From: Hugh Dickins <hugh@veritas.com>
Rajesh Venkatasubramanian's implementation of a radix priority search tree of
vmas, to handle object-based reverse mapping corner cases well.
Amongst the objections to object-based rmap were test cases by akpm and by
mingo, in which large numbers of vmas mapping disjoint or overlapping parts of
a file showed strikingly poor performance of the i_mmap lists. Perhaps those
tests are irrelevant in the real world? We cannot be too sure: the prio_tree
is well-suited to solving precisely that problem, so unless it turns out to
bring too much overhead, let's include it.
Why is this prio_tree.c placed in mm rather than lib? See GET_INDEX: this
implementation is geared throughout to use with vmas, though the first half of
the file appears more general than the second half.
Each node of the prio_tree is itself (contained within) a vma: might save
memory by allocating distinct nodes from which to hang vmas, but wouldn't save
much, and would complicate the usage with preallocations. Off each node of
the prio_tree itself hangs a list of like vmas, if any.
The connection from node to list is a little awkward, but probably the best
compromise: it would be more straightforward to list likes directly from the
tree node, but that would use more memory per vma, for the list_head and to
identify that head. Instead, node's shared.vm_set.head points to next vma
(whose shared.vm_set.head points back to node vma), and that next contains the
list_head from which the rest hang - reusing fields already used in the
prio_tree node itself.
Currently lacks prefetch: Rajesh hopes to add some soon.
---
25-akpm/include/linux/mm.h | 37 --
25-akpm/include/linux/prio_tree.h | 57 ++-
25-akpm/init/main.c | 2
25-akpm/mm/Makefile | 5
25-akpm/mm/mmap.c | 25 -
25-akpm/mm/prio_tree.c | 654 ++++++++++++++++++++++++++++++++++++++
6 files changed, 723 insertions(+), 57 deletions(-)
diff -puN include/linux/mm.h~rmap-17-real-prio_tree include/linux/mm.h
--- 25/include/linux/mm.h~rmap-17-real-prio_tree 2004-04-27 20:25:20.514277864 -0700
+++ 25-akpm/include/linux/mm.h 2004-04-27 20:25:20.524276344 -0700
@@ -72,7 +72,15 @@ struct vm_area_struct {
* For areas with an address space and backing store,
* one of the address_space->i_mmap{,shared} trees.
*/
- struct list_head shared;
+ union {
+ struct {
+ struct list_head list;
+ void *parent; /* aligns with prio_tree_node parent */
+ struct vm_area_struct *head;
+ } vm_set;
+
+ struct prio_tree_node prio_tree_node;
+ } shared;
/* Function pointers to deal with this struct. */
struct vm_operations_struct * vm_ops;
@@ -553,27 +561,16 @@ extern void si_meminfo_node(struct sysin
static inline void vma_prio_tree_init(struct vm_area_struct *vma)
{
- INIT_LIST_HEAD(&vma->shared);
-}
-
-static inline void vma_prio_tree_add(struct vm_area_struct *vma,
- struct vm_area_struct *old)
-{
- list_add(&vma->shared, &old->shared);
-}
-
-static inline void vma_prio_tree_insert(struct vm_area_struct *vma,
- struct prio_tree_root *root)
-{
- list_add_tail(&vma->shared, &root->list);
-}
-
-static inline void vma_prio_tree_remove(struct vm_area_struct *vma,
- struct prio_tree_root *root)
-{
- list_del_init(&vma->shared);
+ vma->shared.vm_set.list.next = NULL;
+ vma->shared.vm_set.list.prev = NULL;
+ vma->shared.vm_set.parent = NULL;
+ vma->shared.vm_set.head = NULL;
}
+/* prio_tree.c */
+void vma_prio_tree_add(struct vm_area_struct *, struct vm_area_struct *old);
+void vma_prio_tree_insert(struct vm_area_struct *, struct prio_tree_root *);
+void vma_prio_tree_remove(struct vm_area_struct *, struct prio_tree_root *);
struct vm_area_struct *vma_prio_tree_next(
struct vm_area_struct *, struct prio_tree_root *,
struct prio_tree_iter *, pgoff_t begin, pgoff_t end);
diff -puN include/linux/prio_tree.h~rmap-17-real-prio_tree include/linux/prio_tree.h
--- 25/include/linux/prio_tree.h~rmap-17-real-prio_tree 2004-04-27 20:25:20.515277712 -0700
+++ 25-akpm/include/linux/prio_tree.h 2004-04-27 20:25:20.524276344 -0700
@@ -1,27 +1,64 @@
#ifndef _LINUX_PRIO_TREE_H
#define _LINUX_PRIO_TREE_H
-/*
- * Dummy version of include/linux/prio_tree.h, just for this patch:
- * no radix priority search tree whatsoever, just implement interfaces
- * using the old lists.
