[Qemu-block] [PATCH v2 0/4] qemu-img: Fix preallocation with -S 0 for convert

[Max Reitz]

Using -S 0 is supposed to allocate everything in the output image; or at
least it is supposed to always explicitly write zeros even if the area
in question is known to only contain zeros. That doesn't always work
right now, so this series fixes it (patch 1, to be specific).

I only noticed after I had written the test added by patch 4 that we
already had an -S 0 test case which is included in the iotest 122.
However, the test added here works for all image formats and is maybe
more of a direct test (instead of querying the format whether it thinks
it allocated all of the data we directly ask du whether everything has
been allocated) so maybe it reflects better what users expect -S 0 to
do. Maybe.

Patches 2 and 3 are required for the test. I could have written the test
without doing a convert with null-co as the source, but that would have
been boring, so I did not.

If you want to argue that in light of the existence of test 122 the new
test added here is unnecessary and we therefore do not need patches 2, 3
and 4, please go ahead. I won't put up too much of a fight.


**
A note about dependencies: When applied to Kevin's block branch, patch 4
will conflict in the qemu-iotests/group file. I had to base it on master
master because right now about a fourth of all iotests break for qcow2
(for me, at least) on the block branch.
**


v2:
- Patch 1: The additional state BLK_ZERO_DATA actually made things more
  complicated than they are without. Drop it. [Kevin]
- Patch 2: Made reading zeros optional and used "zeroes" throughout the
  patch so the spelling confirms with the "detect-zeroes" option. [Eric]
  (I personally like "zeros" better so it differs from the 3rd p. sg. of
  "to zero".)
- Patch 3: If read-zeroes is false, we shouldn't indicate the BDS to
  only return zero(e)s when read.
- Patch 4: Moved test to 150, and now we need to set the read-zeroes
  option to true.


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

001/4:[0025] [FC] 'qemu-img: Fix preallocation with -S 0 for convert'
002/4:[down] 'block/null-{co,aio}: Allow reading zeroes'
       ^^^^ Actually just a reworded commit title, but there are
            functional changes here
003/4:[0007] [FC] 'block/null-{co,aio}: Implement get_block_status()'
004/4:[0008] [FC] 'iotests: Test qemu-img convert -S 0 behavior'


Max Reitz (4):
  qemu-img: Fix preallocation with -S 0 for convert
  block/null-{co,aio}: Allow reading zeroes
  block/null-{co,aio}: Implement get_block_status()
  iotests: Test qemu-img convert -S 0 behavior

 block/null.c               |  42 ++++++++++++++++++
 qemu-img.c                 |  26 ++++++-----
 tests/qemu-iotests/122.out |   6 +--
 tests/qemu-iotests/150     | 105 +++++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/150.out |  14 ++++++
 tests/qemu-iotests/group   |   1 +
 6 files changed, 179 insertions(+), 15 deletions(-)
 create mode 100755 tests/qemu-iotests/150
 create mode 100644 tests/qemu-iotests/150.out

-- 
2.7.4