1 files changed, 58 insertions, 24 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 4b903517fdc3..bd10b8d44b5d 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -544,6 +544,33 @@ int __pure btrfs_is_empty_uuid(u8 *uuid)
 	return 1;
 }
 
+/*
+ * Calculate the number of transaction items to reserve for creating a subvolume
+ * or snapshot, not including the inode, directory entries, or parent directory.
+ */
+static unsigned int create_subvol_num_items(struct btrfs_qgroup_inherit *inherit)
+{
+	/*
+	 * 1 to add root block
+	 * 1 to add root item
+	 * 1 to add root ref
+	 * 1 to add root backref
+	 * 1 to add UUID item
+	 * 1 to add qgroup info
+	 * 1 to add qgroup limit
+	 *
+	 * Ideally the last two would only be accounted if qgroups are enabled,
+	 * but that can change between now and the time we would insert them.
+	 */
+	unsigned int num_items = 7;
+
+	if (inherit) {
+		/* 2 to add qgroup relations for each inherited qgroup */
+		num_items += 2 * inherit->num_qgroups;
+	}
+	return num_items;
+}
+
 static noinline int create_subvol(struct user_namespace *mnt_userns,
 				  struct inode *dir, struct dentry *dentry,
 				  struct btrfs_qgroup_inherit *inherit)
@@ -560,7 +587,12 @@ static noinline int create_subvol(struct user_namespace *mnt_userns,
 	struct btrfs_root *new_root;
 	struct btrfs_block_rsv block_rsv;
 	struct timespec64 cur_time = current_time(dir);
-	struct inode *inode;
+	struct btrfs_new_inode_args new_inode_args = {
+		.dir = dir,
+		.dentry = dentry,
+		.subvol = true,
+	};
+	unsigned int trans_num_items;
 	int ret;
 	dev_t anon_dev;
 	u64 objectid;
@@ -587,26 +619,27 @@ static noinline int create_subvol(struct user_namespace *mnt_userns,
 	if (ret < 0)
 		goto out_root_item;
 
-	inode = btrfs_new_subvol_inode(mnt_userns, dir);
-	if (!inode) {
+	new_inode_args.inode = btrfs_new_subvol_inode(mnt_userns, dir);
+	if (!new_inode_args.inode) {
 		ret = -ENOMEM;
 		goto out_anon_dev;
 	}
+	ret = btrfs_new_inode_prepare(&new_inode_args, &trans_num_items);
+	if (ret)
+		goto out_inode;
+	trans_num_items += create_subvol_num_items(inherit);
 
 	btrfs_init_block_rsv(&block_rsv, BTRFS_BLOCK_RSV_TEMP);
-	/*
-	 * The same as the snapshot creation, please see the comment
-	 * of create_snapshot().
-	 */
-	ret = btrfs_subvolume_reserve_metadata(root, &block_rsv, 8, false);
+	ret = btrfs_subvolume_reserve_metadata(root, &block_rsv,
+					       trans_num_items, false);
 	if (ret)
-		goto out_inode;
+		goto out_new_inode_args;
 
 	trans = btrfs_start_transaction(root, 0);
 	if (IS_ERR(trans)) {
 		ret = PTR_ERR(trans);
 		btrfs_subvolume_release_metadata(root, &block_rsv);
-		goto out_inode;
+		goto out_new_inode_args;
 	}
 	trans->block_rsv = &block_rsv;
 	trans->bytes_reserved = block_rsv.size;
@@ -689,8 +722,8 @@ static noinline int create_subvol(struct user_namespace *mnt_userns,
 	}
 	/* anon_dev is owned by new_root now. */
 	anon_dev = 0;
-	BTRFS_I(inode)->root = new_root;
-	/* ... and new_root is owned by inode now. */
+	BTRFS_I(new_inode_args.inode)->root = new_root;
+	/* ... and new_root is owned by new_inode_args.inode now. */
 
 	ret = btrfs_record_root_in_trans(trans, new_root);
 	if (ret) {
@@ -698,7 +731,7 @@ static noinline int create_subvol(struct user_namespace *mnt_userns,
 		goto out;
 	}
 
-	ret = btrfs_create_subvol_root(trans, root, inode);
+	ret = btrfs_create_subvol_root(trans, root, &new_inode_args);
 	if (ret) {
 		/* We potentially lose an unused inode item here */
 		btrfs_abort_transaction(trans, ret);
@@ -751,11 +784,13 @@ out:
 		ret = btrfs_commit_transaction(trans);
 
 	if (!ret) {
-		d_instantiate(dentry, inode);
-		inode = NULL;
+		d_instantiate(dentry, new_inode_args.inode);
+		new_inode_args.inode = NULL;
 	}
+out_new_inode_args:
+	btrfs_new_inode_args_destroy(&new_inode_args);
 out_inode:
-	iput(inode);
+	iput(new_inode_args.inode);
 out_anon_dev:
 	if (anon_dev)
 		free_anon_bdev(anon_dev);
@@ -771,6 +806,7 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
 	struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
 	struct inode *inode;
 	struct btrfs_pending_snapshot *pending_snapshot;
+	unsigned int trans_num_items;
 	struct btrfs_trans_handle *trans;
 	int ret;
 
@@ -808,16 +844,14 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
 	btrfs_init_block_rsv(&pending_snapshot->block_rsv,
 			     BTRFS_BLOCK_RSV_TEMP);
 	/*
-	 * 1 - parent dir inode
-	 * 2 - dir entries
-	 * 1 - root item
-	 * 2 - root ref/backref
-	 * 1 - root of snapshot
-	 * 1 - UUID item
+	 * 1 to add dir item
+	 * 1 to add dir index
+	 * 1 to update parent inode item
 	 */
+	trans_num_items = create_subvol_num_items(inherit) + 3;
 	ret = btrfs_subvolume_reserve_metadata(BTRFS_I(dir)->root,
-					&pending_snapshot->block_rsv, 8,
-					false);
+					       &pending_snapshot->block_rsv,
+					       trans_num_items, false);
 	if (ret)
 		goto free_pending;