/*
 * Copyright (C) 2011 Red Hat, Inc.
 *
 * This file is released under the GPL.
 */

#include "dm-space-map-common.h"
#include "dm-transaction-manager.h"
#include "dm-btree-internal.h"
#include "dm-persistent-data-internal.h"

#include <linux/bitops.h>
#include <linux/device-mapper.h>

#define DM_MSG_PREFIX "space map common"

/*----------------------------------------------------------------*/

/*
 * Index validator.
 */
#define INDEX_CSUM_XOR 160478

static void index_prepare_for_write(struct dm_block_validator *v,
				    struct dm_block *b,
				    size_t block_size)
{
	struct disk_metadata_index *mi_le = dm_block_data(b);

	mi_le->blocknr = cpu_to_le64(dm_block_location(b));
	mi_le->csum = cpu_to_le32(dm_bm_checksum(&mi_le->padding,
						 block_size - sizeof(__le32),
						 INDEX_CSUM_XOR));
}

static int index_check(struct dm_block_validator *v,
		       struct dm_block *b,
		       size_t block_size)
{
	struct disk_metadata_index *mi_le = dm_block_data(b);
	__le32 csum_disk;

	if (dm_block_location(b) != le64_to_cpu(mi_le->blocknr)) {
		DMERR_LIMIT("index_check failed: blocknr %llu != wanted %llu",
			    le64_to_cpu(mi_le->blocknr), dm_block_location(b));
		return -ENOTBLK;
	}

	csum_disk = cpu_to_le32(dm_bm_checksum(&mi_le->padding,
					       block_size - sizeof(__le32),
					       INDEX_CSUM_XOR));
	if (csum_disk != mi_le->csum) {
		DMERR_LIMIT("index_check failed: csum %u != wanted %u",
			    le32_to_cpu(csum_disk), le32_to_cpu(mi_le->csum));
		return -EILSEQ;
	}

	return 0;
}

static struct dm_block_validator index_validator = {
	.name = "index",
	.prepare_for_write = index_prepare_for_write,
	.check = index_check
};

/*----------------------------------------------------------------*/

/*
 * Bitmap validator
 */
#define BITMAP_CSUM_XOR 240779

static void dm_bitmap_prepare_for_write(struct dm_block_validator *v,
					struct dm_block *b,
					size_t block_size)
{
	struct disk_bitmap_header *disk_header = dm_block_data(b);

	disk_header->blocknr = cpu_to_le64(dm_block_location(b));
	disk_header->csum = cpu_to_le32(dm_bm_checksum(&disk_header->not_used,
						       block_size - sizeof(__le32),
						       BITMAP_CSUM_XOR));
}

static int dm_bitmap_check(struct dm_block_validator *v,
			   struct dm_block *b,
			   size_t block_size)
{
	struct disk_bitmap_header *disk_header = dm_block_data(b);
	__le32 csum_disk;

	if (dm_block_location(b) != le64_to_cpu(disk_header->blocknr)) {
		DMERR_LIMIT("bitmap check failed: blocknr %llu != wanted %llu",
			    le64_to_cpu(disk_header->blocknr), dm_block_location(b));
		return -ENOTBLK;
	}

	csum_disk = cpu_to_le32(dm_bm_checksum(&disk_header->not_used,
					       block_size - sizeof(__le32),
					       BITMAP_CSUM_XOR));
	if (csum_disk != disk_header->csum) {
		DMERR_LIMIT("bitmap check failed: csum %u != wanted %u",
			    le32_to_cpu(csum_disk), le32_to_cpu(disk_header->csum));
		return -EILSEQ;
	}

	return 0;
}

static struct dm_block_validator dm_sm_bitmap_validator = {
	.name = "sm_bitmap",
	.prepare_for_write = dm_bitmap_prepare_for_write,
	.check = dm_bitmap_check,
};

/*----------------------------------------------------------------*/

#define ENTRIES_PER_WORD 32
#define ENTRIES_SHIFT	5

static void *dm_bitmap_data(struct dm_block *b)
{
	return dm_block_data(b) + sizeof(struct disk_bitmap_header);
}

