/*
* Copyright (C) 2009 Oracle. All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License v2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 021110-1307, USA.
*/
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/sort.h>
#include "ctree.h"
#include "delayed-ref.h"
#include "transaction.h"
/*
* delayed back reference update tracking. For subvolume trees
* we queue up extent allocations and backref maintenance for
* delayed processing. This avoids deep call chains where we
* add extents in the middle of btrfs_search_slot, and it allows
* us to buffer up frequently modified backrefs in an rb tree instead
* of hammering updates on the extent allocation tree.
*/
/*
* compare two delayed tree backrefs with same bytenr and type
*/
static int comp_tree_refs(struct btrfs_delayed_tree_ref *ref2,
struct btrfs_delayed_tree_ref *ref1)
{
if (ref1->node.type == BTRFS_TREE_BLOCK_REF_KEY) {
if (ref1->root < ref2->root)
return -1;
if (ref1->root > ref2->root)
return 1;
} else {
if (ref1->parent < ref2->parent)
return -1;
if (ref1->parent > ref2->parent)
return 1;
}
return 0;
}
/*
* compare two delayed data backrefs with same bytenr and type
*/
static int comp_data_refs(struct btrfs_delayed_data_ref *ref2,
struct btrfs_delayed_data_ref *ref1)
{
if (ref1->node.type == BTRFS_EXTENT_DATA_REF_KEY) {
if (ref1->root < ref2->root)
return -1;
if (ref1->root > ref2->root)
return 1;
if (ref1->objectid < ref2->objectid)
return -1;
if (ref1->objectid > ref2->objectid)
return 1;
if (ref1->offset < ref2->offset)
return -1;
if (ref1->offset > ref2->offset)
return 1;
} else {
if (ref1->parent < ref2->parent)
return -1;
if (ref1->parent > ref2->parent)
return 1;
}
return 0;
}
/*
* entries in the rb tree are ordered by the byte number of the extent,
* type of the delayed backrefs and content of delayed backrefs.
*/
static int comp_entry(struct btrfs_delayed_ref_node *ref2,
struct btrfs_delayed_ref_node *ref1)
{
if (ref1->bytenr < ref2->bytenr)
return -1;
if (ref1->bytenr > ref2->bytenr)
return 1;
if (ref1->is_head && ref2->is_head)
return 0;
if (ref2->is_head)
return -1;
if (ref1->is_head)
return 1;
if (ref1->type < ref2->type)
return -1;
if (ref1->type > ref2->type)
return 1;
if (ref1->type == BTRFS_TREE_BLOCK_REF_KEY ||
ref1->type == BTRFS_SHARED_BLOCK_REF_KEY) {
return comp_tree_refs(btrfs_delayed_node_to_tree_ref(ref2),
btrfs_delayed_node_to_tree_ref(ref1));
} else if (ref1->type == BTRFS_EXTENT_DATA_REF_KEY ||
ref1->type == BTRFS_SHARED_DATA_REF_KEY) {
return comp_data_refs(btrfs_delayed_node_to_data_ref(ref2),
btrfs_delayed_node_to_data_ref(ref1));
}
BUG();
return 0;
}
/*
* insert a new ref into the rbtree. This returns any existing refs
* for the same (bytenr,parent) tuple, or NULL if the new node was properly
* inserted.
