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From: Duy Nguyen <pclouds@gmail.com>
To: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Cc: Elijah Newren <newren@gmail.com>,
	Junio C Hamano <gitster@pobox.com>,
	Git Mailing List <git@vger.kernel.org>
Subject: Re: [PATCH v3] unpack_trees: fix breakage when o->src_index != o->dst_index
Date: Mon, 30 Apr 2018 16:42:31 +0200	[thread overview]
Message-ID: <CACsJy8Cqq5c1QC=2EjfajS3=+ofAF8eoFG2V4QeY+LzSykJOFw@mail.gmail.com> (raw)
In-Reply-To: <nycvar.QRO.7.76.6.1804292251000.79@tvgsbejvaqbjf.bet>

On Sun, Apr 29, 2018 at 10:53 PM, Johannes Schindelin
<Johannes.Schindelin@gmx.de> 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.

I was right about the invalidation stuff. I knew about
invalidate_ce_path() in this file. What I didn't remember was this
function actually invalidates entries from the _source_ index, not the
result one. What kind of logic is that? You copy/move entries from
source to result than you go invalidate the source. Since the original
move_index_extensions() call moves extensions from the source, these
are already properly invalidated (both untracked cache and cache
tree), it it looks like it does the right thing. Two wrongs make a
right, I guess.

Sorry for venting. I was not happy with what I found. And sorry for
wasting your time making this move_index.. change then remove it.

> I have a couple of worktrees which are *huge*. And edf3b90553 really
> helped relieve the pain a bit when running `git status`. Now you say that
> even a `git checkout -b new-branch` would blow the untracked cache away
> again?
>
> It would be *really* nice if we could prevent that performance regression
> somehow.
>
> Ciao,
> Dscho



-- 
Duy

  reply	other threads:[~2018-04-30 14:43 UTC|newest]

