[mirror_ubuntu-artful-kernel.git] / fs / btrfs / extent-tree.c

#include <stdio.h>
#include <stdlib.h>
#include "kerncompat.h"
#include "radix-tree.h"
#include "ctree.h"
#include "disk-io.h"
#include "print-tree.h"

static int find_free_extent(struct ctree_root *orig_root, u64 num_blocks,
			    u64 search_start, u64 search_end, struct key *ins);
static int finish_current_insert(struct ctree_root *extent_root);
static int run_pending(struct ctree_root *extent_root);

/*
 * pending extents are blocks that we're trying to allocate in the extent
 * map while trying to grow the map because of other allocations.  To avoid
 * recursing, they are tagged in the radix tree and cleaned up after
 * other allocations are done.  The pending tag is also used in the same
 * manner for deletes.
 */
#define CTREE_EXTENT_PENDING_DEL 0

static int inc_block_ref(struct ctree_root *root, u64 blocknr)
{
	struct ctree_path path;
	int ret;
	struct key key;
	struct leaf *l;
	struct extent_item *item;
	struct key ins;

	find_free_extent(root->extent_root, 0, 0, (u64)-1, &ins);
	init_path(&path);
	key.objectid = blocknr;
	key.flags = 0;
	key.offset = 1;
	ret = search_slot(root->extent_root, &key, &path, 0, 1);
	if (ret != 0)
		BUG();
	BUG_ON(ret != 0);
	l = &path.nodes[0]->leaf;
	item = (struct extent_item *)(l->data +
				      l->items[path.slots[0]].offset);
	item->refs++;

	BUG_ON(list_empty(&path.nodes[0]->dirty));
	release_path(root->extent_root, &path);
	finish_current_insert(root->extent_root);
	run_pending(root->extent_root);
	return 0;
}

static int lookup_block_ref(struct ctree_root *root, u64 blocknr, u32 *refs)
{
	struct ctree_path path;
	int ret;
	struct key key;
	struct leaf *l;
	struct extent_item *item;
	init_path(&path);
	key.objectid = blocknr;
	key.flags = 0;
	key.offset = 1;
	ret = search_slot(root->extent_root, &key, &path, 0, 0);
	if (ret != 0)
		BUG();
	l = &path.nodes[0]->leaf;
	item = (struct extent_item *)(l->data +
				      l->items[path.slots[0]].offset);
	*refs = item->refs;
	release_path(root->extent_root, &path);
	return 0;
}

int btrfs_inc_ref(struct ctree_root *root, struct tree_buffer *buf)
{
	u64 blocknr;
	int i;

	if (root == root->extent_root)
		return 0;
	if (btrfs_is_leaf(&buf->node))
		return 0;

	for (i = 0; i < btrfs_header_nritems(&buf->node.header); i++) {
		blocknr = buf->node.blockptrs[i];
		inc_block_ref(root, blocknr);
	}
	return 0;
}

int btrfs_finish_extent_commit(struct ctree_root *root)
{
	struct ctree_root *extent_root = root->extent_root;
	unsigned long gang[8];
	int ret;
	int i;

	while(1) {
		ret = radix_tree_gang_lookup(&extent_root->pinned_radix,
						 (void **)gang, 0,
						 ARRAY_SIZE(gang));
		if (!ret)
			break;
		for (i = 0; i < ret; i++) {
			radix_tree_delete(&extent_root->pinned_radix, gang[i]);
		}
	}
	extent_root->last_insert.objectid = 0;
	extent_root->last_insert.offset = 0;
	return 0;
}

static int finish_current_insert(struct ctree_root *extent_root)
{
	struct key ins;
	struct extent_item extent_item;
	int i;
	int ret;

	extent_item.refs = 1;
	extent_item.owner =
		btrfs_header_parentid(&extent_root->node->node.header);
	ins.offset = 1;
	ins.flags = 0;

	for (i = 0; i < extent_root->current_insert.flags; i++) {
		ins.objectid = extent_root->current_insert.objectid + i;
		ret = insert_item(extent_root, &ins, &extent_item,
				  sizeof(extent_item));
		BUG_ON(ret);
	}
	extent_root->current_insert.offset = 0;
	return 0;
}