#define WORD_MASK_HIGH 0xAAAAAAAAAAAAAAAAULL

static unsigned dm_bitmap_word_used(void *addr, unsigned b)
{
	__le64 *words_le = addr;
	__le64 *w_le = words_le + (b >> ENTRIES_SHIFT);

	uint64_t bits = le64_to_cpu(*w_le);
	uint64_t mask = (bits + WORD_MASK_HIGH + 1) & WORD_MASK_HIGH;

	return !(~bits & mask);
}

static unsigned sm_lookup_bitmap(void *addr, unsigned b)
{
	__le64 *words_le = addr;
	__le64 *w_le = words_le + (b >> ENTRIES_SHIFT);
	unsigned hi, lo;

	b = (b & (ENTRIES_PER_WORD - 1)) << 1;
	hi = !!test_bit_le(b, (void *) w_le);
	lo = !!test_bit_le(b + 1, (void *) w_le);
	return (hi << 1) | lo;
}

static void sm_set_bitmap(void *addr, unsigned b, unsigned val)
{
	__le64 *words_le = addr;
	__le64 *w_le = words_le + (b >> ENTRIES_SHIFT);

	b = (b & (ENTRIES_PER_WORD - 1)) << 1;

	if (val & 2)
		__set_bit_le(b, (void *) w_le);
	else
		__clear_bit_le(b, (void *) w_le);

	if (val & 1)
		__set_bit_le(b + 1, (void *) w_le);
	else
		__clear_bit_le(b + 1, (void *) w_le);
}

static int sm_find_free(void *addr, unsigned begin, unsigned end,
			unsigned *result)
{
	while (begin < end) {
		if (!(begin & (ENTRIES_PER_WORD - 1)) &&
		    dm_bitmap_word_used(addr, begin)) {
			begin += ENTRIES_PER_WORD;
			continue;
		}

		if (!sm_lookup_bitmap(addr, begin)) {
			*result = begin;
			return 0;
		}

		begin++;
	}

	return -ENOSPC;
}

/*----------------------------------------------------------------*/

static int sm_ll_init(struct ll_disk *ll, struct dm_transaction_manager *tm)
{
	memset(ll, 0, sizeof(struct ll_disk));

	ll->tm = tm;

	ll->bitmap_info.tm = tm;
	ll->bitmap_info.levels = 1;

	/*
	 * Because the new bitmap blocks are created via a shadow
	 * operation, the old entry has already had its reference count
	 * decremented and we don't need the btree to do any bookkeeping.
	 */
	ll->bitmap_info.value_type.size = sizeof(struct disk_index_entry);
	ll->bitmap_info.value_type.inc = NULL;
	ll->bitmap_info.value_type.dec = NULL;
	ll->bitmap_info.value_type.equal = NULL;

	ll->ref_count_info.tm = tm;
	ll->ref_count_info.levels = 1;
	ll->ref_count_info.value_type.size = sizeof(uint32_t);
	ll->ref_count_info.value_type.inc = NULL;
	ll->ref_count_info.value_type.dec = NULL;
	ll->ref_count_info.value_type.equal = NULL;

	ll->block_size = dm_bm_block_size(dm_tm_get_bm(tm));

	if (ll->block_size > (1 << 30)) {
		DMERR("block size too big to hold bitmaps");
		return -EINVAL;
	}

	ll->entries_per_block = (ll->block_size - sizeof(struct disk_bitmap_header)) *
		ENTRIES_PER_BYTE;
	ll->nr_blocks = 0;
	ll->bitmap_root = 0;
	ll->ref_count_root = 0;
	ll->bitmap_index_changed = false;

	return 0;
}

int sm_ll_extend(struct ll_disk *ll, dm_block_t extra_blocks)
{
	int r;
	dm_block_t i, nr_blocks, nr_indexes;
	unsigned old_blocks, blocks;

	nr_blocks = ll->nr_blocks + extra_blocks;
	old_blocks = dm_sector_div_up(ll->nr_blocks, ll->entries_per_block);
	blocks = dm_sector_div_up(nr_blocks, ll->entries_per_block);

	nr_indexes = dm_sector_div_up(nr_blocks, ll->entries_per_block);
	if (nr_indexes > ll->max_entries(ll)) {
		DMERR("space map too large");
		return -EINVAL;
	}

	/*
	 * We need to set this before the dm_tm_new_block() call below.
	 */
	ll->nr_blocks = nr_blocks;
	for (i = old_blocks; i < blocks; i++) {
		struct dm_block *b;
		struct disk_index_entry idx;

		r = dm_tm_new_block(ll->tm, &dm_sm_bitmap_validator, &b);
		if (r < 0)
			return r;

		idx.blocknr = cpu_to_le64(dm_block_location(b));

		dm_tm_unlock(ll->tm, b);

		idx.nr_free = cpu_to_le32(ll->entries_per_block);
		idx.none_free_before = 0;

		r = ll->save_ie(ll, i, &idx);
		if (r < 0)
			return r;
	}

	return 0;
}

int sm_ll_lookup_bitmap(struct ll_disk *ll, dm_block_t b, uint32_t *result)
{
	int r;
	dm_block_t index = b;
	struct disk_index_entry ie_disk;
	struct dm_block *blk;

	b = do_div(index, ll->entries_per_block);
	r = ll->load_ie(ll, index, &ie_disk);
	if (r < 0)
		return r;

	r = dm_tm_read_lock(ll->tm, le64_to_cpu(ie_disk.blocknr),
			    &dm_sm_bitmap_validator, &blk);
	if (r < 0)
		return r;

