btrfs: move common inode creation code into btrfs_create_new_inode()

All of our inode creation code paths duplicate the calls to
btrfs_init_inode_security() and btrfs_add_link(). Subvolume creation
additionally duplicates property inheritance and the call to
btrfs_set_inode_index(). Fix this by moving the common code into
btrfs_create_new_inode(). This accomplishes a few things at once:

1. It reduces code duplication.

2. It allows us to set up the inode completely before inserting the
   inode item, removing calls to btrfs_update_inode().

3. It fixes a leak of an inode on disk in some error cases. For example,
   in btrfs_create(), if btrfs_new_inode() succeeds, then we have
   inserted an inode item and its inode ref. However, if something after
   that fails (e.g., btrfs_init_inode_security()), then we end the
   transaction and then decrement the link count on the inode. If the
   transaction is committed and the system crashes before the failed
   inode is deleted, then we leak that inode on disk. Instead, this
   refactoring aborts the transaction when we can't recover more
   gracefully.

4. It exposes various ways that subvolume creation diverges from mkdir
   in terms of inheriting flags, properties, permissions, and POSIX
   ACLs, a lot of which appears to be accidental. This patch explicitly
   does _not_ change the existing non-standard behavior, but it makes
   those differences more clear in the code and documents them so that
   we can discuss whether they should be changed.

Reviewed-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 162 insertions, 239 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index beafdb4ff873..dbf059926141 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6105,9 +6105,6 @@ static void btrfs_inherit_iflags(struct inode *inode, struct inode *dir)
 {
 	unsigned int flags;
 
-	if (!dir)
-		return;
-
 	flags = BTRFS_I(dir)->flags;
 
 	if (flags & BTRFS_INODE_NOCOMPRESS) {
@@ -6128,14 +6125,13 @@ static void btrfs_inherit_iflags(struct inode *inode, struct inode *dir)
 }
 
 int btrfs_create_new_inode(struct btrfs_trans_handle *trans,
-			   struct btrfs_new_inode_args *args,
-			   u64 *index)
+			   struct btrfs_new_inode_args *args)
 {
-	struct inode *dir = args->subvol ? NULL : args->dir;
+	struct inode *dir = args->dir;
 	struct inode *inode = args->inode;
-	const char *name;
-	int name_len;
-	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+	const char *name = args->orphan ? NULL : args->dentry->d_name.name;
+	int name_len = args->orphan ? 0 : args->dentry->d_name.len;
+	struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
 	struct btrfs_root *root;
 	struct btrfs_inode_item *inode_item;
 	struct btrfs_key *location;
@@ -6148,49 +6144,31 @@ int btrfs_create_new_inode(struct btrfs_trans_handle *trans,
 	unsigned long ptr;
 	int ret;
 
-	if (args->subvol) {
-		name = "..";
-		name_len = 2;
-	} else if (args->orphan) {
-		name = NULL;
-		name_len = 0;
-	} else {
-		name = args->dentry->d_name.name;
-		name_len = args->dentry->d_name.len;
-	}
-
 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;
 
-	/*
-	 * O_TMPFILE, set link count to 0, so that after this point,
-	 * we fill in an inode item with the correct link count.
-	 */
-	if (!name)
-		set_nlink(inode, 0);
-
 	if (!args->subvol)
 		BTRFS_I(inode)->root = btrfs_grab_root(BTRFS_I(dir)->root);
 	root = BTRFS_I(inode)->root;
 
 	ret = btrfs_get_free_objectid(root, &objectid);
-	if (ret) {
-		btrfs_free_path(path);
-		return ret;
-	}
+	if (ret)
+		goto out;
 	inode->i_ino = objectid;
 
-	if (dir && name) {
+	if (args->orphan) {
+		/*
+		 * O_TMPFILE, set link count to 0, so that after this point, we
+		 * fill in an inode item with the correct link count.
+		 */
+		set_nlink(inode, 0);
+	} else {
 		trace_btrfs_inode_request(dir);
 
