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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 */
30static inline bool vmacache_valid_mm(struct mm_struct *mm)
31{
32 return current->mm == mm && !(current->flags & PF_KTHREAD);
33}
34
35void 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
41static 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
61struct 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
92struct 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
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 * Flush vma caches for threads that share a given mm.
10 *
11 * The operation is safe because the caller holds the mmap_sem
12 * exclusively and other threads accessing the vma cache will
13 * have mmap_sem held at least for read, so no extra locking
14 * is required to maintain the vma cache.
15 */
16void vmacache_flush_all(struct mm_struct *mm)
17{
18 struct task_struct *g, *p;
19
20 rcu_read_lock();
21 for_each_process_thread(g, p) {
22 /*
23 * Only flush the vmacache pointers as the
24 * mm seqnum is already set and curr's will
25 * be set upon invalidation when the next
26 * lookup is done.
27 */
28 if (mm == p->mm)
29 vmacache_flush(p);
30 }
31 rcu_read_unlock();
32}
33
34/*
35 * This task may be accessing a foreign mm via (for example)
36 * get_user_pages()->find_vma(). The vmacache is task-local and this
37 * task's vmacache pertains to a different mm (ie, its own). There is
38 * nothing we can do here.
39 *
40 * Also handle the case where a kernel thread has adopted this mm via use_mm().
41 * That kernel thread's vmacache is not applicable to this mm.
42 */
43static bool vmacache_valid_mm(struct mm_struct *mm)
44{
45 return current->mm == mm && !(current->flags & PF_KTHREAD);
46}
47
48void vmacache_update(unsigned long addr, struct vm_area_struct *newvma)
49{
50 if (vmacache_valid_mm(newvma->vm_mm))
51 current->vmacache[VMACACHE_HASH(addr)] = newvma;
52}
53
54static bool vmacache_valid(struct mm_struct *mm)
55{
56 struct task_struct *curr;
57
58 if (!vmacache_valid_mm(mm))
59 return false;
60
61 curr = current;
62 if (mm->vmacache_seqnum != curr->vmacache_seqnum) {
63 /*
64 * First attempt will always be invalid, initialize
65 * the new cache for this task here.
66 */
67 curr->vmacache_seqnum = mm->vmacache_seqnum;
68 vmacache_flush(curr);
69 return false;
70 }
71 return true;
72}
73
74struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
75{
76 int i;
77
78 if (!vmacache_valid(mm))
79 return NULL;
80
81 for (i = 0; i < VMACACHE_SIZE; i++) {
82 struct vm_area_struct *vma = current->vmacache[i];
83
84 if (!vma)
85 continue;
86 if (WARN_ON_ONCE(vma->vm_mm != mm))
87 break;
88 if (vma->vm_start <= addr && vma->vm_end > addr)
89 return vma;
90 }
91
92 return NULL;
93}
94
95#ifndef CONFIG_MMU
96struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm,
97 unsigned long start,
98 unsigned long end)
99{
100 int i;
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[i];
107
108 if (vma && vma->vm_start == start && vma->vm_end == end)
109 return vma;
110 }
111
112 return NULL;
113}
114#endif