Add disk format requirements for subvol backward and forward refs

ctree.h

@@ -443,6 +443,15 @@ struct btrfs_root_item {
 	u8 level;
 } __attribute__ ((__packed__));
 
+/*
+ * this is used for both forward and backward root refs
+ */
+struct btrfs_root_ref {
+	__le64 dirid;
+	__le64 sequence;
+	__le16 name_len;
+} __attribute__ ((__packed__));
+
 #define BTRFS_FILE_EXTENT_INLINE 0
 #define BTRFS_FILE_EXTENT_REG 1
 #define BTRFS_FILE_EXTENT_PREALLOC 2
@@ -635,50 +644,64 @@ struct btrfs_root {
  * the FS
  */
 #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 3-15 close to the inode for later flexibility */
+#define BTRFS_INODE_REF_KEY		12
+#define BTRFS_XATTR_ITEM_KEY		24
+#define BTRFS_ORPHAN_ITEM_KEY		48
 
+#define BTRFS_DIR_LOG_ITEM_KEY  60
+#define BTRFS_DIR_LOG_INDEX_KEY 72
 /*
  * dir items are the name -> inode pointers in a directory.  There is one
  * for every name in a directory.
  */
-#define BTRFS_DIR_ITEM_KEY	16
-#define BTRFS_DIR_INDEX_KEY	17
+#define BTRFS_DIR_ITEM_KEY	84
+#define BTRFS_DIR_INDEX_KEY	96
+
 /*
  * extent data is for file data
  */
-#define BTRFS_EXTENT_DATA_KEY	18
+#define BTRFS_EXTENT_DATA_KEY	108
+
 /*
  * csum items have the checksums for data in the extents
  */
-#define BTRFS_CSUM_ITEM_KEY	19
-
-/* reserve 20-31 for other file stuff */
+#define BTRFS_CSUM_ITEM_KEY	120
 
 /*
  * root items point to tree roots.  There are typically in the root
  * tree used by the super block to find all the other trees
  */
-#define BTRFS_ROOT_ITEM_KEY	32
+#define BTRFS_ROOT_ITEM_KEY	132
+
+/*
+ * root backrefs tie subvols and snapshots to the directory entries that
+ * reference them
+ */
+#define BTRFS_ROOT_BACKREF_KEY	144
+
+/*
+ * root refs make a fast index for listing all of the snapshots and
+ * subvolumes referenced by a given root.  They point directly to the
+ * directory item in the root that references the subvol
+ */
+#define BTRFS_ROOT_REF_KEY	156
+
 /*
  * extent items are in the extent map tree.  These record which blocks
  * are used, and how many references there are to each block
  */
-#define BTRFS_EXTENT_ITEM_KEY	33
-#define BTRFS_EXTENT_REF_KEY	34
+#define BTRFS_EXTENT_ITEM_KEY	168
+#define BTRFS_EXTENT_REF_KEY	180
 
 /*
  * block groups give us hints into the extent allocation trees.  Which
  * blocks are free etc etc
  */
-#define BTRFS_BLOCK_GROUP_ITEM_KEY 50
+#define BTRFS_BLOCK_GROUP_ITEM_KEY 192
 
-#define BTRFS_DEV_EXTENT_KEY	75
-#define BTRFS_DEV_ITEM_KEY	76
-#define BTRFS_CHUNK_ITEM_KEY	77
+#define BTRFS_DEV_EXTENT_KEY	204
+#define BTRFS_DEV_ITEM_KEY	216
+#define BTRFS_CHUNK_ITEM_KEY	228
 
 /*
  * string items are for debugging.  They just store a short string of
@@ -1104,6 +1127,13 @@ static inline void btrfs_set_item_key(struct extent_buffer *eb,
 	write_eb_member(eb, item, struct btrfs_item, key, disk_key);
 }
 
+/*
+ * struct btrfs_root_ref
+ */
+BTRFS_SETGET_FUNCS(root_ref_dirid, struct btrfs_root_ref, dirid, 64);
+BTRFS_SETGET_FUNCS(root_ref_sequence, struct btrfs_root_ref, sequence, 64);
+BTRFS_SETGET_FUNCS(root_ref_name_len, struct btrfs_root_ref, name_len, 16);
+
 /* struct btrfs_dir_item */
 BTRFS_SETGET_FUNCS(dir_data_len, struct btrfs_dir_item, data_len, 16);
 BTRFS_SETGET_FUNCS(dir_type, struct btrfs_dir_item, type, 8);

print-tree.c

@@ -159,6 +159,21 @@ static void print_file_extent_item(struct extent_buffer *eb,
 }
 
 
+static void print_root_ref(struct extent_buffer *leaf, int slot, char *tag)
+{
+	struct btrfs_root_ref *ref;
+	char namebuf[BTRFS_NAME_LEN];
+	int namelen;
+
+	ref = btrfs_item_ptr(leaf, slot, struct btrfs_root_ref);
+	namelen = btrfs_root_ref_name_len(leaf, ref);
+	read_extent_buffer(leaf, namebuf, (unsigned long)(ref + 1), namelen);
+	printf("\t\troot %s key dirid %llu sequence %llu name %.*s\n", tag,
+	       (unsigned long long)btrfs_root_ref_dirid(leaf, ref),
+	       (unsigned long long)btrfs_root_ref_sequence(leaf, ref),
+	       namelen, namebuf);
+}
+
 void btrfs_print_leaf(struct btrfs_root *root, struct extent_buffer *l)
 {
 	int i;
@@ -240,6 +255,12 @@ void btrfs_print_leaf(struct btrfs_root *root, struct extent_buffer *l)
 				       root_item.drop_level);
 			}
 			break;
+		case BTRFS_ROOT_REF_KEY:
+			print_root_ref(l, i, "ref");
+			break;
+		case BTRFS_ROOT_BACKREF_KEY:
+			print_root_ref(l, i, "backref");
+			break;
 		case BTRFS_EXTENT_ITEM_KEY:
 			ei = btrfs_item_ptr(l, i, struct btrfs_extent_item);
 			printf("\t\textent data refs %u\n",

root-tree.c

@@ -32,7 +32,7 @@ int btrfs_find_last_root(struct btrfs_root *root, u64 objectid,
 	int slot;
 
 	search_key.objectid = objectid;
-	search_key.type = (u8)-1;
+	search_key.type = BTRFS_ROOT_ITEM_KEY;
 	search_key.offset = (u64)-1;
 
 	path = btrfs_alloc_path();