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[PATCH v15 30/48] branch.c: use ref transaction for all ref updates

From
Ronnie Sahlberg <sahlberg@google.com>
Date
Jun 10, 2014, 22:29 UTC
Message-ID
<1402439376-25839-31-git-send-email-sahlberg@google.com>
In-Reply-To
<1402439376-25839-1-git-send-email-sahlberg@google.com>
Change create_branch to use a ref transaction when creating the new branch.

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 | 30 ++++++++++++++++--------------
 1 file changed, 16 insertions(+), 14 deletions(-)
diff --git a/branch.c b/branch.c
index 660097b..c1eae00 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 +291,25 @@ 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(&err);
+		if (!transaction ||
+		    ref_transaction_update(transaction, ref.buf, sha1,
+					   null_sha1, 0, !forcing, &err) ||
+		    ref_transaction_commit(transaction, msg, &err))
+			die("%s", err.buf);
+		ref_transaction_free(transaction);
+	}
+
 	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);
 }

-- 
2.0.0.574.g30c2c5e
Previous: Ronnie SahlbergNext: Ronnie Sahlberg
Message 31 of 51 in “Use ref transactions”
  1. 00/48 Use ref transactionsRonnie Sahlberg, Jun 10, 2014
  2. 01/48 refs.c: remove ref_transaction_rollbackRonnie Sahlberg, Jun 10, 2014
  3. 02/48 refs.c: ref_transaction_commit should not free the transactionRonnie Sahlberg, Jun 10, 2014
  4. 03/48 refs.c: constify the sha arguments for ref_transaction_create|delete|updateRonnie Sahlberg, Jun 10, 2014
  5. 04/48 refs.c: allow passing NULL to ref_transaction_freeRonnie Sahlberg, Jun 10, 2014
  6. 05/48 refs.c: add a strbuf argument to ref_transaction_commit for error loggingRonnie Sahlberg, Jun 10, 2014
  7. 06/48 lockfile.c: add a new public function unable_to_lock_messageRonnie Sahlberg, Jun 10, 2014
  8. 07/48 lockfile.c: make lock_file return a meaningful errno on failureiRonnie Sahlberg, Jun 10, 2014
  9. 08/48 refs.c: add an err argument to repack_without_refsRonnie Sahlberg, Jun 10, 2014
  10. 09/48 refs.c: make sure log_ref_setup returns a meaningful errnoRonnie Sahlberg, Jun 10, 2014
  11. 10/48 refs.c: verify_lock should set errno to something meaningfulRonnie Sahlberg, Jun 10, 2014
  12. 11/48 refs.c: make remove_empty_directories alwasy set errno to something saneRonnie Sahlberg, Jun 10, 2014
  13. 12/48 refs.c: commit_packed_refs to return a meaningful errno on failureRonnie Sahlberg, Jun 10, 2014
  14. 13/48 refs.c: make resolve_ref_unsafe set errno to something meaningful on errorRonnie Sahlberg, Jun 10, 2014
  15. 14/48 refs.c: log_ref_write should try to return meaningful errnoRonnie Sahlberg, Jun 10, 2014
  16. 15/48 refs.c: make ref_update_reject_duplicates take a strbuf argument for errorsRonnie Sahlberg, Jun 10, 2014
  17. 16/48 refs.c: add an err argument to delete_ref_looseRonnie Sahlberg, Jun 10, 2014
  18. 17/48 refs.c: make update_ref_write update a strbuf on failureRonnie Sahlberg, Jun 10, 2014
  19. 18/48 update-ref: use err argument to get error from ref_transaction_commitRonnie Sahlberg, Jun 10, 2014
  20. 19/48 refs.c: remove the onerr argument to ref_transaction_commitRonnie Sahlberg, Jun 10, 2014
  21. 20/48 refs.c: change ref_transaction_update() to do error checking and return statusRonnie Sahlberg, Jun 10, 2014
  22. 21/48 refs.c: change ref_transaction_create to do error checking and return statusRonnie Sahlberg, Jun 10, 2014
  23. 22/48 refs.c: update ref_transaction_delete to check for error and return statusRonnie Sahlberg, Jun 10, 2014
  24. 23/48 refs.c: make ref_transaction_begin take an err argumentRonnie Sahlberg, Jun 10, 2014
  25. 24/48 refs.c: add transaction.status and track OPEN/CLOSED/ERRORRonnie Sahlberg, Jun 10, 2014
  26. 25/48 tag.c: use ref transactions when doing updatesRonnie Sahlberg, Jun 10, 2014
  27. 26/48 replace.c: use the ref transaction functions for updatesRonnie Sahlberg, Jun 10, 2014
  28. 27/48 commit.c: use ref transactions for updatesRonnie Sahlberg, Jun 10, 2014
  29. 28/48 sequencer.c: use ref transactions for all ref updatesRonnie Sahlberg, Jun 10, 2014
  30. 29/48 fast-import.c: change update_branch to use ref transactionsRonnie Sahlberg, Jun 10, 2014
  31. 30/48 branch.c: use ref transaction for all ref updatesRonnie Sahlberg, Jun 10, 2014
  32. 31/48 refs.c: change update_ref to use a transactionRonnie Sahlberg, Jun 10, 2014
  33. 32/48 receive-pack.c: use a reference transaction for updating the refsRonnie Sahlberg, Jun 10, 2014
  34. 33/48 fast-import.c: use a ref transaction when dumping tagsRonnie Sahlberg, Jun 10, 2014
  35. 34/48 walker.c: use ref transaction for ref updatesRonnie Sahlberg, Jun 10, 2014
  36. 35/48 refs.c: make lock_ref_sha1 staticRonnie Sahlberg, Jun 10, 2014
  37. 36/48 refs.c: remove the update_ref_lock functionRonnie Sahlberg, Jun 10, 2014
  38. 37/48 refs.c: remove the update_ref_write functionRonnie Sahlberg, Jun 10, 2014
  39. 38/48 refs.c: remove lock_ref_sha1Ronnie Sahlberg, Jun 10, 2014
  40. 39/48 refs.c: make prune_ref use a transaction to delete the refRonnie Sahlberg, Jun 10, 2014
  41. 40/48 refs.c: make delete_ref use a transactionRonnie Sahlberg, Jun 10, 2014
  42. 41/48 refs.c: pass the ref log message to _create/delete/update instead of _commitRonnie Sahlberg, Jun 10, 2014
  43. 42/48 refs.c: pass NULL as *flags to read_ref_fullRonnie Sahlberg, Jun 10, 2014
  44. 43/48 refs.c: move the check for valid refname to lock_ref_sha1_basicRonnie Sahlberg, Jun 10, 2014
  45. 44/48 refs.c: call lock_ref_sha1_basic directly from commitRonnie Sahlberg, Jun 10, 2014
  46. 45/48 refs.c: pass a skip list to name_conflict_fnRonnie Sahlberg, Jun 10, 2014
  47. 46/48 refs.c: propagate any errno==ENOTDIR from _commit back to the callersRonnie Sahlberg, Jun 10, 2014
  48. 47/48 fetch.c: change s_update_ref to use a ref transactionRonnie Sahlberg, Jun 10, 2014
  49. 48/48 refs.c: make write_ref_sha1 staticRonnie Sahlberg, Jun 10, 2014
  50. Junio C HamanoJun 12, 2014
  51. Ronnie SahlbergJun 13, 2014

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