[Bug 593086] [NEW] Need CONFIG_LBDAF set to prevent silent wraparound on > 2 TB disks

[Phillip Susi]

Public bug reported:

Ubuntu kernels silently wrap access to disk locations above 2 TB back
around to zero.  This can easily be reproduced using lvm to create a
thin provisioned virtual disk:

lvcreate --type zero -L 3t -n empty vg0
lvcreate -s -n thin vg0/zero -L 1g

mke2fs -t ext4 -E lazy_itable_init /dev/vg0/thin
e2fsck -f /dev/vg0/thin

Fsck will find errors in the bitmap because it is actually reading the
superblock instead of the allocation bitmap situated just after the 2 tb
mark.  I emailed the dm-devel mailing list about the issue and was told
that this happens when CONFIG_LBDAF is not set, and that it would be
rather daft of a distribution not to set that option.  I checked my
config for kernel 2.6.32-22-generic on lucid amd64 and indeed, this
option does not seem to be there.  I also first observed this bug on
i386 karmic.

I believe that this bug effects all users who have a > 2tb disk, be it
virtual, physical, or raid, and can lead to unexplained loss of data.
Therefore I feel it meets the criteria for a high priority bug, if not
critical.

** Affects: linux (Ubuntu)
     Importance: High
         Status: Triaged

** Changed in: linux (Ubuntu)
   Importance: Undecided => High

** Changed in: linux (Ubuntu)
       Status: New => Triaged

-- 
Need CONFIG_LBDAF set to prevent silent wraparound on > 2 TB disks
https://bugs.launchpad.net/bugs/593086
You received this bug notification because you are a member of Kernel
Bugs, which is subscribed to linux in ubuntu.