Coda File System

Re: Coda on NetBSD

From: <>
Date: Tue, 17 Jan 2012 08:38:55 +0100
On Mon, Jan 16, 2012 at 01:42:17PM -0500, Greg Troxel wrote:
> Are you running with DIAGNOSTIC?

Just out-of-the-box whatever it is...

> What provokes the crash?

Unfortunately I don't know - simple/few operations do not,
the crash happens when I am running scripts fecthing and starting
many binaries and mmap()-ing a lot of libraries.

The actual test was a try to start vncserver, running
among others bash, perl, Xvnc with its libraries and
a number of X clients (unsure how long it comes, probably
far from having started all of the programs involved).

>   linux binary reading a directory in coda

Does not crash on itself.

> or
>   linux binary in coda being run, not trying to read data from coda

Can not exclude this but I assume that people are running Linux
binaries on NetBSD (without Coda) successfully. Thus - hardly.

> or
>   you have to do both?

I actually do both as I my binaries are Linux-ABI and are on Coda.

Note though that the majority of the file system accesses are not
directory/file enumeration but plain open(), chdir(), execve(),
that is, the lookup being done implicitly in the kernel.

Wonder if it can be the concurrency (which the scripts do trigger, a shell
pipeline means several parallel execve()s) combined with the "unexpected"
(Coda) file system latency which can trigger races. I recall that on
Linux Coda triggered corner cases in the file system framework with the
bugs persisting for very long time. Finally somebody managed to observe
the same problem, as a very rare case, with local file systems too.

Another apparent suspect is the broken directory reading code
which can lead to misaligned data and reading quite unexpected things?

> The big issue with coda and NetBSD now is that getcwd() seems not to
> work right.

I remember submitting a patch to uClibc long ago as this was a problem
on Linux too.

Received on 2012-01-17 02:39:50