2 * mm/prio_tree.c - priority search tree for mapping->i_mmap
4 * Copyright (C) 2004, Rajesh Venkatasubramanian <vrajesh@umich.edu>
6 * This file is released under the GPL v2.
8 * Based on the radix priority search tree proposed by Edward M. McCreight
9 * SIAM Journal of Computing, vol. 14, no.2, pages 257-276, May 1985
11 * 02Feb2004 Initial version
15 #include <linux/prio_tree.h>
18 * See lib/prio_tree.c for details on the general radix priority search tree
23 * The following #defines are mirrored from lib/prio_tree.c. They're only used
24 * for debugging, and should be removed (along with the debugging code using
25 * them) when switching also VMAs to the regular prio_tree code.
28 #define RADIX_INDEX(vma) ((vma)->vm_pgoff)
29 #define VMA_SIZE(vma) (((vma)->vm_end - (vma)->vm_start) >> PAGE_SHIFT)
31 #define HEAP_INDEX(vma) ((vma)->vm_pgoff + (VMA_SIZE(vma) - 1))
34 * Radix priority search tree for address_space->i_mmap
36 * For each vma that map a unique set of file pages i.e., unique [radix_index,
37 * heap_index] value, we have a corresponding priority search tree node. If
38 * multiple vmas have identical [radix_index, heap_index] value, then one of
39 * them is used as a tree node and others are stored in a vm_set list. The tree
40 * node points to the first vma (head) of the list using vm_set.head.
46 * L R -> H-I-J-K-M-N-O-P-Q-S
47 * ^ ^ <-- vm_set.list -->
50 * We need some way to identify whether a vma is a tree node, head of a vm_set
51 * list, or just a member of a vm_set list. We cannot use vm_flags to store
52 * such information. The reason is, in the above figure, it is possible that
53 * vm_flags' of R and H are covered by the different mmap_sems. When R is
54 * removed under R->mmap_sem, H replaces R as a tree node. Since we do not hold
55 * H->mmap_sem, we cannot use H->vm_flags for marking that H is a tree node now.
56 * That's why some trick involving shared.vm_set.parent is used for identifying
57 * tree nodes and list head nodes.
59 * vma radix priority search tree node rules:
61 * vma->shared.vm_set.parent != NULL ==> a tree node
62 * vma->shared.vm_set.head != NULL ==> list of others mapping same range
63 * vma->shared.vm_set.head == NULL ==> no others map the same range
65 * vma->shared.vm_set.parent == NULL
66 * vma->shared.vm_set.head != NULL ==> list head of vmas mapping same range
67 * vma->shared.vm_set.head == NULL ==> a list node
71 * Add a new vma known to map the same set of pages as the old vma:
72 * useful for fork's dup_mmap as well as vma_prio_tree_insert below.
73 * Note that it just happens to work correctly on i_mmap_nonlinear too.
