From patchwork Thu Oct 8 13:56:52 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Philippe Blain via GitGitGadget X-Patchwork-Id: 11823015 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E41DC4363A for ; Thu, 8 Oct 2020 13:57:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C6ECA217BA for ; Thu, 8 Oct 2020 13:56:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="P0qBZr9n" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729829AbgJHN46 (ORCPT ); Thu, 8 Oct 2020 09:56:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51594 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726875AbgJHN46 (ORCPT ); Thu, 8 Oct 2020 09:56:58 -0400 Received: from mail-wr1-x443.google.com (mail-wr1-x443.google.com [IPv6:2a00:1450:4864:20::443]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CEE3DC061755 for ; Thu, 8 Oct 2020 06:56:56 -0700 (PDT) Received: by mail-wr1-x443.google.com with SMTP id y12so1346299wrp.6 for ; Thu, 08 Oct 2020 06:56:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=message-id:from:date:subject:fcc:content-transfer-encoding :mime-version:to:cc; bh=EPQnwrtqXRnotRfd5BkBwcS4KzLm96Y9ramLHwlNn68=; b=P0qBZr9nddUdSgJsketcJD7wsmeCfdWyVzINXhpJWjh3Fgid8nW/gCynTg4qCi0HVW 6behA14pgqu0Ra3/6i+siCi0Wle2kwphsBi7GKIigvAP/yK984dIfb/egqxUc6jLvF2h TF9EM9QXyg/XFz5EFF8D7sWET2u7pWKFa9AOPuiRkWjYORh4y6pa4DXPa/06eqGD7dRt URLnzZvthabgQdbn4Cl2E0oyN7581piUx9/7d7RJ9sYGwcGyV7BdF7dOBdVs/m9vSm1s dHvJtgoqtEwFl/YxZuX/xEdyYo3HICpEdb3/rDQSReXYJfk3nz+tsPp2U2du5swBpJe3 k1UA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:from:date:subject:fcc :content-transfer-encoding:mime-version:to:cc; bh=EPQnwrtqXRnotRfd5BkBwcS4KzLm96Y9ramLHwlNn68=; b=RjOmmEeK4ulRL8uijwXDtDrxRpXJOs1fF1Y9Nz4Mps6uus8d8J/cCuu74lKaE3GFw2 flPU3OvP48yJ2hq+LzTdY/HPDMfwafaopdXlwNaHf0N+HlvnZasLyOnYjZGsm3NYsDU7 DrMkYLzg/I6juvmcCQ/XxXBcOhz5UHCuT1EwSeglvESxt1o9Tc7qy8bUZOBbo2Unlex9 TAi5Xe5A8WFUnwfutUJEdKZFPr1s3BwipRxJaWrU0uBuKQrFOxzrDk6qBVZLPwFpTNsA NS8vo0suSZwmn2BaSLYHUuna1Ijk41SbR66hSgcGoZuZcRo1Nc0jiJtVj+mrOZDlJQHV wipw== X-Gm-Message-State: AOAM531yP7LWR1F7GQ7TEKgcLHVde/uexP0ECHe7qP2P7atzI0JXTlwl 56SzDrurO1n5rstZjPw6wBoiQTncIt0= X-Google-Smtp-Source: ABdhPJyL3cl0pPjI/hymDbjZRysJ8VhYz/N2aX4P4IS58QkRjhusC6Ofz8wc6zdU2Kh79h35p4Cw9Q== X-Received: by 2002:adf:deca:: with SMTP id i10mr4200820wrn.96.1602165415106; Thu, 08 Oct 2020 06:56:55 -0700 (PDT) Received: from [127.0.0.1] ([13.74.141.28]) by smtp.gmail.com with ESMTPSA id l18sm7539847wrp.84.2020.10.08.06.56.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Oct 2020 06:56:54 -0700 (PDT) Message-Id: From: "Derrick Stolee via GitGitGadget" Date: Thu, 08 Oct 2020 13:56:52 +0000 Subject: [PATCH] commit-graph: ignore duplicates when merging layers Fcc: Sent MIME-Version: 1.0 To: git@vger.kernel.org Cc: Derrick Stolee , Derrick Stolee Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org From: Derrick Stolee Thomas reported [1] that a "git fetch" command was failing with an error saying "unexpected duplicate commit id". The root cause is that they had fetch.writeCommitGraph enabled which generates commit-graph chains, and this instance was merging two layers that both contained the same commit ID. [1] https://lore.kernel.org/git/55f8f00c-a61c-67d4-889e-a9501c596c39@virtuell-zuhause.de/ The initial assumption is that Git would not write a commit ID into a commit-graph layer if it already exists in a lower commit-graph layer. Somehow, this specific case did get into that situation, leading to this error. While unexpected, this isn't actually invalid (as long as the two layers agree on the metadata for the commit). When we parse a commit that does not have a graph_pos in the commit_graph_data_slab, we use binary search in the commit-graph layers to find the commit and set graph_pos. That position is never used again in this case. However, when we parse a