From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
The eXtensible Bitmap is a sparse bitmap representation which is
efficient for set bits which tend to cluster. It supports up to
'unsigned long' worth of bits, and this commit adds the bare bones --
xb_set_bit(), xb_clear_bit() and xb_test_bit().
Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx>
---
include/linux/radix-tree.h | 2 +
include/linux/xbitmap.h | 49 ++++++++++++++++
lib/radix-tree.c | 139 ++++++++++++++++++++++++++++++++++++++++++++-
3 files changed, 188 insertions(+), 2 deletions(-)
create mode 100644 include/linux/xbitmap.h
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index 3e57350..428ccc9 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -317,6 +317,8 @@ void radix_tree_iter_delete(struct radix_tree_root *,
struct radix_tree_iter *iter, void __rcu **slot);
void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);
void *radix_tree_delete(struct radix_tree_root *, unsigned long);
+bool __radix_tree_delete(struct radix_tree_root *root,
+ struct radix_tree_node *node, void __rcu **slot);
void radix_tree_clear_tags(struct radix_tree_root *, struct radix_tree_node *,
void __rcu **slot);
unsigned int radix_tree_gang_lookup(const struct radix_tree_root *,
diff --git a/include/linux/xbitmap.h b/include/linux/xbitmap.h
new file mode 100644
index 0000000..0b93a46
--- /dev/null
+++ b/include/linux/xbitmap.h
@@ -0,0 +1,49 @@
+/*
+ * eXtensible Bitmaps
+ * Copyright (c) 2017 Microsoft Corporation <mawilcox@xxxxxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * eXtensible Bitmaps provide an unlimited-size sparse bitmap facility.
+ * All bits are initially zero.
+ */
+
+#include <linux/idr.h>
+
+struct xb {
+ struct radix_tree_root xbrt;
+};
+
+#define XB_INIT { \
+ .xbrt = RADIX_TREE_INIT(IDR_RT_MARKER | GFP_NOWAIT), \
+}
+#define DEFINE_XB(name) struct xb name = XB_INIT
+
+static inline void xb_init(struct xb *xb)
+{
+ INIT_RADIX_TREE(&xb->xbrt, IDR_RT_MARKER | GFP_NOWAIT);
+}
+
+int xb_set_bit(struct xb *xb, unsigned long bit);
+bool xb_test_bit(const struct xb *xb, unsigned long bit);
+int xb_clear_bit(struct xb *xb, unsigned long bit);
+
+static inline bool xb_empty(const struct xb *xb)
+{
+ return radix_tree_empty(&xb->xbrt);
+}
+
+void xb_preload(gfp_t gfp);
+
+static inline void xb_preload_end(void)
+{
+ preempt_enable();
+}
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 898e879..d8c3c18 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -37,6 +37,7 @@
#include <linux/rcupdate.h>
#include <linux/slab.h>
#include <linux/string.h>
+#include <linux/xbitmap.h>
/* Number of nodes in fully populated tree of given height */
@@ -78,6 +79,14 @@ static struct kmem_cache *radix_tree_node_cachep;
#define IDA_PRELOAD_SIZE (IDA_MAX_PATH * 2 - 1)
/*
+ * The XB can go up to unsigned long, but also uses a bitmap.
+ */
+#define XB_INDEX_BITS (BITS_PER_LONG - ilog2(IDA_BITMAP_BITS))
+#define XB_MAX_PATH (DIV_ROUND_UP(XB_INDEX_BITS, \
+ RADIX_TREE_MAP_SHIFT))
+#define XB_PRELOAD_SIZE (XB_MAX_PATH * 2 - 1)
+
+/*
* Per-cpu pool of preloaded nodes
*/
struct radix_tree_preload {
@@ -840,6 +849,8 @@ int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
offset, 0, 0);
if (!child)
return -ENOMEM;
+ if (is_idr(root))
+ all_tag_set(child, IDR_FREE);
rcu_assign_pointer(*slot, node_to_entry(child));
if (node)
node->count++;
@@ -1986,8 +1997,8 @@ void __radix_tree_delete_node(struct radix_tree_root *root,
delete_node(root, node, update_node, private);
}
