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 */
vmacache_flush_all(struct mm_struct * mm)16 void vmacache_flush_all(struct mm_struct *mm)
17 {
18 struct task_struct *g, *p;
19
20 count_vm_vmacache_event(VMACACHE_FULL_FLUSHES);
21
22 /*
23 * Single threaded tasks need not iterate the entire
24 * list of process. We can avoid the flushing as well
25 * since the mm's seqnum was increased and don't have
26 * to worry about other threads' seqnum. Current's
27 * flush will occur upon the next lookup.
28 */
29 if (atomic_read(&mm->mm_users) == 1)
30 return;
31
32 rcu_read_lock();
33 for_each_process_thread(g, p) {
34 /*
35 * Only flush the vmacache pointers as the
36 * mm seqnum is already set and curr's will
37 * be set upon invalidation when the next
38 * lookup is done.
39 */
40 if (mm == p->mm)
41 vmacache_flush(p);
42 }
43 rcu_read_unlock();
44 }
45
46 /*
47 * This task may be accessing a foreign mm via (for example)
48 * get_user_pages()->find_vma(). The vmacache is task-local and this
49 * task's vmacache pertains to a different mm (ie, its own). There is
50 * nothing we can do here.
51 *
52 * Also handle the case where a kernel thread has adopted this mm via use_mm().
53 * That kernel thread's vmacache is not applicable to this mm.
54 */
vmacache_valid_mm(struct mm_struct * mm)55 static inline bool vmacache_valid_mm(struct mm_struct *mm)
56 {
57 return current->mm == mm && !(current->flags & PF_KTHREAD);
58 }
59
vmacache_update(unsigned long addr,struct vm_area_struct * newvma)60 void vmacache_update(unsigned long addr, struct vm_area_struct *newvma)
61 {
62 if (vmacache_valid_mm(newvma->vm_mm))
63 current->vmacache[VMACACHE_HASH(addr)] = newvma;
64 }
65
vmacache_valid(struct mm_struct * mm)66 static bool vmacache_valid(struct mm_struct *mm)
67 {
68 struct task_struct *curr;
69
70 if (!vmacache_valid_mm(mm))
71 return false;
72
73 curr = current;
74 if (mm->vmacache_seqnum != curr->vmacache_seqnum) {
75 /*
76 * First attempt will always be invalid, initialize
77 * the new cache for this task here.
78 */
79 curr->vmacache_seqnum = mm->vmacache_seqnum;
80 vmacache_flush(curr);
81 return false;
82 }
83 return true;
84 }
85
vmacache_find(struct mm_struct * mm,unsigned long addr)86 struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
87 {
88 int i;
89
90 count_vm_vmacache_event(VMACACHE_FIND_CALLS);
91
92 if (!vmacache_valid(mm))
93 return NULL;
94
95 for (i = 0; i < VMACACHE_SIZE; i++) {
96 struct vm_area_struct *vma = current->vmacache[i];
97
98 if (!vma)
99 continue;
100 if (WARN_ON_ONCE(vma->vm_mm != mm))
101 break;
102 if (vma->vm_start <= addr && vma->vm_end > addr) {
103 count_vm_vmacache_event(VMACACHE_FIND_HITS);
104 return vma;
105 }
106 }
107
108 return NULL;
109 }
110
111 #ifndef CONFIG_MMU
vmacache_find_exact(struct mm_struct * mm,unsigned long start,unsigned long end)112 struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm,
113 unsigned long start,
114 unsigned long end)
115 {
116 int i;
117
118 count_vm_vmacache_event(VMACACHE_FIND_CALLS);
119
120 if (!vmacache_valid(mm))
121 return NULL;
122
123 for (i = 0; i < VMACACHE_SIZE; i++) {
124 struct vm_area_struct *vma = current->vmacache[i];
125
126 if (vma && vma->vm_start == start && vma->vm_end == end) {
127 count_vm_vmacache_event(VMACACHE_FIND_HITS);
128 return vma;
129 }
130 }
131
132 return NULL;
133 }
134 #endif
135