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From: Amir Goldstein <amir73il@gmail.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Sargun Dhillon <sargun@sargun.me>,
	overlayfs <linux-unionfs@vger.kernel.org>,
	Miklos Szeredi <miklos@szeredi.hu>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Giuseppe Scrivano <gscrivan@redhat.com>,
	Daniel J Walsh <dwalsh@redhat.com>,
	David Howells <dhowells@redhat.com>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Chengguang Xu <cgxu519@mykernel.net>
Subject: Re: [RFC PATCH 3/3] overlay: Add the ability to remount volatile directories when safe
Date: Wed, 18 Nov 2020 09:24:04 +0200	[thread overview]
Message-ID: <CAOQ4uxjkmooYY-NAVrSZOU9BDP0azmbrrmkKNKgyQOURR6eqEg@mail.gmail.com> (raw)
In-Reply-To: <20201117182940.GA91497@redhat.com>

On Tue, Nov 17, 2020 at 8:29 PM Vivek Goyal <vgoyal@redhat.com> wrote:
>
> On Tue, Nov 17, 2020 at 08:03:16PM +0200, Amir Goldstein wrote:
> > > > C. "shutdown" the filesystem if writeback errors happened and return
> > > >      EIO from any read, like some blockdev filesystems will do in face
> > > >      of metadata write errors
> > > >
> > > > I happen to have a branch ready for that ;-)
> > > > https://github.com/amir73il/linux/commits/ovl-shutdown
> > >
> > >
> > > This branch seems to implement shutdown ioctl. So it will still need
> > > glue code to detect writeback failure in upper/ and trigger shutdown
> > > internally?
> > >
> >
> > Yes.
> > ovl_get_acess() can check both the administrative ofs->goingdown
> > command and the upper writeback error condition for volatile ovl
> > or something like that.
>
> This approach will not help mmaped() pages though, if I do.
>
> - Store to addr
> - msync
> - Load from addr
>
> There is a chance that I can still read back old data.
>

msync does not go through overlay. It goes directly to upper fs,
so it will sync pages and return error on volatile overlay as well.

Maybe there will still be weird corner cases, but the shutdown approach
should cover most or all of the interesting cases.

Thanks,
Amir.

  reply	other threads:[~2020-11-18  7:24 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-16  4:57 [RFC PATCH 0/3] Make overlayfs volatile mounts reusable Sargun Dhillon
2020-11-16  4:57 ` [RFC PATCH 1/3] fs: Add s_instance_id field to superblock for unique identification Sargun Dhillon
2020-11-16  5:07   ` Sargun Dhillon
2020-11-16  4:57 ` [RFC PATCH 2/3] overlay: Add ovl_do_getxattr helper Sargun Dhillon
2020-11-16 11:00   ` Amir Goldstein
2020-11-16  4:57 ` [RFC PATCH 3/3] overlay: Add the ability to remount volatile directories when safe Sargun Dhillon
2020-11-16  9:31   ` Amir Goldstein
2020-11-16 10:30     ` Sargun Dhillon
2020-11-16 11:17       ` Amir Goldstein
2020-11-16 12:52         ` Amir Goldstein
2020-11-16 14:42   ` Vivek Goyal
2020-11-16 14:45     ` Vivek Goyal
2020-11-16 15:20     ` Amir Goldstein
2020-11-16 16:36       ` Vivek Goyal
2020-11-16 18:25         ` Sargun Dhillon
2020-11-16 19:27           ` Vivek Goyal
2020-11-16 20:18         ` Amir Goldstein
2020-11-16 21:09           ` Vivek Goyal
2020-11-17  5:33             ` Amir Goldstein
2020-11-17 14:48               ` Vivek Goyal
2020-11-17 15:24                 ` Amir Goldstein
2020-11-17 15:40                   ` Vivek Goyal
2020-11-17 16:46                   ` Vivek Goyal
2020-11-17 18:03                     ` Amir Goldstein
2020-11-17 18:29                       ` Vivek Goyal
2020-11-18  7:24                         ` Amir Goldstein [this message]
2020-11-18  8:27                           ` Sargun Dhillon
2020-11-18 10:46                             ` Amir Goldstein
2020-11-18 14:55                           ` Vivek Goyal
2020-11-16 21:26           ` Vivek Goyal
2020-11-16 22:14             ` Sargun Dhillon
2020-11-17  5:41               ` Amir Goldstein
2020-11-17 17:05               ` Vivek Goyal
2020-11-16 17:38     ` Sargun Dhillon

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