75 void vma_prio_tree_add(struct vm_area_struct
*vma
, struct vm_area_struct
*old
)
77 /* Leave these BUG_ONs till prio_tree patch stabilizes */
78 BUG_ON(RADIX_INDEX(vma
) != RADIX_INDEX(old
));
79 BUG_ON(HEAP_INDEX(vma
) != HEAP_INDEX(old
));
81 vma
->shared
.vm_set
.head
= NULL
;
82 vma
->shared
.vm_set
.parent
= NULL
;
84 if (!old
->shared
.vm_set
.parent
)
85 list_add(&vma
->shared
.vm_set
.list
,
86 &old
->shared
.vm_set
.list
);
87 else if (old
->shared
.vm_set
.head
)
88 list_add_tail(&vma
->shared
.vm_set
.list
,
89 &old
->shared
.vm_set
.head
->shared
.vm_set
.list
);
91 INIT_LIST_HEAD(&vma
->shared
.vm_set
.list
);
92 vma
->shared
.vm_set
.head
= old
;
93 old
->shared
.vm_set
.head
= vma
;
97 void vma_prio_tree_insert(struct vm_area_struct
*vma
,
98 struct prio_tree_root
*root
)
100 struct prio_tree_node
*ptr
;
101 struct vm_area_struct
*old
;
103 vma
->shared
.vm_set
.head
= NULL
;
105 ptr
= raw_prio_tree_insert(root
, &vma
->shared
.prio_tree_node
);
106 if (ptr
!= (struct prio_tree_node
*) &vma
->shared
.prio_tree_node
) {
107 old
= prio_tree_entry(ptr
, struct vm_area_struct
,
108 shared
.prio_tree_node
);
109 vma_prio_tree_add(vma
, old
);
113 void vma_prio_tree_remove(struct vm_area_struct
*vma
,
114 struct prio_tree_root
*root
)
116 struct vm_area_struct
*node
, *head
, *new_head
;
118 if (!vma
->shared
.vm_set
.head
) {
119 if (!vma
->shared
.vm_set
.parent
)
120 list_del_init(&vma
->shared
.vm_set
.list
);
122 raw_prio_tree_remove(root
, &vma
->shared
.prio_tree_node
);
124 /* Leave this BUG_ON till prio_tree patch stabilizes */
125 BUG_ON(vma
->shared
.vm_set
.head
->shared
.vm_set
.head
!= vma
);
126 if (vma
->shared
.vm_set
.parent
) {
127 head
= vma
->shared
.vm_set
.head
;
128 if (!list_empty(&head
->shared
.vm_set
.list
)) {
129 new_head
= list_entry(
130 head
->shared
.vm_set
.list
.next
,
131 struct vm_area_struct
,
133 list_del_init(&head
->shared
.vm_set
.list
);
137 raw_prio_tree_replace(root
, &vma
->shared
.prio_tree_node
,
138 &head
->shared
.prio_tree_node
);
139 head
->shared
.vm_set
.head
= new_head
;
141 new_head
->shared
.vm_set
.head
= head
;
144 node
= vma
->shared
.vm_set
.head
;
145 if (!list_empty(&vma
->shared
.vm_set
.list
)) {
146 new_head
= list_entry(
147 vma
->shared
.vm_set
.list
.next
,
148 struct vm_area_struct
,
150 list_del_init(&vma
->shared
.vm_set
.list
);
151 node
->shared
.vm_set
.head
= new_head
;
152 new_head
->shared
.vm_set
.head
= node
;
154 node
->shared
.vm_set
.head
= NULL
;
160 * Helper function to enumerate vmas that map a given file page or a set of
161 * contiguous file pages. The function returns vmas that at least map a single
162 * page in the given range of contiguous file pages.
164 struct vm_area_struct
*vma_prio_tree_next(struct vm_area_struct
*vma
,
165 struct prio_tree_iter
*iter
)
167 struct prio_tree_node
*ptr
;
168 struct vm_area_struct
*next
;
172 * First call is with NULL vma
174 ptr
= prio_tree_next(iter
);
176 next
= prio_tree_entry(ptr
, struct vm_area_struct
,
177 shared
.prio_tree_node
);
178 prefetch(next
->shared
.vm_set
.head
);
184 if (vma
->shared
.vm_set
.parent
) {
185 if (vma
->shared
.vm_set
.head
) {
186 next
= vma
->shared
.vm_set
.head
;
187 prefetch(next
->shared
.vm_set
.list
.next
);
191 next
= list_entry(vma
->shared
.vm_set
.list
.next
,
192 struct vm_area_struct
, shared
.vm_set
.list
);
193 if (!next
->shared
.vm_set
.head
) {
194 prefetch(next
->shared
.vm_set
.list
.next
);
199 ptr
= prio_tree_next(iter
);
201 next
= prio_tree_entry(ptr
, struct vm_area_struct
,
202 shared
.prio_tree_node
);
203 prefetch(next
->shared
.vm_set
.head
);
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