git/list[1] front-page[2] threads[3] people[4] search[5] about
 

[PATCH 3/6] commit-graph: return the prepared commit graph from `prepare_commit_graph()`

From
Patrick Steinhardt <ps@pks.im>
Date
Sep 4, 2025, 12:49 UTC
Message-ID
<20250904-b4-pks-commit-graph-via-source-v1-3-d932c2481e1a@pks.im>
In-Reply-To
<20250904-b4-pks-commit-graph-via-source-v1-0-d932c2481e1a@pks.im>

When making use of commit graphs, one needs to first prepare them by calling `prepare_commit_graph()`. Once that function was called and the commit graph was prepared successfully, the caller is now expected to access the graph directly via `struct object_database::commit_graph`.

In a subsequent change, we're going to move the commit graph pointer from `struct object_database` into `struct odb_source`. With this change, semantics will change so that we use the commit graph of the first source that has one. Consequently, all callers that currently deference the `commit_graph` pointer would now have to loop around the list of sources to find the commit graph.

This would become quite unwieldy. So instead of shifting the burden onto such callers, adapt `prepare_commit_graph()` to return the prepared commit graph, if any. Like this, callers are expected to call that function and then use the returned commit graph.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 commit-graph.c | 82 +++++++++++++++++++++++-----------------------------------
 1 file changed, 32 insertions(+), 50 deletions(-)
diff --git a/commit-graph.c b/commit-graph.c
index 3cd9e73e2a..62260a2026 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -735,7 +735,7 @@ struct commit_graph *read_commit_graph_one(struct odb_source *source)
  * On the first invocation, this function attempts to load the commit
  * graph if the repository is configured to have one.
  */
-static int prepare_commit_graph(struct repository *r)
+static struct commit_graph *prepare_commit_graph(struct repository *r)
 {
 	struct odb_source *source;
 
@@ -747,10 +747,10 @@ static int prepare_commit_graph(struct repository *r)
 	 * we want to disable even an already-loaded graph file.
 	 */
 	if (!r->gitdir || r->commit_graph_disabled)
-		return 0;
+		return NULL;
 
 	if (r->objects->commit_graph_attempted)
-		return !!r->objects->commit_graph;
+		return r->objects->commit_graph;
 	r->objects->commit_graph_attempted = 1;
 
 	prepare_repo_settings(r);
@@ -763,10 +763,10 @@ static int prepare_commit_graph(struct repository *r)
 		 * so that commit graph loading is not attempted again for this
 		 * repository.)
 		 */
-		return 0;
+		return NULL;
 
 	if (!commit_graph_compatible(r))
-		return 0;
+		return NULL;
 
 	odb_prepare_alternates(r->objects);
 	for (source = r->objects->sources; source; source = source->next) {
@@ -775,20 +775,17 @@ static int prepare_commit_graph(struct repository *r)
 			break;
 	}
 
-	return !!r->objects->commit_graph;
+	return r->objects->commit_graph;
 }
 
 int generation_numbers_enabled(struct repository *r)
 {
 	uint32_t first_generation;
 	struct commit_graph *g;
-	if (!prepare_commit_graph(r))
-	       return 0;
 
-	g = r->objects->commit_graph;
-
-	if (!g->num_commits)
-		return 0;
+	g = prepare_commit_graph(r);
+	if (!g || !g->num_commits)
+	       return 0;
 
 	first_generation = get_be32(g->chunk_commit_data +
 				    g->hash_algo->rawsz + 8) >> 2;
@@ -799,12 +796,9 @@ int generation_numbers_enabled(struct repository *r)
 int corrected_commit_dates_enabled(struct repository *r)
 {
 	struct commit_graph *g;
-	if (!prepare_commit_graph(r))
-		return 0;
 