*/
static struct btrfs_delayed_ref_node *tree_insert(struct rb_root *root,
struct rb_node *node)
{
struct rb_node **p = &root->rb_node;
struct rb_node *parent_node = NULL;
struct btrfs_delayed_ref_node *entry;
struct btrfs_delayed_ref_node *ins;
int cmp;
ins = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
while (*p) {
parent_node = *p;
entry = rb_entry(parent_node, struct btrfs_delayed_ref_node,
rb_node);
cmp = comp_entry(entry, ins);
if (cmp < 0)
p = &(*p)->rb_left;
else if (cmp > 0)
p = &(*p)->rb_right;
else
return entry;
}
rb_link_node(node, parent_node, p);
rb_insert_color(node, root);
return NULL;
}
/*
* find an head entry based on bytenr. This returns the delayed ref
* head if it was able to find one, or NULL if nothing was in that spot
*/
static struct btrfs_delayed_ref_node *find_ref_head(struct rb_root *root,
u64 bytenr,
struct btrfs_delayed_ref_node **last)
{
struct rb_node *n = root->rb_node;
struct btrfs_delayed_ref_node *entry;
int cmp;
while (n) {
entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
WARN_ON(!entry->in_tree);
if (last)
*last = entry;
if (bytenr < entry->bytenr)
cmp = -1;
else if (bytenr > entry->bytenr)
cmp = 1;
else if (!btrfs_delayed_ref_is_head(entry))
cmp = 1;
else
cmp = 0;
if (cmp < 0)
n = n->rb_left;
else if (cmp > 0)
n = n->rb_right;
else
return entry;
}
return NULL;
}
int btrfs_delayed_ref_lock(struct btrfs_trans_handle *trans,
struct btrfs_delayed_ref_head *head)
{
struct btrfs_delayed_ref_root *delayed_refs;
delayed_refs = &trans->transaction->delayed_refs;
assert_spin_locked(&delayed_refs->lock);
if (mutex_trylock(&head->mutex))
return 0;
atomic_inc(&head->node.refs);
spin_unlock(&delayed_refs->lock);
mutex_lock(&head->mutex);
spin_lock(&delayed_refs->lock);
if (!head->node.in_tree) {
mutex_unlock(&head->mutex);
btrfs_put_delayed_ref(&head->node);
return -EAGAIN;
}
btrfs_put_delayed_ref(&head->node);
return 0;
}
int btrfs_find_ref_cluster(struct btrfs_trans_handle *trans,
struct list_head *cluster, u64 start)
{
int count = 0;
struct btrfs_delayed_ref_root *delayed_refs;
struct rb_node *node;
struct btrfs_delayed_ref_node *ref;
struct btrfs_delayed_ref_head *head;
delayed_refs = &trans->transaction->delayed_refs;
if (start == 0) {
node = rb_first(&delayed_refs->root);
} else {
ref = NULL;
find_ref_head(&delayed_refs->root, start, &ref);
if (ref) {
struct btrfs_delayed_ref_node *tmp;
node = rb_prev(&ref->rb_node);
while (node) {
tmp = rb_entry(node,
struct btrfs_delayed_ref_node,
rb_node);
if (tmp->bytenr < start)
break;
ref = tmp;
node = rb_prev(&ref->rb_node);
}
node = &ref->rb_node;
} else
node = rb_first(&delayed_refs->root);
}
again:
while (node && count < 32) {
ref = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
if (btrfs_delayed_ref_is_head(ref)) {
head = btrfs_delayed_node_to_head(ref);
if (list_empty(&head->cluster)) {
list_add_tail(&head->cluster, cluster);
delayed_refs->run_delayed_start =
head->node.bytenr;
count++;
WARN_ON(delayed_refs->num_heads_ready == 0);
delayed_refs->num_heads_ready--;
} else if (count) {
/* the goal of the clustering is to find extents
* that are likely to end up in the same extent
* leaf on disk. So, we don't want them spread
* all over the tree. Stop now if we've hit
* a head that was already in use
*/
break;
}
}
node = rb_next(node);
}
if (count) {
return 0;
} else if (start) {
/*
* we've gone to the end of the rbtree without finding any
* clusters. start from the beginning and try again
*/
start = 0;
node = rb_first(&delayed_refs->root);
goto again;
}
return 1;
}
/*
* This checks to see if there are any delayed refs in the
* btree for a given bytenr. It returns one if it finds any
* and zero otherwise.
*
* If it only finds a head node, it returns 0.
*
* The idea is to use this when deciding if you can safely delete an
* extent from the extent allocation tree. There may be a pending
* ref in the rbtree that adds or removes references, so as long as this
* returns one you need to leave the BTRFS_EXTENT_ITEM in the extent
* allocation tree.
