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615d6e87 DB |
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 | ||
50f5aa8a LT |
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) | |
615d6e87 | 89 | return vma; |
615d6e87 DB |
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 |