f2fs: add support for FS_IOC_GETFSSYSFSPATH

FS_IOC_GETFSSYSFSPATH ioctl expects sysfs sub-path of a filesystem, the
format can be "$FSTYP/$SYSFS_IDENTIFIER" under /sys/fs, it can helps to
standardizes exporting sysfs datas across filesystems.

This patch wires up FS_IOC_GETFSSYSFSPATH for f2fs, it will output
"f2fs/<dev>".
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/super.c

@@ -4481,6 +4481,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 	sb->s_flags = (sb->s_flags & ~SB_POSIXACL) |
 		(test_opt(sbi, POSIX_ACL) ? SB_POSIXACL : 0);
 	super_set_uuid(sb, (void *) raw_super->uuid, sizeof(raw_super->uuid));
+	super_set_sysfs_name_bdev(sb);
 	sb->s_iflags |= SB_I_CGROUPWB;
 
 	/* init f2fs-specific super block info */