Re: [PATCH] qemu-xen-3.4-testing: Fix read-only image file handling

[Michal Novotny <minovotn@redhat.com>]

Oh, just one more thing that should be mentioned:

When you want to mount an image that is set as read-only in the domain 
configuration file but you omit to set mode to read-only it results into 
I/O errors when processing the requests. Remounting as read-only or 
unmounting and remounting using the `mount /dev/* /path/to/mount -o ro` 
shall do the mounting the correct way, i.e. with no I/O errors, so make 
sure you mount those disks as read-only otherwise you can be getting 
errors like:

end_request: I/O error, dev hdb, sector 52

Buffer I/O error on device hdb1, logical block 1

lost page write due to I/O error on hdb1


and for IDE devices you'll be getting several additional DeviceFault 
errors since mounting the device read-write (default setting) writes 
some data onto a disk at the mount-time.

Michal

On 06/03/2010 04:04 PM, Michal Novotny wrote:
> [Well, I did send an e-mail to the list using git but it's not here so 
> I'm forwarding the e-mail to the list for sure:]
>
> Hi,
> this is the patch for qemu-xen-3.4-testing to fix the read-only
> image file handling since the image file was always treated as
> read-write which means that all the HVM guests were able to
> write to all the disk images available in domain configuration
> file no matter what the mode of the image was defined. This
> patch fixes this functionality to honor the O_RDONLY in the
> BDRV_O_ACCESS flag in block.c and also fixes the IDE and SCSI
> interfaces that uses it.
>
> It's been tested on RHEL-5 with xen-3.4-testing version of
> upstream xen with xen-3.4-testing qemu implementation.
>
> For SCSI devices the DATA PROTECT request sense has been added
> as found at: http://en.wikipedia.org/wiki/SCSI_Request_Sense_Command
>
> file no matter what the mode of the image was defined. This
> patch fixes this functionality to honor the O_RDONLY in the
> BDRV_O_ACCESS flag in block.c and also fixes the IDE and SCSI
> interfaces that uses it.
>
> It's been tested on RHEL-5 with xen-3.4-testing version of
> Michal
>
> Signed-off-by: Michal Novotny <minovotn@redhat.com>
>
>
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> http://lists.xensource.com/xen-devel
>    


-- 
Michal Novotny<minovotn@redhat.com>, RHCE
Virtualization Team (xen userspace), Red Hat