mempolicy: introduce __get_vma_policy(), export get_task_policy()

Extract the code which looks for vma's policy from get_vma_policy()
into the new helper, __get_vma_policy(). Export get_task_policy().

Signed-off-by: Oleg Nesterov <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Cyrill Gorcunov <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: oleg-nesterov

include/linux/mempolicy.h

@@ -134,6 +134,9 @@ void mpol_free_shared_policy(struct shared_policy *p);
 struct mempolicy *mpol_shared_policy_lookup(struct shared_policy *sp,
 					    unsigned long idx);
 
+struct mempolicy *get_task_policy(struct task_struct *p);
+struct mempolicy *__get_vma_policy(struct vm_area_struct *vma,
+		unsigned long addr);
 struct mempolicy *get_vma_policy(struct task_struct *tsk,
 		struct vm_area_struct *vma, unsigned long addr);
 bool vma_policy_mof(struct vm_area_struct *vma);

mm/mempolicy.c

@@ -123,7 +123,7 @@ static struct mempolicy default_policy = {
 
 static struct mempolicy preferred_node_policy[MAX_NUMNODES];
 
-static struct mempolicy *get_task_policy(struct task_struct *p)
+struct mempolicy *get_task_policy(struct task_struct *p)
 {
 	struct mempolicy *pol = p->mempolicy;
 	int node;
@@ -1603,23 +1603,8 @@ COMPAT_SYSCALL_DEFINE6(mbind, compat_ulong_t, start, compat_ulong_t, len,
 
 #endif
 
-/*
- * get_vma_policy(@task, @vma, @addr)
- * @task: task for fallback if vma policy == default
- * @vma: virtual memory area whose policy is sought
- * @addr: address in @vma for shared policy lookup
- *
- * Returns effective policy for a VMA at specified address.
- * Falls back to @task or system default policy, as necessary.
- * Current or other task's task mempolicy and non-shared vma policies must be
- * protected by task_lock(task) by the caller.
- * Shared policies [those marked as MPOL_F_SHARED] require an extra reference
- * count--added by the get_policy() vm_op, as appropriate--to protect against
- * freeing by another task.  It is the caller's responsibility to free the
- * extra reference for shared policies.
- */
-struct mempolicy *get_vma_policy(struct task_struct *task,
-		struct vm_area_struct *vma, unsigned long addr)
+struct mempolicy *__get_vma_policy(struct vm_area_struct *vma,
+						unsigned long addr)
 {
 	struct mempolicy *pol = NULL;
 
@@ -1640,6 +1625,29 @@ struct mempolicy *get_vma_policy(struct task_struct *task,
 		}
 	}
 
+	return pol;
+}
+
+/*
+ * get_vma_policy(@task, @vma, @addr)
+ * @task: task for fallback if vma policy == default
+ * @vma: virtual memory area whose policy is sought
+ * @addr: address in @vma for shared policy lookup
+ *
+ * Returns effective policy for a VMA at specified address.
+ * Falls back to @task or system default policy, as necessary.
+ * Current or other task's task mempolicy and non-shared vma policies must be
+ * protected by task_lock(task) by the caller.
+ * Shared policies [those marked as MPOL_F_SHARED] require an extra reference
+ * count--added by the get_policy() vm_op, as appropriate--to protect against
+ * freeing by another task.  It is the caller's responsibility to free the
+ * extra reference for shared policies.
+ */
+struct mempolicy *get_vma_policy(struct task_struct *task,
+		struct vm_area_struct *vma, unsigned long addr)
+{
+	struct mempolicy *pol = __get_vma_policy(vma, addr);
+
 	if (!pol)
 		pol = get_task_policy(task);