[v7,0/4] virtio/block: handle zoned backing devices

Message

Dmitry Fomichev Sept. 7, 2019, 10:38 p.m. UTC

Currently, attaching zoned block devices (i.e., storage devices
compliant to ZAC/ZBC standards) using several virtio methods doesn't
work properly as zoned devices appear as regular block devices at the
guest. This may cause unexpected i/o errors and, potentially, some
data corruption.

To be more precise, attaching a zoned device via virtio-pci-blk,
virtio-scsi-pci/scsi-disk or virtio-scsi-pci/scsi-hd demonstrates the
above behavior. The virtio-scsi-pci/scsi-block method works with a
recent patch. The virtio-scsi-pci/scsi-generic method also appears to
handle zoned devices without problems.

This patch set adds code to check if the backing device that is being
opened is a zoned Host Managed device. If this is the case, the patch
prohibits attaching such device for all use cases lacking proper
zoned support.

Host Aware zoned block devices are designed to work as regular block
devices at a guest system that does not support ZBD. Therefore, this
patch set doesn't prohibit attachment of Host Aware devices.

Considering that there is still a couple of different working ways
to attach a ZBD, this patch set provides a reasonable short-term
solution for this problem.

ZBD support for virtio-scsi-pci/scsi-disk and virtio-scsi-pci/scsi-hd
does not seem as necessary. Users will be expected to attach zoned
block devices via virtio-scsi-pci/scsi-block instead.

This patch set contains some Linux-specific code. This code is
necessary to obtain Zoned Block Device model value from Linux sysfs.

History:

v1 -> v2:
- rework code to be permission-based
- always allow Host Aware devices to be attached
- add fix for Host Aware attachments aka RCAP output snoop

v2 -> v3:
- drop the patch for RCAP output snoop - merged separately

v3 -> v4:
- rebase to the current code

v4 -> v5:
- avoid checkpatch warning

v5 -> v6:
- address review comments from Stefan Hajnoczi

v6 -> v7:
- address review comment from Stefano Garzarella
  * fix BLK_PERM_ALL mask
  * add BLK_PERM_SUPPORT_HM_ZONED permission to QAPI schema
  * add a text name for BLK_PERM_SUPPORT_HM_ZONED permission

Dmitry Fomichev (4):
  block: Add zoned device model property
  raw: Recognize zoned backing devices
  block/ide/scsi: Set BLK_PERM_SUPPORT_HM_ZONED
  raw: Don't open ZBDs if backend can't handle them

 block.c                   | 37 +++++++++++-----
 block/file-posix.c        | 89 +++++++++++++++++++++++++++++++++------
 block/io.c                |  5 +++
 hw/block/block.c          |  6 ++-
 hw/block/fdc.c            |  5 ++-
 hw/block/nvme.c           |  2 +-
 hw/block/virtio-blk.c     |  2 +-
 hw/block/xen-block.c      |  2 +-
 hw/ide/qdev.c             |  2 +-
 hw/scsi/scsi-disk.c       | 13 +++---
 hw/scsi/scsi-generic.c    |  2 +-
 hw/usb/dev-storage.c      |  2 +-
 include/block/block.h     | 21 ++++++++-
 include/block/block_int.h |  3 ++
 include/hw/block/block.h  |  3 +-
 qapi/block-core.json      |  5 ++-
 16 files changed, 157 insertions(+), 42 deletions(-)