Btrfs: Add back pointers from the inode to the directory that references it

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

fs/btrfs/ctree.h

@@ -53,7 +53,7 @@ extern struct kmem_cache *btrfs_path_cachep;
 #define BTRFS_CSUM_SIZE 32
 /* four bytes for CRC32 */
 #define BTRFS_CRC32_SIZE 4
-#define BTRFS_EMPTY_DIR_SIZE 6
+#define BTRFS_EMPTY_DIR_SIZE 0
 
 #define BTRFS_FT_UNKNOWN	0
 #define BTRFS_FT_REG_FILE	1
@@ -206,6 +206,11 @@ struct btrfs_extent_ref {
 	__le64 offset;
 } __attribute__ ((__packed__));
 
+struct btrfs_inode_ref {
+	__le16 name_len;
+	/* name goes here */
+} __attribute__ ((__packed__));
+
 struct btrfs_inode_timespec {
 	__le64 sec;
 	__le32 nsec;
@@ -379,7 +384,8 @@ struct btrfs_root {
  * the FS
  */
 #define BTRFS_INODE_ITEM_KEY		1
-#define BTRFS_XATTR_ITEM_KEY		2
+#define BTRFS_INODE_REF_KEY		2
+#define BTRFS_XATTR_ITEM_KEY		8
 /* reserve 2-15 close to the inode for later flexibility */
 
 /*
@@ -486,6 +492,9 @@ BTRFS_SETGET_STACK_FUNCS(block_group_used, struct btrfs_block_group_item,
 BTRFS_SETGET_FUNCS(disk_block_group_used, struct btrfs_block_group_item,
 			 used, 64);
 
+/* struct btrfs_inode_ref */
+BTRFS_SETGET_FUNCS(inode_ref_name_len, struct btrfs_inode_ref, name_len, 16);
+
 /* struct btrfs_inode_item */
 BTRFS_SETGET_FUNCS(inode_generation, struct btrfs_inode_item, generation, 64);
 BTRFS_SETGET_FUNCS(inode_size, struct btrfs_inode_item, size, 64);
@@ -1043,6 +1052,14 @@ int btrfs_find_free_objectid(struct btrfs_trans_handle *trans,
 int btrfs_find_highest_inode(struct btrfs_root *fs_root, u64 *objectid);
 
 /* inode-item.c */
+int btrfs_insert_inode_ref(struct btrfs_trans_handle *trans,
+			   struct btrfs_root *root,
+			   const char *name, int name_len,
+			   u64 inode_objectid, u64 ref_objectid);
+int btrfs_del_inode_ref(struct btrfs_trans_handle *trans,
+			   struct btrfs_root *root,
+			   const char *name, int name_len,
+			   u64 inode_objectid, u64 ref_objectid);
 int btrfs_insert_empty_inode(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root,
 			     struct btrfs_path *path, u64 objectid);

fs/btrfs/inode-item.c

@@ -20,6 +20,142 @@
 #include "disk-io.h"
 #include "transaction.h"
 
