Btrfs: Add a leaf reference cache

Much of the IO done while dropping snapshots is done looking up
leaves in the filesystem trees to see if they point to any extents and
to drop the references on any extents found.

This creates a cache so that IO isn't required.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 72 insertions, 0 deletions

diff --git a/fs/btrfs/ref-cache.h b/fs/btrfs/ref-cache.h
new file mode 100644
index 0000000..79ecc47
--- /dev/null
+++ b/fs/btrfs/ref-cache.h
@@ -0,0 +1,72 @@
+/*
+ * 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.
+ */
+
+struct btrfs_extent_info {
+	u64 bytenr;
+	u64 num_bytes;
+	u64 objectid;
+	u64 offset;
+};
+
+struct btrfs_leaf_ref {
+	struct rb_node rb_node;
+	struct btrfs_key key;
+	int in_tree;
+	atomic_t usage;
+
+	u64 bytenr;
+	u64 owner;
+	u64 generation;
+	int nritems;
+	struct btrfs_extent_info extents[];
+};
+
+struct btrfs_leaf_ref_tree {
+	struct rb_root root;
+	struct btrfs_leaf_ref *last;
+	u64 generation;
+	spinlock_t lock;
+};
+
+static inline size_t btrfs_leaf_ref_size(int nr_extents)
+{
+	return sizeof(struct btrfs_leaf_ref) + 
+	       sizeof(struct btrfs_extent_info) * nr_extents;
+}
+
+static inline void btrfs_leaf_ref_tree_init(struct btrfs_leaf_ref_tree *tree)
+{
+	tree->root.rb_node = NULL;
+	tree->last = NULL;
+	tree->generation = 0;
+	spin_lock_init(&tree->lock);
+}
+
+static inline int btrfs_leaf_ref_tree_empty(struct btrfs_leaf_ref_tree *tree)
+{
+	return RB_EMPTY_ROOT(&tree->root);
+}
+
+void btrfs_leaf_ref_tree_init(struct btrfs_leaf_ref_tree *tree);
+struct btrfs_leaf_ref *btrfs_alloc_leaf_ref(int nr_extents);
+void btrfs_free_leaf_ref(struct btrfs_leaf_ref *ref);
+struct btrfs_leaf_ref *btrfs_lookup_leaf_ref(struct btrfs_root *root,
+					     struct btrfs_key *key);
+int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref);
+int btrfs_remove_leaf_refs(struct btrfs_root *root);
+int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref);