From: Jeff Layton <jlayton@kernel.org>
To: Richard Weinberger <richard@nod.at>, linux-nfs@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
chuck.lever@oracle.com, anna@kernel.org,
trond.myklebust@hammerspace.com, viro@zeniv.linux.org.uk,
raven@themaw.net, chris.chilvers@appsbroker.com,
david.young@appsbroker.com, luis.turcitu@appsbroker.com,
david@sigma-star.at, benmaynard@google.com
Subject: Re: [PATCH 0/3 v2] NFS: NFSD: Allow crossing mounts when re-exporting
Date: Mon, 12 Dec 2022 12:06:01 -0500 [thread overview]
Message-ID: <2de81c537335da895bafcd9f50a239c439fb0439.camel@kernel.org> (raw)
In-Reply-To: <20221207084309.8499-1-richard@nod.at>
On Wed, 2022-12-07 at 09:43 +0100, Richard Weinberger wrote:
> Currently when re-exporting a NFS share the NFS cross mount feature does
> not work [0].
> This patch series outlines an approach to address the problem.
>
> Crossing mounts does not work for two reasons:
>
> 1. As soon the NFS client (on the re-exporting server) sees a different
> filesystem id, it installs an automount. That way the other filesystem
> will be mounted automatically when someone enters the directory.
> But the cross mount logic of KNFS does not know about automount.
> This patch series addresses the problem and teach both KNFSD
> and the exportfs logic of NFS to deal with automount.
>
> 2. When KNFSD detects crossing of a mount point, it asks rpc.mountd to install
> a new export for the target mount point. Beside of authentication rpc.mountd
> also has to find a filesystem id for the new export. Is the to be exported
> filesystem a NFS share, rpc.mountd cannot derive a filesystem id from it and
> refuses to export. In the logs you'll see errors such as:
>
> mountd: Cannot export /srv/nfs/vol0, possibly unsupported filesystem or fsid= required
>
> To deal with that I've changed rpc.mountd to use generate and store fsids [1].
> Since the kernel side of my changes did change for a long time I decided to
> try upstreaming it first.
> A 3rd iteration of my rpc.mountd will happen soon.
>
> [0] https://marc.info/?l=linux-nfs&m=161653016627277&w=2
> [1] https://lore.kernel.org/linux-nfs/20220217131531.2890-1-richard@nod.at/
>
> Changes since v1:
> https://lore.kernel.org/linux-nfs/20221117191151.14262-1-richard@nod.at/
>
> - Use LOOKUP_AUTOMOUNT only when NFSEXP_CROSSMOUNT is set (Jeff Layton)
>
> Richard Weinberger (3):
> NFSD: Teach nfsd_mountpoint() auto mounts
> fs: namei: Allow follow_down() to uncover auto mounts
> NFS: nfs_encode_fh: Remove S_AUTOMOUNT check
>
> fs/namei.c | 6 +++---
> fs/nfs/export.c | 2 +-
> fs/nfsd/vfs.c | 8 ++++++--
> include/linux/namei.h | 2 +-
> 4 files changed, 11 insertions(+), 7 deletions(-)
>
This set looks reasonable to me.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
next prev parent reply other threads:[~2022-12-12 17:06 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-07 8:43 [PATCH 0/3 v2] NFS: NFSD: Allow crossing mounts when re-exporting Richard Weinberger
2022-12-07 8:43 ` [PATCH 1/3] NFSD: Teach nfsd_mountpoint() auto mounts Richard Weinberger
2022-12-07 8:43 ` [PATCH 2/3] fs: namei: Allow follow_down() to uncover " Richard Weinberger
2022-12-14 15:15 ` [PATCH 2/3] " Chuck Lever III
2023-01-03 16:15 ` Chuck Lever III
2023-01-29 15:42 ` Richard Weinberger
2023-01-30 2:15 ` Al Viro
2022-12-07 8:43 ` [PATCH 3/3] NFS: nfs_encode_fh: Remove S_AUTOMOUNT check Richard Weinberger
2022-12-14 15:09 ` Chuck Lever III
2022-12-14 16:37 ` Anna Schumaker
2022-12-14 16:39 ` Chuck Lever III
2022-12-10 16:09 ` [PATCH 0/3 v2] NFS: NFSD: Allow crossing mounts when re-exporting Chuck Lever III
2022-12-10 21:52 ` Richard Weinberger
2022-12-10 21:53 ` Chuck Lever III
2022-12-12 17:06 ` Jeff Layton [this message]
2022-12-13 9:09 ` Ian Kent
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