mm, page_alloc: check multiple page fields with a single branch

[cascardo/linux.git] / mm / util.c

diff --git a/mm/util.c b/mm/util.c
index 6cc81e7..8a1b3a1 100644 (file)
--- a/mm/util.c
+++ b/mm/util.c
@@ -346,6 +346,29 @@ void *page_rmapping(struct page *page)
        return __page_rmapping(page);
 }
 
+/*
+ * Return true if this page is mapped into pagetables.
+ * For compound page it returns true if any subpage of compound page is mapped.
+ */
+bool page_mapped(struct page *page)
+{
+       int i;
+
+       if (likely(!PageCompound(page)))
+               return atomic_read(&page->_mapcount) >= 0;
+       page = compound_head(page);
+       if (atomic_read(compound_mapcount_ptr(page)) >= 0)
+               return true;
+       if (PageHuge(page))
+               return false;
+       for (i = 0; i < hpage_nr_pages(page); i++) {
+               if (atomic_read(&page[i]._mapcount) >= 0)
+                       return true;
+       }
+       return false;
+}
+EXPORT_SYMBOL(page_mapped);
+
 struct anon_vma *page_anon_vma(struct page *page)
 {
        unsigned long mapping;