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Re: [PATCH v2 07/19] make sure partially read index is not changed

From
Thomas Gummerer <t.gummerer@gmail.com>
Date
Jul 17, 2013, 12:56 UTC
Message-ID
<87li55s5t7.fsf@gmail.com>
In-Reply-To
<CACsJy8A61gfWsMecJha-3GoWXFT0bb3zAMJ5YT-a=vs=_3WghQ@mail.gmail.com>
Duy Nguyen <pclouds@gmail.com> writes:
Show 17 quoted lines
> On Sat, Jul 13, 2013 at 12:26 AM, Thomas Gummerer <t.gummerer@gmail.com> wrote:
>> A partially read index file currently cannot be written to disk.  Make
>> sure that never happens, by erroring out when a caller tries to change a
>> partially read index.  The caller is responsible for reading the whole
>> index when it's trying to change it later.
>>
>> Forcing the caller to load the right part of the index file instead of
>> re-reading it when changing it, gives a bit of a performance advantage,
>> by avoiding to read parts of the index twice.
>
> If you want to be strict about this, put similar check in
> fill_stat_cache_info (used by entry.c), cache_tree_invalidate_path and
> convert the code base (maybe except unpack-trees.c, just put a check
> in the beginning of unpack_trees()) to use wrapper function to change
> ce_flags (some still update ce_flags directly, grep them). Some flags
> are in memory only and should be allowed to change in partial index,
> some are to be written on disk and should not be allowed.

I'm not sure anymore we should even be this strict. A partially read index will never make it to the disk, because write_index checks if it's fully read. I think the check in write_index and read_index_filtered would be enough.

The only disadvantage would be that it takes a little longer to catch an error that should never happen in the first place. If it occurs the user has bigger problems than the time that not having caught the error earlier adds to the execution of the command.

I also don't see a clean way to add the check to fill_stat_cache_info or cache_tree_invalidate_path, because we would need an additional parameter for the index_state, or at least for index_state->filter_opts, which doesn't do anything but check if the index is only partially loaded.

Previous: Duy NguyenNext: Thomas Gummerer
Message 13 of 51 in “Index-v5”
  1. 00/19 Index-v5Thomas Gummerer, Jul 12, 2013
  2. 01/19 t2104: Don't fail for index versions other than [23]Thomas Gummerer, Jul 12, 2013
  3. 02/19 read-cache: split index file version specific functionalityThomas Gummerer, Jul 12, 2013
  4. 03/19 read-cache: move index v2 specific functions to their own fileThomas Gummerer, Jul 12, 2013
  5. Duy NguyenJul 14, 2013
  6. Thomas GummererJul 19, 2013
  7. 04/19 read-cache: Re-read index if index file changedThomas Gummerer, Jul 12, 2013
  8. 05/19 Add documentation for the index apiThomas Gummerer, Jul 12, 2013
  9. 06/19 read-cache: add index reading apiThomas Gummerer, Jul 12, 2013
  10. Duy NguyenJul 14, 2013
  11. 07/19 make sure partially read index is not changedThomas Gummerer, Jul 12, 2013
  12. Duy NguyenJul 14, 2013
  13. Thomas GummererJul 17, 2013
  14. 08/19 grep.c: Use index apiThomas Gummerer, Jul 12, 2013
  15. Duy NguyenJul 14, 2013
  16. Thomas GummererJul 15, 2013
  17. 09/19 ls-files.c: use index apiThomas Gummerer, Jul 12, 2013
  18. Duy NguyenJul 14, 2013
  19. Thomas GummererJul 17, 2013
  20. 10/19 documentation: add documentation of the index-v5 file formatThomas Gummerer, Jul 12, 2013
  21. Duy NguyenJul 14, 2013
  22. Thomas GummererJul 17, 2013
  23. Duy NguyenAug 4, 2013
  24. Thomas GummererAug 4, 2013
  25. 11/19 read-cache: make in-memory format aware of stat_crcThomas Gummerer, Jul 12, 2013
  26. 12/19 read-cache: read index-v5Thomas Gummerer, Jul 12, 2013
  27. Duy NguyenJul 14, 2013
  28. Thomas GummererAug 7, 2013
  29. Duy NguyenJul 15, 2013
  30. Thomas GummererJul 17, 2013
  31. Duy NguyenAug 8, 2013
  32. Thomas GummererAug 8, 2013
  33. Thomas GummererAug 9, 2013
  34. Thomas GummererAug 7, 2013
  35. Duy NguyenAug 8, 2013
  36. 13/19 read-cache: read resolve-undo dataThomas Gummerer, Jul 12, 2013
  37. 14/19 read-cache: read cache-tree in index-v5Thomas Gummerer, Jul 12, 2013
  38. 15/19 read-cache: write index-v5Thomas Gummerer, Jul 12, 2013
  39. 16/19 read-cache: write index-v5 cache-tree dataThomas Gummerer, Jul 12, 2013
  40. 17/19 read-cache: write resolve-undo data for index-v5Thomas Gummerer, Jul 12, 2013
  41. 18/19 update-index.c: rewrite index when index-version is givenThomas Gummerer, Jul 12, 2013
  42. 19/19 p0003-index.sh: add perf test for the index formatsThomas Gummerer, Jul 12, 2013
  43. Duy NguyenJul 14, 2013
  44. Thomas GummererJul 15, 2013
  45. Duy NguyenJul 15, 2013
  46. Thomas GummererJul 17, 2013
  47. Junio C HamanoJul 17, 2013
  48. Thomas GummererJul 19, 2013
  49. Junio C HamanoJul 19, 2013
  50. Ramsay JonesJul 16, 2013
  51. Thomas GummererJul 17, 2013

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