208 lines
6.3 KiB
C
208 lines
6.3 KiB
C
/*
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* mm/prio_tree.c - priority search tree for mapping->i_mmap
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*
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* Copyright (C) 2004, Rajesh Venkatasubramanian <vrajesh@umich.edu>
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*
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* This file is released under the GPL v2.
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*
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* Based on the radix priority search tree proposed by Edward M. McCreight
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* SIAM Journal of Computing, vol. 14, no.2, pages 257-276, May 1985
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*
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* 02Feb2004 Initial version
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*/
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#include <linux/mm.h>
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#include <linux/prio_tree.h>
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/*
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* See lib/prio_tree.c for details on the general radix priority search tree
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* code.
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*/
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/*
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* The following #defines are mirrored from lib/prio_tree.c. They're only used
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* for debugging, and should be removed (along with the debugging code using
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* them) when switching also VMAs to the regular prio_tree code.
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*/
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#define RADIX_INDEX(vma) ((vma)->vm_pgoff)
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#define VMA_SIZE(vma) (((vma)->vm_end - (vma)->vm_start) >> PAGE_SHIFT)
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/* avoid overflow */
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#define HEAP_INDEX(vma) ((vma)->vm_pgoff + (VMA_SIZE(vma) - 1))
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/*
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* Radix priority search tree for address_space->i_mmap
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*
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* For each vma that map a unique set of file pages i.e., unique [radix_index,
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* heap_index] value, we have a corresponing priority search tree node. If
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* multiple vmas have identical [radix_index, heap_index] value, then one of
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* them is used as a tree node and others are stored in a vm_set list. The tree
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* node points to the first vma (head) of the list using vm_set.head.
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*
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* prio_tree_root
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* |
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* A vm_set.head
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* / \ /
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* L R -> H-I-J-K-M-N-O-P-Q-S
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* ^ ^ <-- vm_set.list -->
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* tree nodes
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*
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* We need some way to identify whether a vma is a tree node, head of a vm_set
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* list, or just a member of a vm_set list. We cannot use vm_flags to store
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* such information. The reason is, in the above figure, it is possible that
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* vm_flags' of R and H are covered by the different mmap_sems. When R is
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* removed under R->mmap_sem, H replaces R as a tree node. Since we do not hold
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* H->mmap_sem, we cannot use H->vm_flags for marking that H is a tree node now.
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* That's why some trick involving shared.vm_set.parent is used for identifying
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* tree nodes and list head nodes.
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*
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* vma radix priority search tree node rules:
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*
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* vma->shared.vm_set.parent != NULL ==> a tree node
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* vma->shared.vm_set.head != NULL ==> list of others mapping same range
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* vma->shared.vm_set.head == NULL ==> no others map the same range
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*
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* vma->shared.vm_set.parent == NULL
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* vma->shared.vm_set.head != NULL ==> list head of vmas mapping same range
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* vma->shared.vm_set.head == NULL ==> a list node
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*/
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/*
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* Add a new vma known to map the same set of pages as the old vma:
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* useful for fork's dup_mmap as well as vma_prio_tree_insert below.
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* Note that it just happens to work correctly on i_mmap_nonlinear too.
