Re: [PATCH] migration: Truncate state file in xen-save-devices-state

[Dov Murik <dovmurik@linux.vnet.ibm.com>]

On 21/09/2020 14:17, Dr. David Alan Gilbert wrote:
> * Dov Murik (dovmurik@linux.vnet.ibm.com) wrote:
>> When running the xen-save-devices-state QMP command, if the filename
>> already exists it will be truncated before dumping the devices' state
>> into it.
>>
>> Signed-off-by: Dov Murik <dovmurik@linux.vnet.ibm.com>
>> ---
> 
> OK, that looks fine to me, so:
> 
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> 
>>
>> Note that I found the above issue while trying to debug
>> xen-load-devices-state which simply fails (prints "Configuration section
>> missing" to stderr) directly after xen-save-devices-state (in the same
>> VM).  I wonder if I should file a bug report as-is or investigate some
>> more.  Advice welcome.
> 
> I don't try the xen-* commands normally; I've cc'ing in Stefano and
> Anthony.

Thanks Dave.  Just to be clear, I'm running this without Xen at all; but
these commands seem to work OK for dumping/restoring guest's devices
state (without RAM) -- if I modify the code to circumvent the mentioned
problem.

Dov

> 
> Dave
> 
>>
>> -Dov
>>
>> ---
>>   migration/savevm.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/migration/savevm.c b/migration/savevm.c
>> index 304d98ff78..e1b26672cc 100644
>> --- a/migration/savevm.c
>> +++ b/migration/savevm.c
>> @@ -2803,7 +2803,8 @@ void qmp_xen_save_devices_state(const char *filename, bool has_live, bool live,
>>       vm_stop(RUN_STATE_SAVE_VM);
>>       global_state_store_running();
>>   
>> -    ioc = qio_channel_file_new_path(filename, O_WRONLY | O_CREAT, 0660, errp);
>> +    ioc = qio_channel_file_new_path(filename, O_WRONLY | O_CREAT | O_TRUNC,
>> +                                    0660, errp);
>>       if (!ioc) {
>>           goto the_end;
>>       }
>> -- 
>> 2.20.1
>>