/*
 * remove an extent from the root, returns 0 on success
 */
int __free_extent(struct ctree_root *root, u64 blocknr, u64 num_blocks)
{
	struct ctree_path path;
	struct key key;
	struct ctree_root *extent_root = root->extent_root;
	int ret;
	struct item *item;
	struct extent_item *ei;
	struct key ins;

	key.objectid = blocknr;
	key.flags = 0;
	key.offset = num_blocks;

	find_free_extent(root, 0, 0, (u64)-1, &ins);
	init_path(&path);
	ret = search_slot(extent_root, &key, &path, -1, 1);
	if (ret) {
		printf("failed to find %Lu\n", key.objectid);
		print_tree(extent_root, extent_root->node);
		printf("failed to find %Lu\n", key.objectid);
		BUG();
	}
	item = path.nodes[0]->leaf.items + path.slots[0];
	ei = (struct extent_item *)(path.nodes[0]->leaf.data + item->offset);
	BUG_ON(ei->refs == 0);
	ei->refs--;
	if (ei->refs == 0) {
		if (root == extent_root) {
			int err;
			radix_tree_preload(GFP_KERNEL);
			err = radix_tree_insert(&extent_root->pinned_radix,
					  blocknr, (void *)blocknr);
			BUG_ON(err);
			radix_tree_preload_end();
		}
		ret = del_item(extent_root, &path);
		if (root != extent_root &&
		    extent_root->last_insert.objectid < blocknr)
			extent_root->last_insert.objectid = blocknr;
		if (ret)
			BUG();
	}
	release_path(extent_root, &path);
	finish_current_insert(extent_root);
	return ret;
}

/*
 * find all the blocks marked as pending in the radix tree and remove
 * them from the extent map
 */
static int del_pending_extents(struct ctree_root *extent_root)
{
	int ret;
	struct tree_buffer *gang[4];
	int i;

	while(1) {
		ret = radix_tree_gang_lookup_tag(&extent_root->cache_radix,
						 (void **)gang, 0,
						 ARRAY_SIZE(gang),
						 CTREE_EXTENT_PENDING_DEL);
		if (!ret)
			break;
		for (i = 0; i < ret; i++) {
			ret = __free_extent(extent_root, gang[i]->blocknr, 1);
			radix_tree_tag_clear(&extent_root->cache_radix,
						gang[i]->blocknr,
						CTREE_EXTENT_PENDING_DEL);
			tree_block_release(extent_root, gang[i]);
		}
	}
	return 0;
}

static int run_pending(struct ctree_root *extent_root)
{
	while(radix_tree_tagged(&extent_root->cache_radix,
			        CTREE_EXTENT_PENDING_DEL))
		del_pending_extents(extent_root);
	return 0;
}


/*
 * remove an extent from the root, returns 0 on success
 */
int free_extent(struct ctree_root *root, u64 blocknr, u64 num_blocks)
{
	struct key key;
	struct ctree_root *extent_root = root->extent_root;
	struct tree_buffer *t;
	int pending_ret;
	int ret;

	if (root == extent_root) {
		t = find_tree_block(root, blocknr);
		radix_tree_tag_set(&root->cache_radix, blocknr,
				   CTREE_EXTENT_PENDING_DEL);
		return 0;
	}
	key.objectid = blocknr;
	key.flags = 0;
	key.offset = num_blocks;
	ret = __free_extent(root, blocknr, num_blocks);
	pending_ret = run_pending(root->extent_root);
	return ret ? ret : pending_ret;
}

/*
 * walks the btree of allocated extents and find a hole of a given size.
 * The key ins is changed to record the hole:
 * ins->objectid == block start
 * ins->flags = 0
 * ins->offset == number of blocks
 * Any available blocks before search_start are skipped.
 */
static int find_free_extent(struct ctree_root *orig_root, u64 num_blocks,
			    u64 search_start, u64 search_end, struct key *ins)
{
	struct ctree_path path;
	struct key *key;
	int ret;
	u64 hole_size = 0;
	int slot = 0;
	u64 last_block;
	u64 test_block;
	int start_found;
	struct leaf *l;
	struct ctree_root * root = orig_root->extent_root;
	int total_needed = num_blocks;

	total_needed += (btrfs_header_level(&root->node->node.header) + 1) * 3;
	if (root->last_insert.objectid > search_start)
		search_start = root->last_insert.objectid;
check_failed:
	init_path(&path);
	ins->objectid = search_start;
	ins->offset = 0;
	ins->flags = 0;
	start_found = 0;
	ret = search_slot(root, ins, &path, 0, 0);
	if (ret < 0)
		goto error;

	if (path.slots[0] > 0)
		path.slots[0]--;

