Re: [PATCH v11 04/13] copy-on-read: pass overlay base node name to COR driver

[Max Reitz]

On 14.10.20 13:09, Max Reitz wrote:
> On 12.10.20 19:43, Andrey Shinkevich wrote:
>> We are going to use the COR-filter for a block-stream job.
>> To limit COR operations by the base node in the backing chain during
>> stream job, pass the name of overlay base node to the copy-on-read
>> driver as base node itself may change due to possible concurrent jobs.
>> The rest of the functionality will be implemented in the patch that
>> follows.
>>
>> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
>> ---
>>  block/copy-on-read.c | 14 ++++++++++++++
>>  1 file changed, 14 insertions(+)
> 
> Is there a reason why you didn’t add this option to QAPI (as part of a
> yet-to-be-created BlockdevOptionsCor)?  Because I’d really like it there.
> 
>> diff --git a/block/copy-on-read.c b/block/copy-on-read.c
>> index bcccf0f..c578b1b 100644
>> --- a/block/copy-on-read.c
>> +++ b/block/copy-on-read.c
>> @@ -24,19 +24,24 @@
>>  #include "block/block_int.h"
>>  #include "qemu/module.h"
>>  #include "qapi/error.h"
>> +#include "qapi/qmp/qerror.h"
>>  #include "qapi/qmp/qdict.h"
>>  #include "block/copy-on-read.h"
>>  
>>  
>>  typedef struct BDRVStateCOR {
>>      bool active;
>> +    BlockDriverState *base_overlay;
>>  } BDRVStateCOR;
>>  
>>  
>>  static int cor_open(BlockDriverState *bs, QDict *options, int flags,
>>                      Error **errp)
>>  {
>> +    BlockDriverState *base_overlay = NULL;
>>      BDRVStateCOR *state = bs->opaque;
>> +    /* We need the base overlay node rather than the base itself */
>> +    const char *base_overlay_node = qdict_get_try_str(options, "base");
> 
> Shouldn’t it be called base-overlay or above-base then?

While reviewing patch 5, I realized this sould indeed be base-overlay
(i.e. the next allocation-bearing layer above the base, not just a
filter on top of base), but that should be noted somewhere, of course.
Best would be the QAPI documentation for this option. O:)

Max

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