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Re: [Qemu-block] [PATCH v6 11/12] qed: Implement .bdrv_drain
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-block] [PATCH v6 11/12] qed: Implement .bdrv_drain |
Date: |
Thu, 22 Oct 2015 22:59:32 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 |
On 22/10/2015 12:53, Kevin Wolf wrote:
> Am 22.10.2015 um 08:32 hat Fam Zheng geschrieben:
>> The "need_check_timer" is used to clear the "NEED_CHECK" flag in the
>> image header after a grace period once metadata update has finished. In
>> compliance to the bdrv_drain semantics we should make sure it remains
>> deleted once .bdrv_drain is called.
>>
>> We cannot reuse qed_need_check_timer_cb because it calls bdrv_aio_flush
>> with a completion callback that starts more I/O, bdrv_drain cannot cope
>> with this.
>
> For the record: I discussed this with Fam on IRC and we came to the
> conclusion that we should instead fix bdrv_drain() to correctly drain
> in-flight flushes.
>
> In order to achieve this, Fam will send a series that adds a
> BdrvTrackedRequest to all remaining asynchronous operations. So far we
> have identified flush, discard and aio_ioctl. At the same time he will
> send a rebased version of this series that goes back to asynchronous
> flushing in bdrv_qed_drain().
This is a completely separate bug. Can you at least merge all patches
except this, so that everything except QED can do snapshots with
dataplane? Of course there will be a v7 at least for patch 9.
Paolo
- [Qemu-block] [PATCH v6 05/12] block: Introduce "drained begin/end" API, (continued)
- [Qemu-block] [PATCH v6 05/12] block: Introduce "drained begin/end" API, Fam Zheng, 2015/10/22
- [Qemu-block] [PATCH v6 06/12] block: Add "drained begin/end" for transactional external snapshot, Fam Zheng, 2015/10/22
- [Qemu-block] [PATCH v6 07/12] block: Add "drained begin/end" for transactional backup, Fam Zheng, 2015/10/22
- [Qemu-block] [PATCH v6 08/12] block: Add "drained begin/end" for transactional blockdev-backup, Fam Zheng, 2015/10/22
- [Qemu-block] [PATCH v6 09/12] block: Add "drained begin/end" for internal snapshot, Fam Zheng, 2015/10/22
- [Qemu-block] [PATCH v6 10/12] block: Introduce BlockDriver.bdrv_drain callback, Fam Zheng, 2015/10/22
- [Qemu-block] [PATCH v6 11/12] qed: Implement .bdrv_drain, Fam Zheng, 2015/10/22
- [Qemu-block] [PATCH v6 12/12] tests: Add test case for aio_disable_external, Fam Zheng, 2015/10/22