	while (1) {
		l = &path.nodes[0]->leaf;
		slot = path.slots[0];
		if (slot >= btrfs_header_nritems(&l->header)) {
			ret = next_leaf(root, &path);
			if (ret == 0)
				continue;
			if (ret < 0)
				goto error;
			if (!start_found) {
				ins->objectid = search_start;
				ins->offset = (u64)-1;
				start_found = 1;
				goto check_pending;
			}
			ins->objectid = last_block > search_start ?
					last_block : search_start;
			ins->offset = (u64)-1;
			goto check_pending;
		}
		key = &l->items[slot].key;
		if (key->objectid >= search_start) {
			if (start_found) {
				if (last_block < search_start)
					last_block = search_start;
				hole_size = key->objectid - last_block;
				if (hole_size > total_needed) {
					ins->objectid = last_block;
					ins->offset = hole_size;
					goto check_pending;
				}
			}
		}
		start_found = 1;
		last_block = key->objectid + key->offset;
		path.slots[0]++;
	}
	// FIXME -ENOSPC
check_pending:
	/* we have to make sure we didn't find an extent that has already
	 * been allocated by the map tree or the original allocation
	 */
	release_path(root, &path);
	BUG_ON(ins->objectid < search_start);
	for (test_block = ins->objectid;
	     test_block < ins->objectid + total_needed; test_block++) {
		if (radix_tree_lookup(&root->pinned_radix, test_block)) {
			search_start = test_block + 1;
			goto check_failed;
		}
	}
	BUG_ON(root->current_insert.offset);
	root->current_insert.offset = total_needed - num_blocks;
	root->current_insert.objectid = ins->objectid + num_blocks;
	root->current_insert.flags = 0;
	root->last_insert.objectid = ins->objectid;
	ins->offset = num_blocks;
	return 0;
error:
	release_path(root, &path);
	return ret;
}

/*
 * finds a free extent and does all the dirty work required for allocation
 * returns the key for the extent through ins, and a tree buffer for
 * the first block of the extent through buf.
 *
 * returns 0 if everything worked, non-zero otherwise.
 */
int alloc_extent(struct ctree_root *root, u64 num_blocks, u64 search_start,
			 u64 search_end, u64 owner, struct key *ins)
{
	int ret;
	int pending_ret;
	struct ctree_root *extent_root = root->extent_root;
	struct extent_item extent_item;

	extent_item.refs = 1;
	extent_item.owner = owner;

	if (root == extent_root) {
		BUG_ON(extent_root->current_insert.offset == 0);
		BUG_ON(num_blocks != 1);
		BUG_ON(extent_root->current_insert.flags ==
		       extent_root->current_insert.offset);
		ins->offset = 1;
		ins->objectid = extent_root->current_insert.objectid +
				extent_root->current_insert.flags++;
		return 0;
	}
	ret = find_free_extent(root, num_blocks, search_start,
			       search_end, ins);
	if (ret)
		return ret;

	ret = insert_item(extent_root, ins, &extent_item,
			  sizeof(extent_item));

	finish_current_insert(extent_root);
	pending_ret = run_pending(extent_root);
	if (ret)
		return ret;
	if (pending_ret)
		return pending_ret;
	return 0;
}

/*
 * helper function to allocate a block for a given tree
 * returns the tree buffer or NULL.
 */
struct tree_buffer *alloc_free_block(struct ctree_root *root)
{
	struct key ins;
	int ret;
	struct tree_buffer *buf;

	ret = alloc_extent(root, 1, 0, (unsigned long)-1,
			   btrfs_header_parentid(&root->node->node.header),
			   &ins);
	if (ret) {
		BUG();
		return NULL;
	}
	buf = find_tree_block(root, ins.objectid);
	dirty_tree_block(root, buf);
	return buf;
}

int walk_down_tree(struct ctree_root *root, struct ctree_path *path, int *level)
{
	struct tree_buffer *next;
	struct tree_buffer *cur;
	u64 blocknr;
	int ret;
	u32 refs;

	ret = lookup_block_ref(root, path->nodes[*level]->blocknr, &refs);
	BUG_ON(ret);
	if (refs > 1)
		goto out;
	while(*level > 0) {
		cur = path->nodes[*level];
		if (path->slots[*level] >=
		    btrfs_header_nritems(&cur->node.header))
			break;
		blocknr = cur->node.blockptrs[path->slots[*level]];
		ret = lookup_block_ref(root, blocknr, &refs);
		if (refs != 1 || *level == 1) {
			path->slots[*level]++;
			ret = free_extent(root, blocknr, 1);
			BUG_ON(ret);
			continue;
		}
		BUG_ON(ret);
		next = read_tree_block(root, blocknr);
		if (path->nodes[*level-1])
			tree_block_release(root, path->nodes[*level-1]);
		path->nodes[*level-1] = next;
		*level = btrfs_header_level(&next->node.header);
		path->slots[*level] = 0;
	}
out:
	ret = free_extent(root, path->nodes[*level]->blocknr, 1);
	tree_block_release(root, path->nodes[*level]);
	path->nodes[*level] = NULL;
	*level += 1;
	BUG_ON(ret);
	return 0;
}