*/
int btrfs_delayed_ref_pending(struct btrfs_trans_handle *trans, u64 bytenr)
{
struct btrfs_delayed_ref_node *ref;
struct btrfs_delayed_ref_root *delayed_refs;
struct rb_node *prev_node;
int ret = 0;
delayed_refs = &trans->transaction->delayed_refs;
spin_lock(&delayed_refs->lock);
ref = find_ref_head(&delayed_refs->root, bytenr, NULL);
if (ref) {
prev_node = rb_prev(&ref->rb_node);
if (!prev_node)
goto out;
ref = rb_entry(prev_node, struct btrfs_delayed_ref_node,
rb_node);
if (ref->bytenr == bytenr)
ret = 1;
}
out:
spin_unlock(&delayed_refs->lock);
return ret;
}
/*
* helper function to update an extent delayed ref in the
* rbtree. existing and update must both have the same
* bytenr and parent
*
* This may free existing if the update cancels out whatever
* operation it was doing.
*/
static noinline void
update_existing_ref(struct btrfs_trans_handle *trans,
struct btrfs_delayed_ref_root *delayed_refs,
struct btrfs_delayed_ref_node *existing,
struct btrfs_delayed_ref_node *update)
{
if (update->action != existing->action) {
/*
* this is effectively undoing either an add or a
* drop. We decrement the ref_mod, and if it goes
* down to zero we just delete the entry without
* every changing the extent allocation tree.
*/
existing->ref_mod--;
if (existing->ref_mod == 0) {
rb_erase(&existing->rb_node,
&delayed_refs->root);
existing->in_tree = 0;
btrfs_put_delayed_ref(existing);
delayed_refs->num_entries--;
if (trans->delayed_ref_updates)
trans->delayed_ref_updates--;
} else {
WARN_ON(existing->type == BTRFS_TREE_BLOCK_REF_KEY ||
existing->type == BTRFS_SHARED_BLOCK_REF_KEY);
}
} else {
WARN_ON(existing->type == BTRFS_TREE_BLOCK_REF_KEY ||
existing->type == BTRFS_SHARED_BLOCK_REF_KEY);
/*
* the action on the existing ref matches
* the action on the ref we're trying to add.
* Bump the ref_mod by one so the backref that
* is eventually added/removed has the correct
* reference count
*/
existing->ref_mod += update->ref_mod;
}
}
/*
* helper function to update the accounting in the head ref
* existing and update must have the same bytenr
*/
static noinline void
update_existing_head_ref(struct btrfs_delayed_ref_node *existing,
struct btrfs_delayed_ref_node *update)
{
struct btrfs_delayed_ref_head *existing_ref;
struct btrfs_delayed_ref_head *ref;
existing_ref = btrfs_delayed_node_to_head(existing);
ref = btrfs_delayed_node_to_head(update);
BUG_ON(existing_ref->is_data != ref->is_data);
if (ref->must_insert_reserved) {
/* if the extent was freed and then
* reallocated before the delayed ref
* entries were processed, we can end up
* with an existing head ref without
* the must_insert_reserved flag set.
* Set it again here
*/
existing_ref->must_insert_reserved = ref->must_insert_reserved;
/*
* update the num_bytes so we make sure the accounting
* is done correctly
*/
existing->num_bytes = update->num_bytes;
}
if (ref->extent_op) {
if (!existing_ref->extent_op) {
existing_ref->extent_op = ref->extent_op;
} else {
if (ref->extent_op->update_key) {
memcpy(&existing_ref->extent_op->key,
&ref->extent_op->key,
sizeof(ref->extent_op->key));
existing_ref->extent_op->update_key = 1;
}
if (ref->extent_op->update_flags) {
existing_ref->extent_op->flags_to_set |=
ref->extent_op->flags_to_set;
existing_ref->extent_op->update_flags = 1;
}
kfree(ref->extent_op);
}
}
/*
* update the reference mod on the head to reflect this new operation
*/
existing->ref_mod += update->ref_mod;
}
/*
* helper function to actually insert a head node into the rbtree.
* this does all the dirty work in terms of maintaining the correct
* overall modification count.
