Re: [PATCH hci-dev 0/6] block, scsi-disk: honour a size change on child replacement #VSTOR-130961

[Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>]

On 11/4/26 3:45 PM, Denis V. Lunev wrote:
> This is the QEMU side of VSTOR-130961. disk_replace puts the real image
> under the device with vz-x-blockdev-replace, which ends up in
> bdrv_replace_child_bs(), and that swaps the node a BdrvChild points to
> without telling the parent anything about it. If the placeholder had a
> different size, the device never learns about it.
> 
> scsi-disk is the one really hurt by this. check_lba_range() validates
> every guest request against SCSIDevice.max_lba, filled in by
> scsi_disk_reset() and updated only by the READ CAPACITY(10) and (16)
> handlers, which a migrated guest never reissues. Every request past the
> end of the old node is refused with ILLEGAL REQUEST / LOGICAL BLOCK
> ADDRESS OUT OF RANGE for the whole life of the device, which Linux turns
> into EREMOTEIO. It is silent on the host: no BLOCK_IO_ERROR event, and
> io-status stays 'ok'. This is ASUP-3466, ACSSP-965 and ASUP-3678.
> 
> Upstream merged the series as 8b267376df8..28fafb3147f, from
> <20260812121500.1034178-1-den@openvz.org>. Differences:
> 
> - Patch 1 is Fiona's 08736e7584c, which exports
>   bdrv_co_parent_cb_resize(); our tree predates it.
> - Patch 2: our bdrv_replace_child_bs() only adds its steps to the
>   caller's transaction, under the graph write lock, so the length check
>   and the notification move to a .commit action. Reading both lengths
>   there also covers Kevin's review remark that the upstream version reads
>   the old length before draining. His other remark, notifying only the
>   replaced BdrvChild, will come with the upstream follow-up.
> - Patch 6 is new: it covers vz-x-blockdev-replace, the path disk_replace
>   takes, which the upstream test does not.
> 
> Tested on dev-cl04: without patches 1-3 the qtest fails at both the
> qom-set and the vz-x-blockdev-replace step with ILLEGAL REQUEST; with
> them it passes. qos-test quick passes; iotests -g quick for qcow2 and raw
> give the same result with and without the series.
> 
> Denis V. Lunev (5):
>   block: notify the parent when a replaced child has a different size
>     #VSTOR-130961
>   scsi-disk: refresh the cached capacity from the resize callback
>     #VSTOR-130961
>   tests/qtest/virtio-scsi: cover a replacement that changes the size
>     #VSTOR-130961
>   tests/qemu-iotests/qom-set-drive: replace with a differently sized
>     node #VSTOR-130961
>   tests/qtest/virtio-scsi: cover vz-x-blockdev-replace changing the size
>     #VSTOR-130961
> 
> Fiona Ebner (1):
>   block: make bdrv_co_parent_cb_resize() a proper IO API function
>     #VSTOR-130961
> 
>  block.c                                    | 27 +++++++
>  block/io.c                                 |  9 +--
>  hw/scsi/scsi-disk.c                        | 16 +++-
>  include/block/block_int-io.h               |  9 +++
>  tests/qemu-iotests/tests/qom-set-drive     | 14 +++-
>  tests/qemu-iotests/tests/qom-set-drive.out |  2 +
>  tests/qtest/virtio-scsi-test.c             | 85 ++++++++++++++++++++++
>  7 files changed, 149 insertions(+), 13 deletions(-)
> 
> 
> base-commit: 2ac36f063996449791d0db63fc2c9a67864631d1

Ack
Applied to hci-dev