On wed, 12 Dec 2012 11:23:00 +0800, Jeff Liu wrote:
> Add a new ioctl BTRFS_FS_SETLABEL to change the label of a mounted filesystem.
>
>
> Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx>
> Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
>
> ---
> fs/btrfs/ioctl.c | 34 ++++++++++++++++++++++++++++++++++
> fs/btrfs/ioctl.h | 2 ++
> 2 files changed, 36 insertions(+)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index b0a5e17..ebbf634 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -3711,6 +3711,38 @@ static int btrfs_ioctl_get_fslabel(struct btrfs_root *root, void __user *arg)
> return ret ? -EFAULT : 0;
> }
>
> +static int btrfs_ioctl_set_fslabel(struct btrfs_root *root, void __user *arg)
> +{
> + struct btrfs_super_block *super_block = root->fs_info->super_copy;
> + struct btrfs_trans_handle *trans;
> + char label[BTRFS_LABEL_SIZE];
> + int ret = 0;
> +
> + if (!capable(CAP_SYS_ADMIN))
> + return -EPERM;
> +
> + if (btrfs_root_readonly(root))
> + return -EROFS;
Since this label is a global parameter, we needn't check the root
is R/O or not.
The check we need is the write access of the fs, so we need call
mnt_want_write_file()
> +
> + if (copy_from_user(label, arg, sizeof(label)))
> + return -EFAULT;
> +
> + label[BTRFS_LABEL_SIZE - 1] = '\0';
I don't think setting the last byte to '\0' is a good way, because the user would be
very strange that the new label is truncated, but the program told him that it was done
successfully.
> +
> + mutex_lock(&root->fs_info->volume_mutex);
> + trans = btrfs_start_transaction(root, 1);
> + if (IS_ERR(trans)) {
> + ret = PTR_ERR(trans);
> + goto out_unlock;
> + }
> + strcpy(super_block->label, label);
> + btrfs_end_transaction(trans, root);
> +
> +out_unlock:
> + mutex_unlock(&root->fs_info->volume_mutex);
> + return ret;
> +}
> +
> long btrfs_ioctl(struct file *file, unsigned int
> cmd, unsigned long arg)
> {
> @@ -3811,6 +3843,8 @@ long btrfs_ioctl(struct file *file, unsigned int
> return btrfs_ioctl_qgroup_limit(root, argp);
> case BTRFS_IOC_GET_FSLABEL:
> return btrfs_ioctl_get_fslabel(root, argp);
> + case BTRFS_IOC_SET_FSLABEL:
> + return btrfs_ioctl_set_fslabel(root, argp);
> }
>
> return -ENOTTY;
> diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
> index 98f896f..cc4e657 100644
> --- a/fs/btrfs/ioctl.h
> +++ b/fs/btrfs/ioctl.h
> @@ -455,4 +455,6 @@ struct btrfs_ioctl_send_args {
> struct btrfs_ioctl_get_dev_stats)
> #define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 53, \
> char[BTRFS_LABEL_SIZE])
> +#define BTRFS_IOC_SET_FSLABEL _IOW(BTRFS_IOCTL_MAGIC, 54, \
> + char[BTRFS_LABEL_SIZE])
> #endif
number 50 has been reserved for this feature.
Thanks
Miao
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