int walk_up_tree(struct ctree_root *root, struct ctree_path *path, int *level)
{
	int i;
	int slot;
	int ret;
	for(i = *level; i < MAX_LEVEL - 1 && path->nodes[i]; i++) {
		slot = path->slots[i];
		if (slot <
		    btrfs_header_nritems(&path->nodes[i]->node.header)- 1) {
			path->slots[i]++;
			*level = i;
			return 0;
		} else {
			ret = free_extent(root,
					  path->nodes[*level]->blocknr, 1);
			tree_block_release(root, path->nodes[*level]);
			path->nodes[*level] = NULL;
			*level = i + 1;
			BUG_ON(ret);
		}
	}
	return 1;
}

int btrfs_drop_snapshot(struct ctree_root *root, struct tree_buffer *snap)
{
	int ret;
	int level;
	struct ctree_path path;
	int i;
	int orig_level;

	init_path(&path);

	level = btrfs_header_level(&snap->node.header);
	orig_level = level;
	path.nodes[level] = snap;
	path.slots[level] = 0;
	while(1) {
		ret = walk_down_tree(root, &path, &level);
		if (ret > 0)
			break;
		ret = walk_up_tree(root, &path, &level);
		if (ret > 0)
			break;
	}
	for (i = 0; i <= orig_level; i++) {
		if (path.nodes[i]) {
			tree_block_release(root, path.nodes[i]);
		}
	}

