[Qemu-devel] [PATCH V12 00/18] qmp/hmp interfaces for internal snapshot info

[Wenchao Xia]

  This serial let qmp interface show info for internal snapshot/backing chain
on all block device at runtime, it helps management stack to find the correct
image to merge when qemu is running, and retrieve exactly the same info of what
qemu saws, avoiding async trouble if management stack use qemu-img info when
qemu is running(Since qemu-img shows 'static' info, Management stack may need
to guess qemu's logic to rebuild runtime 'dynamic' info, and a lock between
query and blkdev_snapshot_create/delete?). 
  Also hmp code is added, following are the interfaces added/enhanced:

1) qmp: query-block, show info for a block device include image info
Example:
-> { "execute": "query-block" }
<- {
      "return":[
         {
            "io-status": "ok",
            "device":"ide0-hd0",
            "locked":false,
            "removable":false,
            "inserted":{
               "ro":false,
               "drv":"qcow2",
               "encrypted":false,
               "file":"disks/test.qcow2",
               "backing_file_depth":1,
               "bps":1000000,
               "bps_rd":0,
               "bps_wr":0,
               "iops":1000000,
               "iops_rd":0,
               "iops_wr":0,
               "image":{
                  "filename":"disks/test.qcow2",
                  "format":"qcow2",
                  "virtual-size":2048000,
                  "backing_file":"base.qcow2",
                  "full-backing-filename":"disks/base.qcow2",
                  "backing-filename-format:"qcow2",
                  "snapshots":[
                     {
                        "id": "1",
                        "name": "snapshot1",
                        "vm-state-size": 0,
                        "date-sec": 10000200,
                        "date-nsec": 12,
                        "vm-clock-sec": 206,
                        "vm-clock-nsec": 30
                     }
                  ],
                  "backing-image":{
                      "filename":"disks/base.qcow2",
                      "format":"qcow2",
                      "virtual-size":2048000
                  }
               }
            },
            "type":"unknown"
         },
         {
            "io-status": "ok",
            "device":"ide1-cd0",
            "locked":false,
            "removable":true,
            "type":"unknown"
         },
         {
            "device":"floppy0",
            "locked":false,
            "removable":true,
            "type":"unknown"
         },
         {
            "device":"sd0",
            "locked":false,
            "removable":true,
            "type":"unknown"
         }
      ]
   }

2) qmp: query-snapshots, show avaiable vm snapshot info which can be used
in loadvm.
Example:
-> { "execute": "query-snapshots" }
<- {
      "return":[
         {
            "id": "1",
            "name": "snapshot1",
            "vm-state-size": 0,
            "date-sec": 10000200,
            "date-nsec": 12,
            "vm-clock-sec": 206,
            "vm-clock-nsec": 30
         }
      ]
    }

3) hmp: info block, show what got in qmp query-block in monitor

Details:
  These patches follows the rule that use qmp to retieve information,
hmp layer just does a translation from qmp object it got.
  To make code graceful, snapshot and image info retrieving code in
qemu and qemu-img are merged into block layer, and some function name was
adjusted to make it tips better. For the part touch by the serial, it works as:

   qemu          qemu-img

dump_monitor    dump_stdout
     |--------------| 
            |
       block/qapi.c

  Special thanks for Markus, Stefan, Kevin, Eric reviewing many times.

Changelog:
v11:
  General change:
  5/17: check if snapshot > 0 on success in caller, add comments on the
function says that caller need to check it on success.
  7/17: check if snapshot > 0 on success before set info->has_snapshots.

  Address Eric's comments:
  5/17: use error_setg_errno instead of strerror().
  12/17: also move bdrv_snapshot_dump() since it need to be changed using
GString later.
  13/17: using GString as buffer.
  14/17: using GString to dump snapshot info.
  16/17: using GString to dump image info.

  Address Kevin's comments:
  11/17: return void for bdrv_query_info().
  17/17: spell fix in help message, using parameter "-v" to show
verbose info.

V12:
  Address Markus's comments:
  02/18: better incode comments for bdrv_snapshot_find(), add tip about the
logic change in snapshot create/delete/load/info if some snapshot's id is mixed
with name in commit message.
  05/18: better incode comments for bdrv_query_snapshot_info_list(), do not
check return value in caller qemu-img.
  07/18: new patch changing the vm snapshot filter logic, to be exactly the
same with load_vmstate(). To tip it clearly this patch is made a seperate one,
and can be droped if original logic want to be kepted.
  08/18: squash -ENOMEDIUM and -ENOTSUP in switch statement in
bdrv_query_image_info().
  11/18: better incode comments for bdrv_query_image_info().
  12/18: change disk name suffix from .img to .qcow2 in example, to tip better.
  14/18: new funtion message_printf(), which automatically dump to monitor if
it present, discard buffer or GString.
  15/18: use message_printf() instead of buffer.
  17/18: use message_printf() instead of buffer.

  Address Eric's comments:
  05/18: better incode comments for bdrv_query_snapshot_info_list(), do not
check return value in caller qemu-img.

  Address Stefan's comments:
  10/18: added doc about the meaning of "consistent snapshot" in
qmp-commands.hx.

  Address Kevin's comments:
  12/18: use local_error to detect error in qmp_query_snapshots(), in case
caller set errp = NULL.

Wenchao Xia (18):
  1 block: move bdrv_snapshot_find() to block/snapshot.c
  2 block: distinguish id and name in bdrv_find_snapshot()
  3 qemu-img: remove unused parameter in collect_image_info()
  4 block: move collect_snapshots() and collect_image_info() to block/qapi.c
  5 block: add snapshot info query function bdrv_query_snapshot_info_list()
  6 block: add check for VM snapshot in bdrv_query_snapshot_info_list()
  7 block: change VM snapshot checking logic
  8 block: add image info query function bdrv_query_image_info()
  9 block: move qmp_query_block() and bdrv_query_info() to block/qapi.c
  10 qmp: add interface query-snapshots
  11 qmp: add recursive member in ImageInfo
  12 qmp: add ImageInfo in BlockDeviceInfo used by query-block
  13 block: move bdrv_snapshot_dump() and dump_human_image_info() to 
block/qapi.c
  14 block: dump to monitor for bdrv_snapshot_dump() and bdrv_image_info_dump()
  15 hmp: add function hmp_info_snapshots()
  16 hmp: switch snapshot info function to qmp based one
  17 hmp: show ImageInfo in 'info block'
  18 hmp: add parameters device and -v for info block

 block.c                     |  109 -----------
 block/Makefile.objs         |    1 +
 block/qapi.c                |  452 +++++++++++++++++++++++++++++++++++++++++++
 block/snapshot.c            |   78 ++++++++
 hmp.c                       |   63 ++++++
 hmp.h                       |    1 +
 include/block/block.h       |    2 -
 include/block/qapi.h        |   43 ++++
 include/block/snapshot.h    |   37 ++++
 include/qemu/error-report.h |    1 +
 monitor.c                   |    9 +-
 qapi-schema.json            |   24 ++-
 qemu-img.c                  |  165 +---------------
 qmp-commands.hx             |  127 ++++++++++++-
 savevm.c                    |   96 +---------
 util/qemu-error.c           |   18 ++
 16 files changed, 861 insertions(+), 365 deletions(-)
 create mode 100644 block/qapi.c
 create mode 100644 block/snapshot.c
 create mode 100644 include/block/qapi.h
 create mode 100644 include/block/snapshot.h