14197 Implement id_space as a library

Reviewed by: Yuri Pankov <ypankov@tintri.com>
Reviewed by: Andy Fiddaman <andy@omnios.org>
Approved by: Rich Lowe <richlowe@richlowe.net>

1 files changed, 184 insertions, 0 deletions

diff --git a/usr/src/common/idspace/id_space.c b/usr/src/common/idspace/id_space.c
new file mode 100644
index 0000000000..7d28a8f533
--- /dev/null
+++ b/usr/src/common/idspace/id_space.c
@@ -0,0 +1,184 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
+ */
+
+#include <sys/types.h>
+#include <sys/id_space.h>
+#include <sys/debug.h>
+
+/*
+ * ID Spaces
+ *
+ *   The id_space_t provides a simple implementation of a managed range of
+ *   integer identifiers using a vmem arena.  An ID space guarantees that the
+ *   next identifer returned by an allocation is larger than the previous one,
+ *   unless there are no larger slots remaining in the range.  In this case,
+ *   the ID space will return the first available slot in the lower part of the
+ *   range (viewing the previous identifier as a partitioning element).  If no
+ *   slots are available, id_alloc()/id_allocff() will sleep until an
+ *   identifier becomes available.  Accordingly, id_space allocations must be
+ *   initiated from contexts where sleeping is acceptable.  id_alloc_nosleep()/
+ *   id_allocff_nosleep() will return -1 if no slots are available or if the
+ *   system is low on memory.  If id_alloc_nosleep() fails, callers should
+ *   not try to extend the ID space.  This is to avoid making a possible
+ *   low-memory situation worse.
+ *
+ *   As an ID space is designed for representing a range of id_t's, there
+ *   is a preexisting maximal range: [0, MAXUID].  ID space requests outside
+ *   that range will fail on a DEBUG kernel.  The id_allocff*() functions
+ *   return the first available id, and should be used when there is benefit
+ *   to having a compact allocated range.
+ *
+ *   (Presently, the id_space_t abstraction supports only direct allocations; ID
+ *   reservation, in which an ID is allocated but placed in a internal
+ *   dictionary for later use, should be added when a consuming subsystem
+ *   arrives.)
+ *
+ *   This code is also shared with userland. In userland, we don't have the same
+ *   ability to have sleeping variants, so we effectively turn the normal
+ *   versions without _nosleep into _nosleep.
+ */
+
+#define	ID_TO_ADDR(id) ((void *)(uintptr_t)(id + 1))
+#define	ADDR_TO_ID(addr) ((id_t)((uintptr_t)addr - 1))
+
+/*
+ * Create an arena to represent the range [low, high).
+ * Caller must be in a context in which VM_SLEEP is legal,
+ * for the kernel. Always VM_NOSLEEP in userland.
+ */
+id_space_t *
+id_space_create(const char *name, id_t low, id_t high)
+{
+#ifdef _KERNEL
+	int flag = VM_SLEEP;
+#else
+	int flag = VM_NOSLEEP;
+#endif
+	ASSERT(low >= 0);
+	ASSERT(low < high);
+
+	return (vmem_create(name, ID_TO_ADDR(low), high - low, 1,
+	    NULL, NULL, NULL, 0, flag | VMC_IDENTIFIER));
+}
+
+/*
+ * Destroy a previously created ID space.
+ * No restrictions on caller's context.
+ */
+void
+id_space_destroy(id_space_t *isp)
+{
+	vmem_destroy(isp);
+}
+
+void
+id_space_extend(id_space_t *isp, id_t low, id_t high)
+{
+#ifdef _KERNEL
+	int flag = VM_SLEEP;
+#else
+	int flag = VM_NOSLEEP;
+#endif
+	(void) vmem_add(isp, ID_TO_ADDR(low), high - low, flag);
+}
+
+/*
+ * Allocate an id_t from specified ID space.
+ * Caller must be in a context in which VM_SLEEP is legal.
+ */
+id_t
+id_alloc(id_space_t *isp)
+{
+#ifdef _KERNEL
+	int flag = VM_SLEEP;
+#else
+	int flag = VM_NOSLEEP;
+#endif
+	return (ADDR_TO_ID(vmem_alloc(isp, 1, flag | VM_NEXTFIT)));
+}
+
+/*
+ * Allocate an id_t from specified ID space.
+ * Returns -1 on failure (see module block comments for more information on
+ * failure modes).
+ */
+id_t
+id_alloc_nosleep(id_space_t *isp)
+{
+	return (ADDR_TO_ID(vmem_alloc(isp, 1, VM_NOSLEEP | VM_NEXTFIT)));
+}
+
+/*
+ * Allocate an id_t from specified ID space using FIRSTFIT.
+ * Caller must be in a context in which VM_SLEEP is legal.
+ */
+id_t
+id_allocff(id_space_t *isp)
+{
+#ifdef _KERNEL
+	int flag = VM_SLEEP;
+#else
+	int flag = VM_NOSLEEP;
+#endif
+	return (ADDR_TO_ID(vmem_alloc(isp, 1, flag | VM_FIRSTFIT)));
+}
+
+/*
+ * Allocate an id_t from specified ID space using FIRSTFIT
+ * Returns -1 on failure (see module block comments for more information on
+ * failure modes).
+ */
+id_t
+id_allocff_nosleep(id_space_t *isp)
+{
+	return (ADDR_TO_ID(vmem_alloc(isp, 1, VM_NOSLEEP | VM_FIRSTFIT)));
+}
+
+/*
+ * Allocate a specific identifier if possible, returning the id if
+ * successful, or -1 on failure.
+ */
+id_t
+id_alloc_specific_nosleep(id_space_t *isp, id_t id)
+{
+	void *minaddr = ID_TO_ADDR(id);
+	void *maxaddr = ID_TO_ADDR(id + 1);
+
+	/*
+	 * Note that even though we're vmem_free()ing this later, it
+	 * should be OK, since there's no quantum cache.
+	 */
+	return (ADDR_TO_ID(vmem_xalloc(isp, 1, 1, 0, 0,
+	    minaddr, maxaddr, VM_NOSLEEP)));
+}
+
+/*
+ * Free a previously allocated ID.
+ * No restrictions on caller's context.
+ */
+void
+id_free(id_space_t *isp, id_t id)
+{
+	vmem_free(isp, ID_TO_ADDR(id), 1);
+}