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*/
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void vma_prio_tree_add(struct vm_area_struct *vma, struct vm_area_struct *old)
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{
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/* Leave these BUG_ONs till prio_tree patch stabilizes */
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BUG_ON(RADIX_INDEX(vma) != RADIX_INDEX(old));
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BUG_ON(HEAP_INDEX(vma) != HEAP_INDEX(old));
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vma->shared.vm_set.head = NULL;
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vma->shared.vm_set.parent = NULL;
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if (!old->shared.vm_set.parent)
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list_add(&vma->shared.vm_set.list,
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&old->shared.vm_set.list);
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else if (old->shared.vm_set.head)
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list_add_tail(&vma->shared.vm_set.list,
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&old->shared.vm_set.head->shared.vm_set.list);
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else {
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INIT_LIST_HEAD(&vma->shared.vm_set.list);
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vma->shared.vm_set.head = old;
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old->shared.vm_set.head = vma;
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}
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}
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void vma_prio_tree_insert(struct vm_area_struct *vma,
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struct prio_tree_root *root)
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{
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struct prio_tree_node *ptr;
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struct vm_area_struct *old;
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vma->shared.vm_set.head = NULL;
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ptr = raw_prio_tree_insert(root, &vma->shared.prio_tree_node);
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if (ptr != (struct prio_tree_node *) &vma->shared.prio_tree_node) {
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old = prio_tree_entry(ptr, struct vm_area_struct,
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shared.prio_tree_node);
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vma_prio_tree_add(vma, old);
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}
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}
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void vma_prio_tree_remove(struct vm_area_struct *vma,
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struct prio_tree_root *root)
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{
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struct vm_area_struct *node, *head, *new_head;
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if (!vma->shared.vm_set.head) {
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if (!vma->shared.vm_set.parent)
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list_del_init(&vma->shared.vm_set.list);
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else
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raw_prio_tree_remove(root, &vma->shared.prio_tree_node);
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} else {
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/* Leave this BUG_ON till prio_tree patch stabilizes */
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BUG_ON(vma->shared.vm_set.head->shared.vm_set.head != vma);
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if (vma->shared.vm_set.parent) {
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head = vma->shared.vm_set.head;
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if (!list_empty(&head->shared.vm_set.list)) {
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new_head = list_entry(
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head->shared.vm_set.list.next,
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struct vm_area_struct,
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shared.vm_set.list);
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list_del_init(&head->shared.vm_set.list);
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} else
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new_head = NULL;
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raw_prio_tree_replace(root, &vma->shared.prio_tree_node,
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&head->shared.prio_tree_node);
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head->shared.vm_set.head = new_head;
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if (new_head)
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new_head->shared.vm_set.head = head;
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} else {
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node = vma->shared.vm_set.head;
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if (!list_empty(&vma->shared.vm_set.list)) {
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new_head = list_entry(
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vma->shared.vm_set.list.next,
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struct vm_area_struct,
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shared.vm_set.list);
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list_del_init(&vma->shared.vm_set.list);
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node->shared.vm_set.head = new_head;
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new_head->shared.vm_set.head = node;
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} else
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node->shared.vm_set.head = NULL;
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}
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}
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}
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/*
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* Helper function to enumerate vmas that map a given file page or a set of
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* contiguous file pages. The function returns vmas that at least map a single
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* page in the given range of contiguous file pages.
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*/
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struct vm_area_struct *vma_prio_tree_next(struct vm_area_struct *vma,
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struct prio_tree_iter *iter)
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{
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struct prio_tree_node *ptr;
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struct vm_area_struct *next;
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if (!vma) {
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/*
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* First call is with NULL vma
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*/
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ptr = prio_tree_next(iter);
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if (ptr) {
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next = prio_tree_entry(ptr, struct vm_area_struct,
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shared.prio_tree_node);
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prefetch(next->shared.vm_set.head);
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return next;
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} else
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return NULL;
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}
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if (vma->shared.vm_set.parent) {
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if (vma->shared.vm_set.head) {
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next = vma->shared.vm_set.head;
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prefetch(next->shared.vm_set.list.next);
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return next;
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}
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} else {
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next = list_entry(vma->shared.vm_set.list.next,
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struct vm_area_struct, shared.vm_set.list);
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if (!next->shared.vm_set.head) {
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prefetch(next->shared.vm_set.list.next);
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return next;
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}
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}
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ptr = prio_tree_next(iter);
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if (ptr) {
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next = prio_tree_entry(ptr, struct vm_area_struct,
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shared.prio_tree_node);
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prefetch(next->shared.vm_set.head);
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return next;
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} else
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return NULL;
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}
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