Am 10.02.2015 um 21:28 hat Max Reitz geschrieben:
> As of version 3, the qcow2 file format supports different widths for
> refcount entries, ranging from 1 to 64 bit (only powers of two).
> Currently, qemu only supports 16 bit, which is the only width supported
> by version 2 (compat=0.10) images.
>
> This series adds support to qemu for all other valid refcount orders.
> This is mainly done by adding two function pointers into the
> BDRVQcowState structure for reading and writing refcount values
> independently of the current refcount entry width; all in-memory
> refcount arrays (mostly cached refcount blocks) now are void pointers
> and are accessed through these functions alone.
>
> Thanks to previous work of making the qemu code agnostic of e.g. the
> number of refcount entries per refcount block, the rest is fairly
> trivial. The most complex patch in this series is patch 21 which
> implements changing the refcount order through qemu-img amend.
>
> To test different refcount widths, simply invoke the qemu-iotests check
> program with -o refcount_bits=${your_desired_width}. The final test in
> this series adds some tests for operations which do not work with
> certain refcount orders and for refcount order amendment.
>
> In order for iotest 015 to succeed with refcount_bits=32 and
> refcount_bits=64, this series depends on my series
> "qcow2: Respect new_block in alloc_refcount_block()".
In order to avoid re-reviewing the same patches each time you post a new
version, I applied patches 1 to 6 now. I'll continue with reviewing the
rest later today.
Kevin
