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Date: Sun, 12 Nov 1995 06:41:44 +1100
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199511111941.GAA07419@godzilla.zeta.org.au>
To: bugs@freebsd.org, gtc@aloft.att.com, jkh@freebsd.org
Subject: Re: panic: vm_bounce_alloc during initial installation (writing disk info)
Sender: owner-bugs@freebsd.org
Precedence: bulk

>(10/26 if I recall).  When trying to perform the initial installation on my
>machine, after going through all the menus to partition and label the disk,
>when I go to commit the changes to disk, I immediately get the following error
>message (as seen on the debug screen):
>vm_bounce_alloc: b_bufsize(0x200) < b_bcount(0x1ff0a400) !!

This might be caused by a negative block number somehow being passed to
dscheck().  If this happens, then "truncating" the i/o would actually
expand the i/o to the size of the partition plus the absolute value of
the negative block number.  Do you have a (BSD) partition of size
approximately 0x1ff0a400 bytes (500+ MB)?  Negative block numbers are
used by the file system code but are not supposed to reach device drivers.

>My environment is:
>	Pentium 90   (AMI Titan II EISA/PCI motherboard, one CPU installed)
>	BT946C	BusLogic PCI bus-mastering SCSI controller
>...
>One of the problems may be that bounce buffers shouldn't really be used on
>my machine, given that I've got a 32-bit bus-mastering SCSI controller (this
>is probably related to kernel problem #378).  But even if it does want to

Bounce buffers are used because the GENERIC config specifies them and
the `bt' driver handles all BusLogic devices from isa through pci using
much the same code - it requests bounce buffer support for all buses.

Bruce