Date: Thu, 25 Apr 2013 11:58:42 -0500 From: Guy Helmer <guy.helmer@gmail.com> To: Jeremy Chadwick <jdc@koitsu.org> Cc: FreeBSD Stable <freebsd-stable@freebsd.org> Subject: Re: FreeBSD 9: fdisk -It crashes kernel Message-ID: <257D766B-A296-43CD-A2B9-5F70A95A07A2@gmail.com> In-Reply-To: <20130425155818.GA8454@icarus.home.lan> References: <80F41679-9C3A-4E61-8AAD-403410344C32@gmail.com> <20130425155818.GA8454@icarus.home.lan>
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On Apr 25, 2013, at 10:58 AM, Jeremy Chadwick <jdc@koitsu.org> wrote:
> On Thu, Apr 25, 2013 at 09:06:49AM -0500, Guy Helmer wrote:
>> Encountered a surprise when my disk resizing rc.d script caused =
FreeBSD 9.1-STABLE to crash. I used "fdisk -It ada0" to determine what =
the available size of the disk (which happened to be the root disk), and =
on FreeBSD 9.1 the kernel comes crashing down:
>>=20
>> + fdisk -It ada0
>> + /rescue/sed -En 's,.*start ([0-9]+).*size ([0-9]+).*,\1 + \2,p'
>> vnode_pager_getpages: I/O read error
>> vm_fault: pager read error, pid 65 (fdisk)
>> pid 65 (fdisk), uid 0: exited on signal 11
>> eval: arithmetic expression: expecting primary: ""
>> Entropy harvesting: point_to_pointeval: date: Device not configured
>> eval: df: Device not configured
>> eval: dmesg: Device not configured
>> cat: /bin/ls: Device not configured
>> kickstart.
>> eval: cannot open /etc/fstab: Device not configured
>> eval: cannot open /etc/fstab: Device not configured
>> eval: swapon: Device not configured
>> Warning! No /etc/fstab: skipping disk checks
>> fstab: /etc/fstab:0: Device not configured
>>=20
>> Fatal trap 12: page fault while in kernel mode
>> cpuid =3D 1; apic id =3D 01
>> fault virtual address =3D 0x0
>> fault code =3D supervisor read, page not present
>> instruction pointer =3D 0x20:0xc0825fc4
>> stack pointer =3D 0x28:0xc5a088c8
>> frame pointer =3D 0x28:0xc5a08914
>> code segment =3D base 0x0, limit 0xfffff, type 0x1b
>> =3D DLP 0, pres 1, def32 1, gran =
1
>> processor eflags =3D interrupt enabled, resume, IOPL =3D 0
>> current process =3D 91 (mount)
>> [ thread pid 91 tid 100056 ]
>> Stopped at g_access+0x24: mlvl 0(%ebx),%eax
>> db> where
>> Tracing pid 91 tid 100056 td 0xc84c42f0
>> g_access(c8481d34,0,1,1,0,=85) at g_access+0x24/frame 0xc5a08914
>> ffs_mount(c8481d34,c0d78380,2,c5a08c00,c829ae6c,=85) af =
ffs_mount+0xf74/frame 0xc5a08a34
>> vfs_donmount(c84c42f0,10000,0,c84cf200,c84cf200,=85) at =
vfs_donmount+0x1423/frame 0xc5a08c24
>> sys_nmount(c84c42f0,c5a08ccc,c5a08cc4,1010006,c5a08d08,=85) at =
sys_nmount+0x7f/frame 0xc5a08c48
>> syscall(c5a08d08) at syscall+0x443/frame 0xc508cfc
>> Xint0x80_syscall() at Xint0x80_syscall+0x21/frame 0xc5a08cfc
>> --- syscall (378, FreeBSD ELF32, sys_nmount), eip =3D 0x480d5feb, esp =
=3D 0xbfbfce1c, ebp =3D 0xbfbfd378 ---
>>=20
>> I'll fix my script to not do this, but it seems odd that fdisk -It =
can make the disk "go away".
