6.x loosing record of free space after filesystem fills?

Guy Helmer ghelmer at palisadesys.com
Tue Nov 28 12:21:12 PST 2006

Kris Kennaway wrote:
> On Tue, Nov 28, 2006 at 10:45:59AM -0600, Guy Helmer wrote:
>> We're encountering some problems on FreeBSD 6.1 SMP with a number of 
>> end-user systems where a Postgresql database is growing to the point 
>> where the filesystem is nearly full or completely runs out of free 
>> space.  After this point, df shows wildly incorrect values for available 
>> space, sometimes even showing more space available than there allocated 
>> to the partition (and our systems rely on df to determine when to send 
>> warnings to end-users that the free disk space is getting low).  We've 
>> found the only way to correct the situation is to take the system down 
>> to single-user mode and force a non-background fsck on the partition - 
>> simply rebooting the system does not fix the situation.
>> We're going to try setting debug.mpsafevfs to 0 in /boot/loader.conf to 
>> see if this works around the problem.  I've gone through the CVS logs 
>> for src/sys/ufs/ffs/* but I haven't seen anything that would 
>> specifically apply to this problem.  Has anyone else seen this problem, 
>> and by chance is it resolved for 6.2?
> First I've heard of it.  May not be resolved unless a developer can
> reproduce it.
> Kris
I had hoped one of kib's or tegge's recent changes to 
src/sys/ufs/ffs/ffs_softdep.c might be related.  I'll see what I can do 
to get hard details - maybe a kernel with INVARIANTS would find something.


Guy Helmer, Ph.D.
Chief System Architect
Palisade Systems, Inc.

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