mm: replace vma prio_tree with an interval tree

Implement an interval tree as a replacement for the VMA prio_tree.  The
algorithms are similar to lib/interval_tree.c; however that code can't be
directly reused as the interval endpoints are not explicitly stored in the
VMA.  So instead, the common algorithm is moved into a template and the
details (node type, how to get interval endpoints from the node, etc) are
filled in using the C preprocessor.

Once the interval tree functions are available, using them as a
replacement to the VMA prio tree is a relatively simple, mechanical job.

Signed-off-by: Michel Lespinasse <walken@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 208 deletions

diff --git a/mm/prio_tree.c b/mm/prio_tree.c
deleted file mode 100644
index 799dcfd..0000000
--- a/mm/prio_tree.c
+++ /dev/null
@@ -1,208 +0,0 @@
-/*
- * 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>
-#include <linux/prefetch.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 corresponding 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;
-}