Re: [PATCH 3/3] migration: Remove _only suffix for res_postcopy/precopy

[Juan Quintela]

Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> wrote:
> On 08.02.23 16:57, Juan Quintela wrote:
>> Once that res_compatible is removed, they don't make sense anymore.
>> Signed-off-by: Juan Quintela <quintela@redhat.com>
>> ---
>>   include/migration/register.h   | 18 ++++++++----------
>>   migration/savevm.h             |  8 ++++----
>>   hw/s390x/s390-stattrib.c       |  7 +++----
>>   hw/vfio/migration.c            | 10 ++++------
>>   migration/block-dirty-bitmap.c |  6 +++---
>>   migration/block.c              |  7 +++----
>>   migration/ram.c                | 18 ++++++++----------
>>   migration/savevm.c             | 24 ++++++++++--------------
>>   8 files changed, 43 insertions(+), 55 deletions(-)
>> diff --git a/include/migration/register.h
>> b/include/migration/register.h
>> index a958a92a0f..4a4a6d7174 100644
>> --- a/include/migration/register.h
>> +++ b/include/migration/register.h
>> @@ -47,22 +47,20 @@ typedef struct SaveVMHandlers {
>>       /* This runs outside the iothread lock!  */
>>       int (*save_setup)(QEMUFile *f, void *opaque);
>>       /* Note for save_live_pending:
>> -     * - res_precopy_only is for data which must be migrated in precopy 
>> phase
>> +     * - res_precopy is for data which must be migrated in precopy phase
>>        *     or in stopped state, in other words - before target vm start
>> -     * - res_postcopy_only is for data which must be migrated in postcopy 
>> phase
>> +     * - res_postcopy is for data which must be migrated in postcopy phase
>>        *     or in stopped state, in other words - after source vm stop
>
>
> That's now wrong. "postcopy" is everything except "precopy", as it
> includes "compat". Really, for RAM, it can be copied in precopy too,
> and it is copied in precopy until user run command
> migrate-start-postcopy. (In contrast: block-dirty-bitmap cannot
> migrate in precopy at all, it migrate only in stopped state or in
> postcopy).
>
> So, finally:
>
> "precopy"
>
>   definition:
>   - must be migrated in precopy or in stopped state
>   - in other words: must be migrated before target start
>   - in other words: can't be migrated in postcopy
>   - in other words: can't be migrated after target start
>
> "postcopy"
>
>   definition:
>   - can migrate in postcopy
>   - in other words: can migrate after target start
>      some properties:
>   - probably can be migrated in precopy (like RAM), or, may be not (like 
> block-dirty-bitmap)
>   - of course, can be migrated in stopped state

What about (with latest naming)

must_precopy:
* must be migrated in precopy or in stopped state
* i.e. must be migrated before target start

can_postcopy:
* can migrate in postcopy or in stopped state
* i.e. can migrate after target start
* some can also be migrated during precopy (RAM)
* some must be migrated after source stops (block-dirty-bitmap)

> To be absolutely clear, we may rename them to "not_postcopyable" and 
> "postcopyable".

I hate negatives when naming variables.

What about: must_precopy and can_postcopy?

Later, Juan.