[sheepdog] [PATCH 2/2] fix array index error in function add_new_participant

[Ruoyu]

On 2014年08月11日 21:45, Hitoshi Mitake wrote:
> At Mon, 11 Aug 2014 18:11:44 +0800,
> Ruoyu wrote:
>> Nothing wrong with fixing it, alhough I don't know exactly
>> what will be happened if not patching it.
>>
>> Signed-off-by: Ruoyu <liangry at ucweb.com>
>> ---
>>   sheep/vdi.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/sheep/vdi.c b/sheep/vdi.c
>> index 05cae7b..77dc253 100644
>> --- a/sheep/vdi.c
>> +++ b/sheep/vdi.c
>> @@ -372,11 +372,12 @@ static bool add_new_participant(struct vdi_state_entry *entry,
>>   		return true;
>>   	}
>>   
>> -	idx = entry->nr_participants++;
>> +	idx = entry->nr_participants;
>>   	memcpy(&entry->participants[idx], owner, sizeof(*owner));
>>   	entry->participants_state[idx] =
>>   		is_modified(entry) ?
>>   		SHARED_LOCK_STATE_INVALIDATED : SHARED_LOCK_STATE_SHARED;
>> +	entry->nr_participants++;
> I think this patch doesn't change the function. Does this fixes a bug?
It fixes a logical error. Otherwise, there should be a hole in the array 
if new participant is added.
For example,

	// supposed entry->nr_participants is 2;
	idx = entry->nr_participants++;
	// idx is 3 now;
  	memcpy(&entry->participants[idx], owner, sizeof(*owner));
  	entry->participants_state[idx] =
  		is_modified(entry) ?
  		SHARED_LOCK_STATE_INVALIDATED : SHARED_LOCK_STATE_SHARED;
  	// the 4th element is assigned(the 1st is array[0]), but we should modify the 3rd one logically


>
> Thanks,
> Hitoshi