The idea is simple - backup is "written-once" data. It is written block by block and it is large enough. It would be nice to save storage space and compress it.
These patches add the ability to compress data during backup. This functionality is implemented by means of adding options to the qmp/hmp commands(drive-backup, blockdev-backup). The implementation is quite simple, because the responsibility for data compression imposed on the format driver. Changes from v1: - added unittest for backup compression (12, 13) Changes from v2: - implemented a new .bdrv_co_write_compressed interface to replace the old .bdrv_write_compressed (2,3,4,5,6) Changes from v3: - added the byte-based interfaces: blk_pwrite_compressed()/blk_co_pwritev_compressed() (1, 7) - fix drive/blockdev-backup documentation (10, 11) Changes form v4: - added assert that offset and count are aligned (1) - reuse RwCo and bdrv_co_pwritev() for write compressed (2) - converted interfaces to byte-based for format drivers (2, 3, 5, 6) - move an unrelated cleanup in a separate patches (4, 7) - turn on dirty_bitmaps for the compressed writes (9) - added simplify drive/blockdev-backup by using the boxed commands (10, 11) - reworded drive/blockdev-backup documentation about compression (12, 13) - fix s/bakup/backup/ (14) Changes form v5: - rebased on master - fix grammar (5, 8) Signed-off-by: Pavel Butsykin <pbutsy...@virtuozzo.com> Signed-off-by: Denis V. Lunev <d...@openvz.org> CC: Jeff Cody <jc...@redhat.com> CC: Markus Armbruster <arm...@redhat.com> CC: Eric Blake <ebl...@redhat.com> CC: John Snow <js...@redhat.com> CC: Stefan Hajnoczi <stefa...@redhat.com> CC: Kevin Wolf <kw...@redhat.com> Pavel Butsykin (16): block: switch blk_write_compressed() to byte-based interface block: Convert bdrv_pwrite_compressed() to BdrvChild block/io: reuse bdrv_co_pwritev() for write compressed qcow2: add qcow2_co_pwritev_compressed qcow2: cleanup qcow2_co_pwritev_compressed to avoid the recursion vmdk: add vmdk_co_pwritev_compressed qcow: add qcow_co_pwritev_compressed qcow: cleanup qcow_co_pwritev_compressed to avoid the recursion block: remove BlockDriver.bdrv_write_compressed block/io: turn on dirty_bitmaps for the compressed writes block: simplify drive-backup block: simplify blockdev-backup drive-backup: added support for data compression blockdev-backup: added support for data compression qemu-iotests: test backup compression in 055 qemu-iotests: add vmdk for test backup compression in 055 block/backup.c | 12 ++- block/block-backend.c | 27 +----- block/io.c | 48 ++++------ block/qcow.c | 113 +++++++++--------------- block/qcow2.c | 128 ++++++++++----------------- block/vmdk.c | 55 ++---------- blockdev.c | 193 ++++++++++++++--------------------------- hmp-commands.hx | 8 +- hmp.c | 32 ++++--- include/block/block.h | 5 +- include/block/block_int.h | 5 +- include/sysemu/block-backend.h | 4 +- qapi/block-core.json | 18 +++- qemu-img.c | 8 +- qemu-io-cmds.c | 2 +- qmp-commands.hx | 9 +- tests/qemu-iotests/055 | 118 +++++++++++++++++++++++++ tests/qemu-iotests/055.out | 4 +- tests/qemu-iotests/iotests.py | 10 +-- 19 files changed, 374 insertions(+), 425 deletions(-) -- 2.5.0