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Message-ID: <857b150cbd9c99134141475eafdc1e2b4e0ebe91.camel@kernel.org>
Subject: Re: [PATCH] vfs: report an inode version in statx for IS_I_VERSION
 inodes
From:   Jeff Layton <jlayton@kernel.org>
To:     Florian Weimer <fweimer@redhat.com>
Cc:     viro@zeniv.linux.org.uk, linux-api@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org,
        David Howells <dhowells@redhat.com>,
        Frank Filz <ffilzlnx@mindspring.com>
Date:   Tue, 23 Aug 2022 06:16:35 -0400
In-Reply-To: <87o7wb2s9d.fsf@oldenburg.str.redhat.com>
References: <20220819115641.14744-1-jlayton@kernel.org>
         <87o7wb2s9d.fsf@oldenburg.str.redhat.com>
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On Tue, 2022-08-23 at 12:01 +0200, Florian Weimer wrote:
> * Jeff Layton:
>=20
> > From: Jeff Layton <jlayton@redhat.com>
> >=20
> > The NFS server and IMA both rely heavily on the i_version counter, but
> > it's largely invisible to userland, which makes it difficult to test it=
s
> > behavior. This value would also be of use to userland NFS servers, and
> > other applications that want a reliable way to know if there was an
> > explicit change to an inode since they last checked.
> >=20
> > Claim one of the spare fields in struct statx to hold a 64-bit inode
> > version attribute. This value must change with any explicit, observeabl=
e
> > metadata or data change. Note that atime updates are excluded from this=
,
> > unless it is due to an explicit change via utimes or similar mechanism.
> >=20
> > When statx requests this attribute on an IS_I_VERSION inode, do an
> > inode_query_iversion and fill the result in the field. Also, update the
> > test-statx.c program to display the inode version and the mountid.
>=20
> Will the version survive reboots?  Is it stored on disks?  Can backup
> tools (and others) use this to check if the file has changed since the
> last time the version has been observed?
>=20


The answer to all of those question is "yes".
--=20
Jeff Layton <jlayton@kernel.org>