1 files changed, 230 insertions, 0 deletions
diff --git a/fs/btrfs/ref-cache.c b/fs/btrfs/ref-cache.c
new file mode 100644
index 00000000000..6f0acc4c9ea
--- /dev/null
+++ b/fs/btrfs/ref-cache.c
@@ -0,0 +1,230 @@
+/*
+ * 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;
+}