Thread overview: 78+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-19 17:57 [PATCH v10 00/36] Add directory rename detection to git Elijah Newren
2018-04-19 17:57 ` [PATCH v10 01/36] directory rename detection: basic testcases Elijah Newren
2018-04-19 17:57 ` [PATCH v10 02/36] directory rename detection: directory splitting testcases Elijah Newren
2018-04-19 17:57 ` [PATCH v10 03/36] directory rename detection: testcases to avoid taking detection too far Elijah Newren
2018-04-19 17:57 ` [PATCH v10 04/36] directory rename detection: partially renamed directory testcase/discussion Elijah Newren
2018-04-19 17:57 ` [PATCH v10 05/36] directory rename detection: files/directories in the way of some renames Elijah Newren
2018-04-19 17:57 ` [PATCH v10 06/36] directory rename detection: testcases checking which side did the rename Elijah Newren
2018-04-19 17:57 ` [PATCH v10 07/36] directory rename detection: more involved edge/corner testcases Elijah Newren
2018-04-19 17:57 ` [PATCH v10 08/36] directory rename detection: testcases exploring possibly suboptimal merges Elijah Newren
2018-04-19 17:57 ` [PATCH v10 09/36] directory rename detection: miscellaneous testcases to complete coverage Elijah Newren
2018-04-19 17:57 ` [PATCH v10 10/36] directory rename detection: tests for handling overwriting untracked files Elijah Newren
2018-04-19 17:57 ` [PATCH v10 11/36] directory rename detection: tests for handling overwriting dirty files Elijah Newren
2018-04-19 17:57 ` [PATCH v10 12/36] merge-recursive: move the get_renames() function Elijah Newren
2018-04-19 17:58 ` [PATCH v10 13/36] merge-recursive: introduce new functions to handle rename logic Elijah Newren
2018-04-19 17:58 ` [PATCH v10 14/36] merge-recursive: fix leaks of allocated renames and diff_filepairs Elijah Newren
2018-04-19 17:58 ` [PATCH v10 15/36] merge-recursive: make !o->detect_rename codepath more obvious Elijah Newren
2018-04-19 17:58 ` [PATCH v10 16/36] merge-recursive: split out code for determining diff_filepairs Elijah Newren
2018-04-19 17:58 ` [PATCH v10 17/36] merge-recursive: make a helper function for cleanup for handle_renames Elijah Newren
2018-04-19 17:58 ` [PATCH v10 18/36] merge-recursive: add get_directory_renames() Elijah Newren
2018-05-06 23:41   ` SZEDER Gábor
2018-05-07 15:45     ` [PATCH] fixup! " Elijah Newren
2019-10-09 20:38   ` [PATCH v10 18/36] " Johannes Schindelin
2019-10-11 20:02     ` Elijah Newren
2019-10-12 19:23       ` Johannes Schindelin
2018-04-19 17:58 ` [PATCH v10 19/36] merge-recursive: check for directory level conflicts Elijah Newren
2018-04-19 17:58 ` [PATCH v10 20/36] merge-recursive: add computation of collisions due to dir rename & merging Elijah Newren
2018-04-19 17:58 ` [PATCH v10 21/36] merge-recursive: check for file level conflicts then get new name Elijah Newren
2018-04-19 17:58 ` [PATCH v10 22/36] merge-recursive: when comparing files, don't include trees Elijah Newren
2018-04-19 17:58 ` [PATCH v10 23/36] merge-recursive: apply necessary modifications for directory renames Elijah Newren
2018-04-19 17:58 ` [PATCH v10 24/36] merge-recursive: avoid clobbering untracked files with " Elijah Newren
2018-04-19 17:58 ` [PATCH v10 25/36] merge-recursive: fix overwriting dirty files involved in renames Elijah Newren
2018-04-19 20:48   ` Martin Ågren
2018-04-19 20:54     ` Martin Ågren
2018-04-19 21:06     ` Elijah Newren
2018-04-19 17:58 ` [PATCH v10 26/36] merge-recursive: fix remaining directory rename + dirty overwrite cases Elijah Newren
2018-04-19 17:58 ` [PATCH v10 27/36] directory rename detection: new testcases showcasing a pair of bugs Elijah Newren
2018-04-19 17:58 ` [PATCH v10 28/36] merge-recursive: avoid spurious rename/rename conflict from dir renames Elijah Newren
2018-04-19 17:58 ` [PATCH v10 29/36] merge-recursive: improve add_cacheinfo error handling Elijah Newren
2018-04-19 17:58 ` [PATCH v10 30/36] merge-recursive: move more is_dirty handling to merge_content Elijah Newren
2018-04-19 17:58 ` [PATCH v10 31/36] merge-recursive: avoid triggering add_cacheinfo error with dirty mod Elijah Newren
2018-04-19 17:58 ` [PATCH v10 32/36] t6046: testcases checking whether updates can be skipped in a merge Elijah Newren
2018-04-19 20:26   ` SZEDER Gábor
2018-04-19 20:55     ` Elijah Newren
2018-04-19 17:58 ` [PATCH v10 33/36] merge-recursive: fix was_tracked() to quit lying with some renamed paths Elijah Newren
2018-04-19 20:39   ` Martin Ågren
2018-04-19 20:54     ` Elijah Newren
2018-04-20 12:23   ` SZEDER Gábor
2018-04-20 15:23     ` Elijah Newren
2018-04-21 19:37     ` [RFC PATCH v10 32.5/36] unpack_trees: fix memory corruption with split_index when src != dst Elijah Newren
2018-04-21 20:13       ` Elijah Newren
2018-04-22 12:38       ` Duy Nguyen
2018-04-23 17:09         ` Elijah Newren
2018-04-23 17:37           ` Duy Nguyen
2018-04-23 18:05             ` Elijah Newren
2018-04-24  0:24               ` [PATCH v2] unpack_trees: fix breakage when o->src_index != o->dst_index Elijah Newren
2018-04-24  1:51                 ` Junio C Hamano
2018-04-24  3:05                 ` Junio C Hamano
2018-04-24  6:50                   ` [PATCH v3] " Elijah Newren
2018-04-29 18:05                     ` Duy Nguyen
2018-04-29 20:53                       ` Johannes Schindelin
2018-04-30 14:42                         ` Duy Nguyen [this message]
2018-04-30 14:45                           ` Duy Nguyen
2018-04-30 16:19                             ` Elijah Newren
2018-04-30 16:29                               ` Duy Nguyen
2018-04-19 17:58 ` [PATCH v10 34/36] merge-recursive: fix remainder of was_dirty() to use original index Elijah Newren
2018-04-19 17:58 ` [PATCH v10 35/36] merge-recursive: make "Auto-merging" comment show for other merges Elijah Newren
2018-04-19 17:58 ` [PATCH v10 36/36] merge-recursive: fix check for skipability of working tree updates Elijah Newren
2018-04-19 18:35 ` [PATCH v10 00/36] Add directory rename detection to git Elijah Newren
2018-04-19 18:41   ` Stefan Beller
2018-04-19 19:54     ` Derrick Stolee
2018-04-19 20:22   ` Elijah Newren
2018-04-20  3:05   ` Junio C Hamano
2018-04-23 17:50     ` Elijah Newren
2018-04-24 20:20     ` [PATCH v10 1/2] fixup! merge-recursive: fix was_tracked() to quit lying with some renamed paths Elijah Newren
2018-04-24 20:21       ` [PATCH v10 2/2] fixup! t6046: testcases checking whether updates can be skipped in a merge Elijah Newren
2018-04-23 17:28 ` [PATCH v10 00/36] Add directory rename detection to git Elijah Newren
2018-04-23 23:46   ` Junio C Hamano
2018-04-24  0:15     ` Elijah Newren

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