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Date: Tue, 07 Feb 2012 11:55:04 +0400
From: Konstantin Khlebnikov <khlebnikov@...nvz.org>
To: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
Hugh Dickins <hughd@...gle.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-kernel@...r.kernel.org
Subject: [PATCH 2/4] radix-tree: introduce bit-optimized iterator
This patch implements clean, simple and effective radix-tree iteration routine.
Iterating is divided into two loops: the outer loop iterates though radix tree
chunks on leaf nodes, the nested loop iterates through slots in one chunk.
Main iterator function radix_tree_next_chunk() returns pointer to first slot,
and stores in the struct radix_tree_iter index of next-to-last slot.
For tagged-iterating it also constuct bitmask of tags for retunted chunk.
Thus nested-loop has enough information for iteration.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@...nvz.org>
---
include/linux/radix-tree.h | 129 ++++++++++++++++++++++++++++++++++++++++++++
lib/radix-tree.c | 107 ++++++++++++++++++++++++++++++++++++
2 files changed, 236 insertions(+), 0 deletions(-)
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index 07e360b..c31b895 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -2,6 +2,7 @@
* Copyright (C) 2001 Momchil Velikov
* Portions Copyright (C) 2001 Christoph Hellwig
* Copyright (C) 2006 Nick Piggin
+ * Copyright (C) 2012 Konstantin Khlebnikov
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
@@ -256,4 +257,132 @@ static inline void radix_tree_preload_end(void)
preempt_enable();
}
+struct radix_tree_iter {
+ unsigned long index; /* current slot index */
+ unsigned long next_index; /* next chunk first index */
+ unsigned long tags; /* bitmask for tag-iterating */
+};
+
+static inline void radix_tree_iter_start(struct radix_tree_iter *iter,
+ unsigned long start)
+{
+ iter->index = start;
+ iter->next_index = 1; /* any non-zero */
+}
+
+#define RADIX_TREE_ITER_TAG_MASK 0x00FF
+#define RADIX_TREE_ITER_TAGGED 0x0100 /* search tagged */
+#define RADIX_TREE_ITER_CONTIG 0x0200 /* stop at first hole */
+
+void **radix_tree_next_chunk(struct radix_tree_root *root,
+ struct radix_tree_iter *iter, unsigned flags);
+
+/**
+ * radix_tree_next_tag - find next tagged slot in chunk
+ *
+ * @slot pointer to slot pointer
+ * @iter iterator state
+ *
+ * Eats iter->tags and bumps *slot and iter->index to next tagged slot
+ * Returns true if something found, and false otherwise
+ */
+static inline bool radix_tree_next_tag(void ***slot,
+ struct radix_tree_iter *iter)
+{
+ unsigned long offset;
+
+ if (likely(iter->tags & 1ul))
+ return true;
+ if (unlikely(!iter->tags)) {
+ iter->index = iter->next_index;
+ return false;
+ }
+ offset = __ffs(iter->tags);
+ iter->tags >>= offset;
+ iter->index += offset;
+ *slot += offset;
+ return true;
+}
+
+/**
+ * radix_tree_for_each_chunk - iterate over all slot chunks
+ *
+ * @slot: the void** for pointer to first slot
+ * @root the struct radix_tree_root pointer
+ * @iter the struct radix_tree_iter pointer
+ * @start starting index
+ * @flags RADIX_TREE_ITER_* and tag index
+ */
+#define radix_tree_for_each_chunk(slot, root, iter, start, flags) \
+ for ( radix_tree_iter_start(iter, start) ; \
+ (slot = radix_tree_next_chunk(root, iter, flags)) ; )
+
+/**
+ * radix_tree_for_each_chunk_slot - iterate over all slots in one chunk
+ *
+ * @slot: the void** for pointer to slot
+ * @iter the struct radix_tree_iter pointer
+ */
+#define radix_tree_for_each_chunk_slot(slot, iter) \
+ for ( ; (iter)->index != (iter)->next_index ; \
+ (iter)->index++, slot++ )
+
+/**
+ * radix_tree_for_each_chunk_tagged_slot - iterate over all tagged slots
+ * in one chunk
+ *
+ * @slot: the void** for pointer to slot
+ * @iter the struct radix_tree_iter pointer
+ */
+#define radix_tree_for_each_chunk_tagged_slot(slot, iter) \
+ for ( ; radix_tree_next_tag(&slot, iter) ; \
+ (iter)->tags >>= 1, (iter)->index++, slot++ )
+
+/**
+ * radix_tree_for_each_slot - iterate over all non-empty slots
+ *
+ * @slot: the void** for pointer to slot
+ * @root the struct radix_tree_root pointer
+ * @iter the struct radix_tree_iter pointer
+ * @start starting index
+ *
+ * This is double-loop, break does not work.
+ */
+#define radix_tree_for_each_slot(slot, root, iter, start) \
+ radix_tree_for_each_chunk(slot, root, iter, start, 0) \
+ radix_tree_for_each_chunk_slot(slot, iter) \
+ if (!*slot) { continue; } else
+
+/**
+ * radix_tree_for_each_contig - iterate over all contiguous non-empty slots
+ *
+ * @slot: the void** for pointer to slot
+ * @root the struct radix_tree_root pointer
+ * @iter the struct radix_tree_iter pointer
+ * @start starting index
+ *
+ * This is double-loop, break does not work.
