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


From: Max Reitz
Subject: Re: [Qemu-devel] [PATCH v5 00/11] qcow2: Fix image repairing
Date: Wed, 08 Oct 2014 21:25:31 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.2

On 29.08.2014 23:40, Max Reitz wrote:
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


Ping. Patch 8 still requires a review. I know it's probably the hardest patch of the series, but well...

Max



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