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Date: Mon, 08 Oct 2012 16:37:30 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 12/30] QAPI: add command for live block
 commit, 'block-commit'
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To: Eric Blake <eblake@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Jeff Cody <jcody@redhat.com>, qemu-devel@nongnu.org, anthony@codemonkey.ws

Il 05/10/2012 20:05, Eric Blake ha scritto:
> 
> If I commit snap1 into base, should /dir/active encode the backing file
> as '/dir/base' (keep things absolute, since /dir/active had already been
> absolute) or as 'base' (relative, since the part of the chain previously
> referring to base was using relative).  And if we store relative names,
> we need to make sure that the relative name stored in /dir/active
> correctly points to the correct file name, even if the ultimate base
> file lives in a different directory (similar problems exist with
> relative chains during block pull).
> 
> I'm wondering if this means 'block-stream' and 'block-commit' both need
> to add @mode:#optional arguments, similar to Paolo's 'drive-mirror'
> command [1], so that the user can request 'absolute-paths' vs.
> 'relative-paths' as the mode for which of two file names will be written
> as the backing file at the end of the operation.

Yes, everything that calls bdrv_change_backing_file should have such a
@mode argument.  Good point!

Paolo

> [1] https://lists.gnu.org/archive/html/qemu-devel/2012-09/msg04592.html