- */
+
+struct prio_tree_node {
+ struct prio_tree_node *left;
+ struct prio_tree_node *right;
+ struct prio_tree_node *parent;
+};
struct prio_tree_root {
- struct list_head list;
+ struct prio_tree_node *prio_tree_node;
+ unsigned int index_bits;
};
struct prio_tree_iter {
- int not_used_yet;
+ struct prio_tree_node *cur;
+ unsigned long mask;
+ unsigned long value;
+ int size_level;
};
#define INIT_PRIO_TREE_ROOT(ptr) \
do { \
- INIT_LIST_HEAD(&(ptr)->list); \
-} while (0) \
+ (ptr)->prio_tree_node = NULL; \
+ (ptr)->index_bits = 1; \
+} while (0)
+
+#define INIT_PRIO_TREE_NODE(ptr) \
+do { \
+ (ptr)->left = (ptr)->right = (ptr)->parent = (ptr); \
+} while (0)
+
+#define INIT_PRIO_TREE_ITER(ptr) \
+do { \
+ (ptr)->cur = NULL; \
+ (ptr)->mask = 0UL; \
+ (ptr)->value = 0UL; \
+ (ptr)->size_level = 0; \
+} while (0)
+
+#define prio_tree_entry(ptr, type, member) \
+ ((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))
static inline int prio_tree_empty(const struct prio_tree_root *root)
{
- return list_empty(&root->list);
+ return root->prio_tree_node == NULL;
+}
+
+static inline int prio_tree_root(const struct prio_tree_node *node)
+{
+ return node->parent == node;
+}
+
+static inline int prio_tree_left_empty(const struct prio_tree_node *node)
+{
+ return node->left == node;
+}
+
+static inline int prio_tree_right_empty(const struct prio_tree_node *node)
+{
+ return node->right == node;
}
#endif /* _LINUX_PRIO_TREE_H */
diff -puN init/main.c~rmap-17-real-prio_tree init/main.c
--- 25/init/main.c~rmap-17-real-prio_tree 2004-04-27 20:25:20.517277408 -0700
+++ 25-akpm/init/main.c 2004-04-27 20:25:20.525276192 -0700
@@ -84,6 +84,7 @@ extern void signals_init(void);
extern void buffer_init(void);
extern void pidhash_init(void);
extern void pidmap_init(void);
+extern void prio_tree_init(void);
extern void radix_tree_init(void);
extern void free_initmem(void);
extern void populate_rootfs(void);
@@ -456,6 +457,7 @@ asmlinkage void __init start_kernel(void
calibrate_delay();
pidmap_init();
pgtable_cache_init();
+ prio_tree_init();
#ifdef CONFIG_X86
if (efi_enabled)
efi_enter_virtual_mode();
diff -puN mm/Makefile~rmap-17-real-prio_tree mm/Makefile
--- 25/mm/Makefile~rmap-17-real-prio_tree 2004-04-27 20:25:20.518277256 -0700
+++ 25-akpm/mm/Makefile 2004-04-27 20:25:20.525276192 -0700
@@ -8,8 +8,9 @@ mmu-$(CONFIG_MMU) := fremap.o highmem.o
shmem.o vmalloc.o
obj-y := bootmem.o filemap.o mempool.o oom_kill.o fadvise.o \
- page_alloc.o page-writeback.o pdflush.o readahead.o \
- slab.o swap.o truncate.o vmscan.o $(mmu-y)
+ page_alloc.o page-writeback.o pdflush.o prio_tree.o \
+ readahead.o slab.o swap.o truncate.o vmscan.o \
+ $(mmu-y)
obj-$(CONFIG_SWAP) += page_io.o swap_state.o swapfile.o
obj-$(CONFIG_HUGETLBFS) += hugetlb.o
diff -puN mm/mmap.c~rmap-17-real-prio_tree mm/mmap.c
--- 25/mm/mmap.c~rmap-17-real-prio_tree 2004-04-27 20:25:20.520276952 -0700
+++ 25-akpm/mm/mmap.c 2004-04-27 20:25:20.527275888 -0700
