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From: Fam Zheng <famz@redhat.com>
Date: Thu, 8 Mar 2018 17:01:56 +0800
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Subject: Re: [Qemu-devel] block migration and dirty bitmap reset
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To: Peter Lieven <pl@kamp.de>
Cc: Stefan Hajnoczi <stefanha@gmail.com>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>, wency@cn.fujitsu.com, qemu block <qemu-block@nongnu.org>, Juan Quintela <quintela@redhat.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, Stefan Hajnoczi <stefanha@redhat.com>

On Thu, Mar 8, 2018 at 4:57 PM, Peter Lieven <pl@kamp.de> wrote:
>
>
>> Am 08.03.2018 um 02:28 schrieb Fam Zheng <famz@redhat.com>:
>>
>>> On Wed, 03/07 09:06, Peter Lieven wrote:
>>> Hi,
>>>
>>> while looking at the code I wonder if the blk_aio_preadv and the bdrv_reset_dirty_bitmap order must
>>> be swapped in mig_save_device_bulk:
>>>
>>>    qemu_mutex_lock_iothread();
>>>    aio_context_acquire(blk_get_aio_context(bmds->blk));
>>>    blk->aiocb = blk_aio_preadv(bb, cur_sector * BDRV_SECTOR_SIZE, &blk->qiov,
>>>                                0, blk_mig_read_cb, blk);
>>>
>>>    bdrv_reset_dirty_bitmap(bmds->dirty_bitmap, cur_sector * BDRV_SECTOR_SIZE,
>>>                            nr_sectors * BDRV_SECTOR_SIZE);
>>>    aio_context_release(blk_get_aio_context(bmds->blk));
>>>    qemu_mutex_unlock_iothread();
>>>
>>> In mig_save_device_dirty we first reset the dirty bitmap and read then which shoulds like
>>> a better idea.
>>
>> Yes, that sounds right to me.
>>
>> Fam
>
> You mean the order should be swapped in mig_save_device_bulk as well?

Yeah, resetting the dirty bitmap before reading makes sure we don't
miss any new data.

Fam

>
> Peter
>