1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2014 Davidlohr Bueso.
4 */
5 #include <linux/sched/signal.h>
6 #include <linux/sched/task.h>
7 #include <linux/mm.h>
8 #include <linux/vmacache.h>
9
10 /*
11 * Hash based on the pmd of addr if configured with MMU, which provides a good
12 * hit rate for workloads with spatial locality. Otherwise, use pages.
13 */
14 #ifdef CONFIG_MMU
15 #define VMACACHE_SHIFT PMD_SHIFT
16 #else
17 #define VMACACHE_SHIFT PAGE_SHIFT
18 #endif
19 #define VMACACHE_HASH(addr) ((addr >> VMACACHE_SHIFT) & VMACACHE_MASK)
20
21 /*
22 * This task may be accessing a foreign mm via (for example)
23 * get_user_pages()->find_vma(). The vmacache is task-local and this
24 * task's vmacache pertains to a different mm (ie, its own). There is
25 * nothing we can do here.
26 *
27 * Also handle the case where a kernel thread has adopted this mm via
28 * kthread_use_mm(). That kernel thread's vmacache is not applicable to this mm.
29 */
vmacache_valid_mm(struct mm_struct * mm)30 static inline bool vmacache_valid_mm(struct mm_struct *mm)
31 {
32 return current->mm == mm && !(current->flags & PF_KTHREAD);
33 }
34
vmacache_update(unsigned long addr,struct vm_area_struct * newvma)35 void vmacache_update(unsigned long addr, struct vm_area_struct *newvma)
36 {
37 if (vmacache_valid_mm(newvma->vm_mm))
38 current->vmacache.vmas[VMACACHE_HASH(addr)] = newvma;
39 }
40
vmacache_valid(struct mm_struct * mm)41 static bool vmacache_valid(struct mm_struct *mm)
42 {
43 struct task_struct *curr;
44
45 if (!vmacache_valid_mm(mm))
46 return false;
47
48 curr = current;
49 if (mm->vmacache_seqnum != curr->vmacache.seqnum) {
50 /*
51 * First attempt will always be invalid, initialize
52 * the new cache for this task here.
53 */
54 curr->vmacache.seqnum = mm->vmacache_seqnum;
55 vmacache_flush(curr);
56 return false;
57 }
58 return true;
59 }
60
vmacache_find(struct mm_struct * mm,unsigned long addr)61 struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
62 {
63 int idx = VMACACHE_HASH(addr);
64 int i;
65
66 count_vm_vmacache_event(VMACACHE_FIND_CALLS);
67
68 if (!vmacache_valid(mm))
69 return NULL;
70
71 for (i = 0; i < VMACACHE_SIZE; i++) {
72 struct vm_area_struct *vma = current->vmacache.vmas[idx];
73
74 if (vma) {
75 #ifdef CONFIG_DEBUG_VM_VMACACHE
76 if (WARN_ON_ONCE(vma->vm_mm != mm))
77 break;
78 #endif
79 if (vma->vm_start <= addr && vma->vm_end > addr) {
80 count_vm_vmacache_event(VMACACHE_FIND_HITS);
81 return vma;
82 }
83 }
84 if (++idx == VMACACHE_SIZE)
85 idx = 0;
86 }
87
88 return NULL;
89 }
90
91 #ifndef CONFIG_MMU
vmacache_find_exact(struct mm_struct * mm,unsigned long start,unsigned long end)92 struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm,
93 unsigned long start,
94 unsigned long end)
95 {
96 int idx = VMACACHE_HASH(start);
97 int i;
98
99 count_vm_vmacache_event(VMACACHE_FIND_CALLS);
100
101 if (!vmacache_valid(mm))
102 return NULL;
103
104 for (i = 0; i < VMACACHE_SIZE; i++) {
105 struct vm_area_struct *vma = current->vmacache.vmas[idx];
106
107 if (vma && vma->vm_start == start && vma->vm_end == end) {
108 count_vm_vmacache_event(VMACACHE_FIND_HITS);
109 return vma;
110 }
111 if (++idx == VMACACHE_SIZE)
112 idx = 0;
113 }
114
115 return NULL;
116 }
117 #endif
118