>=20
> Please provide a full, unmodified copy of your script.
>=20
> What's confusing to me is that after your sed call (which I don't even
> understand, because it doesn't appear to be operating on anything =
except
> stdin/stdout, and we don't know what that is -- again, show the =
script),
> the kernel starts outputting indications that the root disk/filesystem
> or its related metadata disappeared:
>=20
>> vnode_pager_getpages: I/O read error
>> vm_fault: pager read error, pid 65 (fdisk)
>> pid 65 (fdisk), uid 0: exited on signal 11
>=20
> Except the kernel stack trace indicates something called sys_nmount(),
> which called vfs_donmount(), which called ffs_mount(), which calls
> g_access(). All of those scream to me "someone tried to mount
> something". fdisk does not do mounting.
Right, which is why I copied the entire screen output -- it appears to =
me that the rc scripts had stumbled on until the kernel panicked.
>=20
> fdisk also shouldn't be writing to LBA 0 (the MBR) if you used -I -t.
> I've been staring at fdisk.c for about 20 minutes now and I can't work
> out a situation where -I -t would cause the MBR to be rewritten
> actively.
>=20
> The only GEOM calls I see in fdisk.c that would get called are
> g_device_path(), g_open(), and g_close(). Actual device I/O uses =
read()
> and write() (only in write_s0() which shouldn't be called).
>=20
> Furthermore, GEOM has foot-shooting-prevention mechanisms in place =
(I'm
> talking about kern.geom.debugflags) to keep LBA 0 from being modified.
> Is your script setting that sysctl to 16/0x10 blindly? Ahem.
No. The script is intended only to work for drives other than the one =
containing the boot partition.
>=20
> It would also help if you could state exactly what 9.1-STABLE source
> you're using; if using svn provide revision (rXXXXXX), else provide
> uname -a output.
rev 249788
>=20
> Finally: I would suggest using gpart(8) instead going forward. This =
is
> a separate recommendation though; if somehow I'm overlooking something
> in fdisk.c where writes to LBA 0 really do happen, then that needs to
> get fixed. But gpart(8) is what you should use in general these days
> anyway.
>=20
Seems like gpart was giving me some frustration with earlier versions of =
FreeBSD (7, I think) so I went with fdisk instead. Might work OK now...
I have included the full script below.
#!/bin/sh
#
# PROVIDE: growfs_vm
# REQUIRE: root
# BEFORE: disks
#
# Check the disks and partitions on them to see whether partitions
# need to be resized.
#
# Copyright 2011 Palisade Systems, Inc.
#
# $Id: growfs_vm.sh 6687 2012-06-13 19:53:29Z ghelmer $
. /etc/rc.subr
prefix=3D"/usr/local"
name=3D"growfs_vm"
rcvar=3D$(set_rcvar)
load_rc_config "${name}"
growfs_vm_enable=3D${growfs_vm_enable-"YES"}
start_cmd=3D"growfs_vm_start"
growfs_vm_min_increase=3D${growfs_vm_min_increase-"16384"}
SED=3D/rescue/sed
disk_mounted()
{
local DISK=3D$1
local mounts
mounts=3D$(mount | $SED -En -e "s,^/dev/(${DISK})s[0-9]+[a-z]+ on =
.*,\1,p")
if [ -z "$mounts" ]; then
return 1
fi
return 0
}
grow_disk()
{
local DISK=3D$1
local physsize
local curroff
local currsize
local delta
local part
local bsd_part
local old_label
local new_label
# The last partititon offset + size is the disk size.
physsize=3D$(($(fdisk -It $DISK | $SED -En 's,.*start ([0-9]+).*size =
([0-9]+).*,\1 + \2,p')))
eval $(fdisk -v $DISK | $SED -En 's,.*start ([0-9]+).*size =
([0-9]+).*,curroff=3D\1 currsize=3D\2,p')
delta=3D$(($physsize - $curroff - $currsize))
if [ $delta -le $growfs_vm_min_increase ]; then
echo "No change in size for disk ${DISK}: delta ${delta} <=3D =
min ${growfs_vm_min_increase}"
