Btrfs: Add back pointers from extents to the btree or file referencing them

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

fs/btrfs/ctree.h

@@ -544,11 +544,12 @@ BTRFS_SETGET_FUNCS(ref_generation, struct btrfs_extent_ref, generation, 64);
 BTRFS_SETGET_FUNCS(ref_objectid, struct btrfs_extent_ref, objectid, 64);
 BTRFS_SETGET_FUNCS(ref_offset, struct btrfs_extent_ref, offset, 64);
 
-BTRFS_SETGET_STACK_FUNCS(ref_root, struct btrfs_extent_ref, root, 64);
-BTRFS_SETGET_STACK_FUNCS(ref_generation, struct btrfs_extent_ref,
+BTRFS_SETGET_STACK_FUNCS(stack_ref_root, struct btrfs_extent_ref, root, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_ref_generation, struct btrfs_extent_ref,
 			 generation, 64);
-BTRFS_SETGET_STACK_FUNCS(ref_objectid, struct btrfs_extent_ref, objectid, 64);
-BTRFS_SETGET_STACK_FUNCS(ref_offset, struct btrfs_extent_ref, offset, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_ref_objectid, struct btrfs_extent_ref,
+			 objectid, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_ref_offset, struct btrfs_extent_ref, offset, 64);
 
 BTRFS_SETGET_STACK_FUNCS(stack_extent_refs, struct btrfs_extent_item,
 			 refs, 32);
@@ -914,24 +915,45 @@ struct btrfs_block_group_cache *btrfs_find_block_group(struct btrfs_root *root,
 						 *hint, u64 search_start,
 						 int data, int owner);
 int btrfs_inc_root_ref(struct btrfs_trans_handle *trans,
-		       struct btrfs_root *root);
+		       struct btrfs_root *root, u64 owner_objectid);
 struct extent_buffer *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
 					    struct btrfs_root *root, u32 size,
+					    u64 root_objectid,
 					    u64 hint, u64 empty_size);
+struct extent_buffer *__btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
+					     struct btrfs_root *root,
+					     u32 blocksize,
+					     u64 root_objectid,
+					     u64 ref_generation,
+					     u64 first_objectid,
+					     int level,
+					     u64 hint,
+					     u64 empty_size);
+int btrfs_insert_extent_backref(struct btrfs_trans_handle *trans,
+				 struct btrfs_root *root,
+				 struct btrfs_path *path, u64 bytenr,
+				 u64 root_objectid, u64 ref_generation,
+				 u64 owner, u64 owner_offset);
 int btrfs_alloc_extent(struct btrfs_trans_handle *trans,
-		       struct btrfs_root *root, u64 owner,
-		       u64 num_bytes, u64 empty_size, u64 search_start,
+		       struct btrfs_root *root,
+		       u64 num_bytes, u64 root_objectid, u64 ref_generation,
+		       u64 owner, u64 owner_offset,
+		       u64 empty_size, u64 hint_byte,
 		       u64 search_end, struct btrfs_key *ins, int data);
 int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 		  struct extent_buffer *buf);
 int btrfs_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
-		      *root, u64 bytenr, u64 num_bytes, int pin);
+		      *root, u64 bytenr, u64 num_bytes,
+		      u64 root_objectid, u64 ref_generation,
+		      u64 owner_objectid, u64 owner_offset, int pin);
 int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans,
 			       struct btrfs_root *root,
 			       struct extent_map_tree *unpin);
 int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
 				struct btrfs_root *root,
-				u64 bytenr, u64 num_bytes);
+				u64 bytenr, u64 num_bytes,
+				u64 root_objectid, u64 ref_generation,
+				u64 owner, u64 owner_offset);
 int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans,
 				    struct btrfs_root *root);
 int btrfs_free_block_groups(struct btrfs_fs_info *info);
@@ -966,6 +988,7 @@ int btrfs_insert_empty_item(struct btrfs_trans_handle *trans, struct btrfs_root
 			    *root, struct btrfs_path *path, struct btrfs_key
 			    *cpu_key, u32 data_size);
 int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path);
+int btrfs_prev_leaf(struct btrfs_root *root, struct btrfs_path *path);
 int btrfs_leaf_free_space(struct btrfs_root *root, struct extent_buffer *leaf);
 int btrfs_drop_snapshot(struct btrfs_trans_handle *trans, struct btrfs_root
 			*root);

