Re: [PATCH 5/6] block/nbd: Do not force-cap *pnum

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

18.06.2021 23:20, Eric Blake wrote:
> On Thu, Jun 17, 2021 at 05:52:46PM +0200, Max Reitz wrote:
>> bdrv_co_block_status() does it for us, we do not need to do it here.
>>
>> The advantage of not capping *pnum is that bdrv_co_block_status() can
>> cache larger data regions than requested by its caller.
>>
>> Signed-off-by: Max Reitz <mreitz@redhat.com>
>> ---
>>   block/nbd.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Reviewed-by: Eric Blake <eblake@redhat.com>
> 
>>
>> diff --git a/block/nbd.c b/block/nbd.c
>> index 616f9ae6c4..930bd234de 100644
>> --- a/block/nbd.c
>> +++ b/block/nbd.c
>> @@ -1702,7 +1702,7 @@ static int coroutine_fn nbd_client_co_block_status(
>>           .type = NBD_CMD_BLOCK_STATUS,
>>           .from = offset,
>>           .len = MIN(QEMU_ALIGN_DOWN(INT_MAX, bs->bl.request_alignment),
>> -                   MIN(bytes, s->info.size - offset)),
>> +                   s->info.size - offset),
>>           .flags = NBD_CMD_FLAG_REQ_ONE,
> 
> I'd love to someday get rid of using NBD_CMD_FLAG_REQ_ONE (so the
> server can reply with more extents in one go), but that's a bigger
> task and unrelated to your block-layer cache.
> 

I think for this to work, the generic block_status should be updated so we can work with several extents in one go.


-- 
Best regards,
Vladimir