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[PATCH v3 39/44] refs: always handle non-normal refs in files backend

From
David Turner <dturner@twopensource.com>
Date
Oct 12, 2015, 21:52 UTC
Message-ID
<1444686725-27660-41-git-send-email-dturner@twopensource.com>
In-Reply-To
<1444686725-27660-1-git-send-email-dturner@twopensource.com>

Always handle non-normal (per-worktree or pseudo) refs in the files backend instead of alternate backends.

Sometimes a ref transaction will update both a per-worktree ref and a normal ref. For instance, an ordinary commit might update refs/heads/master and HEAD (or at least HEAD's reflog).

We handle three cases here:
1. updates to normal refs continue to go through the chosen backend
2. updates to non-normal refs with REF_NODEREF or to non-symbolic refs
are moved to a separate files backend transaction.
3. updates to symbolic refs are dereferenced to their base ref.  The
update to the base ref then goes through the ordinary backend, while
the files backend is directly called to update the symref's reflog.
Signed-off-by: David Turner <dturner@twopensource.com>
---
 refs.c | 141 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 139 insertions(+), 2 deletions(-)
diff --git a/refs.c b/refs.c
index b00f910..025cc08 100644
--- a/refs.c
+++ b/refs.c
@@ -7,6 +7,11 @@
 #include "object.h"
 #include "tag.h"
 
+const char split_transaction_fail_warning[] =
+	"A ref transaction was split across two refs backends.  Part of the "
+	"transaction succeeded, but then the update to the per-worktree refs "
+	"failed.  Your repository may be in an inconsistent state.";
+
 /*
  * We always have a files backend and it is the default.
  */
@@ -963,6 +968,13 @@ void ref_transaction_free(struct ref_transaction *transaction)
 	free(transaction);
 }
 
+static void add_update_obj(struct ref_transaction *transaction,
+			   struct ref_update *update)
+{
+	ALLOC_GROW(transaction->updates, transaction->nr + 1, transaction->alloc);
+	transaction->updates[transaction->nr++] = update;
+}
+
 static struct ref_update *add_update(struct ref_transaction *transaction,
 				     const char *refname)
 {
@@ -970,8 +982,7 @@ static struct ref_update *add_update(struct ref_transaction *transaction,
 	struct ref_update *update = xcalloc(1, sizeof(*update) + len);
 
 	memcpy((char *)update->refname, refname, len); /* includes NUL */
-	ALLOC_GROW(transaction->updates, transaction->nr + 1, transaction->alloc);
-	transaction->updates[transaction->nr++] = update;
+	add_update_obj(transaction, update);
 	return update;
 }
 
@@ -1160,11 +1171,87 @@ int refs_initdb(struct strbuf *err, int shared)
 	return the_refs_backend->initdb(err, shared);
 }
 
+/*
+ * Special case for non-normal refs.  For symbolic-refs when
+ * REF_NODEREF is not turned on, we dereference them here and replace
+ * updates to the symbolic refs with updates to the underlying ref.
+ * Then we do our own reflogging for the symbolic ref.
+ *
+ * We move other non-normal ref updates with into a specially-created
+ * files-backend transaction
+ */
+static int move_abnormal_ref_updates(struct ref_transaction *transaction,
+				     struct ref_transaction *files_transaction,
+				     struct string_list *symrefs)
+{
+	int i;
+
+	for (i = 0; i < transaction->nr; i++) {
+		struct ref_update *update = transaction->updates[i];
+		const char *resolved;
+		int flags = 0;
+		unsigned char sha1[20];
+
+		if (ref_type(update->refname) == REF_TYPE_NORMAL)
+			continue;
+
+		resolved = resolve_ref_unsafe(update->refname, 0, sha1, &flags);
+
+		if (update->flags & REF_NODEREF || !(flags & REF_ISSYMREF)) {
+			int last;
+
+			add_update_obj(files_transaction, update);
+			/*
+			 * Replace this transaction with the
+			 * last transaction, removing it from
+			 * the list of backend transactions
+			 */
+			last = --transaction->nr;
+			transaction->updates[i] = transaction->updates[last];
+			continue;
+		}
+
+		if (resolved) {
+			struct ref_update *new_update;
+			struct string_list_item *item;
+
+			if (ref_type(resolved) != REF_TYPE_NORMAL)
+				die("Non-normal symbolic ref `%s` points to non-normal ref `%s`", update->refname, resolved);
+
+			new_update = xmalloc(sizeof(*new_update) +
+					     strlen(resolved) + 1);
+			memcpy(new_update, update, sizeof(*update));
+
+			if (update->flags & REF_HAVE_OLD &&
+			    hashcmp(sha1, update->old_sha1)) {
+				/* consistency check failed */
+				free(new_update);
+				return -1;
+			} else {
+				hashcpy(update->old_sha1, sha1);
+			}
+
+			strcpy((char *)new_update->refname, resolved);
+			transaction->updates[i] = new_update;
+
+			item = string_list_append(symrefs, update->refname);
+			item->util = new_update;
+			free(update);
+		}
+	}
+
+	return 0;
+}
+
 int ref_transaction_commit(struct ref_transaction *transaction,
 			   struct strbuf *err)
 {
 	int ret = -1;
 	struct string_list affected_refnames = STRING_LIST_INIT_NODUP;
+	struct string_list files_affected_refnames = STRING_LIST_INIT_NODUP;
+	struct string_list symrefs = STRING_LIST_INIT_DUP;
+	struct string_list_item *item;
+	struct ref_transaction *files_transaction = NULL;
 
