Btrfs: set/change the label of a mounted file system

With this new ioctl(2) BTRFS_IOC_SET_FSLABEL, we can set/change the label of a mounted file system.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Miao Xie <miaox@cn.fujitsu.com>
Reviewed-by: Goffredo Baroncelli <kreijack@inwind.it>
Reviewed-by: David Sterba <dsterba@suse.cz>
Reviewed-by: Goffredo Baroncelli <kreijack@inwind.it>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index fcc15a6..0f68729 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3936,6 +3936,46 @@ static int btrfs_ioctl_get_fslabel(struct file *file, void __user *arg)
        return ret ? -EFAULT : 0;
 }
 
+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) {
+               pr_err("btrfs: unable to set label with more than %d bytes\n",
+                      BTRFS_LABEL_SIZE - 1);
+               return -EINVAL;
+       }
+
+       ret = mnt_want_write_file(file);
+       if (ret)
+               return ret;
+
+       mutex_lock(&root->fs_info->volume_mutex);
+       trans = btrfs_start_transaction(root, 0);
+       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;
+}
+
 long btrfs_ioctl(struct file *file, unsigned int
                cmd, unsigned long arg)
 {
@@ -4038,6 +4078,8 @@ long btrfs_ioctl(struct file *file, unsigned int
                return btrfs_ioctl_dev_replace(root, argp);
        case BTRFS_IOC_GET_FSLABEL:
                return btrfs_ioctl_get_fslabel(file, argp);
+       case BTRFS_IOC_SET_FSLABEL:
+               return btrfs_ioctl_set_fslabel(file, argp);
        }
 
        return -ENOTTY;

diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index 51c0b33..fa3a5f9 100644 (file)
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -504,6 +504,8 @@ struct btrfs_ioctl_send_args {
                               struct btrfs_ioctl_qgroup_limit_args)
 #define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 49, \
                                   char[BTRFS_LABEL_SIZE])
+#define BTRFS_IOC_SET_FSLABEL _IOW(BTRFS_IOCTL_MAGIC, 50, \
+                                  char[BTRFS_LABEL_SIZE])
 #define BTRFS_IOC_GET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 52, \
                                      struct btrfs_ioctl_get_dev_stats)
 #define BTRFS_IOC_DEV_REPLACE _IOWR(BTRFS_IOCTL_MAGIC, 53, \