	*result = sm_lookup_bitmap(dm_bitmap_data(blk), b);

	dm_tm_unlock(ll->tm, blk);

	return 0;
}

static int sm_ll_lookup_big_ref_count(struct ll_disk *ll, dm_block_t b,
				      uint32_t *result)
{
	__le32 le_rc;
	int r;

	r = dm_btree_lookup(&ll->ref_count_info, ll->ref_count_root, &b, &le_rc);
	if (r < 0)
		return r;

	*result = le32_to_cpu(le_rc);

	return r;
}

int sm_ll_lookup(struct ll_disk *ll, dm_block_t b, uint32_t *result)
{
	int r = sm_ll_lookup_bitmap(ll, b, result);

	if (r)
		return r;

	if (*result != 3)
		return r;

	return sm_ll_lookup_big_ref_count(ll, b, result);
}

int sm_ll_find_free_block(struct ll_disk *ll, dm_block_t begin,
			  dm_block_t end, dm_block_t *result)
{
	int r;
	struct disk_index_entry ie_disk;
	dm_block_t i, index_begin = begin;
	dm_block_t index_end = dm_sector_div_up(end, ll->entries_per_block);

	/*
	 * FIXME: Use shifts
	 */
	begin = do_div(index_begin, ll->entries_per_block);
	end = do_div(end, ll->entries_per_block);
	if (end == 0)
		end = ll->entries_per_block;

	for (i = index_begin; i < index_end; i++, begin = 0) {
		struct dm_block *blk;
		unsigned position;
		uint32_t bit_end;

		r = ll->load_ie(ll, i, &ie_disk);
		if (r < 0)
			return r;

		if (le32_to_cpu(ie_disk.nr_free) == 0)
			continue;

		r = dm_tm_read_lock(ll->tm, le64_to_cpu(ie_disk.blocknr),
				    &dm_sm_bitmap_validator, &blk);
		if (r < 0)
			return r;

		bit_end = (i == index_end - 1) ?  end : ll->entries_per_block;

		r = sm_find_free(dm_bitmap_data(blk),
				 max_t(unsigned, begin, le32_to_cpu(ie_disk.none_free_before)),
				 bit_end, &position);
		if (r == -ENOSPC) {
			/*
			 * This might happen because we started searching
			 * part way through the bitmap.
			 */
			dm_tm_unlock(ll->tm, blk);
			continue;
		}

		dm_tm_unlock(ll->tm, blk);

		*result = i * ll->entries_per_block + (dm_block_t) position;
		return 0;
	}

	return -ENOSPC;
}

int sm_ll_find_common_free_block(struct ll_disk *old_ll, struct ll_disk *new_ll,
	                         dm_block_t begin, dm_block_t end, dm_block_t *b)
{
	int r;
	uint32_t count;

	do {
		r = sm_ll_find_free_block(new_ll, begin, new_ll->nr_blocks, b);
		if (r)
			break;

		/* double check this block wasn't used in the old transaction */
		if (*b >= old_ll->nr_blocks)
			count = 0;
		else {
			r = sm_ll_lookup(old_ll, *b, &count);
			if (r)
				break;

			if (count)
				begin = *b + 1;
		}
	} while (count);

	return r;
}

/*----------------------------------------------------------------*/

int sm_ll_insert(struct ll_disk *ll, dm_block_t b,
		 uint32_t ref_count, int32_t *nr_allocations)
{
	int r;
	uint32_t bit, old;
	struct dm_block *nb;
	dm_block_t index = b;
	struct disk_index_entry ie_disk;
	void *bm_le;
	int inc;

	bit = do_div(index, ll->entries_per_block);
	r = ll->load_ie(ll, index, &ie_disk);
	if (r < 0)
		return r;

	r = dm_tm_shadow_block(ll->tm, le64_to_cpu(ie_disk.blocknr),
			       &dm_sm_bitmap_validator, &nb, &inc);
	if (r < 0) {
		DMERR("dm_tm_shadow_block() failed");
		return r;
	}
	ie_disk.blocknr = cpu_to_le64(dm_block_location(nb));
	bm_le = dm_bitmap_data(nb);

	old = sm_lookup_bitmap(bm_le, bit);
	if (old > 2) {
		r = sm_ll_lookup_big_ref_count(ll, b, &old);
		if (r < 0) {
			dm_tm_unlock(ll->tm, nb);
			return r;
		}
	}

	if (r) {
		dm_tm_unlock(ll->tm, nb);
		return r;
	}

	if (ref_count <= 2) {
		sm_set_bitmap(bm_le, bit, ref_count);
		dm_tm_unlock(ll->tm, nb);

		if (old > 2) {
			r = dm_btree_remove(&ll->ref_count_info,
					    ll->ref_count_root,
					    &b, &ll->ref_count_root);
			if (r)
				return r;
		}

