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Date:      Fri, 1 Mar 2002 17:50:32 -0800 (PST)
From:      Matthew Dillon <dillon@apollo.backplane.com>
To:        Kris Kennaway <kris@obsecurity.org>, Ian Dowse <iedowse@maths.tcd.ie>, Kirk McKusick <mckusick@mckusick.com>, Finch <dot@dotat.at>, fs@FreeBSD.ORG, fanf@chiark.greenend.org.uk
Subject:   Re: UFS panic on -stable
Message-ID:  <200203020150.g221oWS48392@apollo.backplane.com>
References:  <200202260141.g1Q1f8i28365@beastie.mckusick.com> <200202260237.aa51774@salmon.maths.tcd.ie> <20020226184340.A78562@xor.obsecurity.org> <20020228135233.B5586@xor.obsecurity.org> <20020301173740.A21179@xor.obsecurity.org>

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:One of the other machines panicked today; it wasn't even under load at
:the time (last reported load average was 0.00).  A different panic
:this time (I've seen it before, but I couldn't get a crashdump that
:time).
:
:A common thread in all of these panics is that they all seem to
:involve operations on MFS filesystems.  Even though the two UFS disk
:filesystems on the clients have the most read/write load, I don't
:think I've seen a panic involving them.
:
:/var: bad dir ino 24 at offset 0: mangled entry
:panic: ufs_dirbad: bad dir
:Debugger("panic")
:Stopped at      Debugger+0x35:  movb    $0,in_Debugger.426
:db>
:
:Here's the backtrace.

    I wonder if this has anything to do with MFS's VM pages getting
    paged in and out.

    Could you try hacking mount_mfs to mlock() the MFS memory?  As
    shown below.  I'm not entirely sure this will actually do anything,
    but it's worth a shot (assuming you have enough memory to cover all
    your MFS mounted filesystems).

    If this does the trick I'll take a look at the way MFS accesses
    the process's VM space.  If it doesn't at least we will know it
    isn't related to MFS's paging.

						-Matt

Index: mkfs.c
===================================================================
RCS file: /home/ncvs/src/sbin/newfs/mkfs.c,v
retrieving revision 1.29.2.6
diff -u -r1.29.2.6 mkfs.c
--- mkfs.c	21 Sep 2001 19:15:21 -0000	1.29.2.6
+++ mkfs.c	2 Mar 2002 01:49:33 -0000
@@ -236,6 +236,8 @@
 				0);
 			if(membase == MAP_FAILED)
 				err(12, "mmap");
+			mlock(membase, fssize * sectorsize);
+			bzero(membase, fssize * sectorsize);
 			close(fd);
 		} else {
 #ifndef STANDALONE

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