@@ -322,31 +322,6 @@ __insert_vm_struct(struct mm_struct * mm
}
/*
- * Dummy version of vma_prio_tree_next, just for this patch:
- * no radix priority search tree whatsoever, just implement interface
- * using the old lists: return the next vma overlapping [begin,end].
- */
-struct vm_area_struct *vma_prio_tree_next(
- struct vm_area_struct *vma, struct prio_tree_root *root,
- struct prio_tree_iter *iter, pgoff_t begin, pgoff_t end)
-{
- struct list_head *next;
- pgoff_t vba, vea;
-
- next = vma? vma->shared.next: root->list.next;
- while (next != &root->list) {
- vma = list_entry(next, struct vm_area_struct, shared);
- vba = vma->vm_pgoff;
- vea = vba + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) - 1;
- /* Return vma if it overlaps [begin,end] */
- if (vba <= end && vea >= begin)
- return vma;
- next = next->next;
- }
- return NULL;
-}
-
-/*
* We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that is
* already present in an i_mmap{_shared} tree without adjusting the tree.
* The following helper function should be used when such adjustments
diff -puN /dev/null mm/prio_tree.c
--- /dev/null 2003-09-15 06:40:47.000000000 -0700
+++ 25-akpm/mm/prio_tree.c 2004-04-27 20:25:20.530275432 -0700
@@ -0,0 +1,654 @@
+/*
+ * mm/prio_tree.c - priority search tree for mapping->i_mmap{,_shared}
+ *
+ * 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/init.h>
+#include <linux/module.h>
+#include <linux/mm.h>
+#include <linux/prio_tree.h>
+
+/*
+ * A clever mix of heap and radix trees forms a radix priority search tree (PST)
+ * which is useful for storing intervals, e.g, we can consider a vma as a closed
+ * interval of file pages [offset_begin, offset_end], and store all vmas that
+ * map a file in a PST. Then, using the PST, we can answer a stabbing query,
+ * i.e., selecting a set of stored intervals (vmas) that overlap with (map) a
+ * given input interval X (a set of consecutive file pages), in "O(log n + m)"
+ * time where 'log n' is the height of the PST, and 'm' is the number of stored
+ * intervals (vmas) that overlap (map) with the input interval X (the set of
+ * consecutive file pages).
+ *
+ * In our implementation, we store closed intervals of the form [radix_index,
+ * heap_index]. We assume that always radix_index <= heap_index. McCreight's PST
+ * is designed for storing intervals with unique radix indices, i.e., each
+ * interval have different radix_index. However, this limitation can be easily
+ * overcome by using the size, i.e., heap_index - radix_index, as part of the
+ * index, so we index the tree using [(radix_index,size), heap_index].
+ *
+ * When the above-mentioned indexing scheme is used, theoretically, in a 32 bit
+ * machine, the maximum height of a PST can be 64. We can use a balanced version
+ * of the priority search tree to optimize the tree height, but the balanced
+ * tree proposed by McCreight is too complex and memory-hungry for our purpose.
