kern/111766: "panic: ffs_blkfree: freeing free block" during disk activity

[Kris Kennaway]

The following reply was made to PR kern/111766; it has been noted by GNATS.

From: Kris Kennaway <kris at obsecurity.org>
To: Rong-En Fan <rafan at FreeBSD.org>
Cc: Kris Kennaway <kris at obsecurity.org>, FreeBSD-gnats-submit at FreeBSD.org
Subject: Re: kern/111766: "panic: ffs_blkfree: freeing free block" during disk activity
Date: Wed, 18 Apr 2007 00:06:15 -0400

 On Wed, Apr 18, 2007 at 12:01:53PM +0800, Rong-En Fan wrote:
 > On Tue, Apr 17, 2007 at 11:39:41PM -0400, Kris Kennaway wrote:
 > > On Wed, Apr 18, 2007 at 11:19:08AM +0800, Rong-En Fan wrote:
 > > > On our NFS server, this usually happens when one of the exported partitions
 > > > gets full. I have seen this on 4.x, 5.x and 6.x. And I'm pretty sure the
 > > > filesystem is in good state (I do fsck -fy every time after crash). The
 > > > disk in question is an external raid box.
 > > 
 > > Interesting, can you repeat this on demand?
 > 
 > I think I tried once but in vain. Some previous backtrace
 > at http://www.rafan.org/FreeBSD/panic/freeing_free_block/
 > I haven't see this since last Oct, but the filesystem does not
 > get full recently (we got larger disks).
 
 Unfortunately I dont think the backtrace is very useful, it's
 reporting damage that occured at some earlier time.
 
 > 
 > >From previous experience, usually the panic is triggered on
 > the full partition but I saw once or twice that it's triggered
 > on another non-full filesystem.
 
 I am not entirely sure whether it is really due to a full filesystem,
 because I've also come across it in random circumstances.  I have also
 spent some time stressing full filesystems without causing the panic.
 If you can come up with a way to reliably produce it, that would be
 very useful (possibly essential).
 
 Kris