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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
615d6e87 DB |
2 | /* |
3 | * Copyright (C) 2014 Davidlohr Bueso. | |
4 | */ | |
3f07c014 | 5 | #include <linux/sched/signal.h> |
9164bb4a | 6 | #include <linux/sched/task.h> |
615d6e87 DB |
7 | #include <linux/mm.h> |
8 | #include <linux/vmacache.h> | |
ddbf369c DR |
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) | |
615d6e87 DB |
21 | |
22 | /* | |
23 | * Flush vma caches for threads that share a given mm. | |
24 | * | |
25 | * The operation is safe because the caller holds the mmap_sem | |
26 | * exclusively and other threads accessing the vma cache will | |
27 | * have mmap_sem held at least for read, so no extra locking | |
28 | * is required to maintain the vma cache. | |
29 | */ | |
30 | void vmacache_flush_all(struct mm_struct *mm) | |
31 | { | |
32 | struct task_struct *g, *p; | |
33 | ||
f5f302e2 DB |
34 | count_vm_vmacache_event(VMACACHE_FULL_FLUSHES); |
35 | ||
6b4ebc3a DB |
36 | /* |
37 | * Single threaded tasks need not iterate the entire | |
38 | * list of process. We can avoid the flushing as well | |
39 | * since the mm's seqnum was increased and don't have | |
40 | * to worry about other threads' seqnum. Current's | |
41 | * flush will occur upon the next lookup. | |
42 | */ | |
43 | if (atomic_read(&mm->mm_users) == 1) | |
44 | return; | |
45 | ||
615d6e87 DB |
46 | rcu_read_lock(); |
47 | for_each_process_thread(g, p) { | |
48 | /* | |
49 | * Only flush the vmacache pointers as the | |
50 | * mm seqnum is already set and curr's will | |
51 | * be set upon invalidation when the next | |
52 | * lookup is done. | |
53 | */ | |
54 | if (mm == p->mm) | |
55 | vmacache_flush(p); | |
56 | } | |
57 | rcu_read_unlock(); | |
58 | } | |
59 | ||
60 | /* | |
61 | * This task may be accessing a foreign mm via (for example) | |
62 | * get_user_pages()->find_vma(). The vmacache is task-local and this | |
63 | * task's vmacache pertains to a different mm (ie, its own). There is | |
64 | * nothing we can do here. | |
65 | * | |
66 | * Also handle the case where a kernel thread has adopted this mm via use_mm(). | |
67 | * That kernel thread's vmacache is not applicable to this mm. | |
68 | */ | |
a2c1aad3 | 69 | static inline bool vmacache_valid_mm(struct mm_struct *mm) |
615d6e87 DB |
70 | { |
71 | return current->mm == mm && !(current->flags & PF_KTHREAD); | |
72 | } | |
73 | ||
74 | void vmacache_update(unsigned long addr, struct vm_area_struct *newvma) | |
75 | { | |
76 | if (vmacache_valid_mm(newvma->vm_mm)) | |
314ff785 | 77 | current->vmacache.vmas[VMACACHE_HASH(addr)] = newvma; |
615d6e87 DB |
78 | } |
79 | ||
80 | static bool vmacache_valid(struct mm_struct *mm) | |
81 | { | |
82 | struct task_struct *curr; | |
83 | ||
84 | if (!vmacache_valid_mm(mm)) | |
85 | return false; | |
86 | ||
87 | curr = current; | |
314ff785 | 88 | if (mm->vmacache_seqnum != curr->vmacache.seqnum) { |
615d6e87 DB |
89 | /* |
90 | * First attempt will always be invalid, initialize | |
91 | * the new cache for this task here. | |
92 | */ | |
314ff785 | 93 | curr->vmacache.seqnum = mm->vmacache_seqnum; |
615d6e87 DB |
94 | vmacache_flush(curr); |
95 | return false; | |
96 | } | |
97 | return true; | |
98 | } | |
99 | ||
100 | struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr) | |
101 | { | |
ddbf369c | 102 | int idx = VMACACHE_HASH(addr); |
615d6e87 DB |
103 | int i; |
104 | ||
131ddc5c AD |
105 | count_vm_vmacache_event(VMACACHE_FIND_CALLS); |
106 | ||
615d6e87 DB |
107 | if (!vmacache_valid(mm)) |
108 | return NULL; | |
109 | ||
110 | for (i = 0; i < VMACACHE_SIZE; i++) { | |
ddbf369c | 111 | struct vm_area_struct *vma = current->vmacache.vmas[idx]; |
615d6e87 | 112 | |
ddbf369c DR |
113 | if (vma) { |
114 | #ifdef CONFIG_DEBUG_VM_VMACACHE | |
115 | if (WARN_ON_ONCE(vma->vm_mm != mm)) | |
116 | break; | |
117 | #endif | |
118 | if (vma->vm_start <= addr && vma->vm_end > addr) { | |
119 | count_vm_vmacache_event(VMACACHE_FIND_HITS); | |
120 | return vma; | |
121 | } | |
4f115147 | 122 | } |
ddbf369c DR |
123 | if (++idx == VMACACHE_SIZE) |
124 | idx = 0; | |
615d6e87 DB |
125 | } |
126 | ||
127 | return NULL; | |
128 | } | |
129 | ||
130 | #ifndef CONFIG_MMU | |
131 | struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm, | |
132 | unsigned long start, | |
133 | unsigned long end) | |
134 | { | |
ddbf369c | 135 | int idx = VMACACHE_HASH(start); |
615d6e87 DB |
136 | int i; |
137 | ||
131ddc5c AD |
138 | count_vm_vmacache_event(VMACACHE_FIND_CALLS); |
139 | ||
615d6e87 DB |
140 | if (!vmacache_valid(mm)) |
141 | return NULL; | |
142 | ||
143 | for (i = 0; i < VMACACHE_SIZE; i++) { | |
ddbf369c | 144 | struct vm_area_struct *vma = current->vmacache.vmas[idx]; |
615d6e87 | 145 | |
4f115147 DB |
146 | if (vma && vma->vm_start == start && vma->vm_end == end) { |
147 | count_vm_vmacache_event(VMACACHE_FIND_HITS); | |
615d6e87 | 148 | return vma; |
4f115147 | 149 | } |
ddbf369c DR |
150 | if (++idx == VMACACHE_SIZE) |
151 | idx = 0; | |
615d6e87 DB |
152 | } |
153 | ||
154 | return NULL; | |
155 | } | |
156 | #endif |