fs/btrfs/ref-cache.c

   1 /*
   2  * Copyright (C) 2008 Oracle.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include <linux/sched.h>
  20 #include "ctree.h"
  21 #include "ref-cache.h"
  22 #include "transaction.h"
  23
  24 struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(struct btrfs_root *root,
  25                                             int nr_extents)
  26 {
  27         struct btrfs_leaf_ref *ref;
  28         size_t size = btrfs_leaf_ref_size(nr_extents);
  29
  30         ref = kmalloc(size, GFP_NOFS);
  31         if (ref) {
  32                 spin_lock(&root->fs_info->ref_cache_lock);
  33                 root->fs_info->total_ref_cache_size += size;
  34                 spin_unlock(&root->fs_info->ref_cache_lock);
  35
  36                 memset(ref, 0, sizeof(*ref));
  37                 atomic_set(&ref->usage, 1);
  38                 INIT_LIST_HEAD(&ref->list);
  39         }
  40         return ref;
  41 }
  42
  43 void btrfs_free_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
  44 {
  45         if (!ref)
  46                 return;
  47         WARN_ON(atomic_read(&ref->usage) == 0);
  48         if (atomic_dec_and_test(&ref->usage)) {
  49                 size_t size = btrfs_leaf_ref_size(ref->nritems);
  50
  51                 BUG_ON(ref->in_tree);
  52                 kfree(ref);
  53
  54                 spin_lock(&root->fs_info->ref_cache_lock);
  55                 root->fs_info->total_ref_cache_size -= size;
  56                 spin_unlock(&root->fs_info->ref_cache_lock);
  57         }
  58 }
  59
  60 static struct rb_node *tree_insert(struct rb_root *root, u64 bytenr,
  61                                    struct rb_node *node)
  62 {
  63         struct rb_node ** p = &root->rb_node;
  64         struct rb_node * parent = NULL;
  65         struct btrfs_leaf_ref *entry;
  66
  67         while(*p) {
  68                 parent = *p;
  69                 entry = rb_entry(parent, struct btrfs_leaf_ref, rb_node);
  70
  71                 if (bytenr < entry->bytenr)
  72                         p = &(*p)->rb_left;
  73                 else if (bytenr > entry->bytenr)
  74                         p = &(*p)->rb_right;
  75                 else
  76                         return parent;
  77         }
  78
  79         entry = rb_entry(node, struct btrfs_leaf_ref, rb_node);
  80         rb_link_node(node, parent, p);
  81         rb_insert_color(node, root);
  82         return NULL;
  83 }
  84
  85 static struct rb_node *tree_search(struct rb_root *root, u64 bytenr)
  86 {
  87         struct rb_node * n = root->rb_node;
  88         struct btrfs_leaf_ref *entry;
  89
  90         while(n) {
  91                 entry = rb_entry(n, struct btrfs_leaf_ref, rb_node);
  92                 WARN_ON(!entry->in_tree);
  93
  94                 if (bytenr < entry->bytenr)
  95                         n = n->rb_left;
  96                 else if (bytenr > entry->bytenr)
  97                         n = n->rb_right;
  98                 else
  99                         return n;
 100         }
 101         return NULL;
 102 }
 103
 104 int btrfs_remove_leaf_refs(struct btrfs_root *root, u64 max_root_gen,
 105                            int shared)
 106 {
 107         struct btrfs_leaf_ref *ref = NULL;
 108         struct btrfs_leaf_ref_tree *tree = root->ref_tree;
 109
 110         if (shared)
 111                 tree = &root->fs_info->shared_ref_tree;
 112         if (!tree)
 113                 return 0;
 114
 115         spin_lock(&tree->lock);
 116         while(!list_empty(&tree->list)) {
 117                 ref = list_entry(tree->list.next, struct btrfs_leaf_ref, list);
 118                 BUG_ON(ref->tree != tree);
 119                 if (ref->root_gen > max_root_gen)
 120                         break;
 121                 if (!xchg(&ref->in_tree, 0)) {
 122                         cond_resched_lock(&tree->lock);
 123                         continue;
 124                 }
 125
 126                 rb_erase(&ref->rb_node, &tree->root);
 127                 list_del_init(&ref->list);
 128
 129                 spin_unlock(&tree->lock);
 130                 btrfs_free_leaf_ref(root, ref);
 131                 cond_resched();
 132                 spin_lock(&tree->lock);
 133         }
 134         spin_unlock(&tree->lock);
 135         return 0;
 136 }
 137
 138 struct btrfs_leaf_ref *btrfs_lookup_leaf_ref(struct btrfs_root *root,
 139                                              u64 bytenr)
 140 {
 141         struct rb_node *rb;
 142         struct btrfs_leaf_ref *ref = NULL;
 143         struct btrfs_leaf_ref_tree *tree = root->ref_tree;
 144 again:
 145         if (tree) {
 146                 spin_lock(&tree->lock);
 147                 rb = tree_search(&tree->root, bytenr);
 148                 if (rb)
 149                         ref = rb_entry(rb, struct btrfs_leaf_ref, rb_node);
 150                 if (ref)
 151                         atomic_inc(&ref->usage);
 152                 spin_unlock(&tree->lock);
 153                 if (ref)
 154                         return ref;
 155         }
 156         if (tree != &root->fs_info->shared_ref_tree) {
 157                 tree = &root->fs_info->shared_ref_tree;
 158                 goto again;
 159         }
 160         return NULL;
 161 }
 162
 163 int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref,
 164                        int shared)
 165 {
 166         int ret = 0;
 167         struct rb_node *rb;
 168         struct btrfs_leaf_ref_tree *tree = root->ref_tree;
 169
 170         if (shared)
 171                 tree = &root->fs_info->shared_ref_tree;
 172
 173         spin_lock(&tree->lock);
 174         rb = tree_insert(&tree->root, ref->bytenr, &ref->rb_node);
 175         if (rb) {
 176                 ret = -EEXIST;
 177         } else {
 178                 atomic_inc(&ref->usage);
 179                 ref->tree = tree;
 180                 ref->in_tree = 1;
 181                 list_add_tail(&ref->list, &tree->list);
 182         }
 183         spin_unlock(&tree->lock);
 184         return ret;
 185 }
 186
 187 int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref)
 188 {
 189         struct btrfs_leaf_ref_tree *tree;
 190
 191         if (!xchg(&ref->in_tree, 0))
 192                 return 0;
 193
 194         tree = ref->tree;
 195         spin_lock(&tree->lock);
 196
 197         rb_erase(&ref->rb_node, &tree->root);
 198         list_del_init(&ref->list);
 199
 200         spin_unlock(&tree->lock);
 201
 202         btrfs_free_leaf_ref(root, ref);
 203         return 0;
 204 }