-	g = r->objects->commit_graph;
-
-	if (!g->num_commits)
+	g = prepare_commit_graph(r);
+	if (!g || !g->num_commits)
 		return 0;
 
 	return g->read_generation_data;
@@ -1012,23 +1006,26 @@ static int find_commit_pos_in_graph(struct commit *item, struct commit_graph *g,
 int repo_find_commit_pos_in_graph(struct repository *r, struct commit *c,
 				  uint32_t *pos)
 {
-	if (!prepare_commit_graph(r))
+	struct commit_graph *g = prepare_commit_graph(r);
+	if (!g)
 		return 0;
-	return find_commit_pos_in_graph(c, r->objects->commit_graph, pos);
+	return find_commit_pos_in_graph(c, g, pos);
 }
 
 struct commit *lookup_commit_in_graph(struct repository *repo, const struct object_id *id)
 {
 	static int commit_graph_paranoia = -1;
+	struct commit_graph *g;
 	struct commit *commit;
 	uint32_t pos;
 
 	if (commit_graph_paranoia == -1)
 		commit_graph_paranoia = git_env_bool(GIT_COMMIT_GRAPH_PARANOIA, 0);
 
-	if (!prepare_commit_graph(repo))
+	g = prepare_commit_graph(repo);
+	if (!g)
 		return NULL;
-	if (!search_commit_pos_in_graph(id, repo->objects->commit_graph, &pos))
+	if (!search_commit_pos_in_graph(id, g, &pos))
 		return NULL;
 	if (commit_graph_paranoia && !odb_has_object(repo->objects, id, 0))
 		return NULL;
@@ -1039,7 +1036,7 @@ struct commit *lookup_commit_in_graph(struct repository *repo, const struct obje
 	if (commit->object.parsed)
 		return commit;
 
-	if (!fill_commit_in_graph(commit, repo->objects->commit_graph, pos))
+	if (!fill_commit_in_graph(commit, g, pos))
 		return NULL;
 
 	return commit;
@@ -1062,6 +1059,7 @@ static int parse_commit_in_graph_one(struct commit_graph *g,
 int parse_commit_in_graph(struct repository *r, struct commit *item)
 {
 	static int checked_env = 0;
+	struct commit_graph *g;
 
 	if (!checked_env &&
 	    git_env_bool(GIT_TEST_COMMIT_GRAPH_DIE_ON_PARSE, 0))
@@ -1069,9 +1067,10 @@ int parse_commit_in_graph(struct repository *r, struct commit *item)
 		    GIT_TEST_COMMIT_GRAPH_DIE_ON_PARSE);
 	checked_env = 1;
 
-	if (!prepare_commit_graph(r))
+	g = prepare_commit_graph(r);
+	if (!g)
 		return 0;
-	return parse_commit_in_graph_one(r->objects->commit_graph, item);
+	return parse_commit_in_graph_one(g, item);
 }
 
 void load_commit_graph_info(struct repository *r, struct commit *item)
@@ -2519,6 +2518,7 @@ int write_commit_graph(struct odb_source *source,
 	int replace = 0;
 	struct bloom_filter_settings bloom_settings = DEFAULT_BLOOM_FILTER_SETTINGS;
 	struct topo_level_slab topo_levels;
+	struct commit_graph *g;
 
 	prepare_repo_settings(r);
 	if (!r->settings.core_commit_graph) {
@@ -2547,23 +2547,13 @@ int write_commit_graph(struct odb_source *source,
 	init_topo_level_slab(&topo_levels);
 	ctx.topo_levels = &topo_levels;
 
-	prepare_commit_graph(ctx.r);
-	if (ctx.r->objects->commit_graph) {
-		struct commit_graph *g = ctx.r->objects->commit_graph;
-
-		while (g) {
-			g->topo_levels = &topo_levels;
-			g = g->base_graph;
-		}
-	}
+	g = prepare_commit_graph(ctx.r);
+	for (struct commit_graph *chain = g; chain; chain = chain->base_graph)
+		g->topo_levels = &topo_levels;
 
 	if (flags & COMMIT_GRAPH_WRITE_BLOOM_FILTERS)
 		ctx.changed_paths = 1;
 	if (!(flags & COMMIT_GRAPH_NO_WRITE_BLOOM_FILTERS)) {
-		struct commit_graph *g;
-
-		g = ctx.r->objects->commit_graph;
-
 		/* We have changed-paths already. Keep them in the next graph */
 		if (g && g->bloom_filter_settings) {
 			ctx.changed_paths = 1;
@@ -2580,22 +2570,15 @@ int write_commit_graph(struct odb_source *source,
 	bloom_settings.hash_version = bloom_settings.hash_version == 2 ? 2 : 1;
 
 	if (ctx.split) {
-		struct commit_graph *g = ctx.r->objects->commit_graph;
-
-		while (g) {
+		for (struct commit_graph *chain = g; chain; chain = chain->base_graph)
 			ctx.num_commit_graphs_before++;
-			g = g->base_graph;
-		}
 
 		if (ctx.num_commit_graphs_before) {
 			ALLOC_ARRAY(ctx.commit_graph_filenames_before, ctx.num_commit_graphs_before);
 			i = ctx.num_commit_graphs_before;
-			g = ctx.r->objects->commit_graph;
 
