Re: [Qemu-devel] [PATCH 1/7] vnvram: VNVRAM bdrv support

[Corey Bryant <coreyb@linux.vnet.ibm.com>]

On 05/24/2013 11:37 AM, Kevin Wolf wrote:
> Am 24.05.2013 um 17:33 hat Corey Bryant geschrieben:
>>
>>
>> On 05/24/2013 09:06 AM, Kevin Wolf wrote:
>>> Am 23.05.2013 um 19:44 hat Corey Bryant geschrieben:
>>>> Provides low-level VNVRAM functionality that reads and writes data,
>>>> such as an entry's binary blob, to a drive image using the block
>>>> driver.
>>>>
>>>> Signed-off-by: Corey Bryant <coreyb@linux.vnet.ibm.com>
>>>
>>>> +/*
>>>> + * Increase the drive size if it's too small to fit the VNVRAM data
>>>> + */
>>>> +static int vnvram_drv_adjust_size(VNVRAM *vnvram)
>>>> +{
>>>> +    int rc = 0;
>>>> +    int64_t needed_size;
>>>> +
>>>> +    needed_size = 0;
>>>> +
>>>> +    if (bdrv_getlength(vnvram->bds) < needed_size) {
>>>> +        rc = bdrv_truncate(vnvram->bds, needed_size);
>>>> +        if (rc != 0) {
>>>> +            DPRINTF("%s: VNVRAM drive too small\n", __func__);
>>>> +        }
>>>> +    }
>>>> +
>>>> +    return rc;
>>>> +}
>>>
>>> This function doesn't make a whole lot of sense. It truncates the file
>>> to size 0 if and only if bdrv_getlength() returns an error.
>>>
>>
>> There's a later patch that adds a "get size" function and changes
>> the initialization of needed_size to the actual size needed to store
>> VNVRAM data.  Anyway I should probably just include that change in
>> this patch.  I think I'll still need this function or part of it
>> with the new simplified approach that it looks like we're going to
>> take.
>
> Okay. But even then, do you really want to truncate on errors?
>
> Kevin
>
>
>

True, it'll need something to account for bdrv_getlength() failures and 
not truncate in that case.

-- 
Regards,
Corey Bryant