statfs & remote filesystem

Hey all,

So currently I have a system running on the 2.6.18.8 kernel, and I am using NFS to expand it's storage capabilities. This works fine when my connection is up and running, however when the NFS goes down any scripts I have running that touch the NFS mount will hang. Strace shows the hang at statfs. I looked through google, but I couldn't find anything. Has there ever been an effort put into place that allows statfs to timeout on a disconnected mount?
I did see that there was a statvfs, but I'm not sure if this provides what I want. Is this possible?

If you wrote your own C application that queried the remote file system periodically, but that enables a timer interrupt that could signal it when the connection times out, that application could conceivably signal in turn the hung scripts so that they can then terminate normally. You could write it as a server application that your scripts send a message to with their PID when they start so you know which processes are likely needing to be signalled. I'm not sure there isn't something better to do this, but it's a thought.

Yeah I tried something like that. I tried using an alarm to give the stat calls a 30 second timeout and if it fails to return to kill the stat. However stat's sigmask doesn't allow alarm signals, so it didn't work out. I'm considering having stat run in a separate thread and then having the alarm just kill that thread with a sigterm instead. I was just hoping that someone had tried this before, it seems like a problem that other people would have experienced.

You could use a POSIX timer which allows you to register a callback function. Check the timer_create(), timer_gettime(), timer_settime(), timer_delete(), and timer_getoverrun() functions. I'm not sure that they don't use signals, but may be invoked by the kernel. If someone knows for sure, I'd appreciate hearing.