fs/btrfs/disk-io.c

@@ -210,7 +210,7 @@ static int btree_writepages(struct address_space *mapping,
 {
 	struct extent_map_tree *tree;
 	tree = &BTRFS_I(mapping->host)->extent_tree;
-	if (wbc->sync_mode == WB_SYNC_NONE) {
+	if (0 && wbc->sync_mode == WB_SYNC_NONE) {
 		u64 num_dirty;
 		u64 start = 0;
 		unsigned long thresh = 96 * 1024 * 1024;

fs/btrfs/file.c

@@ -496,7 +496,10 @@ int btrfs_drop_extents(struct btrfs_trans_handle *trans,
 						   sizeof(old));
 				if (disk_bytenr != 0) {
 					ret = btrfs_inc_extent_ref(trans, root,
-					         disk_bytenr, disk_num_bytes);
+					         disk_bytenr, disk_num_bytes,
+						 root->root_key.objectid,
+						 trans->transid,
+						 key.objectid, end);
 					BUG_ON(ret);
 				}
 			}
@@ -541,6 +544,14 @@ int btrfs_drop_extents(struct btrfs_trans_handle *trans,
 			u64 disk_bytenr = 0;
 			u64 disk_num_bytes = 0;
 			u64 extent_num_bytes = 0;
+			u64 root_gen;
+
+			if (leaf != root->node) {
+				root_gen =
+					btrfs_header_generation(path->nodes[1]);
+			} else {
+				root_gen = btrfs_header_generation(leaf);
+			}
 			if (found_extent) {
 				disk_bytenr =
 				      btrfs_file_extent_disk_bytenr(leaf,
@@ -563,7 +574,10 @@ int btrfs_drop_extents(struct btrfs_trans_handle *trans,
 				inode->i_blocks -= extent_num_bytes >> 9;
 				ret = btrfs_free_extent(trans, root,
 						disk_bytenr,
-							disk_num_bytes, 0);
+						disk_num_bytes,
+						root->root_key.objectid,
+						root_gen, inode->i_ino,
+						key.offset, 0);
 			}
 
 			BUG_ON(ret);

fs/btrfs/inode.c

@@ -93,7 +93,9 @@ static int run_delalloc_range(struct inode *inode, u64 start, u64 end)
 	if (alloc_hint == EXTENT_MAP_INLINE)
 		goto out;
 
-	ret = btrfs_alloc_extent(trans, root, inode->i_ino, num_bytes, 0,
+	ret = btrfs_alloc_extent(trans, root, num_bytes,
+				 root->root_key.objectid, trans->transid,
+				 inode->i_ino, start, 0,
 				 alloc_hint, (u64)-1, &ins, 1);
 	if (ret) {
 		WARN_ON(1);
@@ -560,6 +562,7 @@ static int btrfs_truncate_in_trans(struct btrfs_trans_handle *trans,
 	u64 extent_start = 0;
 	u64 extent_num_bytes = 0;
 	u64 item_end = 0;
+	u64 root_gen = 0;
 	int found_extent;
 	int del_item;
 	int extent_type = -1;
@@ -670,6 +673,15 @@ static int btrfs_truncate_in_trans(struct btrfs_trans_handle *trans,
 					found_extent = 1;
 					inode->i_blocks -= num_dec;
 				}
+				if (leaf == root->node) {
+					root_gen =
+						btrfs_header_generation(leaf);
+				} else {
+					struct extent_buffer *parent;
+					parent = path->nodes[1];
+					root_gen =
+						btrfs_header_generation(parent);
+				}
 			}
 		} else if (extent_type == BTRFS_FILE_EXTENT_INLINE &&
 			   !del_item) {
@@ -690,7 +702,10 @@ static int btrfs_truncate_in_trans(struct btrfs_trans_handle *trans,
 		btrfs_release_path(root, path);
 		if (found_extent) {
 			ret = btrfs_free_extent(trans, root, extent_start,
-						extent_num_bytes, 0);
+						extent_num_bytes,
+						root->root_key.objectid,
+						root_gen, inode->i_ino,
+						found_key.offset, 0);
 			BUG_ON(ret);
 		}
 	}
@@ -1900,7 +1915,14 @@ static int create_subvol(struct btrfs_root *root, char *name, int namelen)
 	trans = btrfs_start_transaction(root, 1);
 	BUG_ON(!trans);
 