+ */
+
+/*
+ * The following macros are used for implementing prio_tree for i_mmap{_shared}
+ */
+
+#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))
+
+#define GET_INDEX_VMA(vma, radix, heap) \
+do { \
+ radix = RADIX_INDEX(vma); \
+ heap = HEAP_INDEX(vma); \
+} while (0)
+
+#define GET_INDEX(node, radix, heap) \
+do { \
+ struct vm_area_struct *__tmp = \
+ prio_tree_entry(node, struct vm_area_struct, shared.prio_tree_node);\
+ GET_INDEX_VMA(__tmp, radix, heap); \
+} while (0)
+
+static unsigned long index_bits_to_maxindex[BITS_PER_LONG];
+
+void __init prio_tree_init(void)
+{
+ unsigned int i;
+
+ for (i = 0; i < ARRAY_SIZE(index_bits_to_maxindex) - 1; i++)
+ index_bits_to_maxindex[i] = (1UL << (i + 1)) - 1;
+ index_bits_to_maxindex[ARRAY_SIZE(index_bits_to_maxindex) - 1] = ~0UL;
+}
+
+/*
+ * Maximum heap_index that can be stored in a PST with index_bits bits
+ */
+static inline unsigned long prio_tree_maxindex(unsigned int bits)
+{
+ return index_bits_to_maxindex[bits - 1];
+}
+
+/*
+ * Extend a priority search tree so that it can store a node with heap_index
+ * max_heap_index. In the worst case, this algorithm takes O((log n)^2).
+ * However, this function is used rarely and the common case performance is
+ * not bad.
+ */
+static struct prio_tree_node *prio_tree_expand(struct prio_tree_root *root,
+ struct prio_tree_node *node, unsigned long max_heap_index)
+{
+ static void prio_tree_remove(struct prio_tree_root *,
+ struct prio_tree_node *);
+ struct prio_tree_node *first = NULL, *prev, *last = NULL;
+
+ if (max_heap_index > prio_tree_maxindex(root->index_bits))
+ root->index_bits++;
+
+ while (max_heap_index > prio_tree_maxindex(root->index_bits)) {
+ root->index_bits++;
+
+ if (prio_tree_empty(root))
+ continue;
+
+ if (first == NULL) {
+ first = root->prio_tree_node;
+ prio_tree_remove(root, root->prio_tree_node);
+ INIT_PRIO_TREE_NODE(first);
+ last = first;
+ } else {
+ prev = last;
+ last = root->prio_tree_node;
+ prio_tree_remove(root, root->prio_tree_node);
+ INIT_PRIO_TREE_NODE(last);
+ prev->left = last;
+ last->parent = prev;
+ }
+ }
+
+ INIT_PRIO_TREE_NODE(node);
+
+ if (first) {
+ node->left = first;
+ first->parent = node;
+ } else
+ last = node;
+
+ if (!prio_tree_empty(root)) {
+ last->left = root->prio_tree_node;
+ last->left->parent = last;
+ }
+
+ root->prio_tree_node = node;
+ return node;
+}
+
+/*
+ * Replace a prio_tree_node with a new node and return the old node
+ */
+static struct prio_tree_node *prio_tree_replace(struct prio_tree_root *root,
+ struct prio_tree_node *old, struct prio_tree_node *node)
+{
+ INIT_PRIO_TREE_NODE(node);
+
+ if (prio_tree_root(old)) {
+ BUG_ON(root->prio_tree_node != old);
+ /*
+ * We can reduce root->index_bits here. However, it is complex
+ * and does not help much to improve performance (IMO).
