mm: get rid of vmacache_flush_all() entirely
[muen/linux.git] / mm / vmacache.c
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  */
31 static inline bool vmacache_valid_mm(struct mm_struct *mm)
32 {
33         return current->mm == mm && !(current->flags & PF_KTHREAD);
34 }
35
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
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
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
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