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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /mm/prio_tree.c
downloadconfigs-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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+/*
+ * mm/prio_tree.c - priority search tree for mapping->i_mmap
+ *
+ * Copyright (C) 2004, Rajesh Venkatasubramanian <vrajesh@umich.edu>
+ *
+ * This file is released under the GPL v2.
+ *
+ * Based on the radix priority search tree proposed by Edward M. McCreight
+ * SIAM Journal of Computing, vol. 14, no.2, pages 257-276, May 1985
+ *
+ * 02Feb2004 Initial version
+ */
+
+#include <linux/mm.h>
+#include <linux/prio_tree.h>
+
+/*
+ * See lib/prio_tree.c for details on the general radix priority search tree
+ * code.
+ */
+
+/*
+ * The following #defines are mirrored from lib/prio_tree.c. They're only used
+ * for debugging, and should be removed (along with the debugging code using
+ * them) when switching also VMAs to the regular prio_tree code.
+ */
+
+#define RADIX_INDEX(vma) ((vma)->vm_pgoff)
+#define VMA_SIZE(vma) (((vma)->vm_end - (vma)->vm_start) >> PAGE_SHIFT)
+/* avoid overflow */
+#define HEAP_INDEX(vma) ((vma)->vm_pgoff + (VMA_SIZE(vma) - 1))
+
+/*
+ * Radix priority search tree for address_space->i_mmap
+ *
+ * For each vma that map a unique set of file pages i.e., unique [radix_index,
+ * heap_index] value, we have a corresponing priority search tree node. If
+ * multiple vmas have identical [radix_index, heap_index] value, then one of
+ * them is used as a tree node and others are stored in a vm_set list. The tree
+ * node points to the first vma (head) of the list using vm_set.head.
+ *
+ * prio_tree_root
+ * |
+ * A vm_set.head
+ * / \ /
+ * L R -> H-I-J-K-M-N-O-P-Q-S
+ * ^ ^ <-- vm_set.list -->
+ * tree nodes
+ *
+ * We need some way to identify whether a vma is a tree node, head of a vm_set
+ * list, or just a member of a vm_set list. We cannot use vm_flags to store
+ * such information. The reason is, in the above figure, it is possible that
+ * vm_flags' of R and H are covered by the different mmap_sems. When R is
+ * removed under R->mmap_sem, H replaces R as a tree node. Since we do not hold
+ * H->mmap_sem, we cannot use H->vm_flags for marking that H is a tree node now.
+ * That's why some trick involving shared.vm_set.parent is used for identifying
+ * tree nodes and list head nodes.
+ *
+ * vma radix priority search tree node rules:
+ *
+ * vma->shared.vm_set.parent != NULL ==> a tree node
+ * vma->shared.vm_set.head != NULL ==> list of others mapping same range
+ * vma->shared.vm_set.head == NULL ==> no others map the same range
+ *
+ * vma->shared.vm_set.parent == NULL
+ * vma->shared.vm_set.head != NULL ==> list head of vmas mapping same range
+ * vma->shared.vm_set.head == NULL ==> a list node
+ */
+
+/*
+ * Add a new vma known to map the same set of pages as the old vma:
+ * useful for fork's dup_mmap as well as vma_prio_tree_insert below.
+ * Note that it just happens to work correctly on i_mmap_nonlinear too.
