Re: [Qemu-devel] [PATCH v2 00/10] file-posix: Make auto-read-only dynamic

[Peter Krempa <pkrempa@redhat.com>]

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On Mon, Mar 11, 2019 at 17:50:07 +0100, Kevin Wolf wrote:
> We introduced the auto-read-only option to fix the problem that block
> jobs that reopen a backing file read-write don't work any more when all
> nodes are created individually with -blockdev. The reason is that
> bs->file of these backing files doesn't inherit the read-only option
> from the format layer node any more if it's created separately.
> 
> The way auto-read-only was designed to fix this is that it just always
> opens the file node read-write if it can, so reopening the format layer
> node is enough to make the backing file writable when necessary.
> 
> This works in principle, but not when libvirt uses sVirt: Then QEMU
> doesn't even have the permissions to open the image file read-write
> until libvirt performs an operation where write access is needed.
> 
> This series changes auto-read-only so that it works dynamically and
> automatically reopens the file read-only or read-write depending on the
> permissions that users attached to the node requested.
> 
> See also: https://bugzilla.redhat.com/show_bug.cgi?id=1685989
> 
> v2:
> - Added test for and fixed snapshot=on,read-only=on regression [Berto]
> - Added test for and fixed commit regression [Peter]

I've quickly tested it with non-active commit and it works in this
scenario as expected.

I'll give it a bit more thorough test in the morning.

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