Re: [Qemu-devel] [PATCH] vpc: Add missing error handling in alloc_block

[Andreas Färber]

Am 23.11.2011 12:23, schrieb Kevin Wolf:
> Am 23.11.2011 12:01, schrieb Stefan Hajnoczi:
>> On Wed, Nov 23, 2011 at 10:40 AM, Kevin Wolf <address@hidden> wrote:
>>> Signed-off-by: Kevin Wolf <address@hidden>
>>> ---
>>>  block/vpc.c |    5 ++++-
>>>  1 files changed, 4 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/block/vpc.c b/block/vpc.c
>>> index 75d7d4a..89a5ee2 100644
>>> --- a/block/vpc.c
>>> +++ b/block/vpc.c
>>> @@ -362,8 +362,11 @@ static int64_t alloc_block(BlockDriverState* bs, 
>>> int64_t sector_num)
>>>
>>>     // Initialize the block's bitmap
>>>     memset(bitmap, 0xff, s->bitmap_size);
>>> -    bdrv_pwrite_sync(bs->file, s->free_data_block_offset, bitmap,
>>> +    ret = bdrv_pwrite_sync(bs->file, s->free_data_block_offset, bitmap,
>>>         s->bitmap_size);
>>> +    if (ret < 0) {
>>> +        return ret;
>>> +    }
>>
>> I notice that s->pagetable[index] is left modified when the function
>> fails.  But this is a larger issue and could be addressed in a later
>> patch which also looks at the other failure cases in this function.
> 
> Error handling in vpc needs some work anyway. For example, almost all
> places return -1 instead of the real error number. Probably even the
> order of operations is unsafe, didn't check that yet.

As a note, as part of QEMU Test Day(s) I tested VHD images (cf. Wiki) -
booting, installing software, etc. and haven't encountered any problem.
Doesn't mean it's entirely safe though, obviously.

Andreas

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