+ */
+void vma_prio_tree_add(struct vm_area_struct *vma, struct vm_area_struct *old)
+{
+ /* Leave these BUG_ONs till prio_tree patch stabilizes */
+ BUG_ON(RADIX_INDEX(vma) != RADIX_INDEX(old));
+ BUG_ON(HEAP_INDEX(vma) != HEAP_INDEX(old));
+
+ vma->shared.vm_set.head = NULL;
+ vma->shared.vm_set.parent = NULL;
+
+ if (!old->shared.vm_set.parent)
+ list_add(&vma->shared.vm_set.list,
+ &old->shared.vm_set.list);
+ else if (old->shared.vm_set.head)
+ list_add_tail(&vma->shared.vm_set.list,
+ &old->shared.vm_set.head->shared.vm_set.list);
+ else {
+ INIT_LIST_HEAD(&vma->shared.vm_set.list);
+ vma->shared.vm_set.head = old;
+ old->shared.vm_set.head = vma;
+ }
+}
+
+void vma_prio_tree_insert(struct vm_area_struct *vma,
+ struct prio_tree_root *root)
+{
+ struct prio_tree_node *ptr;
+ struct vm_area_struct *old;
+
+ vma->shared.vm_set.head = NULL;
+
+ ptr = raw_prio_tree_insert(root, &vma->shared.prio_tree_node);
+ if (ptr != (struct prio_tree_node *) &vma->shared.prio_tree_node) {
+ old = prio_tree_entry(ptr, struct vm_area_struct,
+ shared.prio_tree_node);
+ vma_prio_tree_add(vma, old);
+ }
+}
+
+void vma_prio_tree_remove(struct vm_area_struct *vma,
+ struct prio_tree_root *root)
+{
+ struct vm_area_struct *node, *head, *new_head;
+
+ if (!vma->shared.vm_set.head) {
+ if (!vma->shared.vm_set.parent)
+ list_del_init(&vma->shared.vm_set.list);
+ else
+ raw_prio_tree_remove(root, &vma->shared.prio_tree_node);
+ } else {
+ /* Leave this BUG_ON till prio_tree patch stabilizes */
+ BUG_ON(vma->shared.vm_set.head->shared.vm_set.head != vma);
+ if (vma->shared.vm_set.parent) {
+ head = vma->shared.vm_set.head;
+ if (!list_empty(&head->shared.vm_set.list)) {
+ new_head = list_entry(
+ head->shared.vm_set.list.next,
+ struct vm_area_struct,
+ shared.vm_set.list);
+ list_del_init(&head->shared.vm_set.list);
+ } else
+ new_head = NULL;
+
+ raw_prio_tree_replace(root, &vma->shared.prio_tree_node,
+ &head->shared.prio_tree_node);
+ head->shared.vm_set.head = new_head;
+ if (new_head)
+ new_head->shared.vm_set.head = head;
+
+ } else {
+ node = vma->shared.vm_set.head;
+ if (!list_empty(&vma->shared.vm_set.list)) {
+ new_head = list_entry(
+ vma->shared.vm_set.list.next,
+ struct vm_area_struct,
+ shared.vm_set.list);
+ list_del_init(&vma->shared.vm_set.list);
+ node->shared.vm_set.head = new_head;
+ new_head->shared.vm_set.head = node;
+ } else
+ node->shared.vm_set.head = NULL;
+ }
+ }
+}
+
+/*
+ * Helper function to enumerate vmas that map a given file page or a set of
+ * contiguous file pages. The function returns vmas that at least map a single
+ * page in the given range of contiguous file pages.
+ */
+struct vm_area_struct *vma_prio_tree_next(struct vm_area_struct *vma,
+ struct prio_tree_iter *iter)
+{
+ struct prio_tree_node *ptr;
+ struct vm_area_struct *next;
+
+ if (!vma) {
+ /*
+ * First call is with NULL vma
+ */
+ ptr = prio_tree_next(iter);
+ if (ptr) {
+ next = prio_tree_entry(ptr, struct vm_area_struct,
+ shared.prio_tree_node);
+ prefetch(next->shared.vm_set.head);
+ return next;
+ } else
+ return NULL;
+ }
+
+ if (vma->shared.vm_set.parent) {
+ if (vma->shared.vm_set.head) {
+ next = vma->shared.vm_set.head;
+ prefetch(next->shared.vm_set.list.next);
+ return next;
+ }
+ } else {
+ next = list_entry(vma->shared.vm_set.list.next,
+ struct vm_area_struct, shared.vm_set.list);
+ if (!next->shared.vm_set.head) {
+ prefetch(next->shared.vm_set.list.next);
+ return next;
+ }
+ }
+
+ ptr = prio_tree_next(iter);
+ if (ptr) {
+ next = prio_tree_entry(ptr, struct vm_area_struct,
+ shared.prio_tree_node);
+ prefetch(next->shared.vm_set.head);
+ return next;
+ } else
+ return NULL;
+}