Btrfs: Add a new ioctl to get the label of a mounted file system

Add a new ioctl(2) BTRFS_IOC_GET_FSLABLE, so that we can get the label upon a mounted filesystem.

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

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index d02ec577f70f53ec461518a9a186400504c27026..fcc15a6804a9be803dbcc5192a8742cc46e47d18 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3917,6 +3917,25 @@ out:
        return ret;
 }
 
+static int btrfs_ioctl_get_fslabel(struct file *file, void __user *arg)
+{
+       struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
+       const char *label = root->fs_info->super_copy->label;
+       size_t len = strnlen(label, BTRFS_LABEL_SIZE);
+       int ret;
+
+       if (len == BTRFS_LABEL_SIZE) {
+               pr_warn("btrfs: label is too long, return the first %zu bytes\n",
+                       --len);
+       }
+
+       mutex_lock(&root->fs_info->volume_mutex);
+       ret = copy_to_user(arg, label, len);
+       mutex_unlock(&root->fs_info->volume_mutex);
+
+       return ret ? -EFAULT : 0;
+}
+
 long btrfs_ioctl(struct file *file, unsigned int
                cmd, unsigned long arg)
 {
@@ -4017,6 +4036,8 @@ long btrfs_ioctl(struct file *file, unsigned int
                return btrfs_ioctl_qgroup_limit(file, argp);
        case BTRFS_IOC_DEV_REPLACE:
                return btrfs_ioctl_dev_replace(root, argp);
+       case BTRFS_IOC_GET_FSLABEL:
+               return btrfs_ioctl_get_fslabel(file, argp);
        }
 
        return -ENOTTY;

diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index dd9f1293ab35e6d5ada367571e116fcad710394c..51c0b335e0c88faef040201dcb3baa1b0ce3b048 100644 (file)
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -502,6 +502,8 @@ struct btrfs_ioctl_send_args {
                               struct btrfs_ioctl_qgroup_create_args)
 #define BTRFS_IOC_QGROUP_LIMIT _IOR(BTRFS_IOCTL_MAGIC, 43, \
                               struct btrfs_ioctl_qgroup_limit_args)
+#define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 49, \
+                                  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, \