scoutfs: add sparse bitmap library

Add a quick library for maintaining a very large bitmap with sparse
allocation.

Signed-off-by: Zach Brown <zab@versity.com>

kmod/src/Makefile

@@ -8,7 +8,7 @@ CFLAGS_scoutfs_trace.o = -I$(src) # define_trace.h double include
 scoutfs-y += bio.o block.o btree.o client.o compact.o counters.o data.o dir.o \
 	     export.o extents.o file.o inode.o ioctl.o item.o lock.o \
 	     manifest.o msg.o net.o options.o per_task.o seg.o server.o \
-	     scoutfs_trace.o sort_priv.o super.o sysfs.o trans.o \
+	     scoutfs_trace.o sort_priv.o spbm.o super.o sysfs.o trans.o \
 	     triggers.o tseq.o xattr.o
 
 #

kmod/src/spbm.c

@@ -0,0 +1,153 @@
+/*
+ * Copyright (C) 2018 Versity Software, Inc.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * 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.
+ */
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/log2.h>
+#include <linux/bitmap.h>
+#include <linux/rbtree.h>
+
+#include "spbm.h"
+
+#define SPBM_BITS	128
+#define SPBM_SHIFT	ilog2(SPBM_BITS)
+#define SPBM_MASK	((u64)SPBM_BITS - 1)
+#define SPBM_LONGS	(SPBM_BITS / BITS_PER_LONG)
+
+/*
+ * Maintain a sparse bitmap in an rbtree.  Setting bits can allocate and
+ * fail but clearing will always succeed.  Locking is left up to the
+ * caller.
+ */
+
+struct spbm_node {
+	struct rb_node node;
+	u64 index;
+	unsigned long bits[SPBM_LONGS];
+};
+
+void scoutfs_spbm_init(struct scoutfs_spbm *spbm)
+{
+	BUILD_BUG_ON(!is_power_of_2(SPBM_BITS));
+
+	spbm->root = RB_ROOT;
+}
+
+enum {
+	/* if a node isn't found then return an allocated new node */
+	SPBM_FIND_ALLOC = 0x1,
+};
+static struct spbm_node *find_node(struct scoutfs_spbm *spbm, u64 index,
+				   int flags)
+{
+	struct rb_node *parent;
+	struct rb_node **node;
+	struct spbm_node *sn;
+
+	node = &spbm->root.rb_node;
+	parent = NULL;
+	sn = NULL;
+	while (*node) {
+		parent = *node;
+		sn = container_of(*node, struct spbm_node, node);
+
+		if (index < sn->index) {
+			node = &(*node)->rb_left;
+		} else if (index > sn->index) {
+			node = &(*node)->rb_right;
+		} else {
+			break;
+		}
+
+		sn = NULL;
+	}
+
+	if (!sn && (flags & SPBM_FIND_ALLOC)) {
+		sn = kzalloc(sizeof(struct spbm_node), GFP_NOFS);
+		if (sn) {
+			sn->index = index;
+			rb_link_node(&sn->node, parent, node);
+			rb_insert_color(&sn->node, &spbm->root);
+		}
+	}
+
+	return sn;
+}
+
+static void calc_index_nr(u64 *index, int *nr, u64 bit)
+{
+	*index = bit >> SPBM_SHIFT;
+	*nr = bit & SPBM_MASK;
+}
+
+int scoutfs_spbm_set(struct scoutfs_spbm *spbm, u64 bit)
+{
+	struct spbm_node *sn;
+	u64 index;
+	int nr;
+
+	calc_index_nr(&index, &nr, bit);
+
+	sn = find_node(spbm, index, SPBM_FIND_ALLOC);
+	if (!sn)
+		return -ENOMEM;
+
+	set_bit(nr, sn->bits);
+
+	return 0;
+}
+
+int scoutfs_spbm_test(struct scoutfs_spbm *spbm, u64 bit)
+{
+	struct spbm_node *sn;
+	u64 index;
+	int nr;
+
+	calc_index_nr(&index, &nr, bit);
+
+	sn = find_node(spbm, index, 0);
+	if (sn)
+		return !!test_bit(nr, sn->bits);
+
+	return 0;
+}
+
+static void free_node(struct scoutfs_spbm *spbm, struct spbm_node *sn)
+{
+	rb_erase(&sn->node, &spbm->root);
+	kfree(sn);
+}
+
+void scoutfs_spbm_clear(struct scoutfs_spbm *spbm, u64 bit)
+{
+	struct spbm_node *sn;
+	u64 index;
+	int nr;
+
+	calc_index_nr(&index, &nr, bit);
+
+	sn = find_node(spbm, index, 0);
+	if (sn) {
+		clear_bit(nr, sn->bits);
+		if (bitmap_empty(sn->bits, SPBM_BITS))
+			free_node(spbm, sn);
+	}
+}
+
+void scoutfs_spbm_destroy(struct scoutfs_spbm *spbm)
+{
+	struct spbm_node *sn;
+	struct spbm_node *pos;
+
+	rbtree_postorder_for_each_entry_safe(sn, pos, &spbm->root, node)
+		free_node(spbm, sn);
+}

kmod/src/spbm.h

@@ -0,0 +1,15 @@
+#ifndef _SCOUTFS_SPBM_H_
+#define _SCOUTFS_SPBM_H_
+
+struct scoutfs_spbm {
+	struct rb_root root;
+};
+
+void scoutfs_spbm_init(struct scoutfs_spbm *spbm);
+void scoutfs_spbm_destroy(struct scoutfs_spbm *spbm);
+
+int scoutfs_spbm_set(struct scoutfs_spbm *spbm, u64 bit);
+int scoutfs_spbm_test(struct scoutfs_spbm *spbm, u64 bit);
+void scoutfs_spbm_clear(struct scoutfs_spbm *spbm, u64 bit);
+
+#endif