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Date: Fri, 13 Sep 2013 11:08:58 +0200
From: Peter Lieven <lieven-lists@dlhnet.de>
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Subject: Re: [Qemu-devel] [PULL 39/42] block: look for zero blocks in
	bs->file
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To: Peter Lieven <pl@kamp.de>
Cc: Anthony Liguori <anthony@codemonkey.ws>, Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>

On 13.09.2013 10:00, Peter Lieven wrote:
> On 06.09.2013 17:39, Stefan Hajnoczi wrote:
>> From: Paolo Bonzini <pbonzini@redhat.com>
>>
>> Reviewed-by: Eric Blake <eblake@redhat.com>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
>> ---
>>   block.c | 16 +++++++++++++++-
>>   1 file changed, 15 insertions(+), 1 deletion(-)
>>
>> diff --git a/block.c b/block.c
>> index 3c39769..a325efc 100644
>> --- a/block.c
>> +++ b/block.c
>> @@ -3075,7 +3075,7 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
>>   {
>>       int64_t length;
>>       int64_t n;
>> -    int64_t ret;
>> +    int64_t ret, ret2;
>>         length = bdrv_getlength(bs);
>>       if (length < 0) {
>> @@ -3117,6 +3117,20 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
>>               }
>>           }
>>       }
>> +
>> +    if (bs->file &&
>> +        (ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
>> +        (ret & BDRV_BLOCK_OFFSET_VALID)) {
>> +        ret2 = bdrv_co_get_block_status(bs->file, ret >> BDRV_SECTOR_BITS,
>> +                                        *pnum, pnum);
>> +        if (ret2 >= 0) {
>> +            /* Ignore errors.  This is just providing extra information, it
>> +             * is useful but not necessary.
>> +             */
>> +            ret |= (ret2 & BDRV_BLOCK_ZERO);
>> +        }
>> +    }
>> +
>>       return ret;
>>   }
> for allocated blocks in iscsi this actually leads to 2 call outs to iscsi_get_block_status.
>
> because the raw driver passes the get_block_status request to bs->file.
>
correct patch?

@@ -3119,9 +3167,8 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
          }
      }

-    if (bs->file &&
-        (ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
-        (ret & BDRV_BLOCK_OFFSET_VALID)) {
+    if (bs->file && (ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
+        (ret & BDRV_BLOCK_OFFSET_VALID) && bs->drv != bdrv_find_format("raw")) {
          ret2 = bdrv_co_get_block_status(bs->file, ret >> BDRV_SECTOR_BITS,
                                          *pnum, pnum);
          if (ret2 >= 0) {