path: root/drivers/md/dm-table.c

/*
 * Copyright (C) 2001 Sistina Software (UK) Limited.
 * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
 *
 * This file is released under the GPL.
 */

#include "dm.h"

#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/blkdev.h>
#include <linux/namei.h>
#include <linux/ctype.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/mutex.h>
#include <linux/delay.h>
#include <linux/atomic.h>

#define DM_MSG_PREFIX "table"

#define MAX_DEPTH 16
#define NODE_SIZE L1_CACHE_BYTES
#define KEYS_PER_NODE (NODE_SIZE / sizeof(sector_t))
#define CHILDREN_PER_NODE (KEYS_PER_NODE + 1)

/*
 * The table has always exactly one reference from either mapped_device->map
 * or hash_cell->new_map. This reference is not counted in table->holders.
 * A pair of dm_create_table/dm_destroy_table functions is used for table
 * creation/destruction.
 *
 * Temporary references from the other code increase table->holders. A pair
 * of dm_table_get/dm_table_put functions is used to manipulate it.
 *
 * When the table is about to be destroyed, we wait for table->holders to
 * drop to zero.
 */

struct dm_table {
	struct mapped_device *md;
	atomic_t holders;
	unsigned type;

	/* btree table */
	unsigned int depth;
	unsigned int counts[MAX_DEPTH];	/* in nodes */
	sector_t *index[MAX_DEPTH];

	unsigned int num_targets;
	unsigned int num_allocated;
	sector_t *highs;
	struct dm_target *targets;

	struct target_type *immutable_target_type;
	unsigned integrity_supported:1;
	unsigned singleton:1;

	/*
	 * Indicates the rw permissions for the new logical
	 * device.  This should be a combination of FMODE_READ
	 * and FMODE_WRITE.
	 */
	fmode_t mode;

	/* a list of devices used by this table */
	struct list_head devices;

	/* events get handed up using this callback */
	void (*event_fn)(void *);
	void *event_context;

	struct dm_md_mempools *mempools;

	struct list_head target_callbacks;
};

/*
 * Similar to ceiling(log_size(n))
 */
static unsigned int int_log(unsigned int n, unsigned int base)
{
	int result = 0;

	while (n > 1) {
		n = dm_div_up(n, base);
		result++;
	}

	return result;
}

/*
 * Calculate the index of the child node of the n'th node k'th k