doc/dev/kernel-client-troubleshooting: Add kernel dynamic debuggin

Signed-off-by: Shinobu Kinjo <[email protected]>

doc/dev/kernel-client-troubleshooting.rst

@@ -7,11 +7,15 @@ figuring out whether the problem is with the client or the MDS. Generally,
 this is easy to work out. If the kernel client broke directly, there
 will be output in dmesg. Collect it and any appropriate kernel state. If
 the problem is with the MDS, there will be hung requests that the client
-is waiting on. Look in ``/sys/kernel/debug/ceph/*/`` and cat the ``mdsc`` file to
-get a listing of requests in progress. If one of them remains there, the
+is waiting on. Look in ``/sys/kernel/debug/ceph/*/`` and cat the ``mdsc`` file to get a listing of requests in progress. If one of them remains there, the
 MDS has probably "forgotten" it.
 We can get hints about what's going on by dumping the MDS cache:
 ceph mds tell 0 dumpcache /tmp/dump.txt
 
 And if high logging levels are set on the MDS, that will almost certainly
 hold the information we need to diagnose and solve the issue.
+
+You can also enable dynamic debug against the cephfs module.
+
+See:
+https://github.com/ceph/ceph/blob/master/src/script/kcon_all.sh