On 7/16/26 13:22, Denis V. Lunev wrote:
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> qmp_block_dirty_bitmap_add() and the incoming-migration bitmap loader
> both create a persistent bitmap with bdrv_create_dirty_bitmap(), which
> always creates it writable, without checking whether the node can
> actually be written to. A persistent bitmap added to an already
> read-only or inactive node stays writable in memory on a node that
> can never store it, and the next global inactivation (migration
> completion, save, or any other bdrv_inactivate_all() caller) fails
> trying to flush it back:
>
>   Lost persistent bitmaps during inactivation of node '<node>': No write 
> access
>   migration_block_inactivate: bdrv_inactivate_all() failed: -22
>
> Patch 1 rejects this at block-dirty-bitmap-add (and, wrapped in a
> transaction, denies the whole transaction). Patch 2 closes the same
> hole on the incoming-migration path. Patch 3 fixes a knock-on
> regression from patch 1's approach: a bitmap that was rejected from
> ever being written can still exist in memory read-only and must
> remain removable without requiring write access.
>
> v1 -> v2
> * approach changed to deny rather than adopt (Vladimir)
> * added patch to add permission check on migration path
> * added patch to change permissions check on bitmap drop to more natural
>
> Signed-off-by: Denis V. Lunev <[email protected]>
> CC: Eric Blake <[email protected]>
> CC: Vladimir Sementsov-Ogievskiy <[email protected]>
> CC: John Snow <[email protected]>
> CC: Andrey Drobyshev <[email protected]>
>
> Denis V. Lunev (3):
>   block/monitor: reject persistent bitmap add on a read-only node
>   migration/block-dirty-bitmap: reject bitmap load onto ro node
>   block/monitor: allow dropping a bitmap never stored on disk
>
>  block/monitor/bitmap-qmp-cmds.c               | 19 +++++++----
>  block/qcow2-bitmap.c                          |  9 +++++
>  migration/block-dirty-bitmap.c                | 22 +++++++++----
>  qapi/block-core.json                          |  4 ++-
>  tests/qemu-iotests/tests/migrate-bitmaps-test | 33 +++++++++++++++++++
>  .../tests/migrate-bitmaps-test.out            |  4 +--
>  .../tests/remove-bitmap-from-backing          | 29 +++++++++++++++-
>  .../tests/remove-bitmap-from-backing.out      | 22 ++++++++++++-
>  8 files changed, 124 insertions(+), 18 deletions(-)
>
Hi, Vladimir!

Will this go through your tree? It is looking like nobody else cares.

Den

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