-		ret = btrfs_set_inode_index(BTRFS_I(dir), index);
-		if (ret) {
-			btrfs_free_path(path);
-			return ret;
-		}
-	} else if (dir) {
-		*index = 0;
+		ret = btrfs_set_inode_index(BTRFS_I(dir), &BTRFS_I(inode)->dir_index);
+		if (ret)
+			goto out;
 	}
 	/*
 	 * index_cnt is ignored for everything but a dir,
@@ -6198,11 +6176,16 @@ int btrfs_create_new_inode(struct btrfs_trans_handle *trans,
 	 * number
 	 */
 	BTRFS_I(inode)->index_cnt = 2;
-	BTRFS_I(inode)->dir_index = *index;
 	BTRFS_I(inode)->generation = trans->transid;
 	inode->i_generation = BTRFS_I(inode)->generation;
 
-	btrfs_inherit_iflags(inode, dir);
+	/*
+	 * Subvolumes don't inherit flags from their parent directory.
+	 * Originally this was probably by accident, but we probably can't
+	 * change it now without compatibility issues.
+	 */
+	if (!args->subvol)
+		btrfs_inherit_iflags(inode, dir);
 
 	if (S_ISREG(inode->i_mode)) {
 		if (btrfs_test_opt(fs_info, NODATASUM))
@@ -6212,6 +6195,55 @@ int btrfs_create_new_inode(struct btrfs_trans_handle *trans,
 				BTRFS_INODE_NODATASUM;
 	}
 
+	location = &BTRFS_I(inode)->location;
+	location->objectid = objectid;
+	location->offset = 0;
+	location->type = BTRFS_INODE_ITEM_KEY;
+
+	ret = btrfs_insert_inode_locked(inode);
+	if (ret < 0) {
+		if (!args->orphan)
+			BTRFS_I(dir)->index_cnt--;
+		goto out;
+	}
+
+	if (args->subvol) {
+		struct inode *parent;
+
+		/*
+		 * Subvolumes inherit properties from their parent subvolume,
+		 * not the directory they were created in.
+		 */
+		parent = btrfs_iget(fs_info->sb, BTRFS_FIRST_FREE_OBJECTID,
+				    BTRFS_I(dir)->root);
+		if (IS_ERR(parent)) {
+			ret = PTR_ERR(parent);
+		} else {
+			ret = btrfs_inode_inherit_props(trans, inode, parent);
+			iput(parent);
+		}
+	} else {
+		ret = btrfs_inode_inherit_props(trans, inode, dir);
+	}
+	if (ret) {
+		btrfs_err(fs_info,
+			  "error inheriting props for ino %llu (root %llu): %d",
+			  btrfs_ino(BTRFS_I(inode)), root->root_key.objectid,
+			  ret);
+	}
+
+	/*
+	 * Subvolumes don't inherit ACLs or get passed to the LSM. This is
+	 * probably a bug.
+	 */
+	if (!args->subvol) {
+		ret = btrfs_init_inode_security(trans, args);
+		if (ret) {
+			btrfs_abort_transaction(trans, ret);
+			goto discard;
+		}
+	}
+
 	/*
 	 * We could have gotten an inode number from somebody who was fsynced
 	 * and then removed in this same transaction, so let's just set full
@@ -6226,7 +6258,7 @@ int btrfs_create_new_inode(struct btrfs_trans_handle *trans,
 
 	sizes[0] = sizeof(struct btrfs_inode_item);
 
-	if (name) {
+	if (!args->orphan) {
 		/*
 		 * Start new inodes with an inode_ref. This is slightly more
 		 * efficient for small numbers of hard links since they will
@@ -6235,53 +6267,59 @@ int btrfs_create_new_inode(struct btrfs_trans_handle *trans,
 		 */
 		key[1].objectid = objectid;
 		key[1].type = BTRFS_INODE_REF_KEY;
-		if (dir)
-			key[1].offset = btrfs_ino(BTRFS_I(dir));
-		else
+		if (args->subvol) {
 			key[1].offset = objectid;
-
-		sizes[1] = name_len + sizeof(*ref);
+			sizes[1] = 2 + sizeof(*ref);
+		} else {
+			key[1].offset = btrfs_ino(BTRFS_I(dir));
+			sizes[1] = name_len + sizeof(*ref);
+		}
 	}
 
