In commit ae8c511757 ("fs: add FS_IOC_GETFSSYSFSPATH"), a
new fs ioctl was introduced to standardize exporting data from
sysfs across filesystems. The returned path will always be of the
form "$FSTYP/$SYSFS_IDENTIFIER", where the sysfs identifier may
be a UUID or a device name.
The ubifs is a file system based on char device, and the common
method to fill s_sysfs_name (super_set_sysfs_name_bdev) is
unavialable. So in order to support FS_IOC_GETFSSYSFSPATH ioctl,
we fill the s_sysfs_name with ubi_volume_info member which keeps
the format defined in macro UBIFS_DFS_DIR_NAME by using
super_set_sysfs_name_generic.
That's for ubifs, it will output "ubifs/<dev>".
```
$ ./ioctl_getfssysfs_path /mnt/ubifs/testfile
path: ubifs/ubi0_0
$ ls /sys/fs/ubifs/ubi0_0/
errors_crc errors_magic errors_node
```
Signed-off-by: Hongbo Li <lihongbo22@huawei.com>
Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
39ba2b9ac6