[Qemu-devel] [PATCH v3 00/10] 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.

v3:
- Reorganised patch 2 and 3 for a smaller diff: [Benoît]
  - Squashed 3 into 2 (makes patch 2 longer but avoids needless diff
    blob resulting from the beginning of qcow2_check_refcounts())
  - check_refblocks() is below calculate_refcounts() after patch 2, this
    minimizes diff for patch 2; patch 3 pulls it up again
  - Made a small functional difference from patch 2 into an own patch
    (patch 4)
  - Patch 2 is now mostly only code movement with additionally adding
    dereferenciation to refcount_table and nb_clusters in
    check_refblocks() and calculate_refcounts(), because those
    parameters are (and must be) given by reference there; the same
    applies to highest_cluster in compare_refcounts()
- Patch 6 (prev. 5): Removed a superfluous empty line and rebased on the
  new patch 2 which no longer changes the g_realloc() (or g_renew() by
  now) call to g_try_realloc() because this call is removed in this
  patch anyway
- Patch 10 (prev. 9): Renamed test file from 101 to 104


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

001/10:[----] [--] 'qcow2: Fix leaks in dirty images'
002/10:[down] 'qcow2: Split qcow2_check_refcounts()'
003/10:[down] 'qcow2: Pull check_refblocks() up'
004/10:[down] 'qcow2: Reuse refcount table in calculate_refcounts()'
005/10:[----] [--] 'qcow2: Fix refcount blocks beyond image end'
006/10:[0013] [FC] 'qcow2: Do not perform potentially damaging repairs'
007/10:[----] [--] 'qcow2: Rebuild refcount structure during check'
008/10:[----] [--] 'qcow2: Clean up after refcount rebuild'
009/10:[----] [--] 'iotests: Fix test outputs'
010/10:[0004] [FC] 'iotests: Add test for potentially damaging repairs'


Max Reitz (10):
  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     | 644 +++++++++++++++++++++++++++++++--------------
 block/qcow2.c              |   2 +-
 tests/qemu-iotests/039.out |  10 +-
 tests/qemu-iotests/060.out |  10 +-
 tests/qemu-iotests/061.out |  18 +-
 tests/qemu-iotests/104     |  98 +++++++
 tests/qemu-iotests/104.out |  46 ++++
 tests/qemu-iotests/group   |   1 +
 8 files changed, 623 insertions(+), 206 deletions(-)
 create mode 100755 tests/qemu-iotests/104
 create mode 100644 tests/qemu-iotests/104.out

-- 
2.0.4