Why an 'ls' Command is Showing 'Uninterruptible Sleep' in a Glusterfs Mount Point?

Issue

When running a plain lscommand in a Gluster file system mount, the command gets stuck and eventually shows as ' D ' in a psoutput:

root     18122  0.0  0.0  18988   916 ?        D    Nov25   0:00 ls --color=auto
root     20605  0.0  0.0  18988   916 ?        D    Nov22   0:00 ls --color=auto
root     21540  0.0  0.0  18988   916 ?        D    Nov25   0:00 ls --color=auto
root     23200  0.0  0.0  21096  1092 ?        D    Nov22   0:00 ls --color=auto -l --color=auto
root     23690  0.0  0.0  18988   920 ?        D    Nov22   0:00 ls --color=auto
root     29787  0.0  0.0  18988   916 ?        D    Nov22   0:00 ls --color=auto

How to get the lscommand working again?