---

yaml
---
r: 7023
b: refs/heads/master
c: 1e40cd3
h: refs/heads/master
i:
  7021: c528faf
  7019: 59cf0f6
  7015: bace277
  7007: 33b96fa
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: ed1b58d8b53519e10a35c6a2bb49cac35f439621
+refs/heads/master: 1e40cd383ccc7c9f8b338c56ce28c326e25eb2fe

trunk/fs/aio.c

@@ -567,6 +567,10 @@ static void use_mm(struct mm_struct *mm)
 	atomic_inc(&mm->mm_count);
 	tsk->mm = mm;
 	tsk->active_mm = mm;
+	/*
+	 * Note that on UML this *requires* PF_BORROWED_MM to be set, otherwise
+	 * it won't work. Update it accordingly if you change it here
+	 */
 	activate_mm(active_mm, mm);
 	task_unlock(tsk);
 

trunk/include/asm-um/mmu_context.h

@@ -20,7 +20,15 @@ extern void force_flush_all(void);
 
 static inline void activate_mm(struct mm_struct *old, struct mm_struct *new)
 {
-	if (old != new)
+	/*
+	 * This is called by fs/exec.c and fs/aio.c. In the first case, for an
+	 * exec, we don't need to do anything as we're called from userspace
+	 * and thus going to use a new host PID. In the second, we're called
+	 * from a kernel thread, and thus need to go doing the mmap's on the
+	 * host. Since they're very expensive, we want to avoid that as far as
+	 * possible.
+	 */
+	if (old != new && (current->flags & PF_BORROWED_MM))
 		force_flush_all();
 }