Fsck drops to a maintenance shell at boot

Issue

• During boot, the system hangs on fsck.

• The machine begins the Checking Filesystems stage and stops with the following error:

  /dev/mapper/U01: UNEXPECTED INCONSISTENCY:     [FAILED]
  
  *** An error occured during the file system check.
  *** Dropping you to a shell; the system will reboot
  *** when you leave the shell.
  Give root password for maintenance
  

• System cannot boot with the following messages in Red Hat Enterprise Linux 7.

  Welcome to emergency mode! After logging in, type "journalctl -xb" to view
  system logs, "systemctl reboot" to reboot, "systemctl default" or ^D to
  try again to boot into default mode.
  

• Then journalctl shows the followings:

  systemd-fsck: /dev/sdb1 contains a file system with errors, check forced.
  systemd-fsck: /dev/sdb1: Inodes that were part of a corrupted orphan linked list found.
  systemd-fsck: /dev/sdb1: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY.
  systemd-fsck: (i.e., without -a or -p options)
  systemd-fsck: fsck failed with error code 4.
  systemd-fsck: Running request emergency.target/start/replace