On Fri, Dec 28, 2012 at 11:42:40AM +0800, Jeff Liu wrote:
> +static int btrfs_ioctl_set_fslabel(struct file *file, void __user *arg)
> +{
> + struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
> + struct btrfs_super_block *super_block = root->fs_info->super_copy;
> + struct btrfs_trans_handle *trans;
> + char label[BTRFS_LABEL_SIZE];
> + int ret;
> +
> + if (!capable(CAP_SYS_ADMIN))
> + return -EPERM;
> +
> + if (copy_from_user(label, arg, sizeof(label)))
> + return -EFAULT;
> +
> + if (strnlen(label, BTRFS_LABEL_SIZE) == BTRFS_LABEL_SIZE)
I would expect a message if this happens, similar to the 'get_fslabel'
one, otherwise it's difficult to find out the reason.
> + return -EINVAL;
> +
> + ret = mnt_want_write_file(file);
> + if (ret)
> + return ret;
> +
> + mutex_lock(&root->fs_info->volume_mutex);
> + trans = btrfs_start_transaction(root, 1);
Do we need to reserve 1 unit here? This does not touch any
non-superblock metadata, modifies superblock in place. This could lead
to an ENOSPC (changing label on a full fs), altghouh it need not happen.
> + if (IS_ERR(trans)) {
> + ret = PTR_ERR(trans);
> + goto out_unlock;
> + }
> +
> + strcpy(super_block->label, label);
> + ret = btrfs_end_transaction(trans, root);
> +
> +out_unlock:
> + mutex_unlock(&root->fs_info->volume_mutex);
> + mnt_drop_write_file(file);
> + return ret;
> +}
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