Re: [PATCH v2 0/3] migration: Add block-bitmap-mapping parameter

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Max Reitz (mreitz@redhat.com) wrote:
> RFC v1: https://lists.nongnu.org/archive/html/qemu-block/2020-05/msg00912.html
> RFC v2: https://lists.nongnu.org/archive/html/qemu-block/2020-05/msg00915.html
> v1: https://lists.nongnu.org/archive/html/qemu-devel/2020-06/msg09792.html
> 
> Branch: https://github.com/XanClic/qemu.git migration-bitmap-mapping-v2
> Branch: https://git.xanclic.moe/XanClic/qemu.git migration-bitmap-mapping-v2
> 
> Based-on: <20200626130658.76498-1-vsementsov@virtuozzo.com>
>           (“migration/block-dirty-bitmap: fix add_bitmaps_to_list”)
> 
> 
> Hi,
> 
> This new migration parameter allows mapping block node names and bitmap
> names to aliases for the purpose of block dirty bitmap migration.

One random thought is that you might find these block name aliases turn
out to be useful in other places, and an alias list may well turn out to
be generically useful.

Dave

> This way, management tools can use different node names on the source
> and destination and pass the mapping of how bitmaps are to be
> transferred to qemu (on the source, the destination, or even both with
> arbitrary aliases in the migration stream).
> 
> 
> v2:
> - Dropped what used to be patch 1 (the memleak fix), I see the exact
>   same fix has been sent concurrently and has been merged as
>   9728ebfb77f0159f4
> 
> - Patch 1:
>   - Changed documentation to clarify the default behavior
>   - s/5.1/5.2/
>   - Dropped dead assignment
>   - Fixed bitmaps_map memleak
>   - Assert that the bs_name given to add_bitmaps_to_list() must be the
>     BDS’s node name if an alias_map is given
>   - On the source side, unmapped bitmaps are simply dropped without
>     error
>   - On the destination side, unmapped aliases still result in errors
>     (see patch 1 for a short explanation on my reasoning)
>   - Fixed a bug in qmp_query_migrate_parameters(): We have to clone
>     s->parameters.block_bitmap_mapping, not
>     params->block_bitmap_mapping, or the latter will just stay NULL (and
>     so qmp_query_migrate_parameters() won’t return a result for the
>     block-bitmap-mapping)
>   - Emit the mapping through HMP’s “info migrate_parameters”
>   - Return an error when trying to set the mapping through HMP (instead
>     of just crashing because of an “assert(0)” signalling an unhandled
>     migration parameter)
> 
> - Patch 3:
>   - Type alias for BlockBitmapMapping
>   - Check the result of “info migrate_parameters” whenever setting the
>     block-bitmap-mapping (just to test the new formatting code)
>   - Catch the qemu.machine.AbnormalShutdown exception on the destination
>     VM whenever the migration is expected to fail
>     (necessary since commit ef5d474472426eda6abf81)
>   - Cases where we don’t set up a mapping for some bitmap on the source
>     are now expected to succeed (without the bitmap being migrated)
> 
> 
> git-backport-diff against v1:
> 
> Key:
> [----] : patches are identical
> [####] : number of functional differences between upstream/downstream patch
> [down] : patch is downstream-only
> The flags [FC] indicate (F)unctional and (C)ontextual differences, respectively
> 
> 001/3:[0117] [FC] 'migration: Add block-bitmap-mapping parameter'
> 002/3:[----] [--] 'iotests.py: Add wait_for_runstate()'
> 003/3:[0202] [FC] 'iotests: Test node/bitmap aliases during migration'
> 
> 
> Max Reitz (3):
>   migration: Add block-bitmap-mapping parameter
>   iotests.py: Add wait_for_runstate()
>   iotests: Test node/bitmap aliases during migration
> 
>  qapi/migration.json            |  92 +++++-
>  migration/migration.h          |   3 +
>  migration/block-dirty-bitmap.c | 373 ++++++++++++++++++++----
>  migration/migration.c          |  30 ++
>  monitor/hmp-cmds.c             |  30 ++
>  tests/qemu-iotests/300         | 511 +++++++++++++++++++++++++++++++++
>  tests/qemu-iotests/300.out     |   5 +
>  tests/qemu-iotests/group       |   1 +
>  tests/qemu-iotests/iotests.py  |   4 +
>  9 files changed, 994 insertions(+), 55 deletions(-)
>  create mode 100755 tests/qemu-iotests/300
>  create mode 100644 tests/qemu-iotests/300.out
> 
> -- 
> 2.26.2
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK