From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-4.0 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI shortcircuit=no autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 3D531215F4 for ; Mon, 30 Apr 2018 16:29:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754757AbeD3Q3i (ORCPT ); Mon, 30 Apr 2018 12:29:38 -0400 Received: from mail-oi0-f53.google.com ([209.85.218.53]:37272 "EHLO mail-oi0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754713AbeD3Q3h (ORCPT ); Mon, 30 Apr 2018 12:29:37 -0400 Received: by mail-oi0-f53.google.com with SMTP id f63-v6so7925752oic.4 for ; Mon, 30 Apr 2018 09:29:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=qP+KSYF8gZFRsUNjo6wYqX1OJl56A+YrHs7juGtY2RU=; b=KTqj3Zd9k7gceRrW61JCnSpAIKFucpluGM5IJObfC2XHFqIoHzFD6KHpGvfF+tjnIC vGNrMxwzaEeDvnAXAdhUDkdlzU/ymD+Qi6TeEGVAGghR1TucHJUOqkDZtFTo0pr0lZP1 1Slder2XQk9wVBwp2h4x1WqfBlpSTLfuGkhGFN2av8hCE0+YgVzJwq0HysSVGx2GroTs PyyBwWIFKuZQEAcQozeuh4U701m/Jb/j++A8mu6RmsRQl1n/JX6xVfiPkuDNjcXlNTHq djYAru8LiriLpTasWTL2vfbJR8fXLAs0dP6hJrAaLOp8ErKSWKiNBuRZL5uAh0B5pS95 lTCA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=qP+KSYF8gZFRsUNjo6wYqX1OJl56A+YrHs7juGtY2RU=; b=CvshZfuxfrxfIvwj3CQtmaImoRBIPgyKungIPoiKese3QjQpi2BYd2PDhB7aXdPxh0 L1AoEl4Nea3tI9iYaFGsjwd05fan+Hw+0Lx7cUMbaYF49jWgqpNT80Q7wzpNuG5TwTE0 9XskaBtHfOuQBnWD8faiQx1zxOsfwoYJWNZkW6oYKiCJqIo3UePwsUomqV+0J6k3qKdI AYeepYQR9DQx3y+ZTsNwwRTHrm/9rOVacHzDq80wo97oxepas8lI25/Xsn9aatVBs8xy SNof38i2oPSjzB0yJ4xAei6HFWKHI6yc7xqPVvzxnOXknEFsH2o25AiY6pbNck878hia 1/qA== X-Gm-Message-State: ALQs6tCULkos9SKHPBAowaLF8lCCGThsvT0X2XhaReteWInZe7cJNuaw KmS14CV6iXqkjm4165UudrYbQn6lGVfPPB5Ss+s= X-Google-Smtp-Source: AB8JxZpzWTI2mExtOB56lrNKFuk8/r1cOcTg+UuopBVMPvJAH4rqqfVuS6y6LSOc2Vk6jtcNt3W6cD/kUZ1c8RITvtM= X-Received: by 2002:aca:51ce:: with SMTP id f197-v6mr7978418oib.32.1525105777353; Mon, 30 Apr 2018 09:29:37 -0700 (PDT) MIME-Version: 1.0 Received: by 10.74.198.152 with HTTP; Mon, 30 Apr 2018 09:29:06 -0700 (PDT) In-Reply-To: References: <20180424065045.13905-1-newren@gmail.com> From: Duy Nguyen Date: Mon, 30 Apr 2018 18:29:06 +0200 Message-ID: Subject: Re: [PATCH v3] unpack_trees: fix breakage when o->src_index != o->dst_index To: Elijah Newren Cc: Johannes Schindelin , Junio C Hamano , Git Mailing List Content-Type: text/plain; charset="UTF-8" Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Mon, Apr 30, 2018 at 6:19 PM, Elijah Newren wrote: > Hi Duy, > > On Mon, Apr 30, 2018 at 7:45 AM, Duy Nguyen wrote: >> On Mon, Apr 30, 2018 at 4:42 PM, Duy Nguyen wrote: >>> On Sun, Apr 29, 2018 at 10:53 PM, Johannes Schindelin >>> wrote: >>>>> > @@ -1412,12 +1422,13 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options >>>>> > WRITE_TREE_SILENT | >>>>> > WRITE_TREE_REPAIR); >>>>> > } >>>>> > - move_index_extensions(&o->result, o->dst_index); >>>>> > + move_index_extensions(&o->result, o->src_index); >>>>> >>>>> While this looks like the right thing to do on paper, I believe it's >>>>> actually broken for a specific case of untracked cache. In short, >>>>> please do not touch this line. I will send a patch to revert >>>>> edf3b90553 (unpack-trees: preserve index extensions - 2017-05-08), >>>>> which essentially deletes this line, with proper explanation and >>>>> perhaps a test if I could come up with one. >>>>> >>>>> When we update the index, we depend on the fact that all updates must >>>>> invalidate the right untracked cache correctly. In this unpack >>>>> operations, we start copying entries over from src to result. Since >>>>> 'result' (at least from the beginning) does not have an untracked >>>>> cache, it has nothing to invalidate when we copy entries over. By the >>>>> time we have done preparing 'result', what's recorded in src's (or >>>>> dst's for that matter) untracked cache may or may not apply to >>>>> 'result' index anymore. This copying only leads to more problems when >>>>> untracked cache is used. >>>> >>>> Is there really no way to invalidate just individual entries? >>> >>> Grr.... the short answer is the current code (i.e. without Elijah's >>> changes) works but in a twisted way. So you get to keep untracked >>> cache in the end. >> >> GAAAHH.. it works _with_ Elijah's changes (since he made the change >> from dst to src) not without (and no performance regression). > > So...is that an Acked-by for the patch Yes, Acked-by: me. > or does the "two wrong make a > right, I guess" comment suggest that we should still drop the > move_index_extensions change (essentially reverting to v1 of the PATCH > as found at 20180421193736.12722-1-newren@gmail.com), and you'll fix > things up further in a separate series? I think I'll stay away from this file for a while. When I gather enough courage, I'll need to read it through since it sounds like a mine field. -- Duy