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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 | /* |
21 | * Single threaded tasks need not iterate the entire |
22 | * list of process. We can avoid the flushing as well |
23 | * since the mm's seqnum was increased and don't have |
24 | * to worry about other threads' seqnum. Current's |
25 | * flush will occur upon the next lookup. |
26 | */ |
27 | if (atomic_read(&mm->mm_users) == 1) |
28 | return; |
29 | |
30 | rcu_read_lock(); |
31 | for_each_process_thread(g, p) { |
32 | /* |
33 | * Only flush the vmacache pointers as the |
34 | * mm seqnum is already set and curr's will |
35 | * be set upon invalidation when the next |
36 | * lookup is done. |
37 | */ |
38 | if (mm == p->mm) |
39 | vmacache_flush(p); |
40 | } |
41 | rcu_read_unlock(); |
42 | } |
43 | |
44 | /* |
45 | * This task may be accessing a foreign mm via (for example) |
46 | * get_user_pages()->find_vma(). The vmacache is task-local and this |
47 | * task's vmacache pertains to a different mm (ie, its own). There is |
48 | * nothing we can do here. |
49 | * |
50 | * Also handle the case where a kernel thread has adopted this mm via use_mm(). |
51 | * That kernel thread's vmacache is not applicable to this mm. |
52 | */ |
53 | static bool vmacache_valid_mm(struct mm_struct *mm) |
54 | { |
55 | return current->mm == mm && !(current->flags & PF_KTHREAD); |
56 | } |
57 | |
58 | void vmacache_update(unsigned long addr, struct vm_area_struct *newvma) |
59 | { |
60 | if (vmacache_valid_mm(newvma->vm_mm)) |
61 | current->vmacache[VMACACHE_HASH(addr)] = newvma; |
62 | } |
63 | |
64 | static bool vmacache_valid(struct mm_struct *mm) |
65 | { |
66 | struct task_struct *curr; |
67 | |
68 | if (!vmacache_valid_mm(mm)) |
69 | return false; |
70 | |
71 | curr = current; |
72 | if (mm->vmacache_seqnum != curr->vmacache_seqnum) { |
73 | /* |
74 | * First attempt will always be invalid, initialize |
75 | * the new cache for this task here. |
76 | */ |
77 | curr->vmacache_seqnum = mm->vmacache_seqnum; |
78 | vmacache_flush(curr); |
79 | return false; |
80 | } |
81 | return true; |
82 | } |
83 | |
84 | struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr) |
85 | { |
86 | int i; |
87 | |
88 | if (!vmacache_valid(mm)) |
89 | return NULL; |
90 | |
91 | count_vm_vmacache_event(VMACACHE_FIND_CALLS); |
92 | |
93 | for (i = 0; i < VMACACHE_SIZE; i++) { |
94 | struct vm_area_struct *vma = current->vmacache[i]; |
95 | |
96 | if (!vma) |
97 | continue; |
98 | if (WARN_ON_ONCE(vma->vm_mm != mm)) |
99 | break; |
100 | if (vma->vm_start <= addr && vma->vm_end > addr) { |
101 | count_vm_vmacache_event(VMACACHE_FIND_HITS); |
102 | return vma; |
103 | } |
104 | } |
105 | |
106 | return NULL; |
107 | } |
108 | |
109 | #ifndef CONFIG_MMU |
110 | struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm, |
111 | unsigned long start, |
112 | unsigned long end) |
113 | { |
114 | int i; |
115 | |
116 | if (!vmacache_valid(mm)) |
117 | return NULL; |
118 | |
119 | count_vm_vmacache_event(VMACACHE_FIND_CALLS); |
120 | |
121 | for (i = 0; i < VMACACHE_SIZE; i++) { |
122 | struct vm_area_struct *vma = current->vmacache[i]; |
123 | |
124 | if (vma && vma->vm_start == start && vma->vm_end == end) { |
125 | count_vm_vmacache_event(VMACACHE_FIND_HITS); |
126 | return vma; |
127 | } |
128 | } |
129 | |
130 | return NULL; |
131 | } |
132 | #endif |
133 |
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Tags:
od-2011-09-04
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v2.6.34-rc5
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