HVM guest disk corruption after shutdown

HVM guest disk corruption after shutdown

[Huang2, Wei]

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We recently found a disk corruption issue with SLES11 SP1 guest. Basically the guest disk becomes non-bootable after guest shutdown. This is a SLES specific issue as we didn't see on other Linux and Windows VMs. Here is the configuration:
============

1.      Xen: xen-4.1-testing, changeset 23096

2.      Dom0: Jeremy's latest pvops 6d94b75 (June 1)

3.      VM: SLES 11 SP1, installed as physical machine with raw disk format
============

Regarding the disk before corruption, "file sles11sp1.img" command read: "/root/guests/sles11-sp1/sles11sp1.img: x86 boot sector; partition 1: ID=0x82, starthead 1, startsector 63, 4208967 sectors; partition 2: ID=0x83, active, starthead 0, startsector 4209030, 16755795 sectors". After corruption, it became a data file: ""/root/guests/sles11-sp1/sles11sp1.img: data".

I traced back to the blkback commit 28080265 by Konrad. If I disabled this change, the corruption issue will disappear.

============
diff --git a/drivers/xen/blkback/blkback.c b/drivers/xen/blkback/blkback.c
index fd88f32..30772ec 100644
--- a/drivers/xen/blkback/blkback.c
+++ b/drivers/xen/blkback/blkback.c
@@ -409,8 +409,7 @@ static void dispatch_rw_block_io(blkif_t *blkif,
                break;
        case BLKIF_OP_WRITE_BARRIER:
                operation = WRITE_BARRIER;
-               /* vbd_translate is alergic to bizzare sectors. */
-               req->sector_number = 0;
                break;
        default:
                operation = 0; /* make gcc happy */
============

Thanks,
-Wei



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Re: HVM guest disk corruption after shutdown

[Konrad Rzeszutek Wilk]

On Wed, Jul 06, 2011 at 02:22:30PM -0700, Huang2, Wei wrote:
> We recently found a disk corruption issue with SLES11 SP1 guest. Basically the guest disk becomes non-bootable after guest shutdown. This is a SLES specific issue as we didn't see on other Linux and Windows VMs. Here is the configuration:
> ============
> 
> 1.      Xen: xen-4.1-testing, changeset 23096
> 
> 2.      Dom0: Jeremy's latest pvops 6d94b75 (June 1)
> 
> 3.      VM: SLES 11 SP1, installed as physical machine with raw disk format
> ============
> 
> Regarding the disk before corruption, "file sles11sp1.img" command read: "/root/guests/sles11-sp1/sles11sp1.img: x86 boot sector; partition 1: ID=0x82, starthead 1, startsector 63, 4208967 sectors; partition 2: ID=0x83, active, starthead 0, startsector 4209030, 16755795 sectors". After corruption, it became a data file: ""/root/guests/sles11-sp1/sles11sp1.img: data".
> 
> I traced back to the blkback commit 28080265 by Konrad. If I disabled this change, the corruption issue will disappear.

Oh nice. I wonder how the fix went in - I vagually remember talking to Jan about this
and having a discussion and then using Jan's patch instead of mine.

Jeremy, can you revert it please? Jan posted a better fix that was ultimately better.
Something along this upstream 8ab521506c4dbb144f0c04c55e3d8bec42c1b2b9 git commit

> 
> ============
> diff --git a/drivers/xen/blkback/blkback.c b/drivers/xen/blkback/blkback.c
> index fd88f32..30772ec 100644
> --- a/drivers/xen/blkback/blkback.c
> +++ b/drivers/xen/blkback/blkback.c
> @@ -409,8 +409,7 @@ static void dispatch_rw_block_io(blkif_t *blkif,
>                 break;
>         case BLKIF_OP_WRITE_BARRIER:
>                 operation = WRITE_BARRIER;
> -               /* vbd_translate is alergic to bizzare sectors. */
> -               req->sector_number = 0;
>                 break;
>         default:
>                 operation = 0; /* make gcc happy */
> ============
> 
> Thanks,
> -Wei
> 
>