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| -rw-r--r-- | doc/dev/kernel-client-troubleshooting.rst | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/doc/dev/kernel-client-troubleshooting.rst b/doc/dev/kernel-client-troubleshooting.rst new file mode 100644 index 00000000..b6f7eff7 --- /dev/null +++ b/doc/dev/kernel-client-troubleshooting.rst @@ -0,0 +1,21 @@ +==================================== + Kernel client troubleshooting (FS) +==================================== + +If there is an issue with the cephfs kernel client, the most important thing is +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 +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 |