lvm2/driver/device-mapper/dm-table.c

/*
 * dm-table.c
 *
 * Copyright (C) 2001 Sistina Software (UK) Limited.
 *
 * This file is released under the GPL.
 */

/*
 * Changelog
 *
 *     16/08/2001 - First version [Joe Thornber]
 */

#include "dm.h"

/* ceiling(n / size) * size */
static inline ulong round_up(ulong n, ulong size)
{
	ulong r = n % size;
	return n + (r ? (size - r) : 0);
}

/* ceiling(n / size) */
static inline ulong div_up(ulong n, ulong size)
{
	return round_up(n, size) / size;
}

/* similar to ceiling(log_size(n)) */
static uint int_log(ulong n, ulong base)
{
	int result = 0;

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

	return result;
}

/*
 * return the highest key that you could lookup
 * from the n'th node on level l of the btree.
 */
static offset_t high(struct dm_table *t, int l, int n)
{
	for (; l < t->depth - 1; l++)
		n = get_child(n, CHILDREN_PER_NODE - 1);

	if (n >= t->counts[l])
		return (offset_t) -1;

	return get_node(t, l, n)[KEYS_PER_NODE - 1];
}

/*
 * fills in a level of the btree based on the
 * highs of the level below it.
 */
static int setup_btree_index(int l, struct dm_table *t)
{
	int n, k;
	offset_t *node;

	for (n = 0; n < t->counts[l]; n++) {
		node = get_node(t, l, n);

		for (k = 0; k < KEYS_PER_NODE; k++)
			node[k] = high(t, l + 1, get_child(n, k));
	}

	return 0;
}

/*
 * highs, and targets are managed as dynamic
 * arrays during a table load.
 */
static int alloc_targets(struct dm_table *t, int num)
{
	offset_t *n_highs;
	struct target *n_targets;
	int n = t->num_targets;
	int size = (sizeof(struct target) + sizeof(offset_t)) * num;

	n_highs = vmalloc(size);
	if (!n_highs)
		return -ENOMEM;

	n_targets = (struct target *) (n_highs + num);

	if (n) {
		memcpy(n_highs, t->highs, sizeof(*n_highs) * n);
		memcpy(n_targets, t->targets, sizeof(*n_targets) * n);
	}

	vfree(t->highs);

	t->num_allocated = num;
	t->highs = n_highs;
	t->targets = n_targets;

	return 0;
}

struct dm_table *dm_table_create(void)
{
	struct dm_table *t = kmalloc(sizeof(struct dm_table), GFP_NOIO);

	if (!t)
		return 0;

	memset(t, 0, sizeof(*t));
	INIT_LIST_HEAD(&t->devices);

	/* allocate a single nodes worth of targets to
	   begin with */
	if (alloc_targets(t, KEYS_PER_NODE)) {
		kfree(t);
		t = 0;
	}

	return t;
}

static void free_devices(struct list_head *devices)
{
	struct list_head *tmp, *next;

	for (tmp = devices->next; tmp != devices; tmp = next) {
		struct dm_dev *dd = list_entry(tmp, struct dm_dev, list);
		next = tmp->next;
		kfree(dd);
	}
}

void dm_table_destroy(struct dm_table *t)
{
	int i;

	/* free the indexes (see dm_table_complete) */
	if (t->depth >= 2)
		vfree(t->index[t->depth - 2]);
	vfree(t->highs);

	/* free the targets */
	for (i = 0; i < t->num_targets; i++) {
		struct target *tgt = &t->targets[i];
		if (tgt->private)
			tgt->type->dtr(t, tgt->private);
	}