+int find_name_in_backref(struct btrfs_path *path, const char * name,
+			 int name_len, struct btrfs_inode_ref **ref_ret)
+{
+	struct extent_buffer *leaf;
+	struct btrfs_inode_ref *ref;
+	unsigned long ptr;
+	unsigned long name_ptr;
+	u32 item_size;
+	u32 cur_offset = 0;
+	int len;
+
+	leaf = path->nodes[0];
+	item_size = btrfs_item_size_nr(leaf, path->slots[0]);
+	ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
+	while (cur_offset < item_size) {
+		ref = (struct btrfs_inode_ref *)(ptr + cur_offset);
+		len = btrfs_inode_ref_name_len(leaf, ref);
+		name_ptr = (unsigned long)(ref + 1);
+		cur_offset += len + sizeof(*ref);
+		if (len != name_len)
+			continue;
+		if (memcmp_extent_buffer(leaf, name, name_ptr, name_len) == 0) {
+			*ref_ret = ref;
+			return 1;
+		}
+	}
+	return 0;
+}
+
+int btrfs_del_inode_ref(struct btrfs_trans_handle *trans,
+			   struct btrfs_root *root,
+			   const char *name, int name_len,
+			   u64 inode_objectid, u64 ref_objectid)
+{
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_inode_ref *ref;
+	struct extent_buffer *leaf;
+	unsigned long ptr;
+	unsigned long item_start;
+	u32 item_size;
+	u32 sub_item_len;
+	int ret;
+	int del_len = name_len + sizeof(*ref);
+
+	key.objectid = inode_objectid;
+	key.offset = ref_objectid;
+	btrfs_set_key_type(&key, BTRFS_INODE_REF_KEY);
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+	if (ret > 0) {
+		ret = -ENOENT;
+		goto out;
+	} else if (ret < 0) {
+		goto out;
+	}
+	if (!find_name_in_backref(path, name, name_len, &ref)) {
+		ret = -ENOENT;
+		goto out;
+	}
+	leaf = path->nodes[0];
+	item_size = btrfs_item_size_nr(leaf, path->slots[0]);
+	if (del_len == item_size) {
+		ret = btrfs_del_item(trans, root, path);
+		goto out;
+	}
+	ptr = (unsigned long)ref;
+	sub_item_len = name_len + sizeof(*ref);
+	item_start = btrfs_item_ptr_offset(leaf, path->slots[0]);
+	memmove_extent_buffer(leaf, ptr, ptr + sub_item_len,
+			      item_size - (ptr + sub_item_len - item_start));
+	ret = btrfs_truncate_item(trans, root, path,
+				  item_size - sub_item_len, 1);
+	BUG_ON(ret);
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+int btrfs_insert_inode_ref(struct btrfs_trans_handle *trans,
+			   struct btrfs_root *root,
+			   const char *name, int name_len,
+			   u64 inode_objectid, u64 ref_objectid)
+{
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_inode_ref *ref;
+	unsigned long ptr;
+	int ret;
+	int ins_len = name_len + sizeof(*ref);
+
+	key.objectid = inode_objectid;
+	key.offset = ref_objectid;
+	btrfs_set_key_type(&key, BTRFS_INODE_REF_KEY);
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	ret = btrfs_insert_empty_item(trans, root, path, &key,
+				      ins_len);
+	if (ret == -EEXIST) {
+		u32 old_size;
+
+		if (find_name_in_backref(path, name, name_len, &ref))
+			goto out;
+
+		old_size = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
+		ret = btrfs_extend_item(trans, root, path, ins_len);
+		BUG_ON(ret);
+		ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
+				     struct btrfs_inode_ref);
+		ref = (struct btrfs_inode_ref *)((unsigned long)ref + old_size);
+		btrfs_set_inode_ref_name_len(path->nodes[0], ref, name_len);
+		ptr = (unsigned long)(ref + 1);
+		ret = 0;
+	} else if (ret < 0) {
+		goto out;
+	} else {
+		ref = btrfs_item_ptr(path->nodes[0], path->slots[0],
+				     struct btrfs_inode_ref);
+		btrfs_set_inode_ref_name_len(path->nodes[0], ref, name_len);
+		ptr = (unsigned long)(ref + 1);
+	}
+	write_extent_buffer(path->nodes[0], name, ptr, name_len);
+	btrfs_mark_buffer_dirty(path->nodes[0]);
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
 int btrfs_insert_empty_inode(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root,
 			     struct btrfs_path *path, u64 objectid)

fs/btrfs/inode.c

@@ -404,6 +404,17 @@ static int btrfs_unlink_trans(struct btrfs_trans_handle *trans,
 	ret = btrfs_delete_one_dir_name(trans, root, path, di);
 
 	dentry->d_inode->i_ctime = dir->i_ctime;
+	if (!S_ISLNK(dentry->d_inode->i_mode)) {
+		ret = btrfs_del_inode_ref(trans, root, name, name_len,
+					  dentry->d_inode->i_ino,
+					  dentry->d_parent->d_inode->i_ino);
+		if (ret) {
+			printk("failed to delete reference to %.*s, "
+			       "inode %lu parent %lu\n", name_len, name,
+			       dentry->d_inode->i_ino,
+			       dentry->d_parent->d_inode->i_ino);
+		}
+	}
 err:
 	btrfs_free_path(path);
 	if (!ret) {
@@ -445,75 +456,27 @@ static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
 	int err;
 	int ret;
 	struct btrfs_root *root = BTRFS_I(dir)->root;
-	struct btrfs_path *path;
-	struct btrfs_key key;
 	struct btrfs_trans_handle *trans;
-	struct btrfs_key found_key;
-	int found_type;
-	struct extent_buffer *leaf;
-	char *goodnames = "..";
 	unsigned long nr;
 
 	if (inode->i_size > BTRFS_EMPTY_DIR_SIZE)
 		return -ENOTEMPTY;
 
