mm: use entire_mapcount in __page_dup_rmap()

Remove the use of the compound_mapcount_ptr() wrapper, and add an
assertion that we're not passing a tail page if we're duplicating a PMD.

Link: https://lkml.kernel.org/r/20230111142915.1001531-12-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index aa682a2a93ce3b2f8d01a6cc125338fda833c496..a6bd1f0a183d91b2753fe08baf5b0f101c0dac78 100644 (file)
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -208,7 +208,14 @@ void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
 
 static inline void __page_dup_rmap(struct page *page, bool compound)
 {
-       atomic_inc(compound ? compound_mapcount_ptr(page) : &page->_mapcount);
+       if (compound) {
+               struct folio *folio = (struct folio *)page;
+
+               VM_BUG_ON_PAGE(compound && !PageHead(page), page);
+               atomic_inc(&folio->_entire_mapcount);
+       } else {
+               atomic_inc(&page->_mapcount);
+       }
 }
 
 static inline void page_dup_file_rmap(struct page *page, bool compound)