-	location = &BTRFS_I(inode)->location;
-	location->objectid = objectid;
-	location->offset = 0;
-	location->type = BTRFS_INODE_ITEM_KEY;
-
-	ret = btrfs_insert_inode_locked(inode);
-	if (ret < 0)
-		goto fail;
-
 	batch.keys = &key[0];
 	batch.data_sizes = &sizes[0];
-	batch.total_data_size = sizes[0] + (name ? sizes[1] : 0);
-	batch.nr = name ? 2 : 1;
+	batch.total_data_size = sizes[0] + (args->orphan ? 0 : sizes[1]);
+	batch.nr = args->orphan ? 1 : 2;
 	ret = btrfs_insert_empty_items(trans, root, path, &batch);
-	if (ret != 0)
-		goto fail_unlock;
+	if (ret != 0) {
+		btrfs_abort_transaction(trans, ret);
+		goto discard;
+	}
 
 	inode->i_mtime = current_time(inode);
 	inode->i_atime = inode->i_mtime;
 	inode->i_ctime = inode->i_mtime;
 	BTRFS_I(inode)->i_otime = inode->i_mtime;
 
+	/*
+	 * We're going to fill the inode item now, so at this point the inode
+	 * must be fully initialized.
+	 */
+
 	inode_item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 				  struct btrfs_inode_item);
 	memzero_extent_buffer(path->nodes[0], (unsigned long)inode_item,
 			     sizeof(*inode_item));
 	fill_inode_item(trans, path->nodes[0], inode_item, inode);
 
-	if (name) {
+	if (!args->orphan) {
 		ref = btrfs_item_ptr(path->nodes[0], path->slots[0] + 1,
 				     struct btrfs_inode_ref);
-		btrfs_set_inode_ref_name_len(path->nodes[0], ref, name_len);
-		btrfs_set_inode_ref_index(path->nodes[0], ref, *index);
 		ptr = (unsigned long)(ref + 1);
-		write_extent_buffer(path->nodes[0], name, ptr, name_len);
+		if (args->subvol) {
+			btrfs_set_inode_ref_name_len(path->nodes[0], ref, 2);
+			btrfs_set_inode_ref_index(path->nodes[0], ref, 0);
+			write_extent_buffer(path->nodes[0], "..", ptr, 2);
+		} else {
+			btrfs_set_inode_ref_name_len(path->nodes[0], ref, name_len);
+			btrfs_set_inode_ref_index(path->nodes[0], ref,
+						  BTRFS_I(inode)->dir_index);
+			write_extent_buffer(path->nodes[0], name, ptr, name_len);
+		}
 	}
 
 	btrfs_mark_buffer_dirty(path->nodes[0]);
-	btrfs_free_path(path);
+	btrfs_release_path(path);
 
 	inode_tree_add(inode);
 
@@ -6290,24 +6328,28 @@ int btrfs_create_new_inode(struct btrfs_trans_handle *trans,
 
 	btrfs_update_root_times(trans, root);
 
-	ret = btrfs_inode_inherit_props(trans, inode, dir);
-	if (ret)
-		btrfs_err(fs_info,
-			  "error inheriting props for ino %llu (root %llu): %d",
-			btrfs_ino(BTRFS_I(inode)), root->root_key.objectid, ret);
+	if (args->orphan) {
+		ret = btrfs_orphan_add(trans, BTRFS_I(inode));
+	} else {
+		ret = btrfs_add_link(trans, BTRFS_I(dir), BTRFS_I(inode), name,
+				     name_len, 0, BTRFS_I(inode)->dir_index);
+	}
+	if (ret) {
+		btrfs_abort_transaction(trans, ret);
+		goto discard;
+	}
 