	/* free the device list */
	if (t->devices.next != &t->devices) {
		WARN("there are still devices present, someone isn't "
		     "calling dm_table_remove_device");

		free_devices(&t->devices);
	}

	kfree(t);
}

/*
 * Checks to see if we need to extend
 * highs or targets.
 */
static inline int check_space(struct dm_table *t)
{
	if (t->num_targets >= t->num_allocated)
		return alloc_targets(t, t->num_allocated * 2);

	return 0;
}


/*
 * convert a device path to a kdev_t.
 */
int lookup_device(const char *path, kdev_t *dev)
{
       int r;
       struct nameidata nd;
       struct inode *inode;

       if (!path_init(path, LOOKUP_FOLLOW, &nd))
               return 0;

       if ((r = path_walk(path, &nd)))
               goto bad;

       inode = nd.dentry->d_inode;
       if (!inode) {
               r = -ENOENT;
               goto bad;
       }

       if (!S_ISBLK(inode->i_mode)) {
               r = -EINVAL;
               goto bad;
       }

       *dev = inode->i_bdev->bd_dev;

 bad:
       path_release(&nd);
       return r;
}

/*
 * see if we've already got a device in the list.
 */
static struct dm_dev *find_device(struct list_head *l, kdev_t dev)
{
	struct list_head *tmp;

	for (tmp = l->next; tmp != l; tmp = tmp->next) {

		struct dm_dev *dd = list_entry(tmp, struct dm_dev, list);
		if (dd->dev == dev)
			return dd;
	}

       return 0;
}

/*
 * add a device to the list, or just increment the
 * usage count if it's already present.
 */
int dm_table_get_device(struct dm_table *t, const char *path,
			struct dm_dev **result)
{
	int r;
	kdev_t dev;
	struct dm_dev *dd;

	/* convert the path to a device */
	if ((r = lookup_device(path, &dev)))
		return r;

	dd = find_device(&t->devices, dev);
	if (!dd) {
		dd = kmalloc(sizeof(*dd), GFP_KERNEL);
		if (!dd)
			return -ENOMEM;

		dd->dev = dev;
		dd->bd = 0;
		atomic_set(&dd->count, 0);
		list_add(&dd->list, &t->devices);
	}
	atomic_inc(&dd->count);
	*result = dd;

	return 0;
}
/*
 * decrement a devices use count and remove it if
 * neccessary.
 */
void dm_table_put_device(struct dm_table *t, struct dm_dev *dd)
{
       if (atomic_dec_and_test(&dd->count)) {
	       list_del(&dd->list);
               kfree(dd);
       }
}

/*
 * adds a target to the map
 */
int dm_table_add_target(struct dm_table *t, offset_t high,
			struct target_type *type, void *private)
{
	int r, n;

	if ((r = check_space(t)))
		return r;

	n = t->num_targets++;
	t->highs[n] = high;
	t->targets[n].type = type;
	t->targets[n].private = private;

	return 0;
}


static int setup_indexes(struct dm_table *t)
{
	int i, total = 0;
	offset_t *indexes;

	/* allocate the space for *all* the indexes */
	for (i = t->depth - 2; i >= 0; i--) {
		t->counts[i] = div_up(t->counts[i + 1], CHILDREN_PER_NODE);
		total += t->counts[i];
	}

	if (!(indexes = vmalloc(NODE_SIZE * total)))
		return -ENOMEM;

	/* set up internal nodes, bottom-up */
	for (i = t->depth - 2, total = 0; i >= 0; i--) {
		t->index[i] = indexes + (KEYS_PER_NODE * t->counts[i]);
		setup_btree_index(i, t);
	}

	return 0;
}


/*
 * builds the btree to index the map
 */
int dm_table_complete(struct dm_table *t)
{
	int leaf_nodes, r = 0;

	/* how many indexes will the btree have ? */
	leaf_nodes = div_up(t->num_targets, KEYS_PER_NODE);
	t->depth = 1 + int_log(leaf_nodes, CHILDREN_PER_NODE);

	/* leaf layer has already been set up */
	t->counts[t->depth - 1] = leaf_nodes;
	t->index[t->depth - 1] = t->highs;

	if (t->depth >= 2)
		r = setup_indexes(t);

	return r;
}

EXPORT_SYMBOL(dm_table_get_device);
EXPORT_SYMBOL(dm_table_put_device);