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Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared bas
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node |
Date: |
Thu, 21 Mar 2019 11:53:57 +0000 |
21.03.2019 13:53, Kevin Wolf wrote:
> Am 20.03.2019 um 18:02 hat Alberto Garcia geschrieben:
>> On Wed 20 Mar 2019 10:16:10 AM CET, Kevin Wolf wrote:
>>>> Oh, I see. Let's use a shorter chain for simplicity:
>>>>
>>>> A <- B <- C <- D <- E
>>>
>>> Written from right to left, i.e. E being the base and A the top layer?
>>> We usually write things the other write round, I hope this doesn't get
>>> too confusing later.
>>
>> Oh my... yes, of course you're right, I should have written it the other
>> way around:
>>
>> E <- D <- C <- B <- A
>>
>>>> 1) If we stream first from E to C we add a filter F:
>>>>
>>>> A <- B <- F <- C <- D <- E
>>
>> ( which should have been written E <- D <- C <- F <- B <- A )
>>
>>>> Now we can't stream from C to A because F is on the way, and the F-C
>>>> link is frozen.
>>>
>>> Why is a frozen link a problem? The streaming operation isn't going to
>>> change this link, it just copies data from the subchain (including F
>>> and C) to A. This is not something that a frozen link should prevent.
>>
>> Not the operation itself, but the first thing that block-stream does is
>> freeze the chain from top (A) to base (C), so this would fail if there's
>> already a frozen link on the way (C <- F on this case?).
>
> Oh, I see. I think this is why I suggested a counter originally instead
> of a bool.
>
>>> So it seems frozen links allow the wrong case, but block the correct
>>> one? :-(
>>
>> Yes, we probably need to rethink this scenario a bit.
>
> But yes, even with a counter, the other problem would still remain (that
> the first job can't remove the filter on completion because the second
> one has frozen its link to the filter).
>
> I don't think that's a case we want to just forbid because nobody needs
> this anyway. It's a sign of a more fundamental problem in our design,
> and I'm sure it will bite us in other places, too.
>
> Kevin
>
Does it mean that we now have problems with other jobs which already has
filter if use them in parallel with stream?
--
Best regards,
Vladimir
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, (continued)
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Alberto Garcia, 2019/03/19
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Kevin Wolf, 2019/03/20
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Vladimir Sementsov-Ogievskiy, 2019/03/20
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Alberto Garcia, 2019/03/20
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Vladimir Sementsov-Ogievskiy, 2019/03/21
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Alberto Garcia, 2019/03/21
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Kevin Wolf, 2019/03/21
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Alberto Garcia, 2019/03/21
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Alberto Garcia, 2019/03/20
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Kevin Wolf, 2019/03/21
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node,
Vladimir Sementsov-Ogievskiy <=
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Alberto Garcia, 2019/03/21
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Alberto Garcia, 2019/03/22
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Andrey Shinkevich, 2019/03/22
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Alberto Garcia, 2019/03/24
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Andrey Shinkevich, 2019/03/21
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Andrey Shinkevich, 2019/03/21
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Vladimir Sementsov-Ogievskiy, 2019/03/22
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Kevin Wolf, 2019/03/22
- Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Andrey Shinkevich, 2019/03/21
Re: [Qemu-devel] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node, Andrey Shinkevich, 2019/03/19