-	return 0;
+	ret = 0;
+	goto out;
 
-fail_unlock:
+discard:
 	/*
 	 * discard_new_inode() calls iput(), but the caller owns the reference
 	 * to the inode.
 	 */
 	ihold(inode);
 	discard_new_inode(inode);
-fail:
-	if (dir && name)
-		BTRFS_I(dir)->index_cnt--;
+out:
 	btrfs_free_path(path);
 	return ret;
 }
@@ -6414,52 +6456,28 @@ static int btrfs_create_common(struct inode *dir, struct dentry *dentry,
 	unsigned int trans_num_items;
 	struct btrfs_trans_handle *trans;
 	int err;
-	u64 index = 0;
 
 	err = btrfs_new_inode_prepare(&new_inode_args, &trans_num_items);
-	if (err) {
-		iput(inode);
-		return err;
-	}
+	if (err)
+		goto out_inode;
 
 	trans = btrfs_start_transaction(root, trans_num_items);
 	if (IS_ERR(trans)) {
-		iput(inode);
 		err = PTR_ERR(trans);
 		goto out_new_inode_args;
 	}
 
-	err = btrfs_create_new_inode(trans, &new_inode_args, &index);
-	if (err) {
-		iput(inode);
-		inode = NULL;
-		goto out_unlock;
-	}
-
-	err = btrfs_init_inode_security(trans, &new_inode_args);
-	if (err)
-		goto out_unlock;
-
-	err = btrfs_update_inode(trans, root, BTRFS_I(inode));
-	if (err)
-		goto out_unlock;
-
-	err = btrfs_add_link(trans, BTRFS_I(dir), BTRFS_I(inode),
-			     dentry->d_name.name, dentry->d_name.len, 0, index);
-	if (err)
-		goto out_unlock;
-
-	d_instantiate_new(dentry, inode);
+	err = btrfs_create_new_inode(trans, &new_inode_args);
+	if (!err)
+		d_instantiate_new(dentry, inode);
 
-out_unlock:
 	btrfs_end_transaction(trans);
-	if (err && inode) {
-		inode_dec_link_count(inode);
-		discard_new_inode(inode);
-	}
 	btrfs_btree_balance_dirty(fs_info);
 out_new_inode_args:
 	btrfs_new_inode_args_destroy(&new_inode_args);
+out_inode:
+	if (err)
+		iput(inode);
 	return err;
 }
 
@@ -8732,34 +8750,6 @@ struct inode *btrfs_new_subvol_inode(struct user_namespace *mnt_userns,
 	return inode;
 }
 
-/*
- * create a new subvolume directory/inode (helper for the ioctl).
- */
-int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
-			     struct btrfs_root *parent_root,
-			     struct btrfs_new_inode_args *args)
-{
-	struct inode *inode = args->inode;
-	struct btrfs_root *new_root = BTRFS_I(inode)->root;
-	int err;
-	u64 index = 0;
-
-	err = btrfs_create_new_inode(trans, args, &index);
-	if (err)
-		return err;
-
-	unlock_new_inode(inode);
-
-	err = btrfs_subvol_inherit_props(trans, new_root, parent_root);
-	if (err)
-		btrfs_err(new_root->fs_info,
-			  "error inheriting subvolume %llu properties: %d",
-			  new_root->root_key.objectid, err);
-
-	err = btrfs_update_inode(trans, new_root, BTRFS_I(inode));
-	return err;
-}
-
 struct inode *btrfs_alloc_inode(struct super_block *sb)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(sb);
@@ -9248,41 +9238,6 @@ static struct inode *new_whiteout_inode(struct user_namespace *mnt_userns,
 	return inode;
 }
 
