git/list[1] front-page[2] threads[3] people[4] search[5] about
 

Re: [PATCH 07/23] expire_reflog(): use a lock_file for rewriting the reflog file

From
Junio C Hamano <gitster@pobox.com>
Date
Dec 9, 2014, 18:47 UTC
Message-ID
<xmqqfvcomzib.fsf@gitster.dls.corp.google.com>
In-Reply-To
<54857871.5090805@alum.mit.edu>
Michael Haggerty <mhagger@alum.mit.edu> writes:
Show 13 quoted lines
> This isn't documented very well. I thought I saw a comment somewhere in
> the code that stated it explicitly, but I can't find it now. In any
> case, my understanding of the locking protocol for reflogs is:
>
>     The reflog for "$refname", which is stored at
>     "$GIT_DIR/logs/$refname", is locked by holding
>     "$GIT_DIR/refs/$refname.lock", *even if the corresponding
>     reference is packed*.
>
> This implies that readers, who don't pay attention to locks, have to be
> prepared for the possibility that the reflog is in the middle of an
> update and that the last line is incomplete. This is handled by
> show_one_reflog_ent(), which discards incomplete lines.

Interesting, as I think I saw Peff did something around that area recently.

I have some more thought around the "transaction" in general, but it will be in a separate message.

Thanks.
Previous: Michael HaggertyNext: Jeff King
Message 19 of 63 in “Add reflog_expire() to the references API”
  1. 00/23 Add reflog_expire() to the references APIMichael Haggerty, Dec 4, 2014
  2. 01/23 refs.c: make ref_transaction_create a wrapper for ref_transaction_updateMichael Haggerty, Dec 4, 2014
  3. 02/23 refs.c: make ref_transaction_delete a wrapper for ref_transaction_updateMichael Haggerty, Dec 4, 2014
  4. 03/23 refs.c: add a function to append a reflog entry to a fdMichael Haggerty, Dec 4, 2014
  5. 04/23 expire_reflog(): remove unused parameterMichael Haggerty, Dec 4, 2014
  6. Jonathan NiederDec 4, 2014
  7. Jonathan NiederDec 4, 2014
  8. Michael HaggertyDec 5, 2014
  9. 05/23 expire_reflog(): rename "ref" parameter to "refname"Michael Haggerty, Dec 4, 2014
  10. Jonathan NiederDec 4, 2014
  11. 06/23 expire_reflog(): exit early if the reference has no reflogMichael Haggerty, Dec 4, 2014
  12. Jonathan NiederDec 4, 2014
  13. Jonathan NiederDec 4, 2014
  14. Michael HaggertyDec 5, 2014
  15. 07/23 expire_reflog(): use a lock_file for rewriting the reflog fileMichael Haggerty, Dec 4, 2014
  16. Jonathan NiederDec 5, 2014
  17. Stefan BellerDec 5, 2014
  18. Michael HaggertyDec 8, 2014
  19. Junio C HamanoDec 9, 2014
  20. Jeff KingDec 9, 2014
  21. Stefan BellerDec 5, 2014
  22. Junio C HamanoDec 5, 2014
  23. Stefan BellerDec 5, 2014
  24. Junio C HamanoDec 5, 2014
  25. Michael HaggertyDec 8, 2014
  26. ronnie sahlbergDec 5, 2014
  27. Michael HaggertyDec 8, 2014
  28. 08/23 Extract function should_expire_reflog_ent()Michael Haggerty, Dec 4, 2014
  29. Stefan BellerDec 8, 2014
  30. 09/23 expire_reflog(): extract two policy-related functionsMichael Haggerty, Dec 4, 2014
  31. Stefan BellerDec 5, 2014
  32. 10/23 expire_reflog(): add a "flags" argumentMichael Haggerty, Dec 4, 2014
  33. Stefan BellerDec 8, 2014
  34. 11/23 expire_reflog(): move dry_run to flags argumentMichael Haggerty, Dec 4, 2014
  35. Stefan BellerDec 8, 2014
  36. 12/23 expire_reflog(): move updateref to flags argumentMichael Haggerty, Dec 4, 2014
  37. Stefan BellerDec 8, 2014
  38. 13/23 Rename expire_reflog_cb to expire_reflog_policy_cbMichael Haggerty, Dec 4, 2014
  39. Stefan BellerDec 8, 2014
  40. 14/23 struct expire_reflog_cb: a new callback data typeMichael Haggerty, Dec 4, 2014
  41. Stefan BellerDec 8, 2014
  42. 15/23 expire_reflog(): pass flags through to expire_reflog_ent()Michael Haggerty, Dec 4, 2014
  43. Stefan BellerDec 8, 2014
  44. 16/23 expire_reflog(): move verbose to flags argumentMichael Haggerty, Dec 4, 2014
  45. Stefan BellerDec 8, 2014
  46. 17/23 expire_reflog(): move rewrite to flags argumentMichael Haggerty, Dec 4, 2014
  47. Stefan BellerDec 8, 2014
  48. 18/23 Move newlog and last_kept_sha1 to "struct expire_reflog_cb"Michael Haggerty, Dec 4, 2014
  49. Stefan BellerDec 8, 2014
  50. 19/23 expire_reflog(): treat the policy callback data as opaqueMichael Haggerty, Dec 4, 2014
  51. Stefan BellerDec 8, 2014
  52. 20/23 reflog_expire(): new function in the reference APIMichael Haggerty, Dec 4, 2014
  53. Stefan BellerDec 8, 2014
  54. Michael HaggertyDec 12, 2014
  55. Jeff KingDec 12, 2014
  56. Junio C HamanoDec 12, 2014
  57. 21/23 refs.c: remove unlock_ref/close_ref/commit_ref from the refs apiMichael Haggerty, Dec 4, 2014
  58. 22/23 lock_any_ref_for_update(): inline functionMichael Haggerty, Dec 4, 2014
  59. Stefan BellerDec 8, 2014
  60. Michael HaggertyDec 11, 2014
  61. 23/23 refs.c: don't expose the internal struct ref_lock in the header fileMichael Haggerty, Dec 4, 2014
  62. Junio C HamanoDec 4, 2014
  63. Stefan BellerDec 5, 2014

Read the whole thread, see it on lore, or plain text.

$ cat FOOTERMessages come from the public archive at lore.kernel.org/git, fetched every hour. The front page is chosen and written each morning by an AI editor and can be wrong; the threads themselves are the record. About and API. For agents: an MCP server at https://gitlist.dev/mcp, and any thread, story or person page as Markdown by adding .md to its URL (or sending Accept: text/markdown). Details in /llms.txt.