archive mirror
 help / color / mirror / Atom feed
From: Miklos Szeredi <>
To: Amir Goldstein <>
Cc: Chengguang Xu <>,
	overlayfs <>
Subject: Re: [PATCH v2 3/3] ovl: copy-up optimization for truncate
Date: Fri, 9 Apr 2021 10:02:11 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Fri, Apr 9, 2021 at 7:50 AM Amir Goldstein <> wrote:

> Anyway, I hold my opinion that the optimization of skipping notify_change()
> has little benefit and is a potential for bugs, even if the specific
> bug I pointed
> out is not real.

I can agree with that.

At this point the only sane way I can see this optimization be
implemented is to split the copy-up into a preparation and a commit

1) copy to tmpfile (can optimize to truncated size)
2) call notify_change() on the tmpfile to truncate
3) if successful, link the tmpfile into upper

With that the truncate still remains a single atomic operation.
Only slight difference is that now ctime will not match mtime after a
copy-up/truncate operation, but I guess that's not something anybody
should be dependent on.


  reply	other threads:[~2021-04-09  8:03 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-06 12:02 [PATCH v2 1/3] ovl: do not restore mtime on copy-up for regular file Chengguang Xu
2021-04-06 12:02 ` [PATCH v2 2/3] ovl: check actual copy-up size Chengguang Xu
2021-04-07  6:56   ` Amir Goldstein
2021-04-06 12:02 ` [PATCH v2 3/3] ovl: copy-up optimization for truncate Chengguang Xu
2021-04-07  7:52   ` Amir Goldstein
2021-04-08 13:23     ` Chengguang Xu
2021-04-08 14:40       ` Amir Goldstein
2021-04-09  3:00         ` Chengguang Xu
2021-04-09  5:50           ` Amir Goldstein
2021-04-09  8:02             ` Miklos Szeredi [this message]
2021-04-07  6:55 ` [PATCH v2 1/3] ovl: do not restore mtime on copy-up for regular file Amir Goldstein

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:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='' \ \ \ \ \

* 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).