mm: differentiate page_mapped() from page_mapcount() for compound pages

Let's define page_mapped() to be true for compound pages if any
sub-pages of the compound page is mapped (with PMD or PTE).

On other hand page_mapcount() return mapcount for this particular small
page.

This will make cases like page_get_anon_vma() behave correctly once we
allow huge pages to be mapped with PTE.

Most users outside core-mm should use page_mapcount() instead of
page_mapped().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Tested-by: Sasha Levin <sasha.levin@oracle.com>
Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/sh/mm/cache.c

@@ -59,7 +59,7 @@ void copy_to_user_page(struct vm_area_struct *vma, struct page *page,
 		       unsigned long vaddr, void *dst, const void *src,
 		       unsigned long len)
 {
-	if (boot_cpu_data.dcache.n_aliases && page_mapped(page) &&
+	if (boot_cpu_data.dcache.n_aliases && page_mapcount(page) &&
 	    test_bit(PG_dcache_clean, &page->flags)) {
 		void *vto = kmap_coherent(page, vaddr) + (vaddr & ~PAGE_MASK);
 		memcpy(vto, src, len);
@@ -78,7 +78,7 @@ void copy_from_user_page(struct vm_area_struct *vma, struct page *page,
 			 unsigned long vaddr, void *dst, const void *src,
 			 unsigned long len)
 {
-	if (boot_cpu_data.dcache.n_aliases && page_mapped(page) &&
+	if (boot_cpu_data.dcache.n_aliases && page_mapcount(page) &&
 	    test_bit(PG_dcache_clean, &page->flags)) {
 		void *vfrom = kmap_coherent(page, vaddr) + (vaddr & ~PAGE_MASK);
 		memcpy(dst, vfrom, len);
@@ -97,7 +97,7 @@ void copy_user_highpage(struct page *to, struct page *from,
 
 	vto = kmap_atomic(to);
 
-	if (boot_cpu_data.dcache.n_aliases && page_mapped(from) &&
+	if (boot_cpu_data.dcache.n_aliases && page_mapcount(from) &&
 	    test_bit(PG_dcache_clean, &from->flags)) {
 		vfrom = kmap_coherent(from, vaddr);
 		copy_page(vto, vfrom);
@@ -153,7 +153,7 @@ void __flush_anon_page(struct page *page, unsigned long vmaddr)
 	unsigned long addr = (unsigned long) page_address(page);
 
 	if (pages_do_alias(addr, vmaddr)) {
-		if (boot_cpu_data.dcache.n_aliases && page_mapped(page) &&
+		if (boot_cpu_data.dcache.n_aliases && page_mapcount(page) &&
 		    test_bit(PG_dcache_clean, &page->flags)) {
 			void *kaddr;