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[PATCH 20/31] refs.c: check for lock conflicts already in _update

From
Ronnie Sahlberg <sahlberg@google.com>
Date
May 14, 2014, 22:13 UTC
Message-ID
<1400105610-21194-21-git-send-email-sahlberg@google.com>
In-Reply-To
<1400105610-21194-1-git-send-email-sahlberg@google.com>

Check for lock conflicts in _update and flag the transaction as errored instead of waiting until _commit for doing these checks. If there was a lock failure we check if this was due to a previous update in the same transaction or not. This so that we can preserve the current error messages on lock failure and log "Multiple updates for ref '%s' not allowed." when we have multiple updates in the same transaction and "Cannot lock the ref '%s'." for any other reason that the lock failed.

This also means that we no longer need to sort all the refs and check for duplicates during _commit so all that code can be removed too.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 refs.c | 85 +++++++++++++++++++++++++++++++++---------------------------------
 1 file changed, 42 insertions(+), 43 deletions(-)
diff --git a/refs.c b/refs.c
index 93f01e8..76cab6e 100644
--- a/refs.c
+++ b/refs.c
@@ -3415,6 +3415,7 @@ int transaction_update_sha1(struct ref_transaction *transaction,
 			    struct strbuf *err)
 {
 	struct ref_update *update;
+	int i;
 
 	if (have_old && !old_sha1)
 		die("BUG: have_old is true but old_sha1 is NULL");
@@ -3438,19 +3439,49 @@ int transaction_update_sha1(struct ref_transaction *transaction,
 	 * we do not need to check against this ref for name collissions
 	 * during locking.
 	 */
-	if (update->flags & REF_ISPACKONLY)
+	if (update->flags & REF_ISPACKONLY) {
 		add_delname(transaction, update->refname);
-	else {
-		update->lock = lock_ref_sha1_basic(update->refname,
-						   (update->have_old ?
-						    update->old_sha1 :
-						    NULL),
-						   update->flags,
-						   &update->type,
-						   transaction->delnames,
-						   transaction->delnum);
+		return 0;
 	}
-	return 0;
+
+	update->lock = lock_ref_sha1_basic(update->refname,
+					   (update->have_old ?
+					    update->old_sha1 :
+					    NULL),
+					   update->flags,
+					   &update->type,
+					   transaction->delnames,
+					   transaction->delnum);
+	if (update->lock)
+		return 0;
+
+	/* If we could not lock the ref it means we either collided with a
+	   different command or that we tried to perform a second update to
+	   the same ref from within the same transaction.
+	*/
+	transaction->status = REF_TRANSACTION_ERROR;
+
+	/* -1 is the update we just added. Start at -2 and find the most recent
+	   previous update for this ref.
+	*/
+	for (i = transaction->nr - 2; i >= 0; i--) {
+		if (transaction->updates[i]->update_type != UPDATE_SHA1) {
+			continue;
+		}
+		if (!strcmp(transaction->updates[i]->refname,
+			    update->refname))
+			break;
+	}
+	if (err)
+		if (i >= 0) {
+			const char *str =
+				"Multiple updates for ref '%s' not allowed.";
+			strbuf_addf(err, str, update->refname);
+		} else {
+			const char *str = "Cannot lock the ref '%s'.";
+			strbuf_addf(err, str, update->refname);
+		}
+	return 1;
 }
 
 int transaction_create_sha1(struct ref_transaction *transaction,
@@ -3525,32 +3556,6 @@ int update_ref(const char *action, const char *refname,
 	return 0;
 }
 
-static int ref_update_compare(const void *r1, const void *r2)
-{
-	const struct ref_update * const *u1 = r1;
-	const struct ref_update * const *u2 = r2;
-	return strcmp((*u1)->refname, (*u2)->refname);
-}
-
-static int ref_update_reject_duplicates(struct ref_update **updates, int n,
-					struct strbuf *err)
-{
-	int i;
-	for (i = 1; i < n; i++) {
-		if (updates[i]->update_type != UPDATE_SHA1)
-			continue;
-		if (!strcmp(updates[i - 1]->refname, updates[i]->refname)) {
-			const char *str =
-				"Multiple updates for ref '%s' not allowed.";
-			if (err)
-				strbuf_addf(err, str, updates[i]->refname);
-
-			return 1;
-		}
-	}
-	return 0;
-}
-
 int transaction_commit(struct ref_transaction *transaction,
 			   struct strbuf *err)
 {
@@ -3569,12 +3574,6 @@ int transaction_commit(struct ref_transaction *transaction,
 		return 0;
 	}
 
-	/* Copy, sort, and reject duplicate refs */
-	qsort(updates, n, sizeof(*updates), ref_update_compare);
-	ret = ref_update_reject_duplicates(updates, n, err);
-	if (ret)
-		goto cleanup;
-
 	/* Acquire all ref locks while verifying old values */
 	for (i = 0; i < n; i++) {
 		struct ref_update *update = updates[i];

