1 /* Copyright (C) 2009 Red Hat, Inc.
2  *
3  * See ../COPYING for licensing terms.
4  */
5 
6 #include <linux/mm.h>
7 #include <linux/mmu_context.h>
8 #include <linux/export.h>
9 #include <linux/sched.h>
10 
11 #include <asm/mmu_context.h>
12 
13 /*
14  * use_mm
15  *	Makes the calling kernel thread take on the specified
16  *	mm context.
17  *	Called by the retry thread execute retries within the
18  *	iocb issuer's mm context, so that copy_from/to_user
19  *	operations work seamlessly for aio.
20  *	(Note: this routine is intended to be called only
21  *	from a kernel thread context)
22  */
use_mm(struct mm_struct * mm)23 void use_mm(struct mm_struct *mm)
24 {
25 	struct mm_struct *active_mm;
26 	struct task_struct *tsk = current;
27 
28 	task_lock(tsk);
29 	active_mm = tsk->active_mm;
30 	if (active_mm != mm) {
31 		atomic_inc(&mm->mm_count);
32 		tsk->active_mm = mm;
33 	}
34 	tsk->mm = mm;
35 	switch_mm(active_mm, mm, tsk);
36 	task_unlock(tsk);
37 
38 	if (active_mm != mm)
39 		mmdrop(active_mm);
40 }
41 EXPORT_SYMBOL_GPL(use_mm);
42 
43 /*
44  * unuse_mm
45  *	Reverses the effect of use_mm, i.e. releases the
46  *	specified mm context which was earlier taken on
47  *	by the calling kernel thread
48  *	(Note: this routine is intended to be called only
49  *	from a kernel thread context)
50  */
unuse_mm(struct mm_struct * mm)51 void unuse_mm(struct mm_struct *mm)
52 {
53 	struct task_struct *tsk = current;
54 
55 	task_lock(tsk);
56 	sync_mm_rss(tsk, mm);
57 	tsk->mm = NULL;
58 	/* active_mm is still 'mm' */
59 	enter_lazy_tlb(mm, tsk);
60 	task_unlock(tsk);
61 }
62 EXPORT_SYMBOL_GPL(unuse_mm);
63