linux-kernel - Re: [PATCH] overlayfs: ignore empty NFSv4 ACLs in ext4 upperdir

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Message-ID: <87woj831ce.fsf@notabene.neil.brown.name>
Date:   Fri, 03 May 2019 09:04:17 +1000
From:   NeilBrown <neilb@...e.com>
To:     Miklos Szeredi <miklos@...redi.hu>,
        Andreas Gruenbacher <agruenba@...hat.com>
Cc:     Amir Goldstein <amir73il@...il.com>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Andreas Grünbacher 
        <andreas.gruenbacher@...il.com>,
        Patrick Plagwitz <Patrick_Plagwitz@....de>,
        "linux-unionfs\@vger.kernel.org" <linux-unionfs@...r.kernel.org>,
        Linux NFS list <linux-nfs@...r.kernel.org>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] overlayfs: ignore empty NFSv4 ACLs in ext4 upperdir

On Thu, May 02 2019, Miklos Szeredi wrote:

> On Thu, May 2, 2019 at 10:05 AM Andreas Gruenbacher <agruenba@...hat.com> wrote:
>>
>> On Thu, 2 May 2019 at 05:57, NeilBrown <neilb@...e.com> wrote:
>> > On Wed, May 01 2019, Amir Goldstein wrote:
>> > > On Wed, May 1, 2019 at 10:03 PM NeilBrown <neilb@...e.com> wrote:
>> > >> On Tue, Dec 06 2016, J. Bruce Fields wrote:
>> > >> > On Tue, Dec 06, 2016 at 02:18:31PM +0100, Andreas Gruenbacher wrote:
>> > >> >> On Tue, Dec 6, 2016 at 11:08 AM, Miklos Szeredi <miklos@...redi.hu> wrote:
>> > >> >> > On Tue, Dec 6, 2016 at 12:24 AM, Andreas Grünbacher
>> > >> >> > <andreas.gruenbacher@...il.com> wrote:
>> > >> >> >> 2016-12-06 0:19 GMT+01:00 Andreas Grünbacher <andreas.gruenbacher@...il.com>:
>> > >> >> >
>> > >> >> >>> It's not hard to come up with a heuristic that determines if a
>> > >> >> >>> system.nfs4_acl value is equivalent to a file mode, and to ignore the
>> > >> >> >>> attribute in that case. (The file mode is transmitted in its own
>> > >> >> >>> attribute already, so actually converting .) That way, overlayfs could
>> > >> >> >>> still fail copying up files that have an actual ACL. It's still an
>> > >> >> >>> ugly hack ...
>> > >> >> >>
>> > >> >> >> Actually, that kind of heuristic would make sense in the NFS client
>> > >> >> >> which could then hide the "system.nfs4_acl" attribute.
>>
>> I still think the nfs client could make this problem mostly go away by
>> not exposing "system.nfs4_acl" xattrs when the acl is equivalent to
>> the file mode. The richacl patches contain a workable abgorithm for
>> that. The problem would remain for files that have an actual NFS4 ACL,
>> which just cannot be mapped to a file mode or to POSIX ACLs in the
>> general case, as well as for files that have a POSIX ACL. Mapping NFS4
>> ACL that used to be a POSIX ACL back to POSIX ACLs could be achieved
>> in many cases as well, but the code would be quite messy. A better way
>> seems to be to using a filesystem that doesn't support POSIX ACLs in
>> the first place. Unfortunately, xfs doesn't allow turning off POSIX
>> ACLs, for example.
>
> How about mounting NFSv4 with noacl?  That should fix this issue, right?

No.
"noacl" only affect NFSv3 (and maybe v2) and it disables use of the
NFSACL side-protocol.
"noacl" has no effect on an NFSv4 mount.

NeilBrown

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