-static int btrfs_whiteout_for_rename(struct btrfs_trans_handle *trans,
-				     struct btrfs_new_inode_args *args)
-{
-	struct inode *inode = args->inode;
-	struct inode *dir = args->dir;
-	struct btrfs_root *root = BTRFS_I(dir)->root;
-	struct dentry *dentry = args->dentry;
-	int ret;
-	u64 index;
-
-	ret = btrfs_create_new_inode(trans, args, &index);
-	if (ret) {
-		iput(inode);
-		return ret;
-	}
-
-	ret = btrfs_init_inode_security(trans, args);
-	if (ret)
-		goto out;
-
-	ret = btrfs_add_link(trans, BTRFS_I(dir), BTRFS_I(inode),
-			     dentry->d_name.name, dentry->d_name.len, 0, index);
-	if (ret)
-		goto out;
-
-	ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
-out:
-	unlock_new_inode(inode);
-	if (ret)
-		inode_dec_link_count(inode);
-	iput(inode);
-
-	return ret;
-}
-
 static int btrfs_rename(struct user_namespace *mnt_userns,
 			struct inode *old_dir, struct dentry *old_dentry,
 			struct inode *new_dir, struct dentry *new_dentry,
@@ -9492,11 +9447,14 @@ static int btrfs_rename(struct user_namespace *mnt_userns,
 				   rename_ctx.index, new_dentry->d_parent);
 
 	if (flags & RENAME_WHITEOUT) {
-		ret = btrfs_whiteout_for_rename(trans, &whiteout_args);
-		whiteout_args.inode = NULL;
+		ret = btrfs_create_new_inode(trans, &whiteout_args);
 		if (ret) {
 			btrfs_abort_transaction(trans, ret);
 			goto out_fail;
+		} else {
+			unlock_new_inode(whiteout_args.inode);
+			iput(whiteout_args.inode);
+			whiteout_args.inode = NULL;
 		}
 	}
 out_fail:
@@ -9735,7 +9693,6 @@ static int btrfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
 	};
 	unsigned int trans_num_items;
 	int err;
-	u64 index = 0;
 	int name_len;
 	int datasize;
 	unsigned long ptr;
@@ -9753,38 +9710,33 @@ static int btrfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
 	inode->i_op = &btrfs_symlink_inode_operations;
 	inode_nohighmem(inode);
 	inode->i_mapping->a_ops = &btrfs_aops;
+	btrfs_i_size_write(BTRFS_I(inode), name_len);
+	inode_set_bytes(inode, name_len);
 
 	new_inode_args.inode = inode;
 	err = btrfs_new_inode_prepare(&new_inode_args, &trans_num_items);
-	if (err) {
-		iput(inode);
-		return err;
-	}
+	if (err)
+		goto out_inode;
 	/* 1 additional item for the inline extent */
 	trans_num_items++;
 
 	trans = btrfs_start_transaction(root, trans_num_items);
 	if (IS_ERR(trans)) {
-		iput(inode);
 		err = PTR_ERR(trans);
 		goto out_new_inode_args;
 	}
 
-	err = btrfs_create_new_inode(trans, &new_inode_args, &index);
-	if (err) {
-		iput(inode);
-		inode = NULL;
-		goto out_unlock;
-	}
-
-	err = btrfs_init_inode_security(trans, &new_inode_args);
+	err = btrfs_create_new_inode(trans, &new_inode_args);
 	if (err)
-		goto out_unlock;
+		goto out;
 
 	path = btrfs_alloc_path();
 	if (!path) {
 		err = -ENOMEM;
-		goto out_unlock;
+		btrfs_abort_transaction(trans, err);
+		discard_new_inode(inode);
+		inode = NULL;
+		goto out;
 	}
 	key.objectid = btrfs_ino(BTRFS_I(inode));
 	key.offset = 0;
@@ -9793,8 +9745,11 @@ static int btrfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
 	err = btrfs_insert_empty_item(trans, root, path, &key,
 				      datasize);
 	if (err) {
+		btrfs_abort_transaction(trans, err);
 		btrfs_free_path(path);
-		goto out_unlock;
+		discard_new_inode(inode);
+		inode = NULL;
+		goto out;
 	}
 	leaf = path->nodes[0];
 	ei = btrfs_item_ptr(leaf, path->slots[0],
@@ -9812,32 +9767,16 @@ static int btrfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
 	btrfs_mark_buffer_dirty(leaf);
 	btrfs_free_path(path);
 
