[PATCH] mm: fix oom roll-back of __vmalloc_area_node

__vunmap must not rely on area->nr_pages when picking the release methode
for area->pages.  It may be too small when __vmalloc_area_node failed early
due to lacking memory.  Instead, use a flag in vmstruct to differentiate.

Signed-off-by: Jan Kiszka <jan.kiszka@web.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/vmalloc.h

@@ -11,6 +11,7 @@ struct vm_area_struct;
 #define VM_ALLOC	0x00000002	/* vmalloc() */
 #define VM_MAP		0x00000004	/* vmap()ed pages */
 #define VM_USERMAP	0x00000008	/* suitable for remap_vmalloc_range */
+#define VM_VPAGES	0x00000010	/* buffer for pages was vmalloc'ed */
 /* bits [20..32] reserved for arch specific ioremap internals */
 
 /*

mm/vmalloc.c

@@ -340,7 +340,7 @@ void __vunmap(void *addr, int deallocate_pages)
 			__free_page(area->pages[i]);
 		}
 
-		if (area->nr_pages > PAGE_SIZE/sizeof(struct page *))
+		if (area->flags & VM_VPAGES)
 			vfree(area->pages);
 		else
 			kfree(area->pages);
@@ -427,9 +427,10 @@ void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
 
 	area->nr_pages = nr_pages;
 	/* Please note that the recursion is strictly bounded. */
-	if (array_size > PAGE_SIZE)
+	if (array_size > PAGE_SIZE) {
 		pages = __vmalloc_node(array_size, gfp_mask, PAGE_KERNEL, node);
-	else
+		area->flags |= VM_VPAGES;
+	} else
 		pages = kmalloc_node(array_size, (gfp_mask & ~__GFP_HIGHMEM), node);
 	area->pages = pages;
 	if (!area->pages) {