Re: [POC/RFC PATCH] overlayfs: fix data inconsistency at copy up

From	Miklos Szeredi <miklos@szeredi.hu>
Newsgroups	linux.kernel
Subject	Re: [POC/RFC PATCH] overlayfs: fix data inconsistency at copy up
Date	2016-10-21 11:40 +0200
Message-ID	<suEsX-3Ew-55@gated-at.bofh.it> (permalink)
References	<srrVg-52p-33@gated-at.bofh.it> <susrL-45X-1@gated-at.bofh.it> <suE9B-3xe-61@gated-at.bofh.it>
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On Fri, Oct 21, 2016 at 11:13 AM, Amir Goldstein <amir73il@gmail.com> wrote:

> I think it would be a good idea in general to stabilize the overlay ino/dev
> throughout copy-up, same as Miklos suggested to do for directories, to
> all files:
> pure upper uses upper ino + overlayfs dev
> non-pure upper uses lower ino + overlayfs dev

Making st_ino, st_dev and d_ino behave consistently would be the next big step.

The above scheme only works if lower and upper are on the same
filesystem.  Otherwise there can be collisions between the lower and
upper inode numbers.  Perhaps you meant:

- pure upper uses upper ino + upper dev
- non-pure upper uses lower ino + overlayfs dev

It works for the single lower layer case, but again breaks if there
are multiple lower layers.   And d_ino in a merged directory could
still get us into trouble.  And find -xdev would not do what you'd
expect with a "normal" filesystem.

So there doesn't appear to be any easy solutions to this...

Thanks,
Miklos

Thread

Re: [POC/RFC PATCH] overlayfs: fix data inconsistency at copy up Vivek Goyal <vgoyal@redhat.com> - 2016-10-20 22:50 +0200
  Re: [POC/RFC PATCH] overlayfs: fix data inconsistency at copy up Vivek Goyal <vgoyal@redhat.com> - 2016-10-20 23:00 +0200
    Re: [POC/RFC PATCH] overlayfs: fix data inconsistency at copy up Amir Goldstein <amir73il@gmail.com> - 2016-10-21 11:00 +0200
      Re: [POC/RFC PATCH] overlayfs: fix data inconsistency at copy up Vivek Goyal <vgoyal@redhat.com> - 2016-10-21 22:20 +0200
        Re: [POC/RFC PATCH] overlayfs: fix data inconsistency at copy up Amir Goldstein <amir73il@gmail.com> - 2016-10-22 09:30 +0200
          Re: [POC/RFC PATCH] overlayfs: fix data inconsistency at copy up Amir Goldstein <amir73il@gmail.com> - 2016-10-22 17:40 +0200
            Re: [POC/RFC PATCH] overlayfs: fix data inconsistency at copy up Miklos Szeredi <miklos@szeredi.hu> - 2016-10-24 10:20 +0200
    Re: [POC/RFC PATCH] overlayfs: fix data inconsistency at copy up Miklos Szeredi <miklos@szeredi.hu> - 2016-10-21 11:20 +0200
      Re: [POC/RFC PATCH] overlayfs: fix data inconsistency at copy up Vivek Goyal <vgoyal@redhat.com> - 2016-10-21 15:40 +0200
  Re: [POC/RFC PATCH] overlayfs: fix data inconsistency at copy up Amir Goldstein <amir73il@gmail.com> - 2016-10-21 11:20 +0200
    Re: [POC/RFC PATCH] overlayfs: fix data inconsistency at copy up Miklos Szeredi <miklos@szeredi.hu> - 2016-10-21 11:40 +0200
      Re: [POC/RFC PATCH] overlayfs: fix data inconsistency at copy up Amir Goldstein <amir73il@gmail.com> - 2016-10-21 15:20 +0200

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