Re: [Qemu-devel] [PATCH 1/3] migration/postcopy: the valid condition is one less then end

[Wei Yang <richardw.yang@linux.intel.com>]

On Fri, Jun 28, 2019 at 04:09:50PM +0100, Dr. David Alan Gilbert wrote:
>* Wei Yang (richardw.yang@linux.intel.com) wrote:
>> If one equals end, it means we have gone through the whole bitmap.
>> 
>> Use a more restrict check to skip a unnecessary condition.
>> 
>> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>
>Yes, I don't think that'll break, since I think the find_next_zero_bit
>will also return end, and then discard_length would be 0; still I think
>it's a correct fix.

Yep, you are exactly right.

>
>Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>
>> ---
>>  migration/ram.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/migration/ram.c b/migration/ram.c
>> index 908517fc2b..b78169e811 100644
>> --- a/migration/ram.c
>> +++ b/migration/ram.c
>> @@ -2777,7 +2777,7 @@ static int postcopy_send_discard_bm_ram(MigrationState *ms,
>>      for (current = 0; current < end; ) {
>>          unsigned long one = find_next_bit(unsentmap, end, current);
>>  
>> -        if (one <= end) {
>> +        if (one < end) {
>>              unsigned long zero = find_next_zero_bit(unsentmap, end, one + 1);
>>              unsigned long discard_length;
>>  
>> -- 
>> 2.19.1
>> 
>--
>Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

-- 
Wei Yang
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