*/
static noinline int add_delayed_ref_head(struct btrfs_trans_handle *trans,
struct btrfs_delayed_ref_node *ref,
u64 bytenr, u64 num_bytes,
int action, int is_data)
{
struct btrfs_delayed_ref_node *existing;
struct btrfs_delayed_ref_head *head_ref = NULL;
struct btrfs_delayed_ref_root *delayed_refs;
int count_mod = 1;
int must_insert_reserved = 0;
/*
* the head node stores the sum of all the mods, so dropping a ref
* should drop the sum in the head node by one.
*/
if (action == BTRFS_UPDATE_DELAYED_HEAD)
count_mod = 0;
else if (action == BTRFS_DROP_DELAYED_REF)
count_mod = -1;
/*
* BTRFS_ADD_DELAYED_EXTENT means that we need to update
* the reserved accounting when the extent is finally added, or
* if a later modification deletes the delayed ref without ever
* inserting the extent into the extent allocation tree.
* ref->must_insert_reserved is the flag used to record
* that accounting mods are required.
*
* Once we record must_insert_reserved, switch the action to
* BTRFS_ADD_DELAYED_REF because other special casing is not required.
*/
if (action == BTRFS_ADD_DELAYED_EXTENT)
must_insert_reserved = 1;
else
must_insert_reserved = 0;
delayed_refs = &trans->transaction->delayed_refs;
/* first set the basic ref node struct up */
atomic_set(&ref->refs, 1);
ref->bytenr = bytenr;
ref->num_bytes = num_bytes;
ref->ref_mod = count_mod;
ref->type = 0;
ref->action = 0;
ref->is_head = 1;
ref->in_tree = 1;
head_ref = btrfs_delayed_node_to_head(ref);
head_ref->must_insert_reserved = must_insert_reserved;
head_ref->is_data = is_data;
INIT_LIST_HEAD(&head_ref->cluster);
mutex_init(&head_ref->mutex);
trace_btrfs_delayed_ref_head(ref, head_ref, action);
existing = tree_insert(&delayed_refs->root, &ref->rb_node);
if (existing) {
update_existing_head_ref(existing, ref);
/*
* we've updated the existing ref, free the newly
* allocated ref
*/
kfree(ref);
} else {
delayed_refs->num_heads++;
delayed_refs->num_heads_ready++;
delayed_refs->num_entries++;
trans->delayed_ref_updates++;
}
return 0;
}
/*
* helper to insert a delayed tree ref into the rbtree.
*/
static noinline int add_delayed_tree_ref(struct btrfs_trans_handle *trans,
struct btrfs_delayed_ref_node *ref,
u64 bytenr, u64 num_bytes, u64 parent,
u64 ref_root, int level, int action)
{
struct btrfs_delayed_ref_node *existing;
struct btrfs_delayed_tree_ref *full_ref;
struct btrfs_delayed_ref_root *delayed_refs;
if (action == BTRFS_ADD_DELAYED_EXTENT)
action = BTRFS_ADD_DELAYED_REF;
delayed_refs = &trans->transaction->delayed_refs;
/* first set the basic ref node struct up */
atomic_set(&ref->refs, 1);
ref->bytenr = bytenr;
ref->num_bytes = num_bytes;
ref->ref_mod = 1;
ref->action = action;
ref->is_head = 0;
ref->in_tree = 1;
full_ref = btrfs_delayed_node_to_tree_ref(ref);
if (parent) {
full_ref->parent = parent;
ref->type = BTRFS_SHARED_BLOCK_REF_KEY;
} else {
full_ref->root = ref_root;
ref->type = BTRFS_TREE_BLOCK_REF_KEY;
}
full_ref->level = level;
trace_btrfs_delayed_tree_ref(ref, full_ref, action);
existing = tree_insert(&delayed_refs->root, &ref->rb_node);
if (existing) {
update_existing_ref(trans, delayed_refs, existing, ref);
/*
* we've updated the existing ref, free the newly
* allocated ref
*/
kfree(ref);
} else {
delayed_refs->num_entries++;
trans->delayed_ref_updates++;
}
return 0;
}
/*
* helper to insert a delayed data ref into the rbtree.
