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

["Denis V. Lunev" <den@openvz.org>]

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
-- 
2.53.0