-	inode_set_bytes(inode, name_len);
-	btrfs_i_size_write(BTRFS_I(inode), name_len);
-	err = btrfs_update_inode(trans, root, BTRFS_I(inode));
-	/*
-	 * Last step, add directory indexes for our symlink inode. This is the
-	 * last step to avoid extra cleanup of these indexes if an error happens
-	 * elsewhere above.
-	 */
-	if (!err)
-		err = btrfs_add_link(trans, BTRFS_I(dir), BTRFS_I(inode),
-				     dentry->d_name.name, dentry->d_name.len, 0,
-				     index);
-	if (err)
-		goto out_unlock;
-
 	d_instantiate_new(dentry, inode);
-
-out_unlock:
+	err = 0;
+out:
 	btrfs_end_transaction(trans);
-	if (err && inode) {
-		inode_dec_link_count(inode);
-		discard_new_inode(inode);
-	}
 	btrfs_btree_balance_dirty(fs_info);
 out_new_inode_args:
 	btrfs_new_inode_args_destroy(&new_inode_args);
+out_inode:
+	if (err)
+		iput(inode);
 	return err;
 }
 
@@ -10095,7 +10034,6 @@ static int btrfs_tmpfile(struct user_namespace *mnt_userns, struct inode *dir,
 		.orphan = true,
 	};
 	unsigned int trans_num_items;
-	u64 index;
 	int ret;
 
 	inode = new_inode(dir->i_sb);
@@ -10108,35 +10046,16 @@ static int btrfs_tmpfile(struct user_namespace *mnt_userns, struct inode *dir,
 
 	new_inode_args.inode = inode;
 	ret = btrfs_new_inode_prepare(&new_inode_args, &trans_num_items);
-	if (ret) {
-		iput(inode);
-		return ret;
-	}
+	if (ret)
+		goto out_inode;
 
 	trans = btrfs_start_transaction(root, trans_num_items);
 	if (IS_ERR(trans)) {
-		iput(inode);
 		ret = PTR_ERR(trans);
 		goto out_new_inode_args;
 	}
 
-	ret = btrfs_create_new_inode(trans, &new_inode_args, &index);
-	if (ret) {
-		iput(inode);
-		inode = NULL;
-		goto out;
-	}
-
-	ret = btrfs_init_inode_security(trans, &new_inode_args);
-	if (ret)
-		goto out;
-
-	ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
-	if (ret)
-		goto out;
-	ret = btrfs_orphan_add(trans, BTRFS_I(inode));
-	if (ret)
-		goto out;
+	ret = btrfs_create_new_inode(trans, &new_inode_args);
 
 	/*
 	 * We set number of links to 0 in btrfs_create_new_inode(), and here we
@@ -10146,16 +10065,20 @@ static int btrfs_tmpfile(struct user_namespace *mnt_userns, struct inode *dir,
 	 *    d_tmpfile() -> inode_dec_link_count() -> drop_nlink()
 	 */
 	set_nlink(inode, 1);
-	d_tmpfile(dentry, inode);
-	unlock_new_inode(inode);
-	mark_inode_dirty(inode);
-out:
+
+	if (!ret) {
+		d_tmpfile(dentry, inode);
+		unlock_new_inode(inode);
+		mark_inode_dirty(inode);
+	}
+
 	btrfs_end_transaction(trans);
-	if (ret && inode)
-		discard_new_inode(inode);
 	btrfs_btree_balance_dirty(fs_info);
 out_new_inode_args:
 	btrfs_new_inode_args_destroy(&new_inode_args);
+out_inode:
+	if (ret)
+		iput(inode);
 	return ret;
 }