From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS3215 2.6.0.0/16 X-Spam-Status: No, score=-4.0 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from out1.vger.email (out1.vger.email [IPv6:2620:137:e000::1:20]) by dcvr.yhbt.net (Postfix) with ESMTP id 4297F1F54E for ; Wed, 13 Jul 2022 17:41:55 +0000 (UTC) Authentication-Results: dcvr.yhbt.net; dkim=pass (1024-bit key; unprotected) header.d=pobox.com header.i=@pobox.com header.b="qvOTRQwM"; dkim-atps=neutral Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230102AbiGMRlu (ORCPT ); Wed, 13 Jul 2022 13:41:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60410 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230481AbiGMRlt (ORCPT ); Wed, 13 Jul 2022 13:41:49 -0400 Received: from pb-smtp2.pobox.com (pb-smtp2.pobox.com [64.147.108.71]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3171C2CE23 for ; Wed, 13 Jul 2022 10:41:48 -0700 (PDT) Received: from pb-smtp2.pobox.com (unknown [127.0.0.1]) by pb-smtp2.pobox.com (Postfix) with ESMTP id 1308E144CA4; Wed, 13 Jul 2022 13:41:47 -0400 (EDT) (envelope-from junio@pobox.com) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed; d=pobox.com; h=from:to:cc :subject:references:date:in-reply-to:message-id:mime-version :content-type; s=sasl; bh=Vzjs4jIPU7MccefA2Xx4T0acWVKgITJRAo0fOU NUEv8=; b=qvOTRQwMPrfzCLfakmlrhZzs0uEVtH9w+7D/wqlYWSkj+8OvEpSn0A qdq1A7XfSvXjTsEnSKy0gHBS9aW3tx/iM25CBg2h3WdX5DNwtoAunVAXLdfpzSv0 fC9lhE76dpdszfFjvC4LERt214DkbqodVFPI31CAPziT5cluL0TWk= Received: from pb-smtp2.nyi.icgroup.com (unknown [127.0.0.1]) by pb-smtp2.pobox.com (Postfix) with ESMTP id 09FF5144CA3; Wed, 13 Jul 2022 13:41:47 -0400 (EDT) (envelope-from junio@pobox.com) Received: from pobox.com (unknown [34.83.92.57]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by pb-smtp2.pobox.com (Postfix) with ESMTPSA id 71D95144CA2; Wed, 13 Jul 2022 13:41:46 -0400 (EDT) (envelope-from junio@pobox.com) From: Junio C Hamano To: Taylor Blau Cc: git@vger.kernel.org, derrickstolee@github.com, peff@peff.net, ps@pks.im, wfc@wfchandler.org Subject: Re: [PATCH 0/3] commit-graph: fix corruption during generation v2 upgrade References: Date: Wed, 13 Jul 2022 10:41:45 -0700 In-Reply-To: (Taylor Blau's message of "Tue, 12 Jul 2022 19:10:18 -0400") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Pobox-Relay-ID: 10FF0E40-02D3-11ED-84C3-CB998F0A682E-77302942!pb-smtp2.pobox.com Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Taylor Blau writes: > This brief series resolves a bug where a commit-graph would become > corrupt when upgrading from generation number v1 to v2, as originally > reported in [1]. > > Some speculation occurred as to what might be causing that bug in the > thread beginning at [1], until the problem was explained in more detail > by Will Chandler in [2]. > > The crux of the issue, as is described in [2] and [3], is that the > commit_graph_data slab is reused for read and write operations involving > the commit-graph, leading to situations where data computed in > preparation of a write is clobbered by a read of existing data. > > The first patch demonstrates the issue, and the second patch prepares to > fix it by introducing a helper function. The crux of the issue is > described and fixed in the third patch. > > [1]: https://lore.kernel.org/git/YqD5dgalb9EPnz85@coredump.intra.peff.net/ > [2]: https://lore.kernel.org/git/DD88D523-0ECA-4474-9AA5-1D4A431E532A@wfchandler.org/ > [3]: https://lore.kernel.org/git/YsS7H4i5DqUZVQ5i@nand.local/ Thanks. Do we know where this breaks? Applying [1/3] on Git 2.32, 2.34, and 2.35 seems to claim that "known breakage vanished".