 	assert(err);
 
@@ -1176,6 +1263,26 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 		return 0;
 	}
 
+	if (the_refs_backend != &refs_be_files) {
+		files_transaction = ref_transaction_begin(err);
+		if (!files_transaction)
+			die("%s", err->buf);
+
+		ret = move_abnormal_ref_updates(transaction, files_transaction,
+						&symrefs);
+		if (ret)
+			goto done;
+
+		/* files backend commit */
+		if (ref_update_reject_duplicates(files_transaction,
+						 &files_affected_refnames,
+						 err)) {
+			ret = TRANSACTION_GENERIC_ERROR;
+			goto done;
+		}
+	}
+
+	/* main backend commit */
 	if (ref_update_reject_duplicates(transaction, &affected_refnames, err)) {
 		ret = TRANSACTION_GENERIC_ERROR;
 		goto done;
@@ -1183,8 +1290,35 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 
 	ret = the_refs_backend->transaction_commit(transaction,
 						   &affected_refnames, err);
+	if (ret)
+		goto done;
+
+	if (the_refs_backend != &refs_be_files) {
+		ret = refs_be_files.transaction_commit(files_transaction,
+						       &files_affected_refnames,
+						       err);
+		if (ret) {
+			warning(split_transaction_fail_warning);
+			goto done;
+		}
+
+		/* reflogging for dereferenced symbolic refs */
+		for_each_string_list_item(item, &symrefs) {
+			struct ref_update *update = item->util;
+			if (files_log_ref_write(item->string, update->old_sha1,
+						update->new_sha1,
+						update->msg, update->flags, err))
+				warning("failed to log ref update for symref %s",
+					item->string);
+		}
+	}
+
 done:
 	string_list_clear(&affected_refnames, 0);
+	string_list_clear(&files_affected_refnames, 0);
+	if (files_transaction)
+		ref_transaction_free(files_transaction);
+	string_list_clear(&symrefs, 0);
 	return ret;
 }
 
@@ -1235,6 +1369,9 @@ int peel_ref(const char *refname, unsigned char *sha1)
 int create_symref(const char *ref_target, const char *refs_heads_master,
 		  const char *logmsg)
 {
+	if (ref_type(ref_target) != REF_TYPE_NORMAL)
+		return refs_be_files.create_symref(ref_target, refs_heads_master,
+						   logmsg);
 	return the_refs_backend->create_symref(ref_target, refs_heads_master,
 					       logmsg);
 }