-	path = btrfs_alloc_path();
-	BUG_ON(!path);
 	mutex_lock(&root->fs_info->fs_mutex);
 	trans = btrfs_start_transaction(root, 1);
-
 	btrfs_set_trans_block_group(trans, dir);
-	key.objectid = inode->i_ino;
-	key.offset = (u64)-1;
-	key.type = (u8)-1;
-	while(1) {
-		ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
-		if (ret < 0) {
-			err = ret;
-			goto out;
-		}
-		BUG_ON(ret == 0);
-		if (path->slots[0] == 0) {
-			err = -ENOENT;
-			goto out;
-		}
-		path->slots[0]--;
-		leaf = path->nodes[0];
-		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
-		found_type = btrfs_key_type(&found_key);
-		if (found_key.objectid != inode->i_ino) {
-			err = -ENOENT;
-			goto out;
-		}
-		if ((found_type != BTRFS_DIR_ITEM_KEY &&
-		     found_type != BTRFS_DIR_INDEX_KEY) ||
-	            (!btrfs_match_dir_item_name(root, path, goodnames, 2) &&
-	            !btrfs_match_dir_item_name(root, path, goodnames, 1))) {
-			err = -ENOTEMPTY;
-			goto out;
-		}
-		ret = btrfs_del_item(trans, root, path);
-		BUG_ON(ret);
-
-		if (found_type == BTRFS_DIR_ITEM_KEY && found_key.offset == 1)
-			break;
-		btrfs_release_path(root, path);
-	}
-	ret = 0;
-	btrfs_release_path(root, path);
 
 	/* now the directory is empty */
 	err = btrfs_unlink_trans(trans, root, dir, dentry);
 	if (!err) {
 		inode->i_size = 0;
 	}
-out:
-	btrfs_release_path(root, path);
-	btrfs_free_path(path);
+
 	nr = trans->blocks_used;
 	ret = btrfs_end_transaction(trans, root);
 	mutex_unlock(&root->fs_info->fs_mutex);
 	btrfs_btree_balance_dirty(root, nr);
+
 	if (ret && !err)
 		err = ret;
 	return err;
@@ -887,21 +850,59 @@ static int btrfs_inode_by_name(struct inode *dir, struct dentry *dentry,
 	struct btrfs_root *root = BTRFS_I(dir)->root;
 	int ret = 0;
 
+	if (namelen == 1 && strcmp(name, ".") == 0) {
+		location->objectid = dir->i_ino;
+		location->type = BTRFS_INODE_ITEM_KEY;
+		location->offset = 0;
+		return 0;
+	}
 	path = btrfs_alloc_path();
 	BUG_ON(!path);
+
+	if (namelen == 1 && strcmp(name, "..") == 0) {
+		struct btrfs_key key;
+		struct extent_buffer *leaf;
+		u32 nritems;
+		int slot;
+
+		key.objectid = dir->i_ino;
+		btrfs_set_key_type(&key, BTRFS_INODE_REF_KEY);
+		key.offset = 0;
+		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+		BUG_ON(ret == 0);
+		ret = 0;
+
+		leaf = path->nodes[0];
+		slot = path->slots[0];
+		nritems = btrfs_header_nritems(leaf);
+		if (slot >= nritems)
+			goto out_err;
+
+		btrfs_item_key_to_cpu(leaf, &key, slot);
+		if (key.objectid != dir->i_ino ||
+		    key.type != BTRFS_INODE_REF_KEY) {
+			goto out_err;
+		}
+		location->objectid = key.offset;
+		location->type = BTRFS_INODE_ITEM_KEY;
+		location->offset = 0;
+		goto out;
+	}
+
 	di = btrfs_lookup_dir_item(NULL, root, path, dir->i_ino, name,
 				    namelen, 0);
 	if (IS_ERR(di))
 		ret = PTR_ERR(di);
 	if (!di || IS_ERR(di)) {
-		location->objectid = 0;
-		goto out;
+		goto out_err;
 	}
 	btrfs_dir_item_key_to_cpu(path->nodes[0], di, location);
 out:
-	btrfs_release_path(root, path);
 	btrfs_free_path(path);
 	return ret;
+out_err:
+	location->objectid = 0;
+	goto out;
 }
 
