uprobes: Fold uprobe_reset_state() into uprobe_dup_mmap()

Now that we have uprobe_dup_mmap() we can fold uprobe_reset_state()
into the new hook and remove it. mmput()->uprobe_clear_state() can't
be called before dup_mmap().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

include/linux/uprobes.h

@@ -118,7 +118,6 @@ extern void uprobe_notify_resume(struct pt_regs *regs);
 extern bool uprobe_deny_signal(void);
 extern bool __weak arch_uprobe_skip_sstep(struct arch_uprobe *aup, struct pt_regs *regs);
 extern void uprobe_clear_state(struct mm_struct *mm);
-extern void uprobe_reset_state(struct mm_struct *mm);
 #else /* !CONFIG_UPROBES */
 struct uprobes_state {
 };
@@ -163,8 +162,5 @@ static inline void uprobe_copy_process(struct task_struct *t)
 static inline void uprobe_clear_state(struct mm_struct *mm)
 {
 }
-static inline void uprobe_reset_state(struct mm_struct *mm)
-{
-}
 #endif /* !CONFIG_UPROBES */
 #endif	/* _LINUX_UPROBES_H */

kernel/events/uprobes.c

@@ -1148,16 +1148,10 @@ void uprobe_clear_state(struct mm_struct *mm)
 	kfree(area);
 }
 
-/*
- * uprobe_reset_state - Free the area allocated for slots.
- */
-void uprobe_reset_state(struct mm_struct *mm)
-{
-	mm->uprobes_state.xol_area = NULL;
-}
-
 void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm)
 {
+	newmm->uprobes_state.xol_area = NULL;
+
 	if (test_bit(MMF_HAS_UPROBES, &oldmm->flags))
 		set_bit(MMF_HAS_UPROBES, &newmm->flags);
 }

kernel/fork.c

@@ -837,8 +837,6 @@ struct mm_struct *dup_mm(struct task_struct *tsk)
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	mm->pmd_huge_pte = NULL;
 #endif
-	uprobe_reset_state(mm);
-
 	if (!mm_init(mm, tsk))
 		goto fail_nomem;