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Re: [PATCH v2 13/15] dir-iterator: option to iterate dirs in pre-order

From
PKPlato Kiorpelidis <kioplato@gmail.com>
Date
May 18, 2022, 17:40 UTC
Message-ID
<20220518173947.4qabalu6mjmzumen@compass>
In-Reply-To
<88421b18-0fa0-236a-b74b-c5ee3ef53279@gmail.com>
On 22/05/10 02:07PM, Phillip Wood wrote:
Show 33 quoted lines
> Hi Plato
> 
> On 09/05/2022 18:51, Plato Kiorpelidis wrote:
> > Introduce a new option to dir-iterator, using dir_iterator_begin()
> > flags parameter, allowing to control whether or not directories will
> > be exposed before their contents. In essence, pre-order traversal over
> > file system entries that are directories.
> > 
> > This changes the default behavior of the dir-iterator API. Instead
> > of iterating directories before doing so over their contents, the new
> > default behavior does not expose directories at all. Iteration is still
> > performed, however, within directories, iterating over any other entry.
> > Only directory paths are ignored.
> > 
> > To iterate over directories in pre-order, reproducing the previous
> > default behavior, enable the new flag DIR_ITERATOR_DIRS_BEFORE in the
> > flags parameter of dir_iterator_begin():
> >    * ignore directories by not setting DIR_ITERATOR_DIRS_BEFORE
> >    * iterate directories pre-order by enabling DIR_ITERATOR_DIRS_BEFORE
> > 
> > Adjust existing callers, in refs/files-backend.c and builtin/clone.c
> > to enable DIR_ITERATOR_DIRS_BEFORE since these callers require iteration
> > over directories before doing so over their contents.
> > 
> > Update t/t0066-dir-iterator.sh and t/helper/test-dir-iterator.c to test
> > the new iteration scheme, which is the new default behavior, and the new
> > flag DIR_ITERATOR_DIRS_BEFORE which reproduces the old default behavior.
> 
> It's great that you've split this change out from the next patch. I had not
> realized when I looked at the last round that all the existing callers
> require pre-order traversal. Given that is the case I'm finding it hard to
> see how changing the default behavior to one that no caller is using is an
> improvement.

Changing the default behavior is required to simplify entry.c remove_subtree(). I would have kept dir-iterator's default iteration scheme as is, but how are we going to deal with remove_subtree()? remove_subtree() requires iterating dirs after their contents. We need to find a flag encoding that is a good design choice and serves both existing and remove_subtree(), without limiting future dir-iterator customers.

This encoding of flags was heavily discussed in the patch series that my work is based on[1], most notably here[2].

[1]: https://lore.kernel.org/git/1493226219-33423-1-git-send-email-bnmvco@gmail.com/ [2]: https://public-inbox.org/git/1751d788-d1f1-1c97-b33b-f53dab78ef86@alum.mit.edu/

Thanks, Plato

Previous: Phillip WoodNext: rsbecker@nexbridge.com
Message 24 of 31 in “[GSoC] iterate dirs before or after their contents”
  1. 00/15 [GSoC] iterate dirs before or after their contentsPlato Kiorpelidis, May 9, 2022
  2. 01/15 t0066: refactor dir-iterator testsPlato Kiorpelidis, May 9, 2022
  3. 02/15 t0066: remove dependency between unrelated testsPlato Kiorpelidis, May 9, 2022
  4. 03/15 t0066: shorter expected and actual output file namesPlato Kiorpelidis, May 9, 2022
  5. 04/15 test-dir-iterator: consistently return EXIT_FAILURE or EXIT_SUCCESSPlato Kiorpelidis, May 9, 2022
  6. Junio C HamanoMay 9, 2022
  7. Plato KiorpelidisMay 18, 2022
  8. Junio C HamanoMay 18, 2022
  9. 05/15 test-dir-iterator: print EACCES and ELOOP errno set by dir_iteratorPlato Kiorpelidis, May 9, 2022
  10. 06/15 test-dir-iterator: print errno name set by dir_iterator_advancePlato Kiorpelidis, May 9, 2022
  11. 09/15 t0066: rename test directoriesPlato Kiorpelidis, May 9, 2022
  12. 08/15 t0066: reorder tests from simple to more complexPlato Kiorpelidis, May 9, 2022
  13. 07/15 t0066: better test coverage for dir-iteratorPlato Kiorpelidis, May 9, 2022
  14. 10/15 dir-iterator: refactor dir_iterator_advance()Plato Kiorpelidis, May 9, 2022
  15. Junio C HamanoMay 9, 2022
  16. Plato KiorpelidisMay 18, 2022
  17. Phillip WoodMay 10, 2022
  18. 11/15 dir-iterator: open root dir in dir_iterator_begin()Plato Kiorpelidis, May 9, 2022
  19. 12/15 t0066: rename subtest descriptionsPlato Kiorpelidis, May 9, 2022
  20. 15/15 entry.c: use dir-iterator to avoid explicit dir traversalPlato Kiorpelidis, May 9, 2022
  21. Phillip WoodMay 10, 2022
  22. 13/15 dir-iterator: option to iterate dirs in pre-orderPlato Kiorpelidis, May 9, 2022
  23. Phillip WoodMay 10, 2022
  24. Plato KiorpelidisMay 18, 2022
  25. rsbecker@nexbridge.comMay 18, 2022
  26. Junio C HamanoMay 18, 2022
  27. rsbecker@nexbridge.comMay 18, 2022
  28. 14/15 dir-iterator: option to iterate dirs in post-orderPlato Kiorpelidis, May 9, 2022
  29. Phillip WoodMay 10, 2022
  30. Junio C HamanoMay 10, 2022
  31. Plato KiorpelidisMay 20, 2022

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