Re: [PATCH v2 0/3] block: reject persistent bitmaps a node can never store

On 7/29/26 21:17, Vladimir Sementsov-Ogievskiy wrote:
> On 27.07.26 15:05, Denis V. Lunev wrote:
>> 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.
>>
> Yes, seems so. Thanks, applied to my block branch.
>
> There's still a chance to stop me within 2-3 weeks before 11.2 cycle opens.
>
Hmmm :-)

11.2 seems opened. Is it right time to push?

Thank you in advance,
    Den