Date: 6 Dec 2003 09:37:10 -0000 From: Colin Percival <cperciva@builder.daemonology.net> To: FreeBSD-gnats-submit@FreeBSD.org Subject: bin/59988: undocumented panic with large malloc-backed md Message-ID: <20031206093710.55357.qmail@builder.daemonology.net> Resent-Message-ID: <200312060940.hB69eHbS012866@freefall.freebsd.org>
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>Number: 59988 >Category: bin >Synopsis: undocumented panic with large malloc-backed md >Confidential: no >Severity: serious >Priority: high >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: doc-bug >Submitter-Id: current-users >Arrival-Date: Sat Dec 06 01:40:16 PST 2003 >Closed-Date: >Last-Modified: >Originator: Colin Percival >Release: >Organization: >Environment: >Description: Large malloc-backed memory disks will cause 5.x systems to panic when they are filled. This isn't documented anywhere. >How-To-Repeat: mdconfig -a -t malloc -s 300M -u 0 dd if=/dev/zero of=/dev/md0 bs=1048576 count=300 <do anything which requires kernel memory> >Fix: Document the panic in mdconfig.8 --- src/sbin/mdconfig/mdconfig.8.orig Sat Dec 6 09:20:15 2003 +++ src/sbin/mdconfig/mdconfig.8 Sat Dec 6 09:26:44 2003 @@ -91,6 +91,11 @@ Storage for this type of memory disk is allocated with .Xr malloc 9 . This limits the size to the malloc bucket limit in the kernel. +If the +.Fl o Cm reserve +option is not set, creating and filling a large +malloc-backed memory disk is a very easy way to +panic a system. .It Cm vnode A file specified with .Fl f Ar file >Release-Note: >Audit-Trail: >Unformatted:
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