On 2/5/19 3:08 AM, Denis Plotnikov wrote: > The patch adds some preparation parts for incompatible compression type > feature into QCOW2 header that indicates that *all* compressed clusters > must be (de)compressed using a certain compression type. > > It is implied that the compression type is set on the image creation and > can be changed only later by image convertion, thus the only compression
s/convertion/conversion/ > algorithm is used for the image. > > The plan is to add support for ZSTD and then may be something more effective > in the future. > > ZSDT compression algorithm consumes 3-5 times less CPU power with a s/ZSDT/ZSTD/ > comparable comression ratio with zlib. It would be wise to use it for s/comression/compression/ > data compression f.e. for backups. > > The default compression is ZLIB. > > Signed-off-by: Denis Plotnikov <dplotni...@virtuozzo.com> > --- > block/qcow2.c | 25 +++++++++++++++++++++++++ > block/qcow2.h | 26 ++++++++++++++++++++++---- > 2 files changed, 47 insertions(+), 4 deletions(-) > > diff --git a/block/qcow2.c b/block/qcow2.c > index 8c91b92865..cb3d6cc1c0 100644 > --- a/block/qcow2.c > +++ b/block/qcow2.c > @@ -73,6 +73,7 @@ typedef struct { > #define QCOW2_EXT_MAGIC_FEATURE_TABLE 0x6803f857 > #define QCOW2_EXT_MAGIC_CRYPTO_HEADER 0x0537be77 > #define QCOW2_EXT_MAGIC_BITMAPS 0x23852875 > +#define QCOW2_EXT_MAGIC_COMPRESSION_TYPE 0x434D5052 This appears to be adding a new header extension magic number, but didn't actually modify the specification. I'd expect this patch to touch docs/interop/qcow2.txt before it can be considered complete. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
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