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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 | */ |
16 | void 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 | */ |
43 | static bool vmacache_valid_mm(struct mm_struct *mm) |
44 | { |
45 | return current->mm == mm && !(current->flags & PF_KTHREAD); |
46 | } |
47 | |
48 | void 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 | |
54 | static 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 | |
74 | struct 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 |
96 | struct 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 |
115 |
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