Bug 1037978

Summary: In RHEL5.10 guest, the MD5 value of the file saved in libiscsi data disk is changed after cut off the host power.
Product: Red Hat Enterprise Linux 7 Reporter: huiqingding <huding>
Component: qemu-kvmAssignee: Paolo Bonzini <pbonzini>
Status: CLOSED WONTFIX QA Contact: Virtualization Bugs <virt-bugs>
Severity: medium Docs Contact:
Priority: medium    
Version: 7.0CC: acathrow, areis, hhuang, huding, juzhang, knoel, pbonzini, virt-maint
Target Milestone: rc   
Target Release: ---   
Hardware: x86_64   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2014-02-21 14:58:01 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:

Description huiqingding 2013-12-04 08:04:15 UTC 
Description of problem:
Boot a RHEL5.10 guest attched a libiscsi data disk, dd a file in this libiscsi data disk, check the MD value of this file, run "sync" and then cut off the host power immediately after fsync command return. Boot host and guest, found the MD value is changed.

Version-Release number of selected component (if applicable):
qemu-kvm-rhev-1.5.3-20.el7.x86_64
kernel-3.10.0-57.el7.x86_64

RHEL5.10 guest:
kernel-2.6.18-371.el5

How reproducible:
100%

Steps to Reproduce:
1. Boot a RHEL5.10 guest, attached a libiscsi data disk
# /usr/libexec/qemu-kvm -M q35 -cpu SandyBridge -enable-kvm -m 2048 -smp 2,sockets=1,cores=2,threads=1 -name rhel7 -uuid 6afa5f93-2d4f-420f-81c6-e5fdddbd1c83 -drive file=iscsi://10.66.6.82:3260/iqn.2013-11.com.example:storage.disk1.juli.xyz/1,if=none,id=drive-virtio-disk0,format=qcow2,serial=40c061dd-5d60-4fc5-865f-55db700407f0,werror=stop,rerror=stop,aio=threads,cache=none -device virtio-blk-pci,scsi=off,drive=drive-virtio-disk0,id=virtio-disk0 -netdev tap,id=hostnet0,vhost=on -device virtio-net-pci,netdev=hostnet0,id=net0,mac=00:1a:4a:42:0a:00 -vnc :1 -monitor stdio -spice port=5900,disable-ticketing  -qmp tcp:0:4445,server,nowait -drive file=iscsi://10.66.6.82:3260/iqn.2013-11.com.example:storage.disk1.juli.xyz/4,if=none,id=drive-virtio-disk1,format=qcow2,serial=40c061dd-5d60-4fc5-865f-55db700407f0,werror=stop,rerror=stop,aio=threads,cache=none -device virtio-blk-pci,scsi=off,drive=drive-virtio-disk1,id=virtio-disk1

2. In guest, create a primary partition and make ext3 filesystem
# fdisk /dev/vdb
# mkfs.ext3 /dev/vdb1

3. In guest, dd a file, check MD value and run "sync"
# dd if=/dev/urandom of=file1 bs=1M count=512 ; md5sum file1 ; sync

4. cut off the host power immediately after sync command return

5. Boot host and guest, check the MD5 value in guest

Actual results:
The MD5 value of step3 is: 01b1dd504106f9cd6fa0536fc4a67252
The MD5 value of step5 is: 8565f264753d432025ab0b96d8f1267a

Expected results:
The MD5 value of step3 and step5 should be same.

Additional info:
Comment 2 Paolo Bonzini 2013-12-17 16:36:53 UTC 
sync may not be enough.  Try using virtio-scsi and "sync; sg_sync /dev/sdX".
Comment 3 juzhang 2013-12-18 02:26:17 UTC 
(In reply to Paolo Bonzini from comment #2)
> sync may not be enough.  Try using virtio-scsi and "sync; sg_sync /dev/sdX".

Hi Huiding,

Could you please have a try and update the testing result in the bz?

Best Regards,
Junyi
Comment 4 huiqingding 2013-12-18 07:38:54 UTC 
(In reply to Paolo Bonzini from comment #2)
> sync may not be enough.  Try using virtio-scsi and "sync; sg_sync /dev/sdX".

Hello, Paolo

I test RHEL7.0 guest using virtio-blk and virtio-scsi. Not hit this bug.

Since the kernel of RHEL5.10 has not the driver of virtio-scsi, I cannot test this bug using virtio-scsi.
Comment 5 Paolo Bonzini 2013-12-18 12:14:14 UTC 
On virtio-blk you can replace sg_sync /dev/sdX with this C program:

#include <fcntl.h>
#include <unistd.h>

int main(int argc, char **argv)
{
  if (argc == 1) return 1;
  int fd = open(argv[1], O_RDWR);
  fsync(fd);
}
Comment 6 huiqingding 2013-12-19 03:07:52 UTC 
(In reply to Paolo Bonzini from comment #5)
> On virtio-blk you can replace sg_sync /dev/sdX with this C program:
> 
> #include <fcntl.h>
> #include <unistd.h>
> 
> int main(int argc, char **argv)
> {
>   if (argc == 1) return 1;
>   int fd = open(argv[1], O_RDWR);
>   fsync(fd);
> }

Hello, Paolo

I use the above C program to sync my virtio-blk device. But the MD5 values are also different.
Comment 7 Paolo Bonzini 2014-02-21 14:58:01 UTC 
I think this is a rhel5 kernel bug.