	} else {
		__le32 le_rc = cpu_to_le32(ref_count);

		sm_set_bitmap(bm_le, bit, 3);
		dm_tm_unlock(ll->tm, nb);

		__dm_bless_for_disk(&le_rc);
		r = dm_btree_insert(&ll->ref_count_info, ll->ref_count_root,
				    &b, &le_rc, &ll->ref_count_root);
		if (r < 0) {
			DMERR("ref count insert failed");
			return r;
		}
	}

	if (ref_count && !old) {
		*nr_allocations = 1;
		ll->nr_allocated++;
		le32_add_cpu(&ie_disk.nr_free, -1);
		if (le32_to_cpu(ie_disk.none_free_before) == bit)
			ie_disk.none_free_before = cpu_to_le32(bit + 1);

	} else if (old && !ref_count) {
		*nr_allocations = -1;
		ll->nr_allocated--;
		le32_add_cpu(&ie_disk.nr_free, 1);
		ie_disk.none_free_before = cpu_to_le32(min(le32_to_cpu(ie_disk.none_free_before), bit));
	} else
		*nr_allocations = 0;

	return ll->save_ie(ll, index, &ie_disk);
}

/*----------------------------------------------------------------*/

/*
 * Holds useful intermediate results for the range based inc and dec
 * operations.
 */
struct inc_context {
	struct disk_index_entry ie_disk;
	struct dm_block *bitmap_block;
	void *bitmap;

	struct dm_block *overflow_leaf;
};

static inline void init_inc_context(struct inc_context *ic)
{
	ic->bitmap_block = NULL;
	ic->bitmap = NULL;
	ic->overflow_leaf = NULL;
}

static inline void exit_inc_context(struct ll_disk *ll, struct inc_context *ic)
{
	if (ic->bitmap_block)
		dm_tm_unlock(ll->tm, ic->bitmap_block);
	if (ic->overflow_leaf)
		dm_tm_unlock(ll->tm, ic->overflow_leaf);
}

static inline void reset_inc_context(struct ll_disk *ll, struct inc_context *ic)
{
	exit_inc_context(ll, ic);
	init_inc_context(ic);
}

/*
 * Confirms a btree node contains a particular key at an index.
 */
static bool contains_key(struct btree_node *n, uint64_t key, int index)
{
	return index >= 0 &&
		index < le32_to_cpu(n->header.nr_entries) &&
		le64_to_cpu(n->keys[index]) == key;
}

static int __sm_ll_inc_overflow(struct ll_disk *ll, dm_block_t b, struct inc_context *ic)
{
	int r;
	int index;
	struct btree_node *n;
	__le32 *v_ptr;
	uint32_t rc;

	/*
	 * bitmap_block needs to be unlocked because getting the
	 * overflow_leaf may need to allocate, and thus use the space map.
	 */
	reset_inc_context(ll, ic);

	r = btree_get_overwrite_leaf(&ll->ref_count_info, ll->ref_count_root,
				     b, &index, &ll->ref_count_root, &ic->overflow_leaf);
	if (r < 0)
		return r;

	n = dm_block_data(ic->overflow_leaf);

	if (!contains_key(n, b, index)) {
		DMERR("overflow btree is missing an entry");
		return -EINVAL;
	}

	v_ptr = value_ptr(n, index);
	rc = le32_to_cpu(*v_ptr) + 1;
	*v_ptr = cpu_to_le32(rc);

	return 0;
}

static int sm_ll_inc_overflow(struct ll_disk *ll, dm_block_t b, struct inc_context *ic)
{
	int index;
	struct btree_node *n;
	__le32 *v_ptr;
	uint32_t rc;

	/*
	 * Do we already have the correct overflow leaf?
	 */
	if (ic->overflow_leaf) {
		n = dm_block_data(ic->overflow_leaf);
		index = lower_bound(n, b);
		if (contains_key(n, b, index)) {
			v_ptr = value_ptr(n, index);
			rc = le32_to_cpu(*v_ptr) + 1;
			*v_ptr = cpu_to_le32(rc);

			return 0;
		}
	}

	return __sm_ll_inc_overflow(ll, b, ic);
}

static inline int shadow_bitmap(struct ll_disk *ll, struct inc_context *ic)
{
	int r, inc;
	r = dm_tm_shadow_block(ll->tm, le64_to_cpu(ic->ie_disk.blocknr),
			       &dm_sm_bitmap_validator, &ic->bitmap_block, &inc);
	if (r < 0) {
		DMERR("dm_tm_shadow_block() failed");
		return r;
	}
	ic->ie_disk.blocknr = cpu_to_le64(dm_block_location(ic->bitmap_block));
	ic->bitmap = dm_bitmap_data(ic->bitmap_block);
	return 0;
}

