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Re: [PATCH v10 18/44] branch.c: use ref transaction for all ref updates

From
Ronnie Sahlberg <sahlberg@google.com>
Date
May 19, 2014, 17:22 UTC
Message-ID
<CAL=YDWkSmRbgjEqS2EytQOcUqs4KKCEv7gOCmTxepPBd5dOfAQ@mail.gmail.com>
In-Reply-To
<53776512.7080504@alum.mit.edu>
On Sat, May 17, 2014 at 6:33 AM, Michael Haggerty <mhagger@alum.mit.edu> wrote:
Show 15 quoted lines
> On 05/16/2014 07:37 PM, Ronnie Sahlberg wrote:
>> Change create_branch to use a ref transaction when creating the new branch.
>> ref_transaction_create will check that the ref does not already exist and fail
>> otherwise meaning that we no longer need to keep a lock on the ref during the
>> setup_tracking. This simplifies the code since we can now do the transaction
>> in one single step.
>>
>> If the forcing flag is false then use ref_transaction_create since this will
>> fail if the ref already exist. Otherwise use ref_transaction_update.
>
> s/exist/exists/
>
> And the references to ref_transaction_create() in the commit message are
> obsolete.
>
Thanks. Fixed typo and deleted obsolete text.
Show 76 quoted lines
>>
>> This also fixes a race condition in the old code where two concurrent
>> create_branch could race since the lock_any_ref_for_update/write_ref_sha1
>> did not protect against the ref already existing. I.e. one thread could end up
>> overwriting a branch even if the forcing flag is false.
>>
>> Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
>> Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
>> ---
>>  branch.c | 29 +++++++++++++++--------------
>>  1 file changed, 15 insertions(+), 14 deletions(-)
>>
>> diff --git a/branch.c b/branch.c
>> index 660097b..8bf7588 100644
>> --- a/branch.c
>> +++ b/branch.c
>> @@ -226,7 +226,6 @@ void create_branch(const char *head,
>>                  int force, int reflog, int clobber_head,
>>                  int quiet, enum branch_track track)
>>  {
>> -     struct ref_lock *lock = NULL;
>>       struct commit *commit;
>>       unsigned char sha1[20];
>>       char *real_ref, msg[PATH_MAX + 20];
>> @@ -285,15 +284,6 @@ void create_branch(const char *head,
>>               die(_("Not a valid branch point: '%s'."), start_name);
>>       hashcpy(sha1, commit->object.sha1);
>>
>> -     if (!dont_change_ref) {
>> -             lock = lock_any_ref_for_update(ref.buf, NULL, 0, NULL);
>> -             if (!lock)
>> -                     die_errno(_("Failed to lock ref for update"));
>> -     }
>> -
>> -     if (reflog)
>> -             log_all_ref_updates = 1;
>> -
>>       if (forcing)
>>               snprintf(msg, sizeof msg, "branch: Reset to %s",
>>                        start_name);
>> @@ -301,13 +291,24 @@ void create_branch(const char *head,
>>               snprintf(msg, sizeof msg, "branch: Created from %s",
>>                        start_name);
>>
>> +     if (reflog)
>> +             log_all_ref_updates = 1;
>> +
>> +     if (!dont_change_ref) {
>> +             struct ref_transaction *transaction;
>> +             struct strbuf err = STRBUF_INIT;
>> +
>> +             transaction = ref_transaction_begin();
>> +             if (!transaction ||
>> +                 ref_transaction_update(transaction, ref.buf, sha1,
>> +                                        null_sha1, 0, !forcing, &err) ||
>> +                 ref_transaction_commit(transaction, msg, &err))
>> +                     die("%s", err.buf);
>> +     }
>> +
>>       if (real_ref && track)
>>               setup_tracking(ref.buf + 11, real_ref, track, quiet);
>>
>> -     if (!dont_change_ref)
>> -             if (write_ref_sha1(lock, sha1, msg) < 0)
>> -                     die_errno(_("Failed to write ref"));
>> -
>>       strbuf_release(&ref);
>>       free(real_ref);
>>  }
>>
>
>
> --
> Michael Haggerty
> mhagger@alum.mit.edu
> http://softwareswirl.blogspot.com/
Previous: Michael HaggertyNext: Ronnie Sahlberg
Message 28 of 65 in “Use ref transactions for all ref updates”
  1. 00/44 Use ref transactions for all ref updatesRonnie Sahlberg, May 16, 2014
  2. 01/44 refs.c: constify the sha arguments for ref_transaction_create|delete|updateRonnie Sahlberg, May 16, 2014
  3. 02/44 refs.c: allow passing NULL to ref_transaction_freeRonnie Sahlberg, May 16, 2014
  4. 03/44 refs.c: add a strbuf argument to ref_transaction_commit for error loggingRonnie Sahlberg, May 16, 2014
  5. 04/44 refs.c: add an err argument to repack_without_refsRonnie Sahlberg, May 16, 2014
  6. Michael HaggertyMay 17, 2014
  7. Ronnie SahlbergMay 27, 2014
