Btrfs: Change the super to point to a tree of trees to enable persistent snapshots

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

1 files changed, 88 insertions, 0 deletions

diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
new file mode 100644
index 0000000..0ab90cf
--- /dev/null
+++ b/fs/btrfs/root-tree.c
@@ -0,0 +1,88 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "kerncompat.h"
+#include "radix-tree.h"
+#include "ctree.h"
+#include "disk-io.h"
+#include "print-tree.h"
+
+int btrfs_find_last_root(struct btrfs_root *root, u64 objectid,
+			struct btrfs_root_item *item, struct btrfs_key *key)
+{
+	struct btrfs_path path;
+	struct btrfs_key search_key;
+	struct btrfs_leaf *l;
+	int ret;
+	int slot;
+
+	search_key.objectid = objectid;
+	search_key.flags = (u32)-1;
+	search_key.offset = (u32)-1;
+
+	btrfs_init_path(&path);
+	ret = btrfs_search_slot(root, &search_key, &path, 0, 0);
+	if (ret < 0)
+		goto out;
+	BUG_ON(ret == 0);
+	l = &path.nodes[0]->leaf;
+	BUG_ON(path.slots[0] == 0);
+	slot = path.slots[0] - 1;
+	if (btrfs_key_objectid(&l->items[slot].key) != objectid) {
+		ret = 1;
+		goto out;
+	}
+	memcpy(item, l->data + btrfs_item_offset(l->items + slot),
+		sizeof(*item));
+	btrfs_disk_key_to_cpu(key, &l->items[slot].key);
+	btrfs_release_path(root, &path);
+	ret = 0;
+out:
+	return ret;
+}
+
+int btrfs_update_root(struct btrfs_root *root, struct btrfs_key *key,
+		      struct btrfs_root_item *item)
+{
+	struct btrfs_path path;
+	struct btrfs_leaf *l;
+	int ret;
+	int slot;
+
+	btrfs_init_path(&path);
+	ret = btrfs_search_slot(root, key, &path, 0, 1);
+	if (ret < 0)
+		goto out;
+	BUG_ON(ret != 0);
+	l = &path.nodes[0]->leaf;
+	slot = path.slots[0];
+	memcpy(l->data + btrfs_item_offset(l->items + slot), item,
+		sizeof(*item));
+out:
+	btrfs_release_path(root, &path);
+	return ret;
+}
+
+int btrfs_insert_root(struct btrfs_root *root, struct btrfs_key *key,
+		      struct btrfs_root_item *item)
+{
+	int ret;
+	ret = btrfs_insert_item(root, key, item, sizeof(*item));
+	BUG_ON(ret);
+	return ret;
+}
+
+int btrfs_del_root(struct btrfs_root *root, struct btrfs_key *key)
+{
+	struct btrfs_path path;
+	int ret;
+
+	btrfs_init_path(&path);
+	ret = btrfs_search_slot(root, key, &path, -1, 1);
+	if (ret < 0)
+		goto out;
+	BUG_ON(ret != 0);
+	ret = btrfs_del_item(root, &path);
+out:
+	btrfs_release_path(root, &path);
+	return ret;
+}