/*
 * Once shadow_bitmap has been called, which always happens at the start of inc/dec,
 * we can reopen the bitmap with a simple write lock, rather than re calling
 * dm_tm_shadow_block().
 */
static inline int ensure_bitmap(struct ll_disk *ll, struct inc_context *ic)
{
	if (!ic->bitmap_block) {
		int r = dm_bm_write_lock(dm_tm_get_bm(ll->tm), le64_to_cpu(ic->ie_disk.blocknr),
					 &dm_sm_bitmap_validator, &ic->bitmap_block);
		if (r) {
			DMERR("unable to re-get write lock for bitmap");
			return r;
		}
		ic->bitmap = dm_bitmap_data(ic->bitmap_block);
	}

	return 0;
}

/*
 * Loops round incrementing entries in a single bitmap.
 */
static inline int sm_ll_inc_bitmap(struct ll_disk *ll, dm_block_t b,
				   uint32_t bit, uint32_t bit_end,
				   int32_t *nr_allocations, dm_block_t *new_b,
				   struct inc_context *ic)
{
	int r;
	__le32 le_rc;
	uint32_t old;

	for (; bit != bit_end; bit++, b++) {
		/*
		 * We only need to drop the bitmap if we need to find a new btree
		 * leaf for the overflow.  So if it was dropped last iteration,
		 * we now re-get it.
		 */
		r = ensure_bitmap(ll, ic);
		if (r)
			return r;

		old = sm_lookup_bitmap(ic->bitmap, bit);
		switch (old) {
		case 0:
			/* inc bitmap, adjust nr_allocated */
			sm_set_bitmap(ic->bitmap, bit, 1);
			(*nr_allocations)++;
			ll->nr_allocated++;
			le32_add_cpu(&ic->ie_disk.nr_free, -1);
			if (le32_to_cpu(ic->ie_disk.none_free_before) == bit)
				ic->ie_disk.none_free_before = cpu_to_le32(bit + 1);
			break;

		case 1:
			/* inc bitmap */
			sm_set_bitmap(ic->bitmap, bit, 2);
			break;

		case 2:
			/* inc bitmap and insert into overflow */
			sm_set_bitmap(ic->bitmap, bit, 3);
			reset_inc_context(ll, ic);

			le_rc = cpu_to_le32(3);
			__dm_bless_for_disk(&le_rc);
			r = dm_btree_insert(&ll->ref_count_info, ll->ref_count_root,
					    &b, &le_rc, &ll->ref_count_root);
			if (r < 0) {
				DMERR("ref count insert failed");
				return r;
			}
			break;

		default:
			/*
			 * inc within the overflow tree only.
			 */
			r = sm_ll_inc_overflow(ll, b, ic);
			if (r < 0)
				return r;
		}
	}

	*new_b = b;
	return 0;
}

/*
 * Finds a bitmap that contains entries in the block range, and increments
 * them.
 */
static int __sm_ll_inc(struct ll_disk *ll, dm_block_t b, dm_block_t e,
		       int32_t *nr_allocations, dm_block_t *new_b)
{
	int r;
	struct inc_context ic;
	uint32_t bit, bit_end;
	dm_block_t index = b;

	init_inc_context(&ic);

	bit = do_div(index, ll->entries_per_block);
	r = ll->load_ie(ll, index, &ic.ie_disk);
	if (r < 0)
		return r;

	r = shadow_bitmap(ll, &ic);
	if (r)
		return r;

	bit_end = min(bit + (e - b), (dm_block_t) ll->entries_per_block);
	r = sm_ll_inc_bitmap(ll, b, bit, bit_end, nr_allocations, new_b, &ic);

	exit_inc_context(ll, &ic);

	if (r)
		return r;

	return ll->save_ie(ll, index, &ic.ie_disk);
}

int sm_ll_inc(struct ll_disk *ll, dm_block_t b, dm_block_t e,
	      int32_t *nr_allocations)
{
	*nr_allocations = 0;
	while (b != e) {
		int r = __sm_ll_inc(ll, b, e, nr_allocations, &b);
		if (r)
			return r;
	}

