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Re: [Qemu-block] [PATCH 00/20] qcow2: External data files

From: Kevin Wolf
Subject: Re: [Qemu-block] [PATCH 00/20] qcow2: External data files
Date: Thu, 7 Mar 2019 17:37:15 +0100
User-agent: Mutt/1.11.3 (2019-02-01)

Am 27.02.2019 um 18:22 hat Kevin Wolf geschrieben:
> There are use cases where raw images are given (e.g. existing physical
> disks), but advanced features like dirty bitmaps or backing files are
> wanted that require use of a proper image format like qcow2.
> This series adds an incompatible feature bit to qcow2 which allows to
> use an external data file: Metadata is kept in the qcow2 file like
> usual, but guest data is written to an external file. Clusters in the
> data file are not reference counted, instead we use a flat layout where
> host cluster offset == guest cluster offset. The external data file is
> therefore readable as a raw image (though writing to it invalidates the
> associated qcow2 metadata). Features that require refcounting such as
> internal snapshots or compression are not supposed in such setups.
> Major changes since the RFC (many more minor changes):
> - Added a 'data-file-raw' flag to the spec to keep the data file a valid
>   self-consistent raw image (write_zeroes must always be propagated)
> - Added QAPI documentation
> - Added some test cases
> - Implemented data file support or error paths for discard, check,
>   compressed writes, snapshots
> - Fixed qcow2_co_block_status()
> - Rearranged qcow2_do_open() code for data files for better error
>   handling (e.g. no more fallback to default data file if an explicit,
>   but invalid data-file option is given)

Thanks, made the trivial changes suggested during review and applied to
the block branch.


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