Re: [Qemu-block] [Qemu-devel] [PATCH v2 15/32] qcow2: Update l2_load() to support L2 slices

[Eric Blake]

On 12/15/2017 06:53 AM, Alberto Garcia wrote:
> Each entry in the qcow2 L2 cache stores a full L2 table (which uses a
> complete cluster in the qcow2 image). A cluster is usually too large
> to be used efficiently as the size for a cache entry, so we want to
> decouple both values by allowing smaller cache entries. Therefore the
> qcow2 L2 cache will no longer return full L2 tables but slices
> instead.
> 
> This patch updates l2_load() so it can handle L2 slices correctly.
> Apart from the offset of the L2 table (which we already had) we also
> need the guest offset in order to calculate which one of the slices
> we need.
> 
> An L2 slice has currently the same size as an L2 table (one cluster),
> so for now this function will load exactly the same data as before.
> 
> This patch also removes a stale comment about the return value being
> a pointer to the L2 table. This function returns an error code since
> 55c17e9821c474d5fcdebdc82ed2fc096777d611.
> 
> Signed-off-by: Alberto Garcia <address@hidden>
> ---
>  block/qcow2-cluster.c | 28 +++++++++++++++++-----------
>  1 file changed, 17 insertions(+), 11 deletions(-)
> 

Reviewed-by: Eric Blake <address@hidden>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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