-static bool __radix_tree_delete(struct radix_tree_root *root,
- struct radix_tree_node *node, void __rcu **slot)
+bool __radix_tree_delete(struct radix_tree_root *root,
+ struct radix_tree_node *node, void __rcu **slot)
{
void *old = rcu_dereference_raw(*slot);
int exceptional = radix_tree_exceptional_entry(old) ? -1 : 0;
@@ -2137,6 +2148,130 @@ int ida_pre_get(struct ida *ida, gfp_t gfp)
}
EXPORT_SYMBOL(ida_pre_get);
+void xb_preload(gfp_t gfp)
+{
+ __radix_tree_preload(gfp, XB_PRELOAD_SIZE);
+ if (!this_cpu_read(ida_bitmap)) {
+ struct ida_bitmap *bitmap = kmalloc(sizeof(*bitmap), gfp);
+
+ if (!bitmap)
+ return;
+ bitmap = this_cpu_cmpxchg(ida_bitmap, NULL, bitmap);
+ kfree(bitmap);
+ }
+}
+EXPORT_SYMBOL(xb_preload);
+
+int xb_set_bit(struct xb *xb, unsigned long bit)
+{
+ int err;
+ unsigned long index = bit / IDA_BITMAP_BITS;
+ struct radix_tree_root *root = &xb->xbrt;
+ struct radix_tree_node *node;
+ void **slot;
+ struct ida_bitmap *bitmap;
+ unsigned long ebit;
+
+ bit %= IDA_BITMAP_BITS;
+ ebit = bit + 2;
+
+ err = __radix_tree_create(root, index, 0, &node, &slot);
+ if (err)
+ return err;
+ bitmap = rcu_dereference_raw(*slot);
+ if (radix_tree_exception(bitmap)) {
+ unsigned long tmp = (unsigned long)bitmap;
+
+ if (ebit < BITS_PER_LONG) {
+ tmp |= 1UL << ebit;
+ rcu_assign_pointer(*slot, (void *)tmp);
+ return 0;
+ }
+ bitmap = this_cpu_xchg(ida_bitmap, NULL);
+ if (!bitmap)
+ return -EAGAIN;
+ memset(bitmap, 0, sizeof(*bitmap));
+ bitmap->bitmap[0] = tmp >> RADIX_TREE_EXCEPTIONAL_SHIFT;
+ rcu_assign_pointer(*slot, bitmap);
+ }
+
+ if (!bitmap) {
+ if (ebit < BITS_PER_LONG) {
+ bitmap = (void *)((1UL << ebit) |
+ RADIX_TREE_EXCEPTIONAL_ENTRY);
+ __radix_tree_replace(root, node, slot, bitmap, NULL,
+ NULL);
+ return 0;
+ }
+ bitmap = this_cpu_xchg(ida_bitmap, NULL);
+ if (!bitmap)
+ return -EAGAIN;
+ memset(bitmap, 0, sizeof(*bitmap));
+ __radix_tree_replace(root, node, slot, bitmap, NULL, NULL);
+ }
+
+ __set_bit(bit, bitmap->bitmap);
+ return 0;
+}
+EXPORT_SYMBOL(xb_set_bit);
+
+int xb_clear_bit(struct xb *xb, unsigned long bit)
+{
+ unsigned long index = bit / IDA_BITMAP_BITS;
+ struct radix_tree_root *root = &xb->xbrt;
+ struct radix_tree_node *node;
+ void **slot;
+ struct ida_bitmap *bitmap;
+ unsigned long ebit;
+
+ bit %= IDA_BITMAP_BITS;
+ ebit = bit + 2;
+
+ bitmap = __radix_tree_lookup(root, index, &node, &slot);
+ if (radix_tree_exception(bitmap)) {
+ unsigned long tmp = (unsigned long)bitmap;
+
+ if (ebit >= BITS_PER_LONG)
+ return 0;
+ tmp &= ~(1UL << ebit);
+ if (tmp == RADIX_TREE_EXCEPTIONAL_ENTRY)
+ __radix_tree_delete(root, node, slot);
+ else
+ rcu_assign_pointer(*slot, (void *)tmp);
+ return 0;
+ }
+
+ if (!bitmap)
+ return 0;
+
+ __clear_bit(bit, bitmap->bitmap);
+ if (bitmap_empty(bitmap->bitmap, IDA_BITMAP_BITS)) {
+ kfree(bitmap);
+ __radix_tree_delete(root, node, slot);
+ }
+
+ return 0;
+}
+
+bool xb_test_bit(const struct xb *xb, unsigned long bit)
+{
+ unsigned long index = bit / IDA_BITMAP_BITS;
+ const struct radix_tree_root *root = &xb->xbrt;
+ struct ida_bitmap *bitmap = radix_tree_lookup(root, index);
+
+ bit %= IDA_BITMAP_BITS;
+
+ if (!bitmap)
+ return false;
+ if (radix_tree_exception(bitmap)) {
+ bit += RADIX_TREE_EXCEPTIONAL_SHIFT;
+ if (bit > BITS_PER_LONG)
+ return false;
+ return (unsigned long)bitmap & (1UL << bit);
+ }
+ return test_bit(bit, bitmap->bitmap);
+}
+
void __rcu **idr_get_free(struct radix_tree_root *root,
struct radix_tree_iter *iter, gfp_t gfp, int end)
{
--
2.7.4
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