[Qemu-devel] [PATCH v5 00/11] qcow2: Fix image repairing

[Max Reitz]

As can be seen in the final patch of this series, there are certain
cases where the current repair implementation of qcow2 actually damages
the image further because it allocates new clusters for the refcount
structure which overlap with existing but according to the on-disk
refcounts (which are assumed to be wrong to begin with) unallocated
clusters.

This series fixes this by completely recreating the refcount structure
based on the in-memory information calculated during the check operation
if the possibility of damaging the image while repairing the refcount
structures in-place exists.


v5:
- Added patch 1 which adds two helper variables to BDRVQcowState
  reflecting the number of entries per refcount block;
  in contrast to v4, we don't need to clamp the refcount order against
  sub-byte widths, because sub-byte widths are actually correct (that
  means, I dropped the MAX() around refcount_order - 3)
- Patch 8 (prev. 7):
  - Use these new variables [Benoît]
  - Use a struct for rt_offset_and_clusters [Benoît]


git-backport-diff against v4:

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

001/11:[down] 'qcow2: Calculate refcount block entry count'
002/11:[----] [--] 'qcow2: Fix leaks in dirty images'
003/11:[----] [--] 'qcow2: Split qcow2_check_refcounts()'
004/11:[----] [--] 'qcow2: Pull check_refblocks() up'
005/11:[----] [--] 'qcow2: Reuse refcount table in calculate_refcounts()'
006/11:[----] [--] 'qcow2: Fix refcount blocks beyond image end'
007/11:[----] [--] 'qcow2: Do not perform potentially damaging repairs'
008/11:[0025] [FC] 'qcow2: Rebuild refcount structure during check'
009/11:[----] [--] 'qcow2: Clean up after refcount rebuild'
010/11:[----] [--] 'iotests: Fix test outputs'
011/11:[----] [-C] 'iotests: Add test for potentially damaging repairs'


Max Reitz (11):
  qcow2: Calculate refcount block entry count
  qcow2: Fix leaks in dirty images
  qcow2: Split qcow2_check_refcounts()
  qcow2: Pull check_refblocks() up
  qcow2: Reuse refcount table in calculate_refcounts()
  qcow2: Fix refcount blocks beyond image end
  qcow2: Do not perform potentially damaging repairs
  qcow2: Rebuild refcount structure during check
  qcow2: Clean up after refcount rebuild
  iotests: Fix test outputs
  iotests: Add test for potentially damaging repairs

 block/qcow2-refcount.c     | 677 ++++++++++++++++++++++++++++++++-------------
 block/qcow2.c              |   4 +-
 block/qcow2.h              |   2 +
 tests/qemu-iotests/039.out |  10 +-
 tests/qemu-iotests/060.out |  10 +-
 tests/qemu-iotests/061.out |  18 +-
 tests/qemu-iotests/104     | 141 ++++++++++
 tests/qemu-iotests/104.out | 110 ++++++++
 tests/qemu-iotests/group   |   1 +
 9 files changed, 767 insertions(+), 206 deletions(-)
 create mode 100755 tests/qemu-iotests/104
 create mode 100644 tests/qemu-iotests/104.out

-- 
2.1.0