2011-01-21
A bit more on listing file locks on Solaris 10
To follow up on my earlier entry on this, it's
amazing what you discover when you take the time go through mdb's full
online help. In particular, if you have an NFS fileserver you can easily
see all NFS locks that it knows about, complete with the remote hold and
even the full filename.
The basic mdb -k command we want is ::nlm_lockson, which does
what you might expect from the name. The state field values that I
know about are '3' for active locks and '4' for attempted locks that
are currently blocked. If there is a specific lock that you want path
information on, take the vnode address and use the mdb command line:
<addr> ::print vnode_t v_path
If you want the paths for most or all of the locks, use ::nlm_lockson
-v instead of the plain version. This will also tell you various sorts
of other additional information, including decoding the numeric state
field to human-readable values.
The help for ::nlm_lockson claims that you can get it to report on
only a single remote host. I've never been able to get this to work,
but I don't care very much since you can always pipe its output through
grep or the like. (I'm probably missing something.)
The other two NLM commands documented in ::nfs_help -d don't seem
to report anything that's useful for sysadmins. It's possible that I'm
missing something; full understanding of this stuff is difficult without
access to the kernel source, and the NLM modules are one of the pieces
of Solaris that are still closed source and available only as binaries.