[Qemu-devel] [PATCH v3 0/3] block: Fix is_allocated() for truncated images

[Max Reitz]

Patch 2:
The bdrv_is_allocated() functions may return a number of zero sectors
e.g. if a sector beyond the image end has been queried. Respect this
case in qemu-io's map implementation so it doesn't run into an infinite
loop (https://bugs.launchpad.net/qemu/+bug/1356969).

Patch 1:
In that bug report, bdrv_co_get_block_status() fell through to the
underlying file to get additional information (whether the sectors are
zeroed). However, the offset reported by the image format (qcow2) was
beyond the size of the underlying file and so this second query returned
only zero clusters which replaced the actual number of sectors queried
in the "formatted" (on qcow2 level) image. This replacement is generally
fine because it allows bdrv_co_get_block_status() to follow the
granularity (holes and non-holes) of the underlying file, but not if
only zero clusters could be queried (which indicates a request beyond
the image end).
This patch makes bdrv_co_get_block_status() respect the underlying
file's EOF and act accordingly.

Patch 3 adds a test for patch 1; a test which depends on patch 2 is
included in v3 of my series "raw-posix: Fix raw_co_get_block_status()".


v3:
- Patch 1:
  - %s/backing_pnum/file_pnum/ [Kevin]
  - ret |= BDRV_BLOCK_ZERO instead of ret = BDRV_BLOCK_ZERO (and modify
    the comment accordingly) [Kevin]
- Patch 3: With the latter change in patch 1, the sectors are now marked
  as allocated instead of not allocated; the qemu-img map output however
  stays the same (and therefore doesn't require the filter from the
  qemu-img/QMP commit series), because the sectors are marked as zero
  and qemu-img only outputs non-zero data clusters.


git-backport-diff against v2:

Key:
[----] : patches are identical
[####] : number of functional differences between upstream/downstream patch
[down] : patch is downstream-only
The flags [FC] indicate (F)unctional and (C)ontextual differences, respectively

001/3:[0015] [FC] 'block: Respect underlying file's EOF'
002/3:[----] [--] 'qemu-io: Respect early image end for map'
003/3:[0002] [FC] 'iotests: Add test for map commands'


Max Reitz (3):
  block: Respect underlying file's EOF
  qemu-io: Respect early image end for map
  iotests: Add test for map commands

 block.c                    | 15 +++++++++--
 qemu-io-cmds.c             |  5 +++-
 tests/qemu-iotests/102     | 64 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/102.out | 10 ++++++++
 tests/qemu-iotests/group   |  1 +
 5 files changed, 92 insertions(+), 3 deletions(-)
 create mode 100755 tests/qemu-iotests/102
 create mode 100644 tests/qemu-iotests/102.out

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1.9.3