Btrfs: Create orphan inode records to prevent lost files after a crash

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

fs/btrfs/ctree.h

@@ -74,6 +74,9 @@ struct btrfs_ordered_sum;
 /* directory objectid inside the root tree */
 #define BTRFS_ROOT_TREE_DIR_OBJECTID 6ULL
 
+/* orhpan objectid for tracking unlinked/truncated files */
+#define BTRFS_ORPHAN_OBJECTID -5ULL
+
 /*
  * All files have objectids higher than this.
  */
@@ -646,6 +649,9 @@ struct btrfs_root {
 
 	/* the dirty list is only used by non-reference counted roots */
 	struct list_head dirty_list;
+
+	spinlock_t orphan_lock;
+	struct list_head orphan_list;
 };
 
 /*
@@ -657,6 +663,7 @@ struct btrfs_root {
 #define BTRFS_INODE_ITEM_KEY		1
 #define BTRFS_INODE_REF_KEY		2
 #define BTRFS_XATTR_ITEM_KEY		8
+#define BTRFS_ORPHAN_ITEM_KEY		9
 /* reserve 2-15 close to the inode for later flexibility */
 
 /*
@@ -1560,6 +1567,13 @@ struct btrfs_dir_item *btrfs_lookup_xattr(struct btrfs_trans_handle *trans,
 					  struct btrfs_path *path, u64 dir,
 					  const char *name, u16 name_len,
 					  int mod);
+
+/* orphan.c */
+int btrfs_insert_orphan_item(struct btrfs_trans_handle *trans,
+			     struct btrfs_root *root, u64 offset);
+int btrfs_del_orphan_item(struct btrfs_trans_handle *trans,
+			  struct btrfs_root *root, u64 offset);
+
 /* inode-map.c */
 int btrfs_find_free_objectid(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *fs_root,