Bug 216555

Summary: Virtual disk size wraps around at 2 TB mark
Product: [Fedora] Fedora Reporter: Daniel Berrangé <berrange>
Component: kernel-xenAssignee: Stephen Tweedie <sct>
Status: CLOSED WONTFIX QA Contact: Virtualization Bugs <virt-bugs>
Severity: medium Docs Contact:
Priority: medium    
Version: 6CC: bstein, robin.bowes, xen-maint
Target Milestone: ---   
Target Release: ---   
Hardware: i686   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2008-02-26 23:45:03 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 216556, 232608    
Attachments:
Description Flags
Patch for blktap based disks none

Description Daniel Berrangé 2006-11-21 01:33:29 UTC
Description of problem:
If I create a virtual disk (either a file, or block device backed) in the dom0
host with a size of 5 TB, and export this to a guest DomU, the domu will only
see it as being 1 TB in size. It looks as if the Xen virtual disk driver is
wrapping around at the 2 TB mark.

Version-Release number of selected component (if applicable):
xen-3.0.3-0.1.rc3
kernel-xen-2.6.18-1.2849.fc6

How reproducible:
Always (on 32-bit)

Steps to Reproduce:
1. Create an block device 7 TB in size
2. Export this to the DomU in the guest config file
3. Look at /proc/partitions inside the guest kernel
4. Look at /proc/partitions in the dom0 host kernel
  
Actual results:
The #blocks column for the disk is different in DomU & Dom0

Expected results:
The #blocks seen in DomU matches #blocks seen in Dom0

Additional info:
The same problem occurs for file backed virtual disks on 32-bit host/guest.

There is no problem on 64-bit kernels - I have exported disks as large as 15 PB
 to the guest.

This is all testing with paravirt guests. Not verified if fully virt guests have
any issues yet.


Post from Ian upstream suggests 32-bit wraparound in blkfront driver

http://lists.xensource.com/archives/html/xen-devel/2006-11/msg01023.html

Comment 1 Robin Bowes 2006-11-21 02:09:13 UTC
I'm seeing the same thing.

I'm trying to make a 2.73TB ext3 FS available to a DomU guest.

It's docmented here:

http://article.gmane.org/gmane.comp.emulators.xen.devel/32640

Comment 2 Daniel Berrangé 2006-11-21 12:39:53 UTC
Patch committed in xen-unstable.hg

http://xenbits.xensource.com/xen-unstable.hg?cs=0c0ef61de06b


Comment 3 Daniel Berrangé 2006-11-21 22:44:56 UTC
I have tested the patch listed in comment #2 and confirmed it fixes operation of
file: and phy: backed disks > 2 TB in size. It does not, however, fix tap:aio:
backed disks.



Comment 4 Daniel Berrangé 2006-11-21 22:45:59 UTC
Created attachment 141844 [details]
Patch for blktap based disks

This additional patch fixes blktap based disks which are > 2TB

Comment 5 Robin Bowes 2006-11-22 10:39:37 UTC
Woohoo! I installed the patched kernel & xen RPMS this morning and I can now see
m y large partition correctly in the DomU guest.

Thanks for the quick fix and help rebuilding the RPMS.

Comment 6 Robin Bowes 2007-01-02 23:51:07 UTC
Can I get an update on the status of this issue?

i.e. has the patch been applied upstream yet? When will we see RPMS with this fixed?

Thanks,

R.

Comment 8 Red Hat Bugzilla 2007-07-25 01:36:19 UTC
change QA contact

Comment 9 Chris Lalancette 2008-02-26 23:45:03 UTC
This report targets FC6, which is now end-of-life.

Please re-test against Fedora 7 or later, and if the issue persists, open a new bug.

Thanks