+ */
+ node->parent = node;
+ root->prio_tree_node = node;
+ } else {
+ node->parent = old->parent;
+ if (old->parent->left == old)
+ old->parent->left = node;
+ else
+ old->parent->right = node;
+ }
+
+ if (!prio_tree_left_empty(old)) {
+ node->left = old->left;
+ old->left->parent = node;
+ }
+
+ if (!prio_tree_right_empty(old)) {
+ node->right = old->right;
+ old->right->parent = node;
+ }
+
+ return old;
+}
+
+/*
+ * Insert a prio_tree_node @node into a radix priority search tree @root. The
+ * algorithm typically takes O(log n) time where 'log n' is the number of bits
+ * required to represent the maximum heap_index. In the worst case, the algo
+ * can take O((log n)^2) - check prio_tree_expand.
+ *
+ * If a prior node with same radix_index and heap_index is already found in
+ * the tree, then returns the address of the prior node. Otherwise, inserts
+ * @node into the tree and returns @node.
+ */
+static struct prio_tree_node *prio_tree_insert(struct prio_tree_root *root,
+ struct prio_tree_node *node)
+{
+ struct prio_tree_node *cur, *res = node;
+ unsigned long radix_index, heap_index;
+ unsigned long r_index, h_index, index, mask;
+ int size_flag = 0;
+
+ GET_INDEX(node, radix_index, heap_index);
+
+ if (prio_tree_empty(root) ||
+ heap_index > prio_tree_maxindex(root->index_bits))
+ return prio_tree_expand(root, node, heap_index);
+
+ cur = root->prio_tree_node;
+ mask = 1UL << (root->index_bits - 1);
+
+ while (mask) {
+ GET_INDEX(cur, r_index, h_index);
+
+ if (r_index == radix_index && h_index == heap_index)
+ return cur;
+
+ if (h_index < heap_index ||
+ (h_index == heap_index && r_index > radix_index)) {
+ struct prio_tree_node *tmp = node;
+ node = prio_tree_replace(root, cur, node);
+ cur = tmp;
+ /* swap indices */
+ index = r_index;
+ r_index = radix_index;
+ radix_index = index;
+ index = h_index;
+ h_index = heap_index;
+ heap_index = index;
+ }
+
+ if (size_flag)
+ index = heap_index - radix_index;
+ else
+ index = radix_index;
+
+ if (index & mask) {
+ if (prio_tree_right_empty(cur)) {
+ INIT_PRIO_TREE_NODE(node);
+ cur->right = node;
+ node->parent = cur;
+ return res;
+ } else
+ cur = cur->right;
+ } else {
+ if (prio_tree_left_empty(cur)) {
+ INIT_PRIO_TREE_NODE(node);
+ cur->left = node;
+ node->parent = cur;
+ return res;
+ } else
+ cur = cur->left;
+ }
+
+ mask >>= 1;
+
+ if (!mask) {
+ mask = 1UL << (root->index_bits - 1);
+ size_flag = 1;
+ }
+ }
+ /* Should not reach here */
+ BUG();
+ return NULL;
+}
+
+/*
+ * Remove a prio_tree_node @node from a radix priority search tree @root. The
+ * algorithm takes O(log n) time where 'log n' is the number of bits required
+ * to represent the maximum heap_index.
+ */
+static void prio_tree_remove(struct prio_tree_root *root,
+ struct prio_tree_node *node)
+{
+ struct prio_tree_node *cur;
+ unsigned long r_index, h_index_right, h_index_left;
+
+ cur = node;
+
+ while (!prio_tree_left_empty(cur) || !prio_tree_right_empty(cur)) {
+ if (!prio_tree_left_empty(cur))
+ GET_INDEX(cur->left, r_index, h_index_left);
+ else {
+ cur = cur->right;
+ continue;
+ }
+
+ if (!prio_tree_right_empty(cur))
+ GET_INDEX(cur->right, r_index, h_index_right);
+ else {
+ cur = cur->left;
+ continue;
+ }
+
+ /* both h_index_left and h_index_right cannot be 0 */
+ if (h_index_left >= h_index_right)
+ cur = cur->left;
+ else
+ cur = cur->right;
+ }
+
+ if (prio_tree_root(cur)) {
+ BUG_ON(root->prio_tree_node != cur);
+ INIT_PRIO_TREE_ROOT(root);
+ return;
+ }
+
+ if (cur->parent->right == cur)
+ cur->parent->right = cur->parent;
+ else
+ cur->parent->left = cur->parent;
+
+ while (cur != node)
+ cur = prio_tree_replace(root, cur->parent, cur);
+}
+
+/*
+ * Following functions help to enumerate all prio_tree_nodes in the tree that
+ * overlap with the input interval X [radix_index, heap_index]. The enumeration
+ * takes O(log n + m) time where 'log n' is the height of the tree (which is
+ * proportional to # of bits required to represent the maximum heap_index) and
+ * 'm' is the number of prio_tree_nodes that overlap the interval X.