	return 0;
}

/*----------------------------------------------------------------*/

static int __sm_ll_del_overflow(struct ll_disk *ll, dm_block_t b,
				struct inc_context *ic)
{
	reset_inc_context(ll, ic);
	return dm_btree_remove(&ll->ref_count_info, ll->ref_count_root,
			       &b, &ll->ref_count_root);
}

static int __sm_ll_dec_overflow(struct ll_disk *ll, dm_block_t b,
				struct inc_context *ic, uint32_t *old_rc)
{
	int r;
	int index = -1;
	struct btree_node *n;
	__le32 *v_ptr;
	uint32_t rc;

	reset_inc_context(ll, ic);
	r = btree_get_overwrite_leaf(&ll->ref_count_info, ll->ref_count_root,
				     b, &index, &ll->ref_count_root, &ic->overflow_leaf);
	if (r < 0)
		return r;

	n = dm_block_data(ic->overflow_leaf);

	if (!contains_key(n, b, index)) {
		DMERR("overflow btree is missing an entry");
		return -EINVAL;
	}

	v_ptr = value_ptr(n, index);
	rc = le32_to_cpu(*v_ptr);
	*old_rc = rc;

	if (rc == 3) {
		return __sm_ll_del_overflow(ll, b, ic);
	} else {
		rc--;
		*v_ptr = cpu_to_le32(rc);
		return 0;
	}
}

static int sm_ll_dec_overflow(struct ll_disk *ll, dm_block_t b,
			      struct inc_context *ic, uint32_t *old_rc)
{
	/*
	 * Do we already have the correct overflow leaf?
	 */
	if (ic->overflow_leaf) {
		int index;
		struct btree_node *n;
		__le32 *v_ptr;
		uint32_t rc;

		n = dm_block_data(ic->overflow_leaf);
		index = lower_bound(n, b);
		if (contains_key(n, b, index)) {
			v_ptr = value_ptr(n, index);
			rc = le32_to_cpu(*v_ptr);
			*old_rc = rc;

			if (rc > 3) {
				rc--;
				*v_ptr = cpu_to_le32(rc);
				return 0;
			} else {
				return __sm_ll_del_overflow(ll, b, ic);
			}

		}
	}

	return __sm_ll_dec_overflow(ll, b, ic, old_rc);
}

/*
 * Loops round incrementing entries in a single bitmap.
 */
static inline int sm_ll_dec_bitmap(struct ll_disk *ll, dm_block_t b,
				   uint32_t bit, uint32_t bit_end,
				   struct inc_context *ic,
				   int32_t *nr_allocations, dm_block_t *new_b)
{
	int r;
	uint32_t old;

	for (; bit != bit_end; bit++, b++) {
		/*
		 * We only need to drop the bitmap if we need to find a new btree
		 * leaf for the overflow.  So if it was dropped last iteration,
		 * we now re-get it.
		 */
		r = ensure_bitmap(ll, ic);
		if (r)
			return r;

		old = sm_lookup_bitmap(ic->bitmap, bit);
		switch (old) {
		case 0:
			DMERR("unable to decrement block");
			return -EINVAL;

		case 1:
			/* dec bitmap */
			sm_set_bitmap(ic->bitmap, bit, 0);
			(*nr_allocations)--;
			ll->nr_allocated--;
			le32_add_cpu(&ic->ie_disk.nr_free, 1);
			ic->ie_disk.none_free_before =
				cpu_to_le32(min(le32_to_cpu(ic->ie_disk.none_free_before), bit));
			break;

		case 2:
			/* dec bitmap and insert into overflow */
			sm_set_bitmap(ic->bitmap, bit, 1);
			break;

		case 3:
			r = sm_ll_dec_overflow(ll, b, ic, &old);
			if (r < 0)
				return r;

			if (old == 3) {
				r = ensure_bitmap(ll, ic);
				if (r)
					return r;

				sm_set_bitmap(ic->bitmap, bit, 2);
			}
			break;
		}
	}

	*new_b = b;
	return 0;
}

static int __sm_ll_dec(struct ll_disk *ll, dm_block_t b, dm_block_t e,
		       int32_t *nr_allocations, dm_block_t *new_b)
{
	int r;
	uint32_t bit, bit_end;
	struct inc_context ic;
	dm_block_t index = b;

	init_inc_context(&ic);

	bit = do_div(index, ll->entries_per_block);
	r = ll->load_ie(ll, index, &ic.ie_disk);
	if (r < 0)
		return r;

	r = shadow_bitmap(ll, &ic);
	if (r)
		return r;

	bit_end = min(bit + (e - b), (dm_block_t) ll->entries_per_block);
	r = sm_ll_dec_bitmap(ll, b, bit, bit_end, &ic, nr_allocations, new_b);
	exit_inc_context(ll, &ic);

	if (r)
		return r;