	return 0;
}
Commit	Line	Data
fec577fb CM	1	#include <stdio.h>
	2	#include <stdlib.h>
	3	#include "kerncompat.h"
	4	#include "radix-tree.h"
	5	#include "ctree.h"
	6	#include "disk-io.h"
	7	#include "print-tree.h"
	8
037e6390 CM	9	static int find_free_extent(struct ctree_root *orig_root, u64 num_blocks,
	10	u64 search_start, u64 search_end, struct key *ins);
	11	static int finish_current_insert(struct ctree_root *extent_root);
	12	static int run_pending(struct ctree_root *extent_root);
	13
fec577fb CM	14	/*
	15	* pending extents are blocks that we're trying to allocate in the extent
	16	* map while trying to grow the map because of other allocations. To avoid
	17	* recursing, they are tagged in the radix tree and cleaned up after
	18	* other allocations are done. The pending tag is also used in the same
	19	* manner for deletes.
	20	*/
037e6390	21	#define CTREE_EXTENT_PENDING_DEL 0
fec577fb	22
02217ed2 CM	23	static int inc_block_ref(struct ctree_root *root, u64 blocknr)
	24	{
	25	struct ctree_path path;
	26	int ret;
	27	struct key key;
	28	struct leaf *l;
	29	struct extent_item *item;
037e6390 CM	30	struct key ins;
	31
	32	find_free_extent(root->extent_root, 0, 0, (u64)-1, &ins);
02217ed2 CM	33	init_path(&path);
	34	key.objectid = blocknr;
	35	key.flags = 0;
	36	key.offset = 1;
	37	ret = search_slot(root->extent_root, &key, &path, 0, 1);
a28ec197 CM	38	if (ret != 0)
a28ec197 CM	39	BUG();
02217ed2 CM	40	BUG_ON(ret != 0);
	41	l = &path.nodes[0]->leaf;
	42	item = (struct extent_item *)(l->data +
	43	l->items[path.slots[0]].offset);
	44	item->refs++;
a28ec197	45
02217ed2 CM	46	BUG_ON(list_empty(&path.nodes[0]->dirty));
02217ed2 CM	47	release_path(root->extent_root, &path);
037e6390 CM	48	finish_current_insert(root->extent_root);
037e6390 CM	49	run_pending(root->extent_root);
02217ed2 CM	50	return 0;
	51	}
	52
20524f02	53	static int lookup_block_ref(struct ctree_root root, u64 blocknr, u32 refs)
a28ec197 CM	54	{
	55	struct ctree_path path;
	56	int ret;
	57	struct key key;
	58	struct leaf *l;
	59	struct extent_item *item;
	60	init_path(&path);
	61	key.objectid = blocknr;
	62	key.flags = 0;
	63	key.offset = 1;
	64	ret = search_slot(root->extent_root, &key, &path, 0, 0);
	65	if (ret != 0)
	66	BUG();
	67	l = &path.nodes[0]->leaf;
	68	item = (struct extent_item *)(l->data +
	69	l->items[path.slots[0]].offset);
	70	*refs = item->refs;
	71	release_path(root->extent_root, &path);
	72	return 0;
	73	}
	74
02217ed2 CM	75	int btrfs_inc_ref(struct ctree_root root, struct tree_buffer buf)
	76	{
	77	u64 blocknr;
	78	int i;
a28ec197 CM	79
	80	if (root == root->extent_root)
	81	return 0;
7518a238	82	if (btrfs_is_leaf(&buf->node))
a28ec197 CM	83	return 0;
a28ec197 CM	84
7518a238	85	for (i = 0; i < btrfs_header_nritems(&buf->node.header); i++) {
02217ed2 CM	86	blocknr = buf->node.blockptrs[i];
	87	inc_block_ref(root, blocknr);
	88	}
	89	return 0;
	90	}
	91
a28ec197 CM	92	int btrfs_finish_extent_commit(struct ctree_root *root)
	93	{
	94	struct ctree_root *extent_root = root->extent_root;
	95	unsigned long gang[8];
	96	int ret;
	97	int i;
	98
	99	while(1) {
	100	ret = radix_tree_gang_lookup(&extent_root->pinned_radix,
	101	(void **)gang, 0,
	102	ARRAY_SIZE(gang));
	103	if (!ret)
	104	break;
0579da42	105	for (i = 0; i < ret; i++) {
a28ec197	106	radix_tree_delete(&extent_root->pinned_radix, gang[i]);
0579da42	107	}
a28ec197	108	}
0579da42 CM	109	extent_root->last_insert.objectid = 0;
0579da42 CM	110	extent_root->last_insert.offset = 0;
a28ec197 CM	111	return 0;
	112	}
	113
037e6390 CM	114	static int finish_current_insert(struct ctree_root *extent_root)
	115	{
	116	struct key ins;
	117	struct extent_item extent_item;
	118	int i;
	119	int ret;
	120
	121	extent_item.refs = 1;
7518a238 CM	122	extent_item.owner =
7518a238 CM	123	btrfs_header_parentid(&extent_root->node->node.header);
037e6390 CM	124	ins.offset = 1;
	125	ins.flags = 0;
	126
	127	for (i = 0; i < extent_root->current_insert.flags; i++) {
	128	ins.objectid = extent_root->current_insert.objectid + i;
	129	ret = insert_item(extent_root, &ins, &extent_item,