return 0
fi
# Get the index of the last FreeBSD partition on the disk.
part=3D$(gpart show $DISK | $SED -En 's,^ *[0-9]+ +[0-9]+ +(4) =
+freebsd .*,\1,p')
if [ -z "$part" ]; then
part=3D$(gpart show $DISK | $SED -En 's,^ *[0-9]+ +[0-9]+ +(3) =
+freebsd .*,\1,p')
fi
if [ -z "$part" ]; then
part=3D$(gpart show $DISK | $SED -En 's,^ *[0-9]+ +[0-9]+ +(2) =
+freebsd .*,\1,p')
fi
if [ -z "$part" ]; then
part=3D$(gpart show $DISK | $SED -En 's,^ *[0-9]+ +[0-9]+ +(1) =
+freebsd .*,\1,p')
fi
# Extend the partition to the end of the disk.
gpart resize -i $part $DISK
if [ "$?" -ne 0 ]; then
echo "gpart resize -i $part $DISK failed"
return 1
fi
# Now, find the last BSD partition and extend it.
old_label=3D$(bsdlabel "${DISK}s${part}")
bsd_part=3D$(echo "$old_label" | $SED -En 's,^ *(g): +[0-9]+ +[0-9]+ =
+4\.2BSD .*,\1,p')
if [ -z "$bsd_part" ]; then
bsd_part=3D$(echo "$old_label" | $SED -En 's,^ *(f): +[0-9]+ =
+[0-9]+ +4\.2BSD .*,\1,p')
fi
if [ -z "$bsd_part" ]; then
bsd_part=3D$(echo "$old_label" | $SED -En 's,^ *(e): +[0-9]+ =
+[0-9]+ +4\.2BSD .*,\1,p')
fi
if [ -z "$bsd_part" ]; then
bsd_part=3D$(echo "$old_label" | $SED -En 's,^ *(d): +[0-9]+ =
+[0-9]+ +4\.2BSD .*,\1,p')
fi
# Extend 'c' pseudo-partition and the last BSD partition
# to the end of the disk.
new_label=3D$(echo "$old_label" | $SED -E \
-e "s,c: ([0-9]+),c: *," \
-e "s,${bsd_part}: ([0-9]+),${bsd_part}: *,")
echo "$new_label" | bsdlabel -R "${DISK}s${part}" /dev/stdin
if [ "$?" -ne 0 ]; then
echo "bsdlabel -R ${DISK}s${part} failed"
return 1
fi
# Finally, run growfs on the extended partition.
growfs -y "${DISK}s${part}${bsd_part}"
if [ "$?" -ne 0 ]; then
echo "growfs -y ${DISK}s${part}${bsd_part} failed"
return 1
fi
return 0
}
growfs_vm_start() {
local maker
maker=3D`/bin/kenv smbios.system.maker`
if [ "$maker" =3D "VMware, Inc." ]; then
echo 'growfs_vm starting.'
disks=3D$(gpart show | $SED -En -e 's,=3D> +[0-9]+ +[0-9]+ =
+([a-z]+[0-9]+) +MBR .*,\1,p')
for disk in $disks; do
if disk_mounted $disk; then
echo "Disk ${disk} is mounted: skipping"
else
grow_disk $disk
fi
done
echo 'growfs_vm finished.'
mounted_root=3D$(mount | $SED -En -e =
's,(^/dev/|^)([a-z]+[0-9a-z]+) on / .*,\2,p')
if [ "$mounted_root" =3D 'cd0' -o "$mounted_root" =3D 'acd0' ]; =
then
# We're running off a boot CD.
echo "Finished growfs_vm. Remove virtual CD and reboot."
halt
fi
fi
}
run_rc_command "$1"
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