scsi: target: tcmu: reset_ring should reset TCMU_DEV_BIT_BROKEN

In case command ring buffer becomes inconsistent, tcmu sets device flag
TCMU_DEV_BIT_BROKEN.  If the bit is set, tcmu rejects new commands from LIO
core with TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE, and no longer processes
completions from the ring.  The reset_ring attribute can be used to
completely clean up the command ring, so after reset_ring the ring no
longer is inconsistent.

Therefore reset_ring also should reset bit TCMU_DEV_BIT_BROKEN to allow
normal processing.

Link: https://lore.kernel.org/r/20200409101026.17872-1-bstroesser@ts.fujitsu.com
Acked-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Bodo Stroesser <bstroesser@ts.fujitsu.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/target/target_core_user.c

@@ -2073,6 +2073,7 @@ static void tcmu_reset_ring(struct tcmu_dev *udev, u8 err_level)
 	mb->cmd_tail = 0;
 	mb->cmd_head = 0;
 	tcmu_flush_dcache_range(mb, sizeof(*mb));
+	clear_bit(TCMU_DEV_BIT_BROKEN, &udev->flags);
 
 	del_timer(&udev->cmd_timer);