Re: [PATCH v3 14/14] builtin/commit-graph.c: introduce '--max-new-filters=<n>'

From: "SZEDER Gábor" <szeder.dev@gmail.com>
To: Taylor Blau <me@ttaylorr.com>
Cc: git@vger.kernel.org, peff@peff.net, dstolee@microsoft.com,
	gitster@pobox.com
Subject: Re: [PATCH v3 14/14] builtin/commit-graph.c: introduce '--max-new-filters=<n>'
Date: Wed, 12 Aug 2020 13:49:29 +0200	[thread overview]
Message-ID: <20200812114929.GA19082@szeder.dev> (raw)
In-Reply-To: <09f6871f66bff838c067a3e0d23cd4622171f3bd.1597178915.git.me@ttaylorr.com>

On Tue, Aug 11, 2020 at 04:52:14PM -0400, Taylor Blau wrote:

> diff --git a/commit-graph.c b/commit-graph.c
> index 6886f319a5..4aae5471e3 100644
> --- a/commit-graph.c
> +++ b/commit-graph.c
> @@ -954,7 +954,8 @@ struct tree *get_commit_tree_in_graph(struct repository *r, const struct commit
>  }
>  
>  static int get_bloom_filter_large_in_graph(struct commit_graph *g,
> -					   const struct commit *c)
> +					   const struct commit *c,
> +					   uint32_t max_changed_paths)
>  {
>  	uint32_t graph_pos = commit_graph_position(c);
>  	if (graph_pos == COMMIT_NOT_FROM_GRAPH)
> @@ -965,6 +966,17 @@ static int get_bloom_filter_large_in_graph(struct commit_graph *g,
>  
>  	if (!(g && g->bloom_large))
>  		return 0;
> +	if (g->bloom_filter_settings->max_changed_paths != max_changed_paths) {
> +		/*
> +		 * Force all commits which are subject to a different
> +		 * 'max_changed_paths' limit to be recomputed from scratch.
> +		 *
> +		 * Note that this could likely be improved, but is ignored since
> +		 * all real-world graphs set the maximum number of changed paths
> +		 * at 512.
> +		 */
> +		return 0;
> +	}
>  	return bitmap_get(g->bloom_large, graph_pos - g->num_commits_in_base);
>  }
>  
> @@ -1470,6 +1482,7 @@ static void compute_bloom_filters(struct write_commit_graph_context *ctx)
>  	int i;
>  	struct progress *progress = NULL;
>  	int *sorted_commits;
> +	int max_new_filters;
>  
>  	init_bloom_filters();
>  	ctx->bloom_large = bitmap_word_alloc(ctx->commits.nr / BITS_IN_EWORD + 1);
> @@ -1486,10 +1499,15 @@ static void compute_bloom_filters(struct write_commit_graph_context *ctx)
>  		ctx->order_by_pack ? commit_pos_cmp : commit_gen_cmp,
>  		&ctx->commits);
>  
> +	max_new_filters = ctx->opts->max_new_filters >= 0 ?
> +		ctx->opts->max_new_filters : ctx->commits.nr;

git_test_write_commit_graph_or_die() invokes
write_commit_graph_reachable() with opts=0x0, so 'ctx->opts' is NULL,
and we get segfault.  This breaks a lot of tests when run with
GIT_TEST_COMMIT_GRAPH=1 GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS=1.