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 */
vmacache_valid_mm(struct mm_struct * mm)17 static inline bool vmacache_valid_mm(struct mm_struct *mm)
18 {
19 return current->mm == mm && !(current->flags & PF_KTHREAD);
20 }
21
vmacache_update(unsigned long addr,struct vm_area_struct * newvma)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
vmacache_valid(struct mm_struct * mm)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
vmacache_find(struct mm_struct * mm,unsigned long addr)48 struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
49 {
50 int i;
51
52 if (!vmacache_valid(mm))
53 return NULL;
54
55 count_vm_vmacache_event(VMACACHE_FIND_CALLS);
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
vmacache_find_exact(struct mm_struct * mm,unsigned long start,unsigned long end)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 if (!vmacache_valid(mm))
81 return NULL;
82
83 count_vm_vmacache_event(VMACACHE_FIND_CALLS);
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