 /*
@@ -1053,13 +1054,50 @@ static int btrfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 	if (root->fs_info->tree_root == root)
 		key_type = BTRFS_DIR_ITEM_KEY;
 
+	/* special case for "." */
+	if (filp->f_pos == 0) {
+		over = filldir(dirent, ".", 1,
+			       1, inode->i_ino,
+			       DT_DIR);
+		if (over)
+			return 0;
+		filp->f_pos = 1;
+	}
+
 	mutex_lock(&root->fs_info->fs_mutex);
 	key.objectid = inode->i_ino;
+	path = btrfs_alloc_path();
+	path->reada = 2;
+
+	/* special case for .., just use the back ref */
+	if (filp->f_pos == 1) {
+		btrfs_set_key_type(&key, BTRFS_INODE_REF_KEY);
+		key.offset = 0;
+		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+		BUG_ON(ret == 0);
+		leaf = path->nodes[0];
+		slot = path->slots[0];
+		nritems = btrfs_header_nritems(leaf);
+		if (slot >= nritems) {
+			btrfs_release_path(root, path);
+			goto read_dir_items;
+		}
+		btrfs_item_key_to_cpu(leaf, &found_key, slot);
+		btrfs_release_path(root, path);
+		if (found_key.objectid != key.objectid ||
+		    found_key.type != BTRFS_INODE_REF_KEY)
+			goto read_dir_items;
+		over = filldir(dirent, "..", 2,
+			       2, found_key.offset, DT_DIR);
+		if (over)
+			goto nopos;
+		filp->f_pos = 2;
+	}
+
+read_dir_items:
 	btrfs_set_key_type(&key, key_type);
 	key.offset = filp->f_pos;
 
-	path = btrfs_alloc_path();
-	path->reada = 2;
 	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 	if (ret < 0)
 		goto err;
@@ -1255,6 +1293,13 @@ static int btrfs_add_link(struct btrfs_trans_handle *trans,
 				    dentry->d_parent->d_inode->i_ino,
 				    &key, btrfs_inode_type(inode));
 	if (ret == 0) {
+		if (!S_ISLNK(inode->i_mode)) {
+			ret = btrfs_insert_inode_ref(trans, root,
+					     dentry->d_name.name,
+					     dentry->d_name.len,
+					     inode->i_ino,
+					     dentry->d_parent->d_inode->i_ino);
+		}
 		parent_inode = dentry->d_parent->d_inode;
 		parent_inode->i_size += dentry->d_name.len * 2;
 		parent_inode->i_mtime = parent_inode->i_ctime = CURRENT_TIME;
@@ -1430,35 +1475,6 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
 	return err;
 }
 
-static int btrfs_make_empty_dir(struct btrfs_trans_handle *trans,
-				struct btrfs_root *root,
-				u64 objectid, u64 dirid)
-{
-	int ret;
-	char buf[2];
-	struct btrfs_key key;
-
-	buf[0] = '.';
-	buf[1] = '.';
-
-	key.objectid = objectid;
-	key.offset = 0;
-	btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY);
-
-	ret = btrfs_insert_dir_item(trans, root, buf, 1, objectid,
-				    &key, BTRFS_FT_DIR);
-	if (ret)
-		goto error;
-
-	key.objectid = dirid;
-	ret = btrfs_insert_dir_item(trans, root, buf, 2, objectid,
-				    &key, BTRFS_FT_DIR);
-	if (ret)
-		goto error;
-error:
-	return ret;
-}
-
 static int btrfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
 {
 	struct inode *inode;
@@ -1496,11 +1512,7 @@ static int btrfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
 	inode->i_fop = &btrfs_dir_file_operations;
 	btrfs_set_trans_block_group(trans, inode);
 
