Re: [Qemu-devel] [PATCH 1/4 for-2.11?] block/dirty-bitmap: add lock to bdrv_enable/disable_dirty_bitmap

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

13.11.2017 20:50, Eric Blake wrote:
> On 11/13/2017 10:20 AM, Vladimir Sementsov-Ogievskiy wrote:
>> Like other setters here these functions should take a lock.
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> ---
>>   block/dirty-bitmap.c | 4 ++++
>>   1 file changed, 4 insertions(+)
> Should this patch be in 2.11?


these functions are unused now, so, no, it's not necessary

>
>> diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
>> index bd04e991b1..2a0bcd9e51 100644
>> --- a/block/dirty-bitmap.c
>> +++ b/block/dirty-bitmap.c
>> @@ -397,15 +397,19 @@ void bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs,
>>   /* Called with BQL taken.  */
>>   void bdrv_disable_dirty_bitmap(BdrvDirtyBitmap *bitmap)
>>   {
>> +    bdrv_dirty_bitmap_lock(bitmap);
>>       assert(!bdrv_dirty_bitmap_frozen(bitmap));
>>       bitmap->disabled = true;
>> +    bdrv_dirty_bitmap_unlock(bitmap);
> Why do we need this lock in addition to BQL?
>
>>   }
>>   
>>   /* Called with BQL taken.  */
>>   void bdrv_enable_dirty_bitmap(BdrvDirtyBitmap *bitmap)
>>   {
>> +    bdrv_dirty_bitmap_lock(bitmap);
>>       assert(!bdrv_dirty_bitmap_frozen(bitmap));
>>       bitmap->disabled = false;
>> +    bdrv_dirty_bitmap_unlock(bitmap);
> Again, why do we need this in addition to BQL?
>
> The commit message needs more details about a scenario where our
> existing BQL lock is insufficient to prevent misuse of bitmap->disabled.
>


-- 
Best regards,
Vladimir