[Qemu-devel] [PATCH v7 0/8] block: Mirror discarded sectors

[Fam Zheng <famz@redhat.com>]

v7: Fix the lost assignment of s->unmap.

v6: Fix pnum in bdrv_get_block_status_above. [Paolo]

v5: Rewrite patch 1.
    Address Eric's comments on patch 3.
    Add Eric's rev-by to patches 2 & 4.
    Check BDRV_BLOCK_DATA in patch 3. [Paolo]

This fixes the mirror assert failure reported by wangxiaolong:

https://lists.gnu.org/archive/html/qemu-devel/2015-04/msg04458.html

The direct cause is that hbitmap code couldn't handle unset of bits *after*
iterator's current position. We could fix that, but the bdrv_reset_dirty() call
is more questionable:

Before, if guest discarded some sectors during migration, it could see
different data after moving to dest side, depending on block backends of the
src and the dest. This is IMO worse than mirroring the actual reading as done
in this series, because we don't know what the guest is doing.

For example if a guest first issues WRITE SAME to wipe out the area then issues
UNMAP to discard it, just to get rid of some sensitive data completely, we may
miss both operations and leave stale data on dest image.


Fam Zheng (8):
  block: Add bdrv_get_block_status_above
  qmp: Add optional bool "unmap" to drive-mirror
  mirror: Do zero write on target if sectors not allocated
  block: Fix dirty bitmap in bdrv_co_discard
  block: Remove bdrv_reset_dirty
  qemu-iotests: Make block job methods common
  qemu-iotests: Add test case for mirror with unmap
  iotests: Use event_wait in wait_ready

 block.c                       | 12 --------
 block/io.c                    | 60 ++++++++++++++++++++++++++++++---------
 block/mirror.c                | 28 +++++++++++++++---
 blockdev.c                    |  5 ++++
 hmp.c                         |  2 +-
 include/block/block.h         |  4 +++
 include/block/block_int.h     |  4 +--
 qapi/block-core.json          |  8 +++++-
 qmp-commands.hx               |  3 ++
 tests/qemu-iotests/041        | 66 ++++++++++---------------------------------
 tests/qemu-iotests/132        | 59 ++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/132.out    |  5 ++++
 tests/qemu-iotests/group      |  1 +
 tests/qemu-iotests/iotests.py | 23 +++++++++++++++
 14 files changed, 196 insertions(+), 84 deletions(-)
 create mode 100644 tests/qemu-iotests/132
 create mode 100644 tests/qemu-iotests/132.out

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2.4.2