*/
static noinline int add_delayed_data_ref(struct btrfs_trans_handle *trans,
struct btrfs_delayed_ref_node *ref,
u64 bytenr, u64 num_bytes, u64 parent,
u64 ref_root, u64 owner, u64 offset,
int action)
{
struct btrfs_delayed_ref_node *existing;
struct btrfs_delayed_data_ref *full_ref;
struct btrfs_delayed_ref_root *delayed_refs;
if (action == BTRFS_ADD_DELAYED_EXTENT)
action = BTRFS_ADD_DELAYED_REF;
delayed_refs = &trans->transaction->delayed_refs;
/* first set the basic ref node struct up */
atomic_set(&ref->refs, 1);
ref->bytenr = bytenr;
ref->num_bytes = num_bytes;
ref->ref_mod = 1;
ref->action = action;
ref->is_head = 0;
ref->in_tree = 1;
full_ref = btrfs_delayed_node_to_data_ref(ref);
if (parent) {
full_ref->parent = parent;
ref->type = BTRFS_SHARED_DATA_REF_KEY;
} else {
full_ref->root = ref_root;
ref->type = BTRFS_EXTENT_DATA_REF_KEY;
}
full_ref->objectid = owner;
full_ref->offset = offset;
trace_btrfs_delayed_data_ref(ref, full_ref, action);
existing = tree_insert(&delayed_refs->root, &ref->rb_node);
if (existing) {
update_existing_ref(trans, delayed_refs, existing, ref);
/*
* we've updated the existing ref, free the newly
* allocated ref
*/
kfree(ref);
} else {
delayed_refs->num_entries++;
trans->delayed_ref_updates++;
}
return 0;
}
/*
* add a delayed tree ref. This does all of the accounting required
* to make sure the delayed ref is eventually processed before this
* transaction commits.
*/
int btrfs_add_delayed_tree_ref(struct btrfs_trans_handle *trans,
u64 bytenr, u64 num_bytes, u64 parent,
u64 ref_root, int level, int action,
struct btrfs_delayed_extent_op *extent_op)
{
struct btrfs_delayed_tree_ref *ref;
struct btrfs_delayed_ref_head *head_ref;
struct btrfs_delayed_ref_root *delayed_refs;
int ret;
BUG_ON(extent_op && extent_op->is_data);
ref = kmalloc(sizeof(*ref), GFP_NOFS);
if (!ref)
return -ENOMEM;
head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
if (!head_ref) {
kfree(ref);
return -ENOMEM;
}
head_ref->extent_op = extent_op;
delayed_refs = &trans->transaction->delayed_refs;
spin_lock(&delayed_refs->lock);
/*
* insert both the head node and the new ref without dropping
* the spin lock
*/
ret = add_delayed_ref_head(trans, &head_ref->node, bytenr, num_bytes,
action, 0);
BUG_ON(ret);
ret = add_delayed_tree_ref(trans, &ref->node, bytenr, num_bytes,
parent, ref_root, level, action);
BUG_ON(ret);
spin_unlock(&delayed_refs->lock);
return 0;
}
/*
* add a delayed data ref. it's similar to btrfs_add_delayed_tree_ref.
*/
int btrfs_add_delayed_data_ref(struct btrfs_trans_handle *trans,
u64 bytenr, u64 num_bytes,
u64 parent, u64 ref_root,
u64 owner, u64 offset, int action,
struct btrfs_delayed_extent_op *extent_op)
{
struct btrfs_delayed_data_ref *ref;
struct btrfs_delayed_ref_head *head_ref;
struct btrfs_delayed_ref_root *delayed_refs;
int ret;
BUG_ON(extent_op && !extent_op->is_data);
ref = kmalloc(sizeof(*ref), GFP_NOFS);
if (!ref)
return -ENOMEM;
head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
if (!head_ref) {
kfree(ref);
return -ENOMEM;
}
head_ref->extent_op = extent_op;
delayed_refs = &trans->transaction->delayed_refs;
spin_lock(&delayed_refs->lock);
/*
* insert both the head node and the new ref without dropping
* the spin lock
*/
ret = add_delayed_ref_head(trans, &head_ref->node, bytenr, num_bytes,
action, 1);
BUG_ON(ret);
ret = add_delayed_data_ref(trans, &ref->node, bytenr, num_bytes,
parent, ref_root, owner, offset, action);
BUG_ON(ret);
spin_unlock(&delayed_refs->lock);
return 0;
}
int btrfs_add_delayed_extent_op(struct btrfs_trans_handle *trans,
u64 bytenr, u64 num_bytes,
struct btrfs_delayed_extent_op *extent_op)
{
struct btrfs_delayed_ref_head *head_ref;
struct btrfs_delayed_ref_root *delayed_refs;
int ret;
head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
if (!head_ref)
return -ENOMEM;
head_ref->extent_op = extent_op;
delayed_refs = &trans->transaction->delayed_refs;
spin_lock(&delayed_refs->lock);
ret = add_delayed_ref_head(trans, &head_ref->node, bytenr,
num_bytes, BTRFS_UPDATE_DELAYED_HEAD,
extent_op->is_data);
BUG_ON(ret);
spin_unlock(&delayed_refs->lock);
return 0;
}
/*
* this does a simple search for the head node for a given extent.