+ */
+#define radix_tree_for_each_contig(slot, root, iter, start) \
+ radix_tree_for_each_chunk(slot, root, iter, start, \
+ RADIX_TREE_ITER_CONTIG) \
+ radix_tree_for_each_chunk_slot(slot, iter) \
+ if (!*slot) { (iter)->next_index = 0; break; } else
+
+/**
+ * radix_tree_for_each_tagged - iterate over all tagged slots
+ *
+ * @slot: the void** for pointer to slot
+ * @root the struct radix_tree_root pointer
+ * @iter the struct radix_tree_iter pointer
+ * @start starting index
+ * @tag tag index
+ *
+ * This is double-loop, break does not work.
+ */
+#define radix_tree_for_each_tagged(slot, root, iter, start, tag)\
+ radix_tree_for_each_chunk(slot, root, iter, start, \
+ RADIX_TREE_ITER_TAGGED | tag) \
+ radix_tree_for_each_chunk_tagged_slot(slot, iter)
+
#endif /* _LINUX_RADIX_TREE_H */
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index dc63d08..32e2bfa 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -3,6 +3,7 @@
* Portions Copyright (C) 2001 Christoph Hellwig
* Copyright (C) 2005 SGI, Christoph Lameter
* Copyright (C) 2006 Nick Piggin
+ * Copyright (C) 2012 Konstantin Khlebnikov
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
@@ -613,6 +614,112 @@ int radix_tree_tag_get(struct radix_tree_root *root,
EXPORT_SYMBOL(radix_tree_tag_get);
/**
+ * radix_tree_next_chunk - find next slots chunk for iteration
+ *
+ * @root: radix tree root
+ * @iter: iterator state
+ * @flags RADIX_TREE_ITER_* flags and tag index
+ *
+ * Returns pointer to first slots, or NULL if there no more left
+ */
+void **radix_tree_next_chunk(struct radix_tree_root *root,
+ struct radix_tree_iter *iter, unsigned flags)
+{
+ unsigned tag = flags & RADIX_TREE_ITER_TAG_MASK;
+ struct radix_tree_node *rnode, *node;
+ unsigned long index, i;
+ unsigned shift;
+
+ /* Overflow after ~0ul, or break in contiguous iteration */
+ if (!iter->next_index)
+ return NULL;
+
+ if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
+ return NULL;
+
+ index = iter->index;
+
+ rnode = rcu_dereference_raw(root->rnode);
+ if (radix_tree_is_indirect_ptr(rnode)) {
+ rnode = indirect_to_ptr(rnode);
+ } else if (rnode && !index) {
+ /* Single-slot tree */
+ iter->tags = 1;
+ iter->next_index = 1;
+ return (void **)&root->rnode;
+ } else
+ return NULL;
+
+restart:
+ shift = (rnode->height - 1) * RADIX_TREE_MAP_SHIFT;
+ i = index >> shift;
+
+ /* Index ouside of the tree */
+ if (i >= RADIX_TREE_MAP_SIZE)
+ return NULL;
+
+ node = rnode;
+ while (1) {
+ if ((flags & RADIX_TREE_ITER_TAGGED) ?
+ !test_bit(i, node->tags[tag]) :
+ !node->slots[i]) {
+ /* Hole detected */
+ if (flags & RADIX_TREE_ITER_CONTIG)
+ return NULL;
+
+ if (flags & RADIX_TREE_ITER_TAGGED)
+ i = __find_next_bit(node->tags[tag],
+ RADIX_TREE_MAP_SIZE, i + 1);
+ else
+ while (++i < RADIX_TREE_MAP_SIZE &&
+ !node->slots[i]);
+
+ index &= ~((RADIX_TREE_MAP_SIZE << shift) - 1);
+ index += i << shift;
+ /* Overflow after ~0UL */
+ if (!index)
+ return NULL;
+ if (i == RADIX_TREE_MAP_SIZE)
+ goto restart;
+ }
+
+ /* This is leaf-node */
+ if (!shift)
+ break;
+
+ node = rcu_dereference_raw(node->slots[i]);
+ if (node == NULL)
+ goto restart;
+ shift -= RADIX_TREE_MAP_SHIFT;
+ i = (index >> shift) & RADIX_TREE_MAP_MASK;
+ }
+
+ iter->index = index;
+ iter->next_index = (index | RADIX_TREE_MAP_MASK) + 1;
+
+ /* Construct iter->tags bitmask from node->tags[tag] array */
+ if (flags & RADIX_TREE_ITER_TAGGED) {
+ unsigned tag_long, tag_bit;
+
+ tag_long = i / BITS_PER_LONG;
+ tag_bit = i % BITS_PER_LONG;
+ iter->tags = node->tags[tag][tag_long] >> tag_bit;
+ /* This never happens if RADIX_TREE_TAG_LONGS == 1 */
+ if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
+ /* Pick tags from next element */
+ if (tag_bit)
+ iter->tags |= node->tags[tag][tag_long + 1] <<
+ (BITS_PER_LONG - tag_bit);
+ /* Clip chunk size, here only BITS_PER_LONG tags */
+ iter->next_index = index + BITS_PER_LONG;
+ }
+ }
+
+ return node->slots + i;
+}
+EXPORT_SYMBOL(radix_tree_next_chunk);
+
+/**
* radix_tree_range_tag_if_tagged - for each item in given range set given
* tag if item has another tag set
* @root: radix tree root
--
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