commit from the commit-graph file, we load its parents from the commit-graph and assign graph_pos at that point. If those parents were already parsed from the commit-graph, then nothing needs to be done. Otherwise, this graph_pos is a valid position in the commit-graph so we can parse the parents, when necessary. Thus, this die() is too aggignoring the duplicates. This leads to some additional complication that we did no have before: if we only ignore the duplicates, then we will produce a commit-graph that has identical commit IDs listed in adjacent positions. This excess data will never be removed from the commit-graph, which could cascade into significantly bloated file sizes. Begrudgingly, the best way to fix this is to copy the commit pointers into a new list that only contains de-duplicated commit IDs. This adds a slight memory overhead, but it is small compared to having all of these commits parsed in memory, so it should be an acceptable cost for avoiding these failures. Since the root cause for producing commit-graph layers with these duplicate commits is currently unknown, it is difficult to create a test for this scenario. For now, we must rely on testing the example data graciously provided in [1]. My local test successfully merged layers, and 'git commit-graph verify' passed. Reported-by: Thomas Braun Co-authored-by: Jeff King Signed-off-by: Derrick Stolee --- commit-graph: ignore duplicates when merging layers This wasn't quite as simple as what Peff had posted, since we really don't want to keep duplicate commits around in the new merged layer. I still don't have a grasp on how this happened in the first place, but will keep looking. Thanks, -Stolee Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-747%2Fderrickstolee%2Fcommit-graph-dup-commits-v1 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-747/derrickstolee/commit-graph-dup-commits-v1 Pull-Request: https://github.com/gitgitgadget/git/pull/747 commit-graph.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) base-commit: d98273ba77e1ab9ec755576bc86c716a97bf59d7 diff --git a/commit-graph.c b/commit-graph.c index cb042bdba8..29bac78dc3 100644 --- a/commit-graph.c +++ b/commit-graph.c @@ -2009,6 +2009,7 @@ static int commit_compare(const void *_a, const void *_b) static void sort_and_scan_merged_commits(struct write_commit_graph_context *ctx) { uint32_t i; + struct packed_commit_list deduped_commits = { NULL, 0, 0 }; if (ctx->report_progress) ctx->progress = start_delayed_progress( @@ -2016,6 +2017,8 @@ static void sort_and_scan_merged_commits(struct write_commit_graph_context *ctx) ctx->commits.nr); QSORT(ctx->commits.list, ctx->commits.nr, commit_compare); + deduped_commits.alloc = ctx->commits.nr; + ALLOC_ARRAY(deduped_commits.list, deduped_commits.alloc); ctx->num_extra_edges = 0; for (i = 0; i < ctx->commits.nr; i++) { @@ -2023,17 +2026,30 @@ static void sort_and_scan_merged_commits(struct write_commit_graph_context *ctx) if (i && oideq(&ctx->commits.list[i - 1]->object.oid, &ctx->commits.list[i]->object.oid)) { - die(_("unexpected duplicate commit id %s"), - oid_to_hex(&ctx->commits.list[i]->object.oid)); + /* + * Silently ignore duplicates. These were likely + * created due to a commit appearing in multiple + * layers of the chain, which is unexpected but + * not invalid. We should make sure there is a + * unique copy in the new layer. + */ } else { unsigned int num_parents; + deduped_commits.list[deduped_commits.nr] = ctx->commits.list[i]; + deduped_commits.nr++; + num_parents = commit_list_count(ctx->commits.list[i]->parents); if (num_parents > 2) ctx->num_extra_edges += num_parents - 1; } } + free(ctx->commits.list); + ctx->commits.list = deduped_commits.list; + ctx->commits.nr = deduped_commits.nr; + ctx->commits.alloc = deduped_commits.alloc; + stop_progress(&ctx->progress); }