/* * 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 <linux/sort.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; }