thp: add compound_trans_head() helper
[linux-2.6.git] / virt / kvm / kvm_main.c
index 4286d47..f29abeb 100644 (file)
@@ -104,34 +104,24 @@ static pfn_t fault_pfn;
 inline int kvm_is_mmio_pfn(pfn_t pfn)
 {
        if (pfn_valid(pfn)) {
-               struct page *head;
+               int reserved;
                struct page *tail = pfn_to_page(pfn);
-               head = compound_head(tail);
+               struct page *head = compound_trans_head(tail);
+               reserved = PageReserved(head);
                if (head != tail) {
-                       smp_rmb();
                        /*
-                        * head may be a dangling pointer.
-                        * __split_huge_page_refcount clears PageTail
-                        * before overwriting first_page, so if
-                        * PageTail is still there it means the head
-                        * pointer isn't dangling.
+                        * "head" is not a dangling pointer
+                        * (compound_trans_head takes care of that)
+                        * but the hugepage may have been splitted
+                        * from under us (and we may not hold a
+                        * reference count on the head page so it can
+                        * be reused before we run PageReferenced), so
+                        * we've to check PageTail before returning
+                        * what we just read.
                         */
-                       if (PageTail(tail)) {
-                               /*
-                                * the "head" is not a dangling
-                                * pointer but the hugepage may have
-                                * been splitted from under us (and we
-                                * may not hold a reference count on
-                                * the head page so it can be reused
-                                * before we run PageReferenced), so
-                                * we've to recheck PageTail before
-                                * returning what we just read.
-                                */
-                               int reserved = PageReserved(head);
-                               smp_rmb();
-                               if (PageTail(tail))
-                                       return reserved;
-                       }
+                       smp_rmb();
+                       if (PageTail(tail))
+                               return reserved;
                }
                return PageReserved(tail);
        }