This series brings internal snapshot support at block devices level, now we have two main methods to do snapshot: 1) backing chain and 2) internal one, and 3) Stefan's unmerged backing up approach. Compared with 1), internal snapshot is faster in R/W/Delete. Compared with 3), it complete faster, take less space in total, but take more space in local image. As a summary, When user want to take a local snapshot quickly, it is encouraged to use internal snapshot when possible for performance reason. If user want to duplicate or backup vm to another place, it is encouraged to use backing up approach.
A full view may be: it can take snapshot by 1), 2), and the snapshot can be exported to 3rd place. it can also directly export/backup data by 3). export means transfering the data out of qemu/libvirt's scope, let 3rd party take over. host A backup server B vm ---------> | backup \|/ Data that can distinguish base/delta, disk/memory snapshot v0 export snapshot v1 ---------> Next steps to better full VM snapshot: Add support to export internal snapshot data lively, possible use qemu-img or qemu-nbd. Better vmstate saving. Note: I think in most case, saving vmstate in an standalone file is better than saving it inside qcow2, So suggest treat internal snapshot as block level methods and not encourage user to savevm in qcow2 any more. We can have "internal snapshot (or backing chain) + standing alone vmstate file" as replacement. Some details: To avoid trouble, this serial have hide ID in interfaces, this make sure no chaos of ID and name will be introduced by these interfaces. There is one patch may be common to Pavel's savvm transaction, patch 4/11, others are not quite related. Patch 4/11 will not set errp when no snapshot find, since patch 7/11 need to distinguish real error case. Thanks Kevin to give advancement about how add it in qmp_transaction, oldest version comes drom Dietmar Maurer. Stefan Hajnoczi (3): 1 blockdev: drop redundant proto_drv check 2 blockdev: rename BlkTransactionStates to singular 3 blockdev: allow BdrvActionOps->commit() to be NULL Wenchao Xia (8): 4 snapshot: new function bdrv_snapshot_find_by_id_and_name() 5 snapshot: add paired functions for internal snapshot id and name 6 snapshot: distinguish id and name in snapshot delete 7 qmp: add internal snapshot support in qmp_transaction 8 qmp: add interface blockdev-snapshot-internal-sync 9 qmp: add interface blockdev-snapshot-delete-internal-sync 10 hmp: add interface hmp_snapshot_internal_blkdev 11 hmp: add interface hmp_snapshot_delete_internal_blkdev block/qcow2-snapshot.c | 55 +++++++--- block/qcow2.h | 5 +- block/rbd.c | 19 +++- block/sheepdog.c | 5 +- block/snapshot.c | 143 +++++++++++++++++++++++- blockdev.c | 278 ++++++++++++++++++++++++++++++++++----------- hmp-commands.hx | 43 +++++++- hmp.c | 20 ++++ hmp.h | 2 + include/block/block_int.h | 5 +- include/block/snapshot.h | 14 ++- qapi-schema.json | 56 +++++++++ qemu-img.c | 5 +- qmp-commands.hx | 93 ++++++++++++++- savevm.c | 10 ++- 15 files changed, 649 insertions(+), 104 deletions(-)
