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Re: [Qemu-block] [PATCH 1/3] block: Don't wait serialising for non-COR r
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From: |
Fam Zheng |
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Subject: |
Re: [Qemu-block] [PATCH 1/3] block: Don't wait serialising for non-COR read requests |
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Date: |
Tue, 1 Dec 2015 18:26:58 +0800 |
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User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Tue, 12/01 10:54, Kevin Wolf wrote:
> Am 01.12.2015 um 10:36 hat Fam Zheng geschrieben:
> > The assertion problem was noticed in 06c3916b35a, but it wasn't
> > completely fixed, because even though the req is not marked as
> > serialising, it still gets serialised by wait_serialising_requests
> > against other serialising requests, which could lead to the same
> > assertion failure.
> >
> > Fix it by even more explicitly skipping the serialising for this
> > specific case.
> >
> > Signed-off-by: Fam Zheng <address@hidden>
>
> And this, my friends, is another example why read/write notifiers are
> wrong and should die sooner rather than later. </broken-record>
>
Yes, I agree, except it's not clear to me what a better alternative solution
should be. A immediate question is, with whatever approach we will have,
wouldn't we still need to do this sort of "reentrant" COW before the data is
overwritten?
Fam