Re: [Qemu-devel] [PATCH] [qemu-devel] fix wrong order when doing live block migration setup

[Chai Wen]

Hi Kevin & Stefan

How about this fix ?

On 05/28/2014 09:13 AM, Chai Wen wrote:

> On 05/27/2014 06:11 PM, Fam Zheng wrote:
> 
>> On Tue, 05/27 16:54, chai wen wrote:
>>> If we want to track dirty blocks using dirty_maps on a BlockDriverState
>>> when doing live block-migration, its correspoding 'BlkMigDevState' should be
>>> add to block_mig_state.bmds_list firstly for subsequent processing.
>>> Otherwise set_dirty_tracking will do nothing on an empty list than 
>>> allocating
>>> dirty_bitmaps for them.
>>>
>>> And what's the worse, bdrv_get_dirty_count will access the
>>> bmds->dirty_maps directly, there could be a segfault as the reasons
>>> above.
>>>
>>> Signed-off-by: chai wen <address@hidden>
>>> ---
>>>  block-migration.c |    2 +-
>>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/block-migration.c b/block-migration.c
>>> index 56951e0..43203aa 100644
>>> --- a/block-migration.c
>>> +++ b/block-migration.c
>>> @@ -626,6 +626,7 @@ static int block_save_setup(QEMUFile *f, void *opaque)
>>>              block_mig_state.submitted, block_mig_state.transferred);
>>>  
>>>      qemu_mutex_lock_iothread();
>>> +    init_blk_migration(f);
>>
>> Thanks for spotting this!
>>
>> I reverted the order of init_blk_migration and set_dirty_tracking in commit
>> b8afb520e (block: Handle error of bdrv_getlength in bdrv_create_dirty_bitmap)
>> incorrectly, thought that in this way, no clean up is needed if
>> set_dirty_tracking fails.
>>
>> But by looking at savevm.c:qemu_savevm_state() we can see that
>> qemu_savevm_state_cancel() will do the clean up automatically, so this fix is
>> valid.
>>
>> Reviewed-by: Fam Zheng <address@hidden>
> 
> 
> Yeah, thank you for the review.
> 
> 
> thanks
> chai wen
> 
>>
>>>  
>>>      /* start track dirty blocks */
>>>      ret = set_dirty_tracking();
>>> @@ -635,7 +636,6 @@ static int block_save_setup(QEMUFile *f, void *opaque)
>>>          return ret;
>>>      }
>>>  
>>> -    init_blk_migration(f);
>>>  
>>>      qemu_mutex_unlock_iothread();
>>>  
>>> -- 
>>> 1.7.1
>>>
>>>
>> .
>>
> 
> 
> 



-- 
Regards

Chai Wen