From: Junio C Hamano <gitster@pobox.com>
To: Paolo Bonzini <bonzini@gnu.org>
Cc: Jonathan Nieder <jrnieder@gmail.com>,
git@vger.kernel.org, 569505-forwarded@bugs.debian.org,
Zygo Blaxell <zblaxell@gibbs.hungrycats.org>
Subject: Re: mmap with MAP_PRIVATE is useless
Date: Sat, 13 Feb 2010 17:53:48 -0800 [thread overview]
Message-ID: <7vy6iw4m6r.fsf@alter.siamese.dyndns.org> (raw)
In-Reply-To: <4B775384.50009@gnu.org> (Paolo Bonzini's message of "Sun\, 14 Feb 2010 02\:36\:04 +0100")
Paolo Bonzini <bonzini@gnu.org> writes:
> This means that MAP_PRIVATE is utterly useless.
I do not think we ever used MAP_PRIVATE in order to protect outselves from
uncontrolled changes made by the outside world in the first place. Back
when most of these mmap calls were written by Linus and myself, we weren't
interested in using MAP_PRIVATE, or any other trick for that matter, to
deal with the case where the user tells git to go index a file, and then
mucks with the file before git finishes and gives back control.
We do use mmap in read-write mode when reading from the index file, and we
use MAP_PRIVATE to protect the outside world from our writing into the
mapped memory. As far as I know that is the only mmap for which
MAP_PRIVATE matters in the core git codebase.
Our calls to mmap() almost all have MAP_PRIVATE, even for read-only mmap,
but that is more or less from inertia, aka "an existing call to mmap is
with these options, I'll add another call imitating that".
next prev parent reply other threads:[~2010-02-14 1:54 UTC|newest]
Thread overview: 84+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20100211234753.22574.48799.reportbug@gibbs.hungrycats.org>
2010-02-12 0:27 ` Bug#569505: git-core: 'git add' corrupts repository if the working directory is modified as it runs Jonathan Nieder
2010-02-12 1:23 ` Zygo Blaxell
2010-02-13 12:12 ` Jonathan Nieder
2010-02-13 13:39 ` Ilari Liusvaara
2010-02-13 14:39 ` Thomas Rast
2010-02-13 16:29 ` Ilari Liusvaara
2010-02-13 22:09 ` Dmitry Potapov
2010-02-13 22:37 ` Zygo Blaxell
2010-02-14 1:18 ` [PATCH] don't use mmap() to hash files Dmitry Potapov
2010-02-14 1:37 ` Junio C Hamano
2010-02-14 2:18 ` Dmitry Potapov
2010-02-14 3:14 ` Junio C Hamano
2010-02-14 11:14 ` Thomas Rast
2010-02-14 11:46 ` Junio C Hamano
2010-02-14 1:53 ` Johannes Schindelin
2010-02-14 2:00 ` Junio C Hamano
2010-02-14 2:42 ` Dmitry Potapov
2010-02-14 11:07 ` Jakub Narebski
2010-02-14 11:55 ` Paolo Bonzini
2010-02-14 18:10 ` Johannes Schindelin
2010-02-14 19:06 ` Dmitry Potapov
2010-02-14 19:22 ` Johannes Schindelin
2010-02-14 19:28 ` Johannes Schindelin
2010-02-14 19:56 ` Dmitry Potapov
2010-02-14 23:52 ` Zygo Blaxell
2010-02-15 5:05 ` Nicolas Pitre
2010-02-15 12:23 ` Dmitry Potapov
2010-02-15 7:48 ` Paolo Bonzini
2010-02-15 12:25 ` Dmitry Potapov
2010-02-14 19:55 ` Dmitry Potapov
2010-02-14 23:13 ` Avery Pennarun
2010-02-15 4:16 ` Nicolas Pitre
2010-02-15 5:01 ` Avery Pennarun
2010-02-15 5:48 ` Nicolas Pitre
2010-02-15 19:19 ` Avery Pennarun
2010-02-15 19:29 ` Nicolas Pitre
2010-02-14 3:05 ` [PATCH v2] " Dmitry Potapov
2010-02-18 1:16 ` [PATCH] Teach "git add" and friends to be paranoid Junio C Hamano
2010-02-18 1:20 ` Junio C Hamano
2010-02-18 15:32 ` Zygo Blaxell
2010-02-19 17:51 ` Junio C Hamano
2010-02-18 1:38 ` Jeff King
2010-02-18 4:55 ` Nicolas Pitre
2010-02-18 5:36 ` Junio C Hamano
2010-02-18 7:27 ` Wincent Colaiuta
2010-02-18 16:18 ` Zygo Blaxell
2010-02-18 18:12 ` Jonathan Nieder
2010-02-18 18:35 ` Junio C Hamano
2010-02-22 12:59 ` Paolo Bonzini
2010-02-22 13:33 ` Dmitry Potapov
2010-02-18 10:14 ` Thomas Rast
2010-02-18 18:16 ` Junio C Hamano
2010-02-18 19:58 ` Nicolas Pitre
2010-02-18 20:11 ` 16 gig, 350,000 file repository Bill Lear
2010-02-18 20:58 ` Nicolas Pitre
2010-02-19 9:27 ` Erik Faye-Lund
2010-02-22 22:20 ` Bill Lear
2010-02-22 22:31 ` Nicolas Pitre
2010-02-18 20:14 ` [PATCH] Teach "git add" and friends to be paranoid Peter Harris
2010-02-18 20:17 ` Junio C Hamano
2010-02-18 21:30 ` Nicolas Pitre
2010-02-19 1:04 ` Jonathan Nieder
2010-02-19 15:26 ` Zygo Blaxell
2010-02-19 17:52 ` Junio C Hamano
2010-02-19 19:08 ` Zygo Blaxell
2010-02-19 8:28 ` Dmitry Potapov
2010-02-19 17:52 ` Junio C Hamano
2010-02-20 19:23 ` Junio C Hamano
2010-02-21 7:21 ` Dmitry Potapov
2010-02-21 19:32 ` Junio C Hamano
2010-02-22 3:35 ` Dmitry Potapov
2010-02-22 6:59 ` Junio C Hamano
2010-02-22 12:25 ` Dmitry Potapov
2010-02-22 15:40 ` Nicolas Pitre
2010-02-22 16:01 ` Dmitry Potapov
2010-02-22 17:31 ` Zygo Blaxell
2010-02-22 18:01 ` Nicolas Pitre
2010-02-22 19:56 ` Junio C Hamano
2010-02-22 20:52 ` Nicolas Pitre
2010-02-22 18:05 ` Dmitry Potapov
2010-02-22 18:14 ` Nicolas Pitre
2010-02-14 1:36 ` mmap with MAP_PRIVATE is useless (was Re: Bug#569505: git-core: 'git add' corrupts repository if the working directory is modified as it runs) Paolo Bonzini
2010-02-14 1:53 ` Junio C Hamano [this message]
2010-02-14 2:11 ` mmap with MAP_PRIVATE is useless Paolo Bonzini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=7vy6iw4m6r.fsf@alter.siamese.dyndns.org \
--to=gitster@pobox.com \
--cc=569505-forwarded@bugs.debian.org \
--cc=bonzini@gnu.org \
--cc=git@vger.kernel.org \
--cc=jrnieder@gmail.com \
--cc=zblaxell@gibbs.hungrycats.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).