+ */
+
+static struct prio_tree_node *prio_tree_left(
+ struct prio_tree_root *root, struct prio_tree_iter *iter,
+ unsigned long radix_index, unsigned long heap_index,
+ unsigned long *r_index, unsigned long *h_index)
+{
+ if (prio_tree_left_empty(iter->cur))
+ return NULL;
+
+ GET_INDEX(iter->cur->left, *r_index, *h_index);
+
+ if (radix_index <= *h_index) {
+ iter->cur = iter->cur->left;
+ iter->mask >>= 1;
+ if (iter->mask) {
+ if (iter->size_level)
+ iter->size_level++;
+ } else {
+ if (iter->size_level) {
+ BUG_ON(!prio_tree_left_empty(iter->cur));
+ BUG_ON(!prio_tree_right_empty(iter->cur));
+ iter->size_level++;
+ iter->mask = ULONG_MAX;
+ } else {
+ iter->size_level = 1;
+ iter->mask = 1UL << (root->index_bits - 1);
+ }
+ }
+ return iter->cur;
+ }
+
+ return NULL;
+}
+
+static struct prio_tree_node *prio_tree_right(
+ struct prio_tree_root *root, struct prio_tree_iter *iter,
+ unsigned long radix_index, unsigned long heap_index,
+ unsigned long *r_index, unsigned long *h_index)
+{
+ unsigned long value;
+
+ if (prio_tree_right_empty(iter->cur))
+ return NULL;
+
+ if (iter->size_level)
+ value = iter->value;
+ else
+ value = iter->value | iter->mask;
+
+ if (heap_index < value)
+ return NULL;
+
+ GET_INDEX(iter->cur->right, *r_index, *h_index);
+
+ if (radix_index <= *h_index) {
+ iter->cur = iter->cur->right;
+ iter->mask >>= 1;
+ iter->value = value;
+ if (iter->mask) {
+ if (iter->size_level)
+ iter->size_level++;
+ } else {
+ if (iter->size_level) {
+ BUG_ON(!prio_tree_left_empty(iter->cur));
+ BUG_ON(!prio_tree_right_empty(iter->cur));
+ iter->size_level++;
+ iter->mask = ULONG_MAX;
+ } else {
+ iter->size_level = 1;
+ iter->mask = 1UL << (root->index_bits - 1);
+ }
+ }
+ return iter->cur;
+ }
+
+ return NULL;
+}
+
+static struct prio_tree_node *prio_tree_parent(struct prio_tree_iter *iter)
+{
+ iter->cur = iter->cur->parent;
+ if (iter->mask == ULONG_MAX)
+ iter->mask = 1UL;
+ else if (iter->size_level == 1)
+ iter->mask = 1UL;
+ else
+ iter->mask <<= 1;
+ if (iter->size_level)
+ iter->size_level--;
+ if (!iter->size_level && (iter->value & iter->mask))
+ iter->value ^= iter->mask;
+ return iter->cur;
+}
+
+static inline int overlap(unsigned long radix_index, unsigned long heap_index,
+ unsigned long r_index, unsigned long h_index)
+{
+ return heap_index >= r_index && radix_index <= h_index;
+}
+
+/*
+ * prio_tree_first:
+ *
+ * Get the first prio_tree_node that overlaps with the interval [radix_index,
+ * heap_index]. Note that always radix_index <= heap_index. We do a pre-order
+ * traversal of the tree.
