mm: Turn head_compound_mapcount() into folio_entire_mapcount()

Adjust documentation to be more clear.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index dede2ed..70f0ca2 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -776,21 +776,26 @@ static inline int is_vmalloc_or_module_addr(const void *x)
 }
 #endif
 
-static inline int head_compound_mapcount(struct page *head)
+/*
+ * How many times the entire folio is mapped as a single unit (eg by a
+ * PMD or PUD entry).  This is probably not what you want, except for
+ * debugging purposes; look at folio_mapcount() or page_mapcount()
+ * instead.
+ */
+static inline int folio_entire_mapcount(struct folio *folio)
 {
-       return atomic_read(compound_mapcount_ptr(head)) + 1;
+       VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
+       return atomic_read(folio_mapcount_ptr(folio)) + 1;
 }
 
 /*
  * Mapcount of compound page as a whole, does not include mapped sub-pages.
  *
- * Must be called only for compound pages or any their tail sub-pages.
+ * Must be called only for compound pages.
  */
 static inline int compound_mapcount(struct page *page)
 {
-       VM_BUG_ON_PAGE(!PageCompound(page), page);
-       page = compound_head(page);
-       return head_compound_mapcount(page);
+       return folio_entire_mapcount(page_folio(page));
 }
 
 /*

diff --git a/mm/debug.c b/mm/debug.c
index c4cf442..eeb7ea3 100644 (file)
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -48,7 +48,8 @@ const struct trace_print_flags vmaflag_names[] = {
 
 static void __dump_page(struct page *page)
 {
-       struct page *head = compound_head(page);
+       struct folio *folio = page_folio(page);
+       struct page *head = &folio->page;
        struct address_space *mapping;
        bool compound = PageCompound(page);
        /*
@@ -76,6 +77,7 @@ static void __dump_page(struct page *page)
                else
                        mapping = (void *)(tmp & ~PAGE_MAPPING_FLAGS);
                head = page;
+               folio = (struct folio *)page;
                compound = false;
        } else {
                mapping = page_mapping(page);
@@ -94,7 +96,7 @@ static void __dump_page(struct page *page)
        if (compound) {
                pr_warn("head:%p order:%u compound_mapcount:%d compound_pincount:%d\n",
                                head, compound_order(head),
-                               head_compound_mapcount(head),
+                               folio_entire_mapcount(folio),
                                head_compound_pincount(head));
        }