Hello everyone! The given feature discards blocks with copy-on-read operation while the streaming process runs. Adding the 'discard' argument to the QMP block-stream command allows dropping a block in the backing chain after it has been copied to the active layer. That will elude the block duplication in the intermediate backing file. It saves the disk space while external snapshots are being merged. The method involves the filter insertion above the active layer to allow write operation in the backing chain. The method is similar to that in the 'commit active' command (mirror.c).
Andrey Shinkevich (2): The discard flag for block stream operation Discard blocks while copy-on-read block/stream.c | 402 ++++++++++++++++++++++++++++++++++++++++++++-- blockdev.c | 8 +- hmp-commands.hx | 4 +- hmp.c | 4 +- include/block/block_int.h | 2 +- qapi/block-core.json | 5 +- 6 files changed, 407 insertions(+), 18 deletions(-) -- 1.8.3.1
