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/*
* Copyright (C) 2008 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 "ctree.h"
#include "ref-cache.h"
#include "transaction.h"
/*
* leaf refs are used to cache the information about which extents
* a given leaf has references on. This allows us to process that leaf
* in btrfs_drop_snapshot without needing to read it back from disk.
*/
/*
* kmalloc a leaf reference struct and update the counters for the
* total ref cache size
*/
struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(struct btrfs_root *root,
int nr_extents)
{
struct btrfs_leaf_ref *ref;
size_t size = btrfs_leaf_ref_size(nr_extents);
ref = kmalloc(size, GFP_NOFS);
if (ref) {
spin_lock(&root->fs_info->ref_cache_lock);
root->fs_info->total_ref_cache_size += size;
spin_unlock(&root->fs_info->ref_cache_lock);
memset(ref, 0, sizeof(*ref));
atomic_set(&ref->usage, 1);
INIT_LIST_HEAD(&ref->list);
}
return ref;
}
/*
* free a leaf reference struct and update the counters for the
* total ref cache size
*/
void btrfs_free_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
{
if (!ref)
return;
WARN_ON(atomic_read(&ref->usage) == 0);
if (atomic_dec_and_test(&ref->usage)) {
size_t size = btrfs_leaf_ref_size(ref->nritems);
BUG_ON(ref->in_tree);
kfree(ref);
spin_lock(&root->fs_info->ref_cache_lock);
root->fs_info->total_ref_cache_size -= size;
spin_unlock(&root->fs_info->ref_cache_lock);
}
}
static struct rb_node *tree_insert(struct rb_root *root, u64 bytenr,
struct rb_node *node)
{
struct rb_node ** p = &root->rb_node;
struct rb_node * parent = NULL;
struct btrfs_leaf_ref *entry;
while(*p) {
parent = *p;
entry = rb_entry(parent, struct btrfs_leaf_ref, rb_node);
if (bytenr < entry->bytenr)
p = &(*p)->rb_left;
else if (bytenr > entry->bytenr)
p = &(*p)->rb_right;
else
return parent;
}
entry = rb_entry(node, struct btrfs_leaf_ref, rb_node);
rb_link_node(node, parent, p);
rb_insert_color(node, root);
return NULL;
}
static struct rb_node *tree_search(struct rb_root *root, u64 bytenr)
{
struct rb_node * n = root->rb_node;
struct btrfs_leaf_ref *entry;
while(n) {
entry = rb_entry(n, struct btrfs_leaf_ref, rb_node);
WARN_ON(!entry->in_tree);
if (bytenr < entry->bytenr)
n = n->rb_left;
else if (bytenr > entry->bytenr)
n = n->rb_right;
else
return n;
}
return NULL;
}
int btrfs_remove_leaf_refs(struct btrfs_root *root, u64 max_root_gen,
int shared)
{
struct btrfs_leaf_ref *ref = NULL;
struct btrfs_leaf_ref_tree *tree = root->ref_tree;
if (shared)
tree = &root->fs_info->shared_ref_tree;
if (!tree)
return 0;
spin_lock(&tree->lock);
while(!list_empty(&tree->list)) {
ref = list_entry(tree->list.next, struct btrfs_leaf_ref, list);
BUG_ON(ref->tree != tree);
if (ref->root_gen > max_root_gen)
break;
if (!xchg(&ref->in_tree, 0)) {
cond_resched_lock(&tree->lock);
continue;
}
rb_erase(&ref->rb_node, &tree->root);
list_del_init(&ref->list);
spin_unlock(&tree->lock);
btrfs_free_leaf_ref(root, ref);
cond_resched();
spin_lock(&tree->lock);
}
spin_unlock(&tree->lock);
return 0;
}
/*
* find the leaf ref for a given extent. This returns the ref struct with
* a usage reference incremented
*/
struct btrfs_leaf_ref *btrfs_lookup_leaf_ref(struct btrfs_root *root,
u64 bytenr)
{
struct rb_node *rb;
struct btrfs_leaf_ref *ref = NULL;
struct btrfs_leaf_ref_tree *tree = root->ref_tree;
again:
if (tree) {
spin_lock(&tree->lock);
rb = tree_search(&tree->root, bytenr);
if (rb)
ref = rb_entry(rb, struct btrfs_leaf_ref, rb_node);
if (ref)
atomic_inc(&ref->usage);
spin_unlock(&tree->lock);
if (ref)
return ref;
}
if (tree != &root->fs_info->shared_ref_tree) {
tree = &root->fs_info->shared_ref_tree;
goto again;
}
return NULL;
}
/*
* add a fully filled in leaf ref struct
* remove all the refs older than a given root generation
*/
int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref,
int shared)
{
int ret = 0;
struct rb_node *rb;
struct btrfs_leaf_ref_tree *tree = root->ref_tree;
if (shared)
tree = &root->fs_info->shared_ref_tree;
spin_lock(&tree->lock);
rb = tree_insert(&tree->root, ref->bytenr, &ref->rb_node);
if (rb) {
ret = -EEXIST;
} else {
atomic_inc(&ref->usage);
ref->tree = tree;
ref->in_tree = 1;
list_add_tail(&ref->list, &tree->list);
}
spin_unlock(&tree->lock);
return ret;
}
/*
* remove a single leaf ref from the tree. This drops the ref held by the tree
* only
*/
int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
{
struct btrfs_leaf_ref_tree *tree;
if (!xchg(&ref->in_tree, 0))
return 0;
tree = ref->tree;
spin_lock(&tree->lock);
rb_erase(&ref->rb_node, &tree->root);
list_del_init(&ref->list);
spin_unlock(&tree->lock);
btrfs_free_leaf_ref(root, ref);
return 0;
}
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