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 #include <asm/pgtable.h>
10
11 /*
12 * Hash based on the pmd of addr if configured with MMU, which provides a good
13 * hit rate for workloads with spatial locality. Otherwise, use pages.
14 */
15 #ifdef CONFIG_MMU
16 #define VMACACHE_SHIFT PMD_SHIFT
17 #else
18 #define VMACACHE_SHIFT PAGE_SHIFT
19 #endif
20 #define VMACACHE_HASH(addr) ((addr >> VMACACHE_SHIFT) & VMACACHE_MASK)
21
22 /*
23 * This task may be accessing a foreign mm via (for example)
24 * get_user_pages()->find_vma(). The vmacache is task-local and this
25 * task's vmacache pertains to a different mm (ie, its own). There is
26 * nothing we can do here.
27 *
28 * Also handle the case where a kernel thread has adopted this mm via use_mm().
29 * That kernel thread's vmacache is not applicable to this mm.
30 */
vmacache_valid_mm(struct mm_struct * mm)31 static inline bool vmacache_valid_mm(struct mm_struct *mm)
32 {
33 return current->mm == mm && !(current->flags & PF_KTHREAD);
34 }
35
vmacache_update(unsigned long addr,struct vm_area_struct * newvma)36 void vmacache_update(unsigned long addr, struct vm_area_struct *newvma)
37 {
38 if (vmacache_valid_mm(newvma->vm_mm))
39 current->vmacache.vmas[VMACACHE_HASH(addr)] = newvma;
40 }
41
vmacache_valid(struct mm_struct * mm)42 static bool vmacache_valid(struct mm_struct *mm)
43 {
44 struct task_struct *curr;
45
46 if (!vmacache_valid_mm(mm))
47 return false;
48
49 curr = current;
50 if (mm->vmacache_seqnum != curr->vmacache.seqnum) {
51 /*
52 * First attempt will always be invalid, initialize
53 * the new cache for this task here.
54 */
55 curr->vmacache.seqnum = mm->vmacache_seqnum;
56 vmacache_flush(curr);
57 return false;
58 }
59 return true;
60 }
61
vmacache_find(struct mm_struct * mm,unsigned long addr)62 struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
63 {
64 int idx = VMACACHE_HASH(addr);
65 int i;
66
67 count_vm_vmacache_event(VMACACHE_FIND_CALLS);
68
69 if (!vmacache_valid(mm))
70 return NULL;
71
72 for (i = 0; i < VMACACHE_SIZE; i++) {
73 struct vm_area_struct *vma = current->vmacache.vmas[idx];
74
75 if (vma) {
76 #ifdef CONFIG_DEBUG_VM_VMACACHE
77 if (WARN_ON_ONCE(vma->vm_mm != mm))
78 break;
79 #endif
80 if (vma->vm_start <= addr && vma->vm_end > addr) {
81 count_vm_vmacache_event(VMACACHE_FIND_HITS);
82 return vma;
83 }
84 }
85 if (++idx == VMACACHE_SIZE)
86 idx = 0;
87 }
88
89 return NULL;
90 }
91
92 #ifndef CONFIG_MMU
vmacache_find_exact(struct mm_struct * mm,unsigned long start,unsigned long end)93 struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm,
94 unsigned long start,
95 unsigned long end)
96 {
97 int idx = VMACACHE_HASH(start);
98 int i;
99
100 count_vm_vmacache_event(VMACACHE_FIND_CALLS);
101
102 if (!vmacache_valid(mm))
103 return NULL;
104
105 for (i = 0; i < VMACACHE_SIZE; i++) {
106 struct vm_area_struct *vma = current->vmacache.vmas[idx];
107
108 if (vma && vma->vm_start == start && vma->vm_end == end) {
109 count_vm_vmacache_event(VMACACHE_FIND_HITS);
110 return vma;
111 }
112 if (++idx == VMACACHE_SIZE)
113 idx = 0;
114 }
115
116 return NULL;
117 }
118 #endif
119