+ */
+static struct prio_tree_node *prio_tree_first(struct prio_tree_root *root,
+ struct prio_tree_iter *iter, unsigned long radix_index,
+ unsigned long heap_index)
+{
+ unsigned long r_index, h_index;
+
+ INIT_PRIO_TREE_ITER(iter);
+
+ if (prio_tree_empty(root))
+ return NULL;
+
+ GET_INDEX(root->prio_tree_node, r_index, h_index);
+
+ if (radix_index > h_index)
+ return NULL;
+
+ iter->mask = 1UL << (root->index_bits - 1);
+ iter->cur = root->prio_tree_node;
+
+ while (1) {
+ if (overlap(radix_index, heap_index, r_index, h_index))
+ return iter->cur;
+
+ if (prio_tree_left(root, iter, radix_index, heap_index,
+ &r_index, &h_index))
+ continue;
+
+ if (prio_tree_right(root, iter, radix_index, heap_index,
+ &r_index, &h_index))
+ continue;
+
+ break;
+ }
+ return NULL;
+}
+
+/*
+ * prio_tree_next:
+ *
+ * Get the next prio_tree_node that overlaps with the input interval in iter
+ */
+static struct prio_tree_node *prio_tree_next(struct prio_tree_root *root,
+ struct prio_tree_iter *iter, unsigned long radix_index,
+ unsigned long heap_index)
+{
+ unsigned long r_index, h_index;
+
+repeat:
+ while (prio_tree_left(root, iter, radix_index,
+ heap_index, &r_index, &h_index)) {
+ if (overlap(radix_index, heap_index, r_index, h_index))
+ return iter->cur;
+ }
+
+ while (!prio_tree_right(root, iter, radix_index,
+ heap_index, &r_index, &h_index)) {
+ while (!prio_tree_root(iter->cur) &&
+ iter->cur->parent->right == iter->cur)
+ prio_tree_parent(iter);
+
+ if (prio_tree_root(iter->cur))
+ return NULL;
+
+ prio_tree_parent(iter);
+ }
+
+ if (overlap(radix_index, heap_index, r_index, h_index))
+ return iter->cur;
+
+ goto repeat;
+}
+
+/*
+ * Radix priority search tree for address_space->i_mmap_{_shared}
+ *
+ * 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.
+ */
+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));
+
+ 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;
+
+ ptr = prio_tree_insert(root, &vma->shared.prio_tree_node);
+ if (ptr != &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
+ 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;
+
+ 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_root *root, struct prio_tree_iter *iter,
+ pgoff_t begin, pgoff_t end)
+{
+ struct prio_tree_node *ptr;
+ struct vm_area_struct *next;
+
+ if (!vma) {
+ /*
+ * First call is with NULL vma
+ */
+ ptr = prio_tree_first(root, iter, begin, end);
+ if (ptr)
+ return prio_tree_entry(ptr, struct vm_area_struct,
+ shared.prio_tree_node);
+ else
+ return NULL;
+ }
+
+ if (vma->shared.vm_set.parent) {
+ if (vma->shared.vm_set.head)
+ return vma->shared.vm_set.head;
+ } else {
+ next = list_entry(vma->shared.vm_set.list.next,
+ struct vm_area_struct, shared.vm_set.list);
+ if (!next->shared.vm_set.head)
+ return next;
+ }
+
+ ptr = prio_tree_next(root, iter, begin, end);
+ if (ptr)
+ return prio_tree_entry(ptr, struct vm_area_struct,
+ shared.prio_tree_node);
+ else
+ return NULL;
+}
+EXPORT_SYMBOL(vma_prio_tree_next);
_