From: Vivek Goyal <vgoyal@redhat.com>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>, zhangyi <yi.zhang@huawei.com>,
overlayfs <linux-unionfs@vger.kernel.org>
Subject: Re: [PATCH v2 06/23] ovl: add support for "verify" feature
Date: Fri, 5 Jan 2018 11:39:51 -0500 [thread overview]
Message-ID: <20180105163951.GF29480@redhat.com> (raw)
In-Reply-To: <CAOQ4uxg35sutZZUCKQxoiuNVfLXxe44wavX95bC_GMntbLn-QQ@mail.gmail.com>
On Fri, Jan 05, 2018 at 05:47:36PM +0200, Amir Goldstein wrote:
> On Fri, Jan 5, 2018 at 5:43 PM, Vivek Goyal <vgoyal@redhat.com> wrote:
> > On Thu, Jan 04, 2018 at 06:40:01PM +0200, Amir Goldstein wrote:
> >> Introduce the "verify" config, module and mount options.
> >>
> >> If the "verify" feature is enabled then overlay filesystems will use
> >> the inodes index dir to verify layers consistency.
> >>
> >> It is possible to enable consistency verification by default during
> >> build time with the OVERLAY_FS_VERIFY config option, during runtime
> >> with the "verify=on" module option or on a filesystem instance basis
> >> with the "verify=on" mount option.
> >>
> >> The "verify" feature will prevent multiple redirects to the same lower
> >> dir and will prevent broken hardlinks from using the same inode number.
> >
> > So how does one end up with multiple redirects to same lower dir.
> >
> > Also what's the issue with broken hardlinks using same inode number. You
> > mean lower and upper are on different fs and upper can use same inode
> > number? With index=on, broken hardlink issue is taken care of so. So
> > why would somebody use verify=on, which looks like will create index
> > for all kind of files/dir.
> >
> > I have not followed this development and there is not much background
> > in patch descrition or header patch, so asking all these basic questions.
> >
>
> I have a ready answer for you :)
> This is how it can happen and this is what can go wrong:
> https://github.com/amir73il/xfstests/commit/f3c18125539660329195f142973ea620d6899418
>
> The test duplicates a redirect dir offline with cp -a, but the
> same thing can be done with a dir with origin.
> In both cases, 'diff' will wrongly report that the files/dir are the same
> even though they may differ (after being copied).
So there are so many things a user can do with overlayfs offline. Should
we need to put runtime checks for all these cases. I mean will
fsck.overlay be a better place to catch these kind of anomalies.
Secondly, verify=foo feels like a very generic option. Its not clear
what all will it verify and will we continue to pile up more checks
down the line under it.
As a user, when should one use verify=on? Its not clear to me.
Vivek
>
> Amir.
> --
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next prev parent reply other threads:[~2018-01-05 16:39 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-04 16:39 [PATCH v2 00/23] Overlayfs consistency verification with full index Amir Goldstein
2018-01-04 16:39 ` [PATCH v2 01/23] ovl: disable index when no xattr support Amir Goldstein
2018-01-04 16:39 ` [PATCH v2 02/23] ovl: ignore index mount option when no upper layer Amir Goldstein
2018-01-04 18:42 ` Vivek Goyal
2018-01-04 19:39 ` Amir Goldstein
2018-01-04 20:05 ` Vivek Goyal
2018-01-04 16:39 ` [PATCH v2 03/23] ovl: store layer index in ovl_layer Amir Goldstein
2018-01-04 21:00 ` Vivek Goyal
2018-01-05 5:05 ` Amir Goldstein
2018-01-05 11:22 ` Amir Goldstein
2018-01-05 15:00 ` Vivek Goyal
2018-01-05 17:51 ` Amir Goldstein
