[Bugme-janitors] [Bug 14638] New: device mapper unaccounted null pointer
bugzilla-daemon at bugzilla.kernel.org
bugzilla-daemon at bugzilla.kernel.org
Wed Nov 18 16:38:00 PST 2009
http://bugzilla.kernel.org/show_bug.cgi?id=14638
Summary: device mapper unaccounted null pointer
Product: IO/Storage
Version: 2.5
Kernel Version: 2.6.32-rc7
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: high
Priority: P1
Component: Other
AssignedTo: io_other at kernel-bugs.osdl.org
ReportedBy: bugzilla at synx.us.to
Regression: No
I've been using cryptsetup to access an external hard drive of mine via an
encrypted mapping, pointing postgresql towards it for (relatively) steady disk
access. I upgraded to Mainline (2.6.32-rc7) and found that within a day or so
the device mapper would somehow mysteriously "lose" its mapping entirely. The
mount point remains mounted, but cannot even be statted, as "ls: cannot access
/media/extern". When I umount /media/extern, it works without error, but
"cryptsetup remove extern" fails permanenty, necessitating a full reboot.
cryptsetup I'm pretty sure is a front-end for the device mapper, using the
dm-crypt module. Not sure if that would specifically be a problem. What happens
is I type "cryptsetup status extern" and it reports to me the following:
/dev/mapper/extern is active:
cipher: aes-cbc-essiv:sha256
keysize: 256 bits
device: (null)
offset: 0 sectors
size: 310472190 sectors
mode: read/write
where it says "device: (null)" it should obviously say "device: /dev/sdb1". It
initially did say that, and worked perfectly normally. But some unknown trigger
(while I was away from the computer to boot) causes the pointer to the device
to be overwritten with a null pointer.
I don't know much about the device mapper, or how to get more detailed
statistics, or any possible solutions to the problem. But I didn't see it
posted as a bug, so thought I'd point it out so wiser folks than me can know
what to look out for. I'm going back to 2.6.31.6 to see if the problem is there
too, or if it was a recent addition.
I'm on an amd64 system, with an external USB hard drive enclosure that's never
given me any problems before. It's still powered up and there's no error
regarding it in dmesg, and fdisk -l /dev/sdb gives me perfectly normal
readings, so I don't think it's a hard disk failure, but instead a failure of
something in the mount-point/device mapper/device chain.
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