-- 
2.4.2.644.g97b850b-twtrsrc
Previous: David TurnerNext: David Turner
Message 66 of 71 in “alternate refs backends”
  1. 00/44 alternate refs backendsDavid Turner, Oct 12, 2015
  2. 01/44 refs.c: create a public version of verify_refname_availableDavid Turner, Oct 12, 2015
  3. Michael HaggertyOct 13, 2015
  4. 02/44 refs: make repack_without_refs and is_branch publicDavid Turner, Oct 12, 2015
  5. Michael HaggertyOct 13, 2015
  6. Michael HaggertyOct 13, 2015
  7. David TurnerOct 13, 2015
  8. 03/44 refs-be-files.c: rename refs to refs-be-filesDavid Turner, Oct 12, 2015
  9. 04/44 refs.c: add a new refs.c file to hold all common refs codeDavid Turner, Oct 12, 2015
  10. 05/44 refs.c: move update_ref to refs.cDavid Turner, Oct 12, 2015
  11. Michael HaggertyOct 13, 2015
  12. David TurnerOct 13, 2015
  13. David TurnerOct 14, 2015
  14. 06/44 refs.c: move delete_ref and delete_refs to the common codeDavid Turner, Oct 12, 2015
  15. Michael HaggertyOct 13, 2015
  16. 07/44 refs.c: move read_ref_at to the common refs fileDavid Turner, Oct 12, 2015
  17. 08/44 refs.c: move the hidden refs functions to the common codeDavid Turner, Oct 12, 2015
  18. 09/44 refs.c: move dwim and friend functions to the common refs codeDavid Turner, Oct 12, 2015
  19. 10/44 refs.c: move warn_if_dangling_symref* to the common codeDavid Turner, Oct 12, 2015
  20. 11/44 refs.c: move read_ref, read_ref_full and ref_exists to the common codeDavid Turner, Oct 12, 2015
  21. 12/44 refs.c: move resolve_refdup to commonDavid Turner, Oct 12, 2015
  22. 13/44 refs.c: move check_refname_format to the common codeDavid Turner, Oct 12, 2015
  23. 14/44 refs.c: move is_branch to the common codeDavid Turner, Oct 12, 2015
  24. 15/44 refs.c: move prettify_refname to the common codeDavid Turner, Oct 12, 2015
  25. 16/44 refs.c: move ref iterators to the common codeDavid Turner, Oct 12, 2015
  26. Michael HaggertyOct 13, 2015
  27. 17/44 refs.c: move head_ref_namespaced to the common codeDavid Turner, Oct 12, 2015
  28. 18/44 refs: move transaction functions into common codeDavid Turner, Oct 12, 2015
  29. Michael HaggertyOct 13, 2015
  30. Michael HaggertyOct 13, 2015
  31. David TurnerOct 13, 2015
  32. David TurnerOct 13, 2015
  33. 19/44 refs: add a backend method structure with transaction functionsDavid Turner, Oct 12, 2015
  34. 19/44 refs-be-files.c: add a backend method structure with transaction functionsDavid Turner, Oct 12, 2015
  35. David TurnerOct 12, 2015
  36. Michael HaggertyOct 13, 2015
  37. David TurnerOct 13, 2015
  38. Michael HaggertyOct 13, 2015
  39. 20/44 refs-be-files.c: add methods for misc ref operationsDavid Turner, Oct 12, 2015
  40. Michael HaggertyOct 13, 2015
  41. 21/44 refs-be-files.c: add methods for the ref iteratorsDavid Turner, Oct 12, 2015
  42. 22/44 refs-be-files.c: add method for for_each_reftype_...David Turner, Oct 12, 2015
  43. 23/44 refs-be-files.c: add do_for_each_per_worktree_refDavid Turner, Oct 12, 2015
  44. 24/44 refs.c: move refname_is_safe to the common codeDavid Turner, Oct 12, 2015
  45. 25/44 refs.h: document make refname_is_safe and add it to headerDavid Turner, Oct 12, 2015
  46. Michael HaggertyOct 13, 2015
  47. Michael HaggertyOct 13, 2015
  48. David TurnerOct 13, 2015
  49. 26/44 refs.c: move copy_msg to the common codeDavid Turner, Oct 12, 2015
  50. Michael HaggertyOct 13, 2015
  51. 27/44 refs.c: move peel_object to the common codeDavid Turner, Oct 12, 2015
  52. Michael HaggertyOct 13, 2015
  53. 28/44 refs.c: move should_autocreate_reflog to common codeDavid Turner, Oct 12, 2015
  54. 29/44 refs.c: add ref backend init functionDavid Turner, Oct 12, 2015
  55. 30/44 refs.c: add methods for reflogDavid Turner, Oct 12, 2015
  56. 31/44 refs.c: add method for initial ref transaction commitDavid Turner, Oct 12, 2015
  57. 32/44 initdb: move safe_create_dir into common codeDavid Turner, Oct 12, 2015
  58. 33/44 refs.c: add method for initializing refs dbDavid Turner, Oct 12, 2015
  59. 34/44 refs-be-files.c: add method to rename refsDavid Turner, Oct 12, 2015
  60. 35/44 refs: make lock genericDavid Turner, Oct 12, 2015
  61. 36/44 refs: make files_log_ref_write functions publicDavid Turner, Oct 12, 2015
  62. 37/44 refs: break out a ref conflict checkDavid Turner, Oct 12, 2015
  63. Michael HaggertyOct 13, 2015
  64. David TurnerOct 13, 2015
  65. 38/44 refs: move duplicate check to common codeDavid Turner, Oct 12, 2015
  66. 39/44 refs: always handle non-normal refs in files backendDavid Turner, Oct 12, 2015
  67. 40/44 refs: allow ref backend to be set for cloneDavid Turner, Oct 12, 2015
  68. 41/44 refs: add register_refs_backendDavid Turner, Oct 12, 2015
  69. 42/44 introduce "extensions" form of core.repositoryformatversionDavid Turner, Oct 12, 2015
  70. 43/44 refs: add LMDB refs backendDavid Turner, Oct 12, 2015
  71. 44/44 refs: tests for db backendDavid Turner, Oct 12, 2015

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