[0/2] blockdev-add transaction

Message

Vladimir Sementsov-Ogievskiy Feb. 24, 2022, 5:13 p.m. UTC

Hi all!

If we want to do incremental backups with help of copy-before-write
filter bitmap parameter introduced in my in-flight series
"[PATCH v4 00/18] Make image fleecing more usable", we actually need to
create filter, insert it into graph and do some operations with bitmaps
in one transaction.

So, here is basic support for blockdev-add transaction, which may be
useful for any scenarios.

Also, I'll need to resend my "[PATCH RFC v2 0/4] blockdev-replace" with
transaction support as well.

Why I say that support is "basic"? Ideally we want an ability to call
several blockdev-add / blockdev-replace commands not updating the
permission and only then update permissions for all touched nodes. That
is more flexible and will allow more strict and simple permission
requirements in filter drivers. Still this means to implement
bdrv_open() transaction action (using Transaction API) which doesn't
update permissions (like most of internal graph update functions works
now). That's of course is more complicated than this patch. So, let's
start with something simple.

Vladimir Sementsov-Ogievskiy (2):
  block: transaction support for blockdev-add
  iotests: add blockdev-add-transaction

 qapi/transaction.json                         | 11 +++
 blockdev.c                                    | 80 +++++++++++++------
 .../tests/blockdev-add-transaction            | 52 ++++++++++++
 .../tests/blockdev-add-transaction.out        |  6 ++
 4 files changed, 124 insertions(+), 25 deletions(-)
 create mode 100755 tests/qemu-iotests/tests/blockdev-add-transaction
 create mode 100644 tests/qemu-iotests/tests/blockdev-add-transaction.out