-	leaf = btrfs_alloc_free_block(trans, root, root->leafsize, 0, 0);
+	ret = btrfs_find_free_objectid(trans, root->fs_info->tree_root,
+				       0, &objectid);
+	if (ret)
+		goto fail;
+
+	leaf = __btrfs_alloc_free_block(trans, root, root->leafsize,
+					objectid, trans->transid, 0, 0,
+					0, 0);
 	if (IS_ERR(leaf))
 		return PTR_ERR(leaf);
 
@@ -1908,7 +1930,8 @@ static int create_subvol(struct btrfs_root *root, char *name, int namelen)
 	btrfs_set_header_level(leaf, 0);
 	btrfs_set_header_bytenr(leaf, leaf->start);
 	btrfs_set_header_generation(leaf, trans->transid);
-	btrfs_set_header_owner(leaf, root->root_key.objectid);
+	btrfs_set_header_owner(leaf, objectid);
+
 	write_extent_buffer(leaf, root->fs_info->fsid,
 			    (unsigned long)btrfs_header_fsid(leaf),
 			    BTRFS_FSID_SIZE);
@@ -1933,11 +1956,6 @@ static int create_subvol(struct btrfs_root *root, char *name, int namelen)
 	free_extent_buffer(leaf);
 	leaf = NULL;
 
-	ret = btrfs_find_free_objectid(trans, root->fs_info->tree_root,
-				       0, &objectid);
-	if (ret)
-		goto fail;
-
 	btrfs_set_root_dirid(&root_item, new_dirid);
 
 	key.objectid = objectid;
@@ -2056,7 +2074,7 @@ static int create_snapshot(struct btrfs_root *root, char *name, int namelen)
 	if (ret)
 		goto fail;
 
-	ret = btrfs_inc_root_ref(trans, root);
+	ret = btrfs_inc_root_ref(trans, root, objectid);
 	if (ret)
 		goto fail;
 fail:

fs/btrfs/print-tree.c

@@ -33,6 +33,7 @@ void btrfs_print_leaf(struct btrfs_root *root, struct extent_buffer *l)
 	struct btrfs_file_extent_item *fi;
 	struct btrfs_key key;
 	struct btrfs_key found_key;
+	struct btrfs_extent_ref *ref;
 	u32 type;
 
 	printk("leaf %llu total ptrs %d free space %d\n",
@@ -73,6 +74,15 @@ void btrfs_print_leaf(struct btrfs_root *root, struct extent_buffer *l)
 			printk("\t\textent data refs %u\n",
 				btrfs_extent_refs(l, ei));
 			break;
+		case BTRFS_EXTENT_REF_KEY:
+			ref = btrfs_item_ptr(l, i, struct btrfs_extent_ref);
+			printk("\t\textent back ref root %llu gen %llu "
+			       "owner %llu offset %llu\n",
+			       (unsigned long long)btrfs_ref_root(l, ref),
+			       (unsigned long long)btrfs_ref_generation(l, ref),
+			       (unsigned long long)btrfs_ref_objectid(l, ref),
+			       (unsigned long long)btrfs_ref_offset(l, ref));
+			break;
 
 		case BTRFS_EXTENT_DATA_KEY:
 			fi = btrfs_item_ptr(l, i,

fs/btrfs/tree-defrag.c

@@ -78,6 +78,8 @@ static int defrag_walk_down(struct btrfs_trans_handle *trans,
 			break;
 
 		if (*level == 1) {
+			WARN_ON(btrfs_header_generation(path->nodes[*level]) !=
+							trans->transid);
 			ret = btrfs_realloc_node(trans, root,
 						 path->nodes[*level],
 						 path->slots[*level],