-	err = btrfs_make_empty_dir(trans, root, inode->i_ino, dir->i_ino);
-	if (err)
-		goto out_fail;
-
-	inode->i_size = 6;
+	inode->i_size = 0;
 	err = btrfs_update_inode(trans, root, inode);
 	if (err)
 		goto out_fail;
@@ -1971,6 +1983,12 @@ static int create_subvol(struct btrfs_root *root, char *name, int namelen)
 	if (ret)
 		goto fail;
 
+	ret = btrfs_insert_inode_ref(trans, root->fs_info->tree_root,
+			     name, namelen, objectid,
+			     root->fs_info->sb->s_root->d_inode->i_ino);
+	if (ret)
+		goto fail;
+
 	ret = btrfs_commit_transaction(trans, root);
 	if (ret)
 		goto fail_commit;
@@ -1989,12 +2007,10 @@ static int create_subvol(struct btrfs_root *root, char *name, int namelen)
 	inode->i_fop = &btrfs_dir_file_operations;
 	new_root->inode = inode;
 
-	ret = btrfs_make_empty_dir(trans, new_root, new_dirid, new_dirid);
-	if (ret)
-		goto fail;
-
+	ret = btrfs_insert_inode_ref(trans, new_root, "..", 2, new_dirid,
+				     new_dirid);
 	inode->i_nlink = 1;
-	inode->i_size = 6;
+	inode->i_size = 0;
 	ret = btrfs_update_inode(trans, new_root, inode);
 	if (ret)
 		goto fail;
@@ -2068,6 +2084,13 @@ static int create_snapshot(struct btrfs_root *root, char *name, int namelen)
 	if (ret)
 		goto fail;
 
+	ret = btrfs_insert_inode_ref(trans, root->fs_info->tree_root,
+			     name, namelen, objectid,
+			     root->fs_info->sb->s_root->d_inode->i_ino);
+
+	if (ret)
+		goto fail;
+
 	ret = btrfs_inc_root_ref(trans, root, objectid);
 	if (ret)
 		goto fail;
@@ -2338,7 +2361,6 @@ static int btrfs_rename(struct inode * old_dir, struct dentry *old_dentry,
 	struct inode *old_inode = old_dentry->d_inode;
 	struct timespec ctime = CURRENT_TIME;
 	struct btrfs_path *path;
-	struct btrfs_dir_item *di;
 	int ret;
 
 	if (S_ISDIR(old_inode->i_mode) && new_inode &&
@@ -2361,52 +2383,6 @@ static int btrfs_rename(struct inode * old_dir, struct dentry *old_dentry,
 	new_dir->i_ctime = new_dir->i_mtime = ctime;
 	old_inode->i_ctime = ctime;
 
-	if (S_ISDIR(old_inode->i_mode) && old_dir != new_dir) {
-		struct btrfs_key *location = &BTRFS_I(new_dir)->location;
-		struct btrfs_key old_parent_key;
-		di = btrfs_lookup_dir_item(trans, root, path, old_inode->i_ino,
-					   "..", 2, -1);
-		if (IS_ERR(di)) {
-			ret = PTR_ERR(di);
-			goto out_fail;
-		}
-		if (!di) {
-			ret = -ENOENT;
-			goto out_fail;
-		}
-		btrfs_dir_item_key_to_cpu(path->nodes[0], di, &old_parent_key);
-		ret = btrfs_del_item(trans, root, path);
-		if (ret) {
-			goto out_fail;
-		}
-		btrfs_release_path(root, path);
-
-		di = btrfs_lookup_dir_index_item(trans, root, path,
-						 old_inode->i_ino,
-						 old_parent_key.objectid,
-						 "..", 2, -1);
-		if (IS_ERR(di)) {
-			ret = PTR_ERR(di);
-			goto out_fail;
-		}
-		if (!di) {
-			ret = -ENOENT;
-			goto out_fail;
-		}
-		ret = btrfs_del_item(trans, root, path);
-		if (ret) {
-			goto out_fail;
-		}
-		btrfs_release_path(root, path);
-
-		ret = btrfs_insert_dir_item(trans, root, "..", 2,
-					    old_inode->i_ino, location,
-					    BTRFS_FT_DIR);
-		if (ret)
-			goto out_fail;
-	}
-
-
 	ret = btrfs_unlink_trans(trans, root, old_dir, old_dentry);
 	if (ret)
 		goto out_fail;