kern/87255: [md] ]panic] largemalloc backed mfs crashes the system

[Kris Kennaway]

The following reply was made to PR kern/87255; it has been noted by GNATS.

From: Kris Kennaway <kris at obsecurity.org>
To: Gergely CZUCZY <phoemix at harmless.hu>
Cc: freebsd-gnats-submit at FreeBSD.org
Subject: Re: kern/87255: [md] ]panic] largemalloc backed mfs crashes the system
Date: Fri, 23 Mar 2007 15:20:15 -0400

 On Fri, Mar 23, 2007 at 02:50:07PM +0000, Gergely CZUCZY wrote:
 > The following reply was made to PR kern/87255; it has been noted by GNATS.
 > 
 > From: Gergely CZUCZY <phoemix at harmless.hu>
 > To: bug-followup at FreeBSD.org
 > Cc:  
 > Subject: Re: kern/87255: [md] ]panic] largemalloc backed mfs crashes the system
 > Date: Fri, 23 Mar 2007 15:12:22 +0100
 > 
 >  --PEIAKu/WMn1b1Hv9
 >  Content-Type: text/plain; charset=utf-8
 >  Content-Disposition: inline
 >  Content-Transfer-Encoding: quoted-printable
 >  
 >  Hello
 >  
 >  I've just hit this issue on a 6.2-STABLE, and it's been verified on freenod=
 >  e/##freebsd on
 >  an other 6.2-STABLE.
 >  FreeBSD  6.2-STABLE FreeBSD 6.2-STABLE #0: Tue Feb 27 12:04:37 CET 2007    =
 >   toor at mort:/usr/obj/usr/src/sys/FREESBIE  i386
 >  FreeBSD sys0 6.2-STABLE FreeBSD 6.2-STABLE #1: Web Mar 21 23:39:54 CET 2007
 >  
 >  how did i triggered it:
 >  # mdconfig -a -t malloc -s 1g
 >  mdX
 >  # newfs /dev/mdX
 >  # mount /dev/mdX /mnt/
 >  # cd /usr/ && tar -czf /mnt/src.tar src
 >  # cd /mnt && tar -xvf src.tar
 >  
 >  the box has 2G of ram in it, i allocated half of that into mfs for
 >  some proposes. so, if i leave enough memory for the system, it still
 >  crashed.
 >  
 >  it crashed the system and rebooted it shortly.
 
 Right, this is a documented limitation of malloc backing.  Use swap
 backing instead, it's just better.
 
 Kris