[Qemu-devel] Re: [PATCH v2] loadvm: improve tests before bdrv_snapshot_goto()

[Kevin Wolf <kwolf@redhat.com>]

Am 19.07.2010 20:25, schrieb Miguel Di Ciurcio Filho:
> This patch improves the resilience of the load_vmstate() function, doing
> further and better ordered tests.
> 
> In load_vmstate(), if there is any error on bdrv_snapshot_goto(), except if the
> error is on VM state device, load_vmstate() will return zero and the VM will be
> started with major corruption chances.
> 
> The current process:
> - test if there is any writable device without snapshot support
>     - if exists return -error
> - get the device that saves the VM state, possible return -error but unlikely
> because it was tested earlier
> - flush I/O
> - run bdrv_snapshot_goto() on devices
>     - if fails, give an warning and goes to the next (not good!)
>     - if fails on the VM state device, return zero (not good!)
> - check if the requested snapshot exists on the device that saves the VM state
> and the state is not zero
>     - if fails return -error
> - open the file with the VM state
>     - if fails return -error
> - load the VM state
>     - if fails return -error
> - return zero
> 
> New behavior:
> - get the device that saves the VM state
>     - if fails return -error
> - check if the requested snapshot exists on the device that saves the VM state
> and the state is not zero
>     - if fails return -error
> - test if there is any writable device without snapshot support
>     - if exists return -error
> - test if the devices with snapshot support have the requested snapshot
>     - if anyone fails, return -error
> - flush I/O
> - run snapshot_goto() on devices
>     - if anyone fails, return -error
> - open the file with the VM state
>     - if fails return -error
> - load the VM state
>     - if fails return -error
> - return zero
> 
> do_loadvm must not call vm_start if any error has occurred in load_vmstate.
> 
> Changelog from v1
> ---------------
> - Use -ENOTSUP instead of -EINVAL when no device supports snapshots
> - Split the verification of the existance of an snapshot on the VM state device
>   and the verification of the size of the saved VM state
> 
> Signed-off-by: Miguel Di Ciurcio Filho <miguel.filho@gmail.com>

Thanks, applied to the block branch.

Kevin