2018-01-09 8:36 ` Miklos Szeredi
2018-01-05 14:57 ` Vivek Goyal
2018-01-04 16:39 ` [PATCH v2 04/23] ovl: factor out ovl_check_origin_fh() Amir Goldstein
2018-01-04 16:40 ` [PATCH v2 05/23] ovl: pass ovl_layer array to ovl_check_origin_fh() Amir Goldstein
2018-01-04 22:35 ` Vivek Goyal
2018-01-05 5:26 ` Amir Goldstein
2018-01-04 16:40 ` [PATCH v2 06/23] ovl: add support for "verify" feature Amir Goldstein
2018-01-05 15:43 ` Vivek Goyal
2018-01-05 15:47 ` Amir Goldstein
2018-01-05 15:48 ` Amir Goldstein
2018-01-05 16:39 ` Vivek Goyal [this message]
2018-01-05 17:07 ` Amir Goldstein
2018-01-05 19:07 ` Vivek Goyal
2018-01-05 20:20 ` Amir Goldstein
2018-01-05 20:37 ` Amir Goldstein
2018-01-09 9:16 ` Miklos Szeredi
2018-01-09 9:54 ` Amir Goldstein
2018-01-09 10:07 ` Miklos Szeredi
2018-01-09 10:44 ` Amir Goldstein
2018-01-09 10:50 ` Miklos Szeredi
2018-01-04 16:40 ` [PATCH v2 07/23] ovl: verify stored origin fh matches lower dir Amir Goldstein
2018-01-05 16:04 ` Vivek Goyal
2018-01-05 16:26 ` Amir Goldstein
2018-01-05 16:35 ` Vivek Goyal
2018-01-05 16:42 ` Amir Goldstein
2018-01-05 18:33 ` Vivek Goyal
2018-01-05 19:00 ` Amir Goldstein
2018-01-09 9:52 ` Miklos Szeredi
2018-01-09 10:04 ` Amir Goldstein
2018-01-09 10:17 ` Miklos Szeredi
2018-01-04 16:40 ` [PATCH v2 08/23] ovl: unbless lower st_ino of files under unverified redirected dir Amir Goldstein
2018-01-09 13:31 ` Miklos Szeredi
2018-01-09 14:24 ` Amir Goldstein
2018-01-09 14:28 ` Miklos Szeredi
2018-01-04 16:40 ` [PATCH v2 09/23] ovl: lookup index for directories Amir Goldstein
2018-01-09 14:49 ` Miklos Szeredi
2018-01-09 16:07 ` Amir Goldstein
2018-01-04 16:40 ` [PATCH v2 10/23] ovl: verify whiteout index entries on mount Amir Goldstein
2018-01-04 16:40 ` [PATCH v2 11/23] ovl: verify directory " Amir Goldstein
2018-01-04 16:40 ` [PATCH v2 12/23] ovl: cleanup temp index entries Amir Goldstein
2018-01-09 15:25 ` Miklos Szeredi
2018-01-09 16:08 ` Amir Goldstein
2018-01-04 16:40 ` [PATCH v2 13/23] ovl: create ovl_need_index() helper Amir Goldstein
2018-01-04 16:40 ` [PATCH v2 14/23] ovl: index all files on copy up with 'verify=on' Amir Goldstein
2018-01-09 16:45 ` Vivek Goyal
2018-01-09 16:50 ` Amir Goldstein
2018-01-04 16:40 ` [PATCH v2 15/23] ovl: index directories " Amir Goldstein
2018-01-09 16:08 ` Miklos Szeredi
2018-01-09 16:31 ` Amir Goldstein
2018-01-09 16:35 ` Miklos Szeredi
2018-01-09 16:48 ` Amir Goldstein
2018-01-04 16:40 ` [PATCH v2 16/23] ovl: cleanup dir index when dir nlink drops to zero Amir Goldstein
2018-01-04 16:40 ` [PATCH v2 17/23] ovl: whiteout index when union " Amir Goldstein
2018-01-09 16:28 ` Miklos Szeredi
2018-01-09 16:41 ` Amir Goldstein
2018-01-04 16:40 ` [PATCH v2 18/23] ovl: whiteout orphan index entries on mount Amir Goldstein
2018-01-04 16:40 ` [PATCH v2 19/23] ovl: factor out ovl_get_index_fh() helper Amir Goldstein
2018-01-04 16:40 ` [PATCH v2 20/23] ovl: do not pass overlay dentry to ovl_get_inode() Amir Goldstein
2018-01-04 16:40 ` [PATCH v2 21/23] ovl: grab i_count reference of lower inode Amir Goldstein
2018-01-04 16:40 ` [PATCH v2 22/23] ovl: use d_splice_alias() in place of d_add() in lookup Amir Goldstein
2018-01-04 16:40 ` [PATCH v2 23/23] ovl: copy up of disconnected dentries Amir Goldstein
2018-01-11 14:47 ` Miklos Szeredi
2018-01-11 15:28 ` Amir Goldstein
2018-01-11 16:55 ` [PATCH v2 00/23] Overlayfs consistency verification with full index Amir Goldstein
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