Merge branch 'hx/negotiator-non-recursive'

The implementation of the default "negotiator", used to find common
ancestor over the network for object tranfer, used to be recursive;
it was updated to be iterative to conserve stackspace usage.

* hx/negotiator-non-recursive:
  negotiator/skipping: fix some problems in mark_common()
  negotiator/default: avoid stack overflow

2 files changed, 44 insertions, 17 deletions

diff --git a/negotiator/default.c b/negotiator/default.c
index 5cb2b1d204..9a5b696327 100644
--- a/negotiator/default.c
+++ b/negotiator/default.c
@@ -56,30 +56,49 @@ static int clear_marks(const char *refname, const struct object_id *oid,
 static void mark_common(struct negotiation_state *ns, struct commit *commit,
 		int ancestors_only, int dont_parse)
 {
-	if (commit != NULL && !(commit->object.flags & COMMON)) {
-		struct object *o = (struct object *)commit;
+	struct prio_queue queue = { NULL };
+
+	if (!commit || (commit->object.flags & COMMON))
+		return;
+
+	prio_queue_put(&queue, commit);
+	if (!ancestors_only) {
+		commit->object.flags |= COMMON;
 
-		if (!ancestors_only)
-			o->flags |= COMMON;
+		if ((commit->object.flags & SEEN) && !(commit->object.flags & POPPED))
+			ns->non_common_revs--;
+	}
+	while ((commit = prio_queue_get(&queue))) {
+		struct object *o = (struct object *)commit;
 
 		if (!(o->flags & SEEN))
 			rev_list_push(ns, commit, SEEN);
 		else {
 			struct commit_list *parents;
 
-			if (!ancestors_only && !(o->flags & POPPED))
-				ns->non_common_revs--;
 			if (!o->parsed && !dont_parse)
 				if (repo_parse_commit(the_repository, commit))
-					return;
+					continue;
 
 			for (parents = commit->parents;
 					parents;
-					parents = parents->next)
-				mark_common(ns, parents->item, 0,
-					    dont_parse);
+					parents = parents->next) {
+				struct commit *p = parents->item;
+
+				if (p->object.flags & COMMON)
+					continue;
+
+				p->object.flags |= COMMON;
+
+				if ((p->object.flags & SEEN) && !(p->object.flags & POPPED))
+					ns->non_common_revs--;
+
+				prio_queue_put(&queue, parents->item);
+			}
 		}
 	}
+
+	clear_prio_queue(&queue);
 }
 
 /*
diff --git a/negotiator/skipping.c b/negotiator/skipping.c
index 97e7e1ae72..5b91520430 100644
--- a/negotiator/skipping.c
+++ b/negotiator/skipping.c
@@ -86,29 +86,37 @@ static int clear_marks(const char *refname, const struct object_id *oid,
 }
 
 /*
- * Mark this SEEN commit and all its SEEN ancestors as COMMON.
+ * Mark this SEEN commit and all its parsed SEEN ancestors as COMMON.
  */
 static void mark_common(struct data *data, struct commit *seen_commit)
 {
 	struct prio_queue queue = { NULL };
 	struct commit *c;
 
+	if (seen_commit->object.flags & COMMON)
+		return;
+
 	prio_queue_put(&queue, seen_commit);
+	seen_commit->object.flags |= COMMON;
 	while ((c = prio_queue_get(&queue))) {
 		struct commit_list *p;
-		if (c->object.flags & COMMON)
-			return;
-		c->object.flags |= COMMON;
+
 		if (!(c->object.flags & POPPED))
 			data->non_common_revs--;
 
 		if (!c->object.parsed)
-			return;
+			continue;
 		for (p = c->parents; p; p = p->next) {
-			if (p->item->object.flags & SEEN)
-				prio_queue_put(&queue, p->item);
+			if (!(p->item->object.flags & SEEN) ||
+			    (p->item->object.flags & COMMON))
+				continue;
+
+			p->item->object.flags |= COMMON;
+			prio_queue_put(&queue, p->item);
 		}
 	}
+
+	clear_prio_queue(&queue);
 }
 
 /*