	return ll->save_ie(ll, index, &ic.ie_disk);
}

int sm_ll_dec(struct ll_disk *ll, dm_block_t b, dm_block_t e,
	      int32_t *nr_allocations)
{
	*nr_allocations = 0;
	while (b != e) {
		int r = __sm_ll_dec(ll, b, e, nr_allocations, &b);
		if (r)
			return r;
	}

	return 0;
}

/*----------------------------------------------------------------*/

int sm_ll_commit(struct ll_disk *ll)
{
	int r = 0;

	if (ll->bitmap_index_changed) {
		r = ll->commit(ll);
		if (!r)
			ll->bitmap_index_changed = false;
	}

	return r;
}

/*----------------------------------------------------------------*/

static int metadata_ll_load_ie(struct ll_disk *ll, dm_block_t index,
			       struct disk_index_entry *ie)
{
	memcpy(ie, ll->mi_le.index + index, sizeof(*ie));
	return 0;
}

static int metadata_ll_save_ie(struct ll_disk *ll, dm_block_t index,
			       struct disk_index_entry *ie)
{
	ll->bitmap_index_changed = true;
	memcpy(ll->mi_le.index + index, ie, sizeof(*ie));
	return 0;
}

static int metadata_ll_init_index(struct ll_disk *ll)
{
	int r;
	struct dm_block *b;

	r = dm_tm_new_block(ll->tm, &index_validator, &b);
	if (r < 0)
		return r;

	ll->bitmap_root = dm_block_location(b);

	dm_tm_unlock(ll->tm, b);

	return 0;
}

static int metadata_ll_open(struct ll_disk *ll)
{
	int r;
	struct dm_block *block;

	r = dm_tm_read_lock(ll->tm, ll->bitmap_root,
			    &index_validator, &block);
	if (r)
		return r;

	memcpy(&ll->mi_le, dm_block_data(block), sizeof(ll->mi_le));
	dm_tm_unlock(ll->tm, block);

	return 0;
}

static dm_block_t metadata_ll_max_entries(struct ll_disk *ll)
{
	return MAX_METADATA_BITMAPS;
}

static int metadata_ll_commit(struct ll_disk *ll)
{
	int r, inc;
	struct dm_block *b;

	r = dm_tm_shadow_block(ll->tm, ll->bitmap_root, &index_validator, &b, &inc);
	if (r)
		return r;

	memcpy(dm_block_data(b), &ll->mi_le, sizeof(ll->mi_le));
	ll->bitmap_root = dm_block_location(b);

	dm_tm_unlock(ll->tm, b);

	return 0;
}

int sm_ll_new_metadata(struct ll_disk *ll, struct dm_transaction_manager *tm)
{
	int r;

	r = sm_ll_init(ll, tm);
	if (r < 0)
		return r;

	ll->load_ie = metadata_ll_load_ie;
	ll->save_ie = metadata_ll_save_ie;
	ll->init_index = metadata_ll_init_index;
	ll->open_index = metadata_ll_open;
	ll->max_entries = metadata_ll_max_entries;
	ll->commit = metadata_ll_commit;

	ll->nr_blocks = 0;
	ll->nr_allocated = 0;

	r = ll->init_index(ll);
	if (r < 0)
		return r;

	r = dm_btree_empty(&ll->ref_count_info, &ll->ref_count_root);
	if (r < 0)
		return r;

	return 0;
}

int sm_ll_open_metadata(struct ll_disk *ll, struct dm_transaction_manager *tm,
			void *root_le, size_t len)
{
	int r;
	struct disk_sm_root smr;

	if (len < sizeof(struct disk_sm_root)) {
		DMERR("sm_metadata root too small");
		return -ENOMEM;
	}

	/*
	 * We don't know the alignment of the root_le buffer, so need to
	 * copy into a new structure.
	 */
	memcpy(&smr, root_le, sizeof(smr));

	r = sm_ll_init(ll, tm);
	if (r < 0)
		return r;

	ll->load_ie = metadata_ll_load_ie;
	ll->save_ie = metadata_ll_save_ie;
	ll->init_index = metadata_ll_init_index;
	ll->open_index = metadata_ll_open;
	ll->max_entries = metadata_ll_max_entries;
	ll->commit = metadata_ll_commit;

	ll->nr_blocks = le64_to_cpu(smr.nr_blocks);
	ll->nr_allocated = le64_to_cpu(smr.nr_allocated);
	ll->bitmap_root = le64_to_cpu(smr.bitmap_root);
	ll->ref_count_root = le64_to_cpu(smr.ref_count_root);

