From: Chengguang Xu <cgxu519@mykernel.net>
To: "Miklos Szeredi" <miklos@szeredi.hu>
Cc: "overlayfs" <linux-unionfs@vger.kernel.org>
Subject: Re: [RFC PATCH 1/2] ovl: skip checking lower file's write permisson on truncate
Date: Wed, 21 Jul 2021 00:01:00 +0800 [thread overview]
Message-ID: <17ac4a6258a.1113fdbb760287.4207934850282026708@mykernel.net> (raw)
In-Reply-To: <CAJfpegvmBggw3bgumMwDF_V_dgn=gvC+a+8oCgYfZ+Qu55U=vw@mail.gmail.com>
---- 在 星期二, 2021-07-20 23:19:16 Miklos Szeredi <miklos@szeredi.hu> 撰写 ----
> On Tue, 20 Jul 2021 at 16:35, Miklos Szeredi <miklos@szeredi.hu> wrote:
> >
> > On Sat, 24 Apr 2021 at 16:04, Chengguang Xu <cgxu519@mykernel.net> wrote:
> > >
> > > Lower files may be shared in overlayfs so strictly checking write
> > > perssmion on lower file will cause interferes between different
> > > overlayfs instances.
> >
> > How so?
> >
> > i_writecount on lower inode is not modified by overlayfs (at least not
> > in this codepath). Which means that there should be no interference
> > between overlayfs instances sharing a lower directory tree.
>
> I'm beginning to see what you are worrying about.
>
> So on one instance a file on lower gets executed and on another
> instance sharing the lower layer the file is truncated. The truncate
> is currently denied due to the negative i_writecount on the lower
> file. Also behavior is inconsistent between open(path, O_TRUNC) and
> truncate(path) even though the two should be equivalent.
Yeah, that's it.
Thanks for applying the patch and supplementary description.
Thanks,
Chengguang
next prev parent reply other threads:[~2021-07-20 16:09 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-24 14:03 [RFC PATCH 1/2] ovl: skip checking lower file's write permisson on truncate Chengguang Xu
2021-04-24 14:03 ` [RFC PATCH 2/2] ovl: enhance write permission check for writable open Chengguang Xu
2021-07-21 13:14 ` Miklos Szeredi
2021-04-28 12:18 ` 回复:[RFC PATCH 1/2] ovl: skip checking lower file's write permisson on truncate Chengguang Xu
2021-07-20 14:35 ` [RFC " Miklos Szeredi
2021-07-20 15:19 ` Miklos Szeredi
2021-07-20 16:01 ` Chengguang Xu [this message]
2021-07-20 16:01 ` Miklos Szeredi
2021-07-20 16:04 ` Chengguang Xu
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