path: root/mm/vmacache.c (plain)
blob: c9ca3dd46b971e2911dba9b5d569cdeb9f509ec2

1	/*
2	* Copyright (C) 2014 Davidlohr Bueso.
3	*/
4	#include <linux/sched.h>
5	#include <linux/mm.h>
6	#include <linux/vmacache.h>
7
8	/*
9	* This task may be accessing a foreign mm via (for example)
10	* get_user_pages()->find_vma(). The vmacache is task-local and this
11	* task's vmacache pertains to a different mm (ie, its own). There is
12	* nothing we can do here.
13	*
14	* Also handle the case where a kernel thread has adopted this mm via use_mm().
15	* That kernel thread's vmacache is not applicable to this mm.
16	*/
17	static inline bool vmacache_valid_mm(struct mm_struct *mm)
18	{
19	return current->mm == mm && !(current->flags & PF_KTHREAD);
20	}
21
22	void vmacache_update(unsigned long addr, struct vm_area_struct *newvma)
23	{
24	if (vmacache_valid_mm(newvma->vm_mm))
25	current->vmacache[VMACACHE_HASH(addr)] = newvma;
26	}
27
28	static bool vmacache_valid(struct mm_struct *mm)
29	{
30	struct task_struct *curr;
31
32	if (!vmacache_valid_mm(mm))
33	return false;
34
35	curr = current;
36	if (mm->vmacache_seqnum != curr->vmacache_seqnum) {
37	/*
38	* First attempt will always be invalid, initialize
39	* the new cache for this task here.
40	*/
41	curr->vmacache_seqnum = mm->vmacache_seqnum;
42	vmacache_flush(curr);
43	return false;
44	}
45	return true;
46	}
47
48	struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
49	{
50	int i;
51
52	count_vm_vmacache_event(VMACACHE_FIND_CALLS);
53
54	if (!vmacache_valid(mm))
55	return NULL;
56
57	for (i = 0; i < VMACACHE_SIZE; i++) {
58	struct vm_area_struct *vma = current->vmacache[i];
59
60	if (!vma)
61	continue;
62	if (WARN_ON_ONCE(vma->vm_mm != mm))
63	break;
64	if (vma->vm_start <= addr && vma->vm_end > addr) {
65	count_vm_vmacache_event(VMACACHE_FIND_HITS);
66	return vma;
67	}
68	}
69
70	return NULL;
71	}
72
73	#ifndef CONFIG_MMU
74	struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm,
75	unsigned long start,
76	unsigned long end)
77	{
78	int i;
79
80	count_vm_vmacache_event(VMACACHE_FIND_CALLS);
81
82	if (!vmacache_valid(mm))
83	return NULL;
84
85	for (i = 0; i < VMACACHE_SIZE; i++) {
86	struct vm_area_struct *vma = current->vmacache[i];
87
88	if (vma && vma->vm_start == start && vma->vm_end == end) {
89	count_vm_vmacache_event(VMACACHE_FIND_HITS);
90	return vma;
91	}
92	}
93
94	return NULL;
95	}
96	#endif
97