	130	sizeof(extent_item));
	131	BUG_ON(ret);
	132	}
	133	extent_root->current_insert.offset = 0;
	134	return 0;
	135	}
	136
fec577fb	137	/*
a28ec197	138	* remove an extent from the root, returns 0 on success
fec577fb	139	*/
a28ec197 CM	140	int __free_extent(struct ctree_root *root, u64 blocknr, u64 num_blocks)
	141	{
	142	struct ctree_path path;
	143	struct key key;
	144	struct ctree_root *extent_root = root->extent_root;
	145	int ret;
	146	struct item *item;
	147	struct extent_item *ei;
037e6390 CM	148	struct key ins;
037e6390 CM	149
a28ec197 CM	150	key.objectid = blocknr;
	151	key.flags = 0;
	152	key.offset = num_blocks;
	153
037e6390	154	find_free_extent(root, 0, 0, (u64)-1, &ins);
a28ec197 CM	155	init_path(&path);
	156	ret = search_slot(extent_root, &key, &path, -1, 1);
	157	if (ret) {
	158	printf("failed to find %Lu\n", key.objectid);
	159	print_tree(extent_root, extent_root->node);
	160	printf("failed to find %Lu\n", key.objectid);
	161	BUG();
	162	}
	163	item = path.nodes[0]->leaf.items + path.slots[0];
	164	ei = (struct extent_item *)(path.nodes[0]->leaf.data + item->offset);
	165	BUG_ON(ei->refs == 0);
	166	ei->refs--;
	167	if (ei->refs == 0) {
	168	if (root == extent_root) {
	169	int err;
	170	radix_tree_preload(GFP_KERNEL);
	171	err = radix_tree_insert(&extent_root->pinned_radix,
	172	blocknr, (void *)blocknr);
	173	BUG_ON(err);
	174	radix_tree_preload_end();
	175	}
	176	ret = del_item(extent_root, &path);
0579da42 CM	177	if (root != extent_root &&
	178	extent_root->last_insert.objectid < blocknr)
	179	extent_root->last_insert.objectid = blocknr;
a28ec197 CM	180	if (ret)
	181	BUG();
	182	}
	183	release_path(extent_root, &path);
037e6390	184	finish_current_insert(extent_root);
a28ec197 CM	185	return ret;
	186	}
	187
a28ec197 CM	188	/*
	189	* find all the blocks marked as pending in the radix tree and remove
	190	* them from the extent map
	191	*/
	192	static int del_pending_extents(struct ctree_root *extent_root)
	193	{
	194	int ret;
	195	struct tree_buffer *gang[4];
	196	int i;
	197
	198	while(1) {
	199	ret = radix_tree_gang_lookup_tag(&extent_root->cache_radix,
	200	(void **)gang, 0,
	201	ARRAY_SIZE(gang),
	202	CTREE_EXTENT_PENDING_DEL);
	203	if (!ret)
	204	break;
	205	for (i = 0; i < ret; i++) {
	206	ret = __free_extent(extent_root, gang[i]->blocknr, 1);
fec577fb CM	207	radix_tree_tag_clear(&extent_root->cache_radix,
fec577fb CM	208	gang[i]->blocknr,
a28ec197	209	CTREE_EXTENT_PENDING_DEL);
fec577fb CM	210	tree_block_release(extent_root, gang[i]);
	211	}
	212	}
	213	return 0;
	214	}
	215
a28ec197 CM	216	static int run_pending(struct ctree_root *extent_root)
	217	{
	218	while(radix_tree_tagged(&extent_root->cache_radix,
037e6390	219	CTREE_EXTENT_PENDING_DEL))
a28ec197	220	del_pending_extents(extent_root);
a28ec197 CM	221	return 0;
	222	}
	223
	224
fec577fb CM	225	/*
	226	* remove an extent from the root, returns 0 on success
	227	*/
	228	int free_extent(struct ctree_root *root, u64 blocknr, u64 num_blocks)
	229	{
fec577fb CM	230	struct key key;
	231	struct ctree_root *extent_root = root->extent_root;
	232	struct tree_buffer *t;
	233	int pending_ret;
	234	int ret;
a28ec197	235
fec577fb	236	if (root == extent_root) {
a28ec197	237	t = find_tree_block(root, blocknr);
037e6390	238	radix_tree_tag_set(&root->cache_radix, blocknr,
a28ec197	239	CTREE_EXTENT_PENDING_DEL);
fec577fb CM	240	return 0;
fec577fb CM	241	}
a28ec197 CM	242	key.objectid = blocknr;
	243	key.flags = 0;
	244	key.offset = num_blocks;
	245	ret = __free_extent(root, blocknr, num_blocks);
	246	pending_ret = run_pending(root->extent_root);
fec577fb CM	247	return ret ? ret : pending_ret;
	248	}
	249
	250	/*
	251	* walks the btree of allocated extents and find a hole of a given size.
	252	* The key ins is changed to record the hole:
	253	* ins->objectid == block start
	254	* ins->flags = 0
	255	* ins->offset == number of blocks
	256	* Any available blocks before search_start are skipped.
	257	*/
0f70abe2 CM	258	static int find_free_extent(struct ctree_root *orig_root, u64 num_blocks,
