1 files changed, 33 insertions, 34 deletions

diff --git a/mm/util.c b/mm/util.c
index 2d28f7930043..4fb14ca5a419 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -230,36 +230,11 @@ void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
 }
 
 /* Check if the vma is being used as a stack by this task */
-static int vm_is_stack_for_task(struct task_struct *t,
-				struct vm_area_struct *vma)
+int vma_is_stack_for_task(struct vm_area_struct *vma, struct task_struct *t)
 {
 	return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
 }
 
-/*
- * Check if the vma is being used as a stack.
- * If is_group is non-zero, check in the entire thread group or else
- * just check in the current task. Returns the task_struct of the task
- * that the vma is stack for. Must be called under rcu_read_lock().
- */
-struct task_struct *task_of_stack(struct task_struct *task,
-				struct vm_area_struct *vma, bool in_group)
-{
-	if (vm_is_stack_for_task(task, vma))
-		return task;
-
-	if (in_group) {
-		struct task_struct *t;
-
-		for_each_thread(task, t) {
-			if (vm_is_stack_for_task(t, vma))
-				return t;
-		}
-	}
-
-	return NULL;
-}
-
 #if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
 void arch_pick_mmap_layout(struct mm_struct *mm)
 {
@@ -386,7 +361,9 @@ struct anon_vma *page_anon_vma(struct page *page)
 
 struct address_space *page_mapping(struct page *page)
 {
-	unsigned long mapping;
+	struct address_space *mapping;
+
+	page = compound_head(page);
 
 	/* This happens if someone calls flush_dcache_page on slab page */
 	if (unlikely(PageSlab(page)))
@@ -399,12 +376,26 @@ struct address_space *page_mapping(struct page *page)
 		return swap_address_space(entry);
 	}
 
-	mapping = (unsigned long)page->mapping;
-	if (mapping & PAGE_MAPPING_FLAGS)
+	mapping = page->mapping;
+	if ((unsigned long)mapping & PAGE_MAPPING_FLAGS)
 		return NULL;
-	return page->mapping;
+	return mapping;
 }
 
+/* Slow path of page_mapcount() for compound pages */
+int __page_mapcount(struct page *page)
+{
+	int ret;
+
+	ret = atomic_read(&page->_mapcount) + 1;
+	page = compound_head(page);
+	ret += atomic_read(compound_mapcount_ptr(page)) + 1;
+	if (PageDoubleMap(page))
+		ret--;
+	return ret;
+}
+EXPORT_SYMBOL_GPL(__page_mapcount);
+
 int overcommit_ratio_handler(struct ctl_table *table, int write,
 			     void __user *buffer, size_t *lenp,
 			     loff_t *ppos)
@@ -460,17 +451,25 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen)
 	int res = 0;
 	unsigned int len;
 	struct mm_struct *mm = get_task_mm(task);
+	unsigned long arg_start, arg_end, env_start, env_end;
 	if (!mm)
 		goto out;
 	if (!mm->arg_end)
 		goto out_mm;	/* Shh! No looking before we're done */
 
-	len = mm->arg_end - mm->arg_start;
+	down_read(&mm->mmap_sem);
+	arg_start = mm->arg_start;
+	arg_end = mm->arg_end;
+	env_start = mm->env_start;
+	env_end = mm->env_end;
+	up_read(&mm->mmap_sem);
+
+	len = arg_end - arg_start;
 
 	if (len > buflen)
 		len = buflen;
 
-	res = access_process_vm(task, mm->arg_start, buffer, len, 0);
+	res = access_process_vm(task, arg_start, buffer, len, 0);
 
 	/*
 	 * If the nul at the end of args has been overwritten, then
@@ -481,10 +480,10 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen)
 		if (len < res) {
 			res = len;
 		} else {
-			len = mm->env_end - mm->env_start;
+			len = env_end - env_start;
 			if (len > buflen - res)
 				len = buflen - res;
-			res += access_process_vm(task, mm->env_start,
+			res += access_process_vm(task, env_start,
 						 buffer+res, len, 0);
 			res = strnlen(buffer, res);
 		}