-- 
2.0.0.rc3.506.g3739a35
Previous: Ronnie SahlbergNext: Ronnie Sahlberg
Message 32 of 43 in “Finish implementing ref and reflog transactions”
  1. 00/31 Finish implementing ref and reflog transactionsRonnie Sahlberg, May 14, 2014
  2. 01/31 refs.c make ref_transaction_create a wrapper to ref_transaction_updateRonnie Sahlberg, May 14, 2014
  3. 02/31 refs.c: make ref_transaction_delete a wrapper for ref_transaction_updateRonnie Sahlberg, May 14, 2014
  4. 03/31 refs.c: rename the transaction functionsRonnie Sahlberg, May 14, 2014
  5. Junio C HamanoMay 16, 2014
  6. Ronnie SahlbergMay 19, 2014
  7. Junio C HamanoMay 19, 2014
  8. 04/31 refs.c: add a new update_type field to ref_updateRonnie Sahlberg, May 14, 2014
  9. 05/31 refs.c: add a function to append a reflog entry to a fdRonnie Sahlberg, May 14, 2014
  10. 06/31 refs.c: add a transaction function to append a reflog entryRonnie Sahlberg, May 14, 2014
  11. 07/31 refs.c: add a flag to allow reflog updates to truncate the logRonnie Sahlberg, May 14, 2014
  12. Junio C HamanoMay 16, 2014
  13. Ronnie SahlbergMay 19, 2014
  14. 08/31 refs.c: only write reflog update if msg is non-NULLRonnie Sahlberg, May 14, 2014
  15. Junio C HamanoMay 16, 2014
  16. Ronnie SahlbergMay 19, 2014
  17. 09/31 refs.c: allow multiple reflog updates during a single transactionRonnie Sahlberg, May 14, 2014
  18. Junio C HamanoMay 16, 2014
  19. Eric SunshineMay 16, 2014
  20. Ronnie SahlbergMay 19, 2014
  21. Ronnie SahlbergMay 19, 2014
  22. 10/31 reflog.c: use a reflog transaction when writing during expireRonnie Sahlberg, May 14, 2014
  23. 11/31 refs.c: null terminate the string in copy_msgRonnie Sahlberg, May 14, 2014
  24. 12/31 refs.c: track the refnames we are deleting in the transaction structureRonnie Sahlberg, May 14, 2014
  25. 13/31 refs.c: update the list of deleted refs during _update instead of _commitRonnie Sahlberg, May 14, 2014
  26. 14/31 refs.c: return error instead of dying when locking fails during transactionRonnie Sahlberg, May 14, 2014
  27. 15/31 refs.c: lock the ref during _update instead of during _commitRonnie Sahlberg, May 14, 2014
  28. 16/31 refs.c: add an error argument to create/delete/update just like commitRonnie Sahlberg, May 14, 2014
  29. 17/31 refs.c: make _update_reflog take an error argumentRonnie Sahlberg, May 14, 2014
  30. 18/31 refs.c: return immediately from _commit if the transaction has an errorRonnie Sahlberg, May 14, 2014
  31. 19/31 tests: move tests for -z update/delete/verify to after the ref is createdRonnie Sahlberg, May 14, 2014
  32. 20/31 refs.c: check for lock conflicts already in _updateRonnie Sahlberg, May 14, 2014
  33. 21/31 refs.c allow multiple updates of the same ref in a transactionRonnie Sahlberg, May 14, 2014
  34. 22/31 refs.c: release all remaining locks during transaction_freeRonnie Sahlberg, May 14, 2014
  35. 23/31 reflog.c: use the existing transaction to also lock and update the refRonnie Sahlberg, May 14, 2014
  36. 24/31 refs.c: make unlock_ref staticRonnie Sahlberg, May 14, 2014
  37. 25/31 refs.c: make close_ref staticRonnie Sahlberg, May 14, 2014
  38. 26/31 refs.c: make commit_ref staticRonnie Sahlberg, May 14, 2014
  39. 27/31 refs.c: remove the function lock_any_ref_for_updateRonnie Sahlberg, May 14, 2014
  40. 28/31 refs.c: make struct ref_lock private to refs.cRonnie Sahlberg, May 14, 2014
  41. 29/31 refs.c: allow passing raw git_committer_info as email to _update_reflogRonnie Sahlberg, May 14, 2014
  42. 30/31 refs.c: move ref_update and other definitions to earlier in the fileRonnie Sahlberg, May 14, 2014
  43. 31/31 refs.c: use the transaction to manage the reflog in rename_refsRonnie Sahlberg, May 14, 2014

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