* It must be called with the delayed ref spinlock held, and it returns
* the head node if any where found, or NULL if not.
*/
struct btrfs_delayed_ref_head *
btrfs_find_delayed_ref_head(struct btrfs_trans_handle *trans, u64 bytenr)
{
struct btrfs_delayed_ref_node *ref;
struct btrfs_delayed_ref_root *delayed_refs;
delayed_refs = &trans->transaction->delayed_refs;
ref = find_ref_head(&delayed_refs->root, bytenr, NULL);
if (ref)
return btrfs_delayed_node_to_head(ref);
return NULL;
}
/*
* add a delayed ref to the tree. This does all of the accounting required
* to make sure the delayed ref is eventually processed before this
* transaction commits.
*
* The main point of this call is to add and remove a backreference in a single
* shot, taking the lock only once, and only searching for the head node once.
*
* It is the same as doing a ref add and delete in two separate calls.
*/
#if 0
int btrfs_update_delayed_ref(struct btrfs_trans_handle *trans,
u64 bytenr, u64 num_bytes, u64 orig_parent,
u64 parent, u64 orig_ref_root, u64 ref_root,
u64 orig_ref_generation, u64 ref_generation,
u64 owner_objectid, int pin)
{
struct btrfs_delayed_ref *ref;
struct btrfs_delayed_ref *old_ref;
struct btrfs_delayed_ref_head *head_ref;
struct btrfs_delayed_ref_root *delayed_refs;
int ret;
ref = kmalloc(sizeof(*ref), GFP_NOFS);
if (!ref)
return -ENOMEM;
old_ref = kmalloc(sizeof(*old_ref), GFP_NOFS);
if (!old_ref) {
kfree(ref);
return -ENOMEM;
}
/*
* the parent = 0 case comes from cases where we don't actually
* know the parent yet. It will get updated later via a add/drop
* pair.
*/
if (parent == 0)
parent = bytenr;
if (orig_parent == 0)
orig_parent = bytenr;
head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
if (!head_ref) {
kfree(ref);
kfree(old_ref);
return -ENOMEM;
}
delayed_refs = &trans->transaction->delayed_refs;
spin_lock(&delayed_refs->lock);
/*
* insert both the head node and the new ref without dropping
* the spin lock
*/
ret = __btrfs_add_delayed_ref(trans, &head_ref->node, bytenr, num_bytes,
(u64)-1, 0, 0, 0,
BTRFS_UPDATE_DELAYED_HEAD, 0);
BUG_ON(ret);
ret = __btrfs_add_delayed_ref(trans, &ref->node, bytenr, num_bytes,
parent, ref_root, ref_generation,
owner_objectid, BTRFS_ADD_DELAYED_REF, 0);
BUG_ON(ret);
ret = __btrfs_add_delayed_ref(trans, &old_ref->node, bytenr, num_bytes,
orig_parent, orig_ref_root,
orig_ref_generation, owner_objectid,
BTRFS_DROP_DELAYED_REF, pin);
BUG_ON(ret);
spin_unlock(&delayed_refs->lock);
return 0;
}
#endif
