Help with filing a [maybe] ZFS/mmap bug.

[George Hartzell]

Andriy Gapon writes:
 > on 18/07/2013 20:44 George Hartzell said the following:
 > > Andriy Gapon writes:
 > >  > on 17/07/2013 23:47 George Hartzell said the following:
 > >  > > How should I move forward with this?
 > >  > 
 > >  > Could you please try to reproduce this problem using a kernel built with
 > >  > INVARIANTS options?
 > > 
 > > I added INVARIANT_SUPPORT and INVARIANTS options to the GENERIC
 > > kernel, rebuilt it, installed it and running through my "test case"
 > > generated a lot of invalid flac files.  I"m not sure what the options
 > > are/were supposed to do though, it looks like they generally lead to
 > > KASSERTS, which lead to abort()'s.  Nothing in /var/log/messages or on
 > > the console.
 > 
 > George,
 > 
 > do you have anything new on this issue?
 > 
 > Could you please try the following patch?
 > http://people.freebsd.org/~avg/zfs-putpages.diff
 > 
 > I expect it to not really fix the issue, but it may help to narrow it down.
 > Please keep INVARIANTS.
 > Thank you.
 > -- 
 > Andriy Gapon

Hi Andriy,

This weekend I built up a system using the 10.0 beta 2 dvd, then
updated /usr/src from head.

I grabbed a fresh copy of your patch this afternoon.

I applied your patch with no problems.  I was unable to build a new
kernel though, you have one reference to m->busy, where m is a
vm_page_t (if I remember correctly).  I dug around a bit and decided
that you meant m->busy_lock, which let me build a usable kernel.

It looks like INVARIANTS and INVARIANT_SUPPORT are included in the
GENERIC conf file.

I ran through my test routine with the original system and was able to
reproduce the problem.

After building and installing a kernel with your patch I was still
able to trigger the problem.  If anything it was worse (sample size =
1, I know...).

I did not see any interesting output in /var/log/messages or to the
console or anywhere else obvious.

I'm not sure what to do next.  It's likely that my m->busy to
m->busy_lock change was not The Right Thing to Do and might have
invalidated what the patch was trying to do.

In any case, I now have a system running HEAD and should be able to
test things more easily.

Thanks for the help,

g.