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Re: [Qemu-block] [PATCH 18/19] block: Allow graph changes in bdrv_drain_
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From: |
Paolo Bonzini |
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Subject: |
Re: [Qemu-block] [PATCH 18/19] block: Allow graph changes in bdrv_drain_all_begin/end sections |
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Date: |
Thu, 12 Apr 2018 10:47:05 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 |
On 11/04/2018 18:39, Kevin Wolf wrote:
> The much easier and more obviously correct way is to fundamentally
> change the way the functions work: Iterate over all BlockDriverStates,
> no matter who owns them, and drain them individually. Compensation is
> only necessary when a new BDS is created inside a drain_all section.
> Removal of a BDS doesn't require any action because it's gone afterwards
> anyway.
Ok, now I see (I think) why you chose the recursive check for in-flight
requests. The higher quiesce_count is not a problem, but I am still not
convinced about the recursion.
Paolo
> This change means that some nodes get a higher bs->quiesce_count now
> because each node propagates its individual drain to all of its parents.
> In the old subtree drain, propagation back to the parent that made the
> recursive drain request was avoided. While this isn't perfectly
> beautiful, accepting the higher counts seems preferable to adding drain
> code to multiple other places that modify the graph.
- Re: [Qemu-block] [PATCH 10/19] block: Drain recursively with a single BDRV_POLL_WHILE(), (continued)
- [Qemu-block] [PATCH 12/19] block: Don't poll in parent drain callbacks, Kevin Wolf, 2018/04/11
- [Qemu-block] [PATCH 14/19] block: Defer .bdrv_drain_begin callback to polling phase, Kevin Wolf, 2018/04/11
- [Qemu-block] [PATCH 16/19] block: Allow AIO_WAIT_WHILE with NULL ctx, Kevin Wolf, 2018/04/11
- [Qemu-block] [PATCH 15/19] test-bdrv-drain: Test that bdrv_drain_invoke() doesn't poll, Kevin Wolf, 2018/04/11
- [Qemu-block] [PATCH 13/19] test-bdrv-drain: Graph change through parent callback, Kevin Wolf, 2018/04/11
- [Qemu-block] [PATCH 19/19] test-bdrv-drain: Test graph changes in drain_all section, Kevin Wolf, 2018/04/11
- [Qemu-block] [PATCH 17/19] block: Move bdrv_drain_all_begin() out of coroutine context, Kevin Wolf, 2018/04/11
- [Qemu-block] [PATCH 18/19] block: Allow graph changes in bdrv_drain_all_begin/end sections, Kevin Wolf, 2018/04/11
- Re: [Qemu-block] [PATCH 18/19] block: Allow graph changes in bdrv_drain_all_begin/end sections,
Paolo Bonzini <=
- Re: [Qemu-block] [Qemu-devel] [PATCH 00/19] Drain fixes and cleanups, part 3, no-reply, 2018/04/11
- Re: [Qemu-block] [Qemu-devel] [PATCH 00/19] Drain fixes and cleanups, part 3, Stefan Hajnoczi, 2018/04/20