0f70abe2 CM	259	u64 search_start, u64 search_end, struct key *ins)
fec577fb CM	260	{
	261	struct ctree_path path;
	262	struct key *key;
	263	int ret;
	264	u64 hole_size = 0;
	265	int slot = 0;
	266	u64 last_block;
037e6390	267	u64 test_block;
fec577fb CM	268	int start_found;
	269	struct leaf *l;
	270	struct ctree_root * root = orig_root->extent_root;
0579da42	271	int total_needed = num_blocks;
fec577fb	272
7518a238	273	total_needed += (btrfs_header_level(&root->node->node.header) + 1) * 3;
0579da42 CM	274	if (root->last_insert.objectid > search_start)
0579da42 CM	275	search_start = root->last_insert.objectid;
fec577fb CM	276	check_failed:
	277	init_path(&path);
	278	ins->objectid = search_start;
	279	ins->offset = 0;
	280	ins->flags = 0;
	281	start_found = 0;
02217ed2	282	ret = search_slot(root, ins, &path, 0, 0);
0f70abe2 CM	283	if (ret < 0)
0f70abe2 CM	284	goto error;
aa5d6bed	285
0579da42 CM	286	if (path.slots[0] > 0)
	287	path.slots[0]--;
	288
fec577fb CM	289	while (1) {
	290	l = &path.nodes[0]->leaf;
	291	slot = path.slots[0];
7518a238	292	if (slot >= btrfs_header_nritems(&l->header)) {
fec577fb CM	293	ret = next_leaf(root, &path);
	294	if (ret == 0)
	295	continue;
0f70abe2 CM	296	if (ret < 0)
0f70abe2 CM	297	goto error;
fec577fb CM	298	if (!start_found) {
fec577fb CM	299	ins->objectid = search_start;
037e6390	300	ins->offset = (u64)-1;
fec577fb CM	301	start_found = 1;
	302	goto check_pending;
	303	}
	304	ins->objectid = last_block > search_start ?
	305	last_block : search_start;
037e6390	306	ins->offset = (u64)-1;
fec577fb CM	307	goto check_pending;
	308	}
	309	key = &l->items[slot].key;
	310	if (key->objectid >= search_start) {
	311	if (start_found) {
0579da42 CM	312	if (last_block < search_start)
0579da42 CM	313	last_block = search_start;
fec577fb	314	hole_size = key->objectid - last_block;
037e6390	315	if (hole_size > total_needed) {
fec577fb	316	ins->objectid = last_block;
037e6390	317	ins->offset = hole_size;
fec577fb CM	318	goto check_pending;
fec577fb CM	319	}
0579da42	320	}
fec577fb	321	}
0579da42 CM	322	start_found = 1;
0579da42 CM	323	last_block = key->objectid + key->offset;
fec577fb CM	324	path.slots[0]++;
	325	}
	326	// FIXME -ENOSPC
	327	check_pending:
	328	/* we have to make sure we didn't find an extent that has already
	329	* been allocated by the map tree or the original allocation
	330	*/
	331	release_path(root, &path);
	332	BUG_ON(ins->objectid < search_start);
037e6390 CM	333	for (test_block = ins->objectid;
	334	test_block < ins->objectid + total_needed; test_block++) {
	335	if (radix_tree_lookup(&root->pinned_radix, test_block)) {
	336	search_start = test_block + 1;
fec577fb CM	337	goto check_failed;
	338	}
	339	}
037e6390	340	BUG_ON(root->current_insert.offset);
0579da42	341	root->current_insert.offset = total_needed - num_blocks;
037e6390 CM	342	root->current_insert.objectid = ins->objectid + num_blocks;
037e6390 CM	343	root->current_insert.flags = 0;
0579da42	344	root->last_insert.objectid = ins->objectid;
037e6390	345	ins->offset = num_blocks;
fec577fb	346	return 0;
0f70abe2 CM	347	error:
	348	release_path(root, &path);
	349	return ret;
fec577fb CM	350	}
fec577fb CM	351
fec577fb CM	352	/*
	353	* finds a free extent and does all the dirty work required for allocation
	354	* returns the key for the extent through ins, and a tree buffer for
	355	* the first block of the extent through buf.
	356	*
	357	* returns 0 if everything worked, non-zero otherwise.
	358	*/
	359	int alloc_extent(struct ctree_root *root, u64 num_blocks, u64 search_start,
037e6390	360	u64 search_end, u64 owner, struct key *ins)
fec577fb CM	361	{
	362	int ret;
	363	int pending_ret;
037e6390	364	struct ctree_root *extent_root = root->extent_root;
fec577fb	365	struct extent_item extent_item;
037e6390	366
fec577fb CM	367	extent_item.refs = 1;
	368	extent_item.owner = owner;
	369
037e6390 CM	370	if (root == extent_root) {
	371	BUG_ON(extent_root->current_insert.offset == 0);
	372	BUG_ON(num_blocks != 1);
	373	BUG_ON(extent_root->current_insert.flags ==