	return ll->open_index(ll);
}

/*----------------------------------------------------------------*/

static inline int ie_cache_writeback(struct ll_disk *ll, struct ie_cache *iec)
{
	iec->dirty = false;
	__dm_bless_for_disk(iec->ie);
	return dm_btree_insert(&ll->bitmap_info, ll->bitmap_root,
			       &iec->index, &iec->ie, &ll->bitmap_root);
}

static inline unsigned hash_index(dm_block_t index)
{
	return dm_hash_block(index, IE_CACHE_MASK);
}

static int disk_ll_load_ie(struct ll_disk *ll, dm_block_t index,
			   struct disk_index_entry *ie)
{
	int r;
	unsigned h = hash_index(index);
	struct ie_cache *iec = ll->ie_cache + h;

	if (iec->valid) {
		if (iec->index == index) {
			memcpy(ie, &iec->ie, sizeof(*ie));
			return 0;
		}

		if (iec->dirty) {
			r = ie_cache_writeback(ll, iec);
			if (r)
				return r;
		}
	}

	r = dm_btree_lookup(&ll->bitmap_info, ll->bitmap_root, &index, ie);
	if (!r) {
		iec->valid = true;
		iec->dirty = false;
		iec->index = index;
		memcpy(&iec->ie, ie, sizeof(*ie));
	}

	return r;
}

static int disk_ll_save_ie(struct ll_disk *ll, dm_block_t index,
			   struct disk_index_entry *ie)
{
	int r;
	unsigned h = hash_index(index);
	struct ie_cache *iec = ll->ie_cache + h;

	ll->bitmap_index_changed = true;
	if (iec->valid) {
		if (iec->index == index) {
			memcpy(&iec->ie, ie, sizeof(*ie));
			iec->dirty = true;
			return 0;
		}

		if (iec->dirty) {
			r = ie_cache_writeback(ll, iec);
			if (r)
				return r;
		}
	}

	iec->valid = true;
	iec->dirty = true;
	iec->index = index;
	memcpy(&iec->ie, ie, sizeof(*ie));
	return 0;
}

static int disk_ll_init_index(struct ll_disk *ll)
{
	unsigned i;
	for (i = 0; i < IE_CACHE_SIZE; i++) {
		struct ie_cache *iec = ll->ie_cache + i;
		iec->valid = false;
		iec->dirty = false;
	}
	return dm_btree_empty(&ll->bitmap_info, &ll->bitmap_root);
}

static int disk_ll_open(struct ll_disk *ll)
{
	return 0;
}

static dm_block_t disk_ll_max_entries(struct ll_disk *ll)
{
	return -1ULL;
}

static int disk_ll_commit(struct ll_disk *ll)
{
	int r = 0;
	unsigned i;

	for (i = 0; i < IE_CACHE_SIZE; i++) {
		struct ie_cache *iec = ll->ie_cache + i;
		if (iec->valid && iec->dirty)
			r = ie_cache_writeback(ll, iec);
	}

	return r;
}

int sm_ll_new_disk(struct ll_disk *ll, struct dm_transaction_manager *tm)
{
	int r;

	r = sm_ll_init(ll, tm);
	if (r < 0)
		return r;

	ll->load_ie = disk_ll_load_ie;
	ll->save_ie = disk_ll_save_ie;
	ll->init_index = disk_ll_init_index;
	ll->open_index = disk_ll_open;
	ll->max_entries = disk_ll_max_entries;
	ll->commit = disk_ll_commit;

	ll->nr_blocks = 0;
	ll->nr_allocated = 0;

	r = ll->init_index(ll);
	if (r < 0)
		return r;

	r = dm_btree_empty(&ll->ref_count_info, &ll->ref_count_root);
	if (r < 0)
		return r;

	return 0;
}

int sm_ll_open_disk(struct ll_disk *ll, struct dm_transaction_manager *tm,
		    void *root_le, size_t len)
{
	int r;
	struct disk_sm_root *smr = root_le;

	if (len < sizeof(struct disk_sm_root)) {
		DMERR("sm_metadata root too small");
		return -ENOMEM;
	}

	r = sm_ll_init(ll, tm);
	if (r < 0)
		return r;

	ll->load_ie = disk_ll_load_ie;
	ll->save_ie = disk_ll_save_ie;
	ll->init_index = disk_ll_init_index;
	ll->open_index = disk_ll_open;
	ll->max_entries = disk_ll_max_entries;
	ll->commit = disk_ll_commit;

	ll->nr_blocks = le64_to_cpu(smr->nr_blocks);
	ll->nr_allocated = le64_to_cpu(smr->nr_allocated);
	ll->bitmap_root = le64_to_cpu(smr->bitmap_root);
	ll->ref_count_root = le64_to_cpu(smr->ref_count_root);

	return ll->open_index(ll);
}

/*----------------------------------------------------------------*/