  8. 05/44 refs.c: make ref_update_reject_duplicates take a strbuf argument for errorsRonnie Sahlberg, May 16, 2014
  9. 06/44 refs.c: add an err argument to delete_ref_looseRonnie Sahlberg, May 16, 2014
  10. 07/44 refs.c: make update_ref_write update a strbuf on failureRonnie Sahlberg, May 16, 2014
  11. 08/44 update-ref.c: log transaction error from the update_refRonnie Sahlberg, May 16, 2014
  12. 09/44 refs.c: remove the onerr argument to ref_transaction_commitRonnie Sahlberg, May 16, 2014
  13. 10/44 refs.c: change ref_transaction_update() to do error checking and return statusRonnie Sahlberg, May 16, 2014
  14. 11/44 refs.c: change ref_transaction_create to do error checking and return statusRonnie Sahlberg, May 16, 2014
  15. 12/44 refs.c: ref_transaction_delete to check for error and return statusRonnie Sahlberg, May 16, 2014
  16. 13/44 tag.c: use ref transactions when doing updatesRonnie Sahlberg, May 16, 2014
  17. Michael HaggertyMay 17, 2014
  18. Ronnie SahlbergMay 19, 2014
  19. Ronnie SahlbergMay 19, 2014
  20. 14/44 replace.c: use the ref transaction functions for updatesRonnie Sahlberg, May 16, 2014
  21. Michael HaggertyMay 17, 2014
  22. Ronnie SahlbergMay 19, 2014
  23. 15/44 commit.c: use ref transactions for updatesRonnie Sahlberg, May 16, 2014
  24. 16/44 sequencer.c: use ref transactions for all ref updatesRonnie Sahlberg, May 16, 2014
  25. 17/44 fast-import.c: change update_branch to use ref transactionsRonnie Sahlberg, May 16, 2014
  26. 18/44 branch.c: use ref transaction for all ref updatesRonnie Sahlberg, May 16, 2014
  27. Michael HaggertyMay 17, 2014
  28. Ronnie SahlbergMay 19, 2014
  29. 19/44 refs.c: change update_ref to use a transactionRonnie Sahlberg, May 16, 2014
  30. 20/44 refs.c: free the transaction before returning when number of updates is 0Ronnie Sahlberg, May 16, 2014
  31. 21/44 refs.c: ref_transaction_commit should not free the transactionRonnie Sahlberg, May 16, 2014
  32. 22/44 fetch.c: clear errno before calling functions that might set itRonnie Sahlberg, May 16, 2014
  33. Michael HaggertyMay 17, 2014
  34. Ronnie SahlbergMay 27, 2014
  35. 23/44 fetch.c: change s_update_ref to use a ref transactionRonnie Sahlberg, May 16, 2014
  36. 24/44 fetch.c: use a single ref transaction for all ref updatesRonnie Sahlberg, May 16, 2014
  37. Michael HaggertyMay 17, 2014
  38. Michael HaggertyMay 17, 2014
  39. 25/44 receive-pack.c: use a reference transaction for updating the refsRonnie Sahlberg, May 16, 2014
  40. Michael HaggertyMay 17, 2014
  41. Ronnie SahlbergMay 19, 2014
  42. Michael HaggertyMay 23, 2014
  43. Ronnie SahlbergMay 23, 2014
  44. Michael HaggertyMay 23, 2014
  45. Ronnie SahlbergMay 27, 2014
  46. 26/44 fast-import.c: use a ref transaction when dumping tagsRonnie Sahlberg, May 16, 2014
  47. 27/44 walker.c: use ref transaction for ref updatesRonnie Sahlberg, May 16, 2014
  48. 28/44 refs.c: make write_ref_sha1 staticRonnie Sahlberg, May 16, 2014
  49. 29/44 refs.c: make lock_ref_sha1 staticRonnie Sahlberg, May 16, 2014
  50. 30/44 refs.c: add transaction.status and track OPEN/CLOSED/ERRORRonnie Sahlberg, May 16, 2014
  51. 31/44 refs.c: remove the update_ref_lock functionRonnie Sahlberg, May 16, 2014
  52. 32/44 refs.c: remove the update_ref_write functionRonnie Sahlberg, May 16, 2014
  53. 33/44 refs.c: remove lock_ref_sha1Ronnie Sahlberg, May 16, 2014
  54. 34/44 refs.c: make prune_ref use a transaction to delete the refRonnie Sahlberg, May 16, 2014
  55. 35/44 refs.c: make delete_ref use a transactionRonnie Sahlberg, May 16, 2014
  56. 36/44 refs.c: pass the ref log message to _create/delete/update instead of _commitRonnie Sahlberg, May 16, 2014
  57. 37/44 refs.c: pass NULL as *flags to read_ref_fullRonnie Sahlberg, May 16, 2014
  58. 38/44 refs.c: pack all refs before we start to rename a refRonnie Sahlberg, May 16, 2014
  59. 39/44 refs.c: move the check for valid refname to lock_ref_sha1_basicRonnie Sahlberg, May 16, 2014
  60. 40/44 refs.c: call lock_ref_sha1_basic directly from commitRonnie Sahlberg, May 16, 2014
  61. 41/44 refs.c: add a new flag for transaction delete for refs we know are packed onlyRonnie Sahlberg, May 16, 2014
  62. 42/44 refs.c: pass a skip list to name_conflict_fnRonnie Sahlberg, May 16, 2014
  63. 43/44 refs.c: make rename_ref use a transactionRonnie Sahlberg, May 16, 2014
  64. 44/44 refs.c: remove forward declaration of write_ref_sha1Ronnie Sahlberg, May 16, 2014
  65. Jonathan NiederMay 16, 2014

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