From: Arnd Bergmann <arnd@arndb.de>
To: Rob Landley <rob@landley.net>
Cc: Taras Kondratiuk <takondra@cisco.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Mimi Zohar <zohar@linux.vnet.ibm.com>,
Jonathan Corbet <corbet@lwn.net>,
James McMechan <james.w.mcmechan@gmail.com>,
initramfs@vger.kernel.org, Victor Kamensky <kamensky@cisco.com>,
linux-doc@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
LSM List <linux-security-module@vger.kernel.org>,
xe-linux-external@cisco.com
Subject: Re: [PATCH v2 01/15] Documentation: add newcx initramfs format description
Date: Fri, 26 Jan 2018 10:04:43 +0100 [thread overview]
Message-ID: <CAK8P3a0B0XK8g4H+4grEru2GKRG91_qKxZ=y8AxaQi9pcPwKRQ@mail.gmail.com> (raw)
In-Reply-To: <0725a45f-45ee-7346-12ee-c3cc4b862654@landley.net>
On Fri, Jan 26, 2018 at 3:39 AM, Rob Landley <rob@landley.net> wrote:
> The problem with 1 second timestamps was you honestly could confuse
> "make" about which file was newer once an exec() could complete in the
> same second having done real work. That was the motivating issue causing
> the change, going to nanoseconds was just the big hammer of "this is
> large enough it won't matter again in our lifetimes". But nanosecond
> time stamps are recording more jitter than useful information, and that
> seems unlikely to change this century?
Sure, the only thing we really need the nanosecond timestamp for is
to keep them identical. E.g. if you use cpio to make an exact copy
of a file system, using microseconds timestamps will round all mtime
values. If you then use 'rsync' to compare/update the two copies
without passing a --modify-window= or --size-only, it will have
to read all files in rather then skipping those with identical size and
mtime.
Side note: the default behavior for file systems is actually to only use
the coarse timestamps of the last timer tick, so you actually do get
identical timestamps in practice, plus six digits of nonsense:
(on tmpfs)
$ for i in {000..999} ; do > $i ; done; stat --format="%y" * | uniq -c
86 2018-01-26 10:01:48.811135084 +0100
469 2018-01-26 10:01:48.815135143 +0100
445 2018-01-26 10:01:48.819135201 +0100
Arnd
next prev parent reply other threads:[~2018-01-26 9:04 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-25 3:27 [PATCH v2 00/15] extend initramfs archive format to support xattrs Taras Kondratiuk
2018-01-25 3:27 ` [PATCH v2 01/15] Documentation: add newcx initramfs format description Taras Kondratiuk
2018-01-25 9:29 ` Arnd Bergmann
2018-01-25 20:26 ` Taras Kondratiuk
2018-01-25 21:02 ` Arnd Bergmann
2018-01-25 22:13 ` Taras Kondratiuk
2018-01-26 2:39 ` Rob Landley
2018-01-26 9:04 ` Arnd Bergmann [this message]
2018-01-26 10:31 ` Henrique de Moraes Holschuh
2018-01-26 15:51 ` Victor Kamensky
2018-01-26 18:15 ` Henrique de Moraes Holschuh
2018-01-26 2:40 ` Rob Landley
2018-01-26 21:02 ` Taras Kondratiuk
2018-01-25 3:27 ` [PATCH v2 02/15] initramfs: replace states with function pointers Taras Kondratiuk
2018-01-25 3:27 ` [PATCH v2 03/15] initramfs: store file name in name_buf Taras Kondratiuk
2018-01-25 3:27 ` [PATCH v2 04/15] initramfs: remove unnecessary symlinks processing shortcut Taras Kondratiuk
2018-01-25 3:27 ` [PATCH v2 05/15] initramfs: move files creation into separate state Taras Kondratiuk
2018-01-25 3:27 ` [PATCH v2 06/15] initramfs: separate reading cpio method from header Taras Kondratiuk
2018-01-25 3:27 ` [PATCH v2 07/15] initramfs: split header layout information from parsing function Taras Kondratiuk
2018-01-25 3:27 ` [PATCH v2 08/15] initramfs: add newcx format Taras Kondratiuk
2018-01-25 3:27 ` [PATCH v2 09/15] initramfs: set extended attributes Taras Kondratiuk
2018-01-25 3:27 ` [PATCH v2 10/15] gen_init_cpio: move header formatting into function Taras Kondratiuk
2018-01-25 3:27 ` [PATCH v2 11/15] gen_init_cpio: add newcx format Taras Kondratiuk
2018-01-26 2:40 ` Rob Landley
2018-01-26 20:37 ` Taras Kondratiuk
2018-01-25 3:27 ` [PATCH v2 12/15] gen_init_cpio: set extended attributes for " Taras Kondratiuk
2018-01-25 3:27 ` [PATCH v2 13/15] gen_initramfs_list.sh: add -x option to enable " Taras Kondratiuk
2018-01-25 3:27 ` [PATCH v2 14/15] selinux: allow setxattr on rootfs so initramfs code can set them Taras Kondratiuk
2018-01-25 3:27 ` [PATCH v2 15/15] selinux: delay sid population for rootfs till init is complete Taras Kondratiuk
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
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAK8P3a0B0XK8g4H+4grEru2GKRG91_qKxZ=y8AxaQi9pcPwKRQ@mail.gmail.com' \
--to=arnd@arndb.de \
--cc=corbet@lwn.net \
--cc=hpa@zytor.com \
--cc=initramfs@vger.kernel.org \
--cc=james.w.mcmechan@gmail.com \
--cc=kamensky@cisco.com \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=rob@landley.net \
--cc=takondra@cisco.com \
--cc=viro@zeniv.linux.org.uk \
--cc=xe-linux-external@cisco.com \
--cc=zohar@linux.vnet.ibm.com \
/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.
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 NNTP newsgroup(s).