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Re: [Qemu-block] [PATCH 5/5] block: Simplify append_open_options()

From: Kevin Wolf
Subject: Re: [Qemu-block] [PATCH 5/5] block: Simplify append_open_options()
Date: Tue, 14 Aug 2018 11:17:50 +0200
User-agent: Mutt/1.9.1 (2017-09-22)

Am 29.06.2018 um 13:37 hat Alberto Garcia geschrieben:
> This function returns a BDS's driver-specific options, excluding also
> those from its children. Since we have just removed all children
> options from bs->options there's no need to do this last step.
> We allow references to children, though ("backing": "node0"), so those
> we still have to remove.
> Signed-off-by: Alberto Garcia <address@hidden>

Hmm, yes, but if I compare this with the example you gave in an earlier

      $ qemu-img create -f qcow2 hd0.qcow2 10M
      $ qemu-img create -f qcow2 -b hd0.qcow2 hd1.qcow2
      $ qemu-img create -f qcow2 -b hd1.qcow2 hd2.qcow2

      $ $QEMU -drive file=hd2.qcow2,node-name=hd2,backing.node-name=hd1

    This opens a chain of images hd0 <- hd1 <- hd2. Now let's remove hd1
    using block_stream:

      (qemu) block_stream hd2 0 hd0.qcow2

    After this hd2 contains backing.node-name=hd1, which is no longer
    correct because hd1 doesn't exist anymore.

Doesn't backing=hd1 actually result in the same kind of inconsistency?
That is, bs->option will still have backing=hd1, but in reality we
reference hd0 now?

Should we get rid of child references in bs->(explicit_)options as well?


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