On Sat, Apr 23, 2016 at 11:41:51AM +0300, Denis V. Lunev wrote: > 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. > > 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> > > Pavel Butsykin (2): > drive-backup: added support for data compression > blockdev-backup: added support for data compression > > block/backup.c | 13 +++++++++++++ > blockdev.c | 20 ++++++++++++++++++-- > hmp-commands.hx | 8 +++++--- > hmp.c | 3 ++- > include/block/block_int.h | 1 + > qapi/block-core.json | 3 ++- > qmp-commands.hx | 7 +++++-- > 7 files changed, 46 insertions(+), 9 deletions(-)
bdrv_write_compressed() hasn't been called from a running VM before, it was purely a synchronous qemu-img operation. The qcow2.c:qcow2_write_compressed() code doesn't seem to be written with coroutine context in mind but I think the lock in block/backup.c:backup_do_cow() will protect against race conditions. Please include a test case (using qcow2?).
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