-			while (g) {
-				ctx.commit_graph_filenames_before[--i] = xstrdup(g->filename);
-				g = g->base_graph;
-			}
+			for (struct commit_graph *chain = g; chain; chain = chain->base_graph)
+				ctx.commit_graph_filenames_before[--i] = xstrdup(chain->filename);
 		}
 
 		if (ctx.opts)
@@ -2604,8 +2587,7 @@ int write_commit_graph(struct odb_source *source,
 
 	ctx.approx_nr_objects = repo_approximate_object_count(r);
 
-	if (ctx.append && ctx.r->objects->commit_graph) {
-		struct commit_graph *g = ctx.r->objects->commit_graph;
+	if (ctx.append && g) {
 		for (i = 0; i < g->num_commits; i++) {
 			struct object_id oid;
 			oidread(&oid, g->chunk_oid_lookup + st_mult(g->hash_algo->rawsz, i),
@@ -2651,7 +2633,7 @@ int write_commit_graph(struct odb_source *source,
 	} else
 		ctx.num_commit_graphs_after = 1;
 
-	ctx.trust_generation_numbers = validate_mixed_generation_chain(ctx.r->objects->commit_graph);
+	ctx.trust_generation_numbers = validate_mixed_generation_chain(g);
 
 	compute_topological_levels(&ctx);
 	if (ctx.write_generation_data)

-- 
2.51.0.417.g1ba7204a04.dirty
Previous: Taylor BlauNext: Taylor Blau
Message 6 of 26 in “odb: track commit graphs via object source”
  1. 0/6 odb: track commit graphs via object sourcePatrick Steinhardt, Sep 4, 2025
  2. 1/6 blame: drop explicit check for commit graphPatrick Steinhardt, Sep 4, 2025
  3. Taylor BlauSep 11, 2025
  4. 2/6 revision: drop explicit check for commit graphPatrick Steinhardt, Sep 4, 2025
  5. Taylor BlauSep 11, 2025
  6. 3/6 commit-graph: return the prepared commit graph from `prepare_commit_graph()`Patrick Steinhardt, Sep 4, 2025
  7. Taylor BlauSep 11, 2025
  8. 4/6 commit-graph: return commit graph from `repo_find_commit_pos_in_graph()`Patrick Steinhardt, Sep 4, 2025
  9. Taylor BlauSep 11, 2025
  10. 5/6 commit-graph: pass graphs that are to be merged as parameterPatrick Steinhardt, Sep 4, 2025
  11. 6/6 odb: move commit-graph into the object sourcesPatrick Steinhardt, Sep 4, 2025
  12. Taylor BlauSep 11, 2025
  13. Junio C HamanoSep 4, 2025
  14. Derrick StoleeSep 5, 2025
  15. Patrick SteinhardtSep 8, 2025
  16. Derrick StoleeSep 8, 2025
  17. Patrick SteinhardtSep 10, 2025
  18. Junio C HamanoSep 25, 2025
  19. Patrick SteinhardtSep 26, 2025
  20. Patrick SteinhardtOct 2, 2025
  21. Patrick SteinhardtOct 2, 2025
  22. Junio C HamanoOct 2, 2025
  23. Derrick StoleeOct 3, 2025
  24. Taylor BlauSep 11, 2025
  25. Junio C HamanoSep 4, 2025
  26. Patrick SteinhardtSep 5, 2025

Read the whole thread, see it on lore, or plain text.

$ cat FOOTERMessages come from the public archive at lore.kernel.org/git, fetched every hour. The front page is chosen and written each morning by an AI editor and can be wrong; the threads themselves are the record. About and API. For agents: an MCP server at https://gitlist.dev/mcp, and any thread, story or person page as Markdown by adding .md to its URL (or sending Accept: text/markdown). Details in /llms.txt.