	374	extent_root->current_insert.offset);
	375	ins->offset = 1;
	376	ins->objectid = extent_root->current_insert.objectid +
	377	extent_root->current_insert.flags++;
fec577fb CM	378	return 0;
fec577fb CM	379	}
037e6390 CM	380	ret = find_free_extent(root, num_blocks, search_start,
	381	search_end, ins);
	382	if (ret)
	383	return ret;
fec577fb	384
037e6390 CM	385	ret = insert_item(extent_root, ins, &extent_item,
	386	sizeof(extent_item));
	387
	388	finish_current_insert(extent_root);
	389	pending_ret = run_pending(extent_root);
	390	if (ret)
	391	return ret;
	392	if (pending_ret)
	393	return pending_ret;
	394	return 0;
fec577fb CM	395	}
	396
	397	/*
	398	* helper function to allocate a block for a given tree
	399	* returns the tree buffer or NULL.
	400	*/
	401	struct tree_buffer alloc_free_block(struct ctree_root root)
	402	{
	403	struct key ins;
	404	int ret;
037e6390	405	struct tree_buffer *buf;
fec577fb CM	406
fec577fb CM	407	ret = alloc_extent(root, 1, 0, (unsigned long)-1,
7518a238	408	btrfs_header_parentid(&root->node->node.header),
037e6390	409	&ins);
fec577fb CM	410	if (ret) {
	411	BUG();
	412	return NULL;
	413	}
037e6390 CM	414	buf = find_tree_block(root, ins.objectid);
037e6390 CM	415	dirty_tree_block(root, buf);
fec577fb CM	416	return buf;
fec577fb CM	417	}
a28ec197	418
20524f02 CM	419	int walk_down_tree(struct ctree_root root, struct ctree_path path, int *level)
	420	{
	421	struct tree_buffer *next;
	422	struct tree_buffer *cur;
	423	u64 blocknr;
	424	int ret;
	425	u32 refs;
	426
	427	ret = lookup_block_ref(root, path->nodes[*level]->blocknr, &refs);
	428	BUG_ON(ret);
	429	if (refs > 1)
	430	goto out;
	431	while(*level > 0) {
	432	cur = path->nodes[*level];
7518a238 CM	433	if (path->slots[*level] >=
7518a238 CM	434	btrfs_header_nritems(&cur->node.header))
20524f02 CM	435	break;
	436	blocknr = cur->node.blockptrs[path->slots[*level]];
	437	ret = lookup_block_ref(root, blocknr, &refs);
	438	if (refs != 1 \|\| *level == 1) {
	439	path->slots[*level]++;
	440	ret = free_extent(root, blocknr, 1);
	441	BUG_ON(ret);
	442	continue;
	443	}
	444	BUG_ON(ret);
	445	next = read_tree_block(root, blocknr);
83e15a28	446	if (path->nodes[*level-1])
20524f02	447	tree_block_release(root, path->nodes[*level-1]);
20524f02	448	path->nodes[*level-1] = next;
7518a238	449	*level = btrfs_header_level(&next->node.header);
20524f02 CM	450	path->slots[*level] = 0;
	451	}
	452	out:
	453	ret = free_extent(root, path->nodes[*level]->blocknr, 1);
83e15a28	454	tree_block_release(root, path->nodes[*level]);
20524f02 CM	455	path->nodes[*level] = NULL;
	456	*level += 1;
	457	BUG_ON(ret);
	458	return 0;
	459	}
	460
	461	int walk_up_tree(struct ctree_root root, struct ctree_path path, int *level)
	462	{
	463	int i;
	464	int slot;
	465	int ret;
	466	for(i = *level; i < MAX_LEVEL - 1 && path->nodes[i]; i++) {
	467	slot = path->slots[i];
7518a238 CM	468	if (slot <
7518a238 CM	469	btrfs_header_nritems(&path->nodes[i]->node.header)- 1) {
20524f02 CM	470	path->slots[i]++;
	471	*level = i;
	472	return 0;
	473	} else {
	474	ret = free_extent(root,
	475	path->nodes[*level]->blocknr, 1);
83e15a28 CM	476	tree_block_release(root, path->nodes[*level]);
83e15a28 CM	477	path->nodes[*level] = NULL;
20524f02 CM	478	*level = i + 1;
	479	BUG_ON(ret);
	480	}
	481	}
	482	return 1;
	483	}
	484
	485	int btrfs_drop_snapshot(struct ctree_root root, struct tree_buffer snap)
	486	{
	487	int ret;
	488	int level;
	489	struct ctree_path path;
	490	int i;
	491	int orig_level;
	492
	493	init_path(&path);
	494
7518a238	495	level = btrfs_header_level(&snap->node.header);
20524f02 CM	496	orig_level = level;
	497	path.nodes[level] = snap;
	498	path.slots[level] = 0;
	499	while(1) {
	500	ret = walk_down_tree(root, &path, &level);
	501	if (ret > 0)
	502	break;
	503	ret = walk_up_tree(root, &path, &level);
	504	if (ret > 0)
	505	break;
	506	}
83e15a28 CM	507	for (i = 0; i <= orig_level; i++) {
83e15a28 CM	508	if (path.nodes[i]) {
20524f02	509	tree_block_release(root, path.nodes[i]);
83e15a28	510	}
20524f02 CM	511	}
	512
	513	return 0;
	514	}