Re: [Qemu-devel] [PATCH 2/4] block: immediately cancel oversized read/write requests

[Peter Lieven <pl@kamp.de>]

On 08.09.2014 15:49, Paolo Bonzini wrote:
> Il 08/09/2014 15:44, Benoît Canet ha scritto:
>>>> +    if (bs->bl.max_transfer_length && nb_sectors > bs->bl.max_transfer_length) {
>>>> +        error_report("read of %d sectors at sector %ld exceeds device max"
>>>> +                     " transfer length of %d sectors.", nb_sectors, sector_num,
>>>> +                     bs->bl.max_transfer_length);
>>>> +        return -EINVAL;
>>>> +    }
>>>> +
>>>>       return bdrv_co_do_preadv(bs, sector_num << BDRV_SECTOR_BITS,
>>>>                                nb_sectors << BDRV_SECTOR_BITS, qiov, flags);
>>>>   }
>>>> @@ -3507,6 +3514,13 @@ static int coroutine_fn bdrv_co_do_writev(BlockDriverState *bs,
>>>>           return -EINVAL;
>>>>       }
>>>>   
>>>> +    if (bs->bl.max_transfer_length && nb_sectors > bs->bl.max_transfer_length) {
>>>> +        error_report("write of %d sectors at sector %ld exceeds device max"
>>>> +                     " transfer length of %d sectors.", nb_sectors, sector_num,
>>>> +                     bs->bl.max_transfer_length);
>>>> +        return -EINVAL;
>>>> +    }
>>>> +
>>>>       return bdrv_co_do_pwritev(bs, sector_num << BDRV_SECTOR_BITS,
>>>>                                 nb_sectors << BDRV_SECTOR_BITS, qiov, flags);
>>>>   }
>>>> -- 
>>>> 1.7.9.5
>>>>
>>>>
>> Look like you are changing the coroutine version.
>>
>> Some hardware like virtio-blk uses the AIO version of read and writes.
>> What would happen if all the block drivers down the chain are AIO enabled ?
> The AIO version still goes through bdrv_co_do_readv/writev.
>
> However, error_report is not something you can use for guest-accessible
> error messages, unless you want your logs to fill up with error messages. :)

So you would not throw an error msg here?

Peter