linux-kernel - Re: [BISECT BUG] NFS v4 root not working after 6d972518b821 ("NFS: Add fs

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Date:   Fri, 17 Jan 2020 10:32:08 -0500
From:   Scott Mayhew <smayhew@...hat.com>
To:     Trond Myklebust <trondmy@...merspace.com>
Cc:     "dhowells@...hat.com" <dhowells@...hat.com>,
        "krzk@...nel.org" <krzk@...nel.org>,
        "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
        "anna.schumaker@...app.com" <anna.schumaker@...app.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "arnd@...db.de" <arnd@...db.de>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>
Subject: Re: [BISECT BUG] NFS v4 root not working after 6d972518b821 ("NFS:
 Add fs_context support.")

On Fri, 17 Jan 2020, Trond Myklebust wrote:

> On Fri, 2020-01-17 at 15:12 +0000, David Howells wrote:
> > Krzysztof Kozlowski <krzk@...nel.org> wrote:
> > 
> > > mount.nfs4 -o vers=4,nolock 192.168.1.10:/srv/nfs/odroidhc1
> > > /new_root
> > 
> > Okay, it looks like the mount command makes two attempts at mounting.
> > Firstly, it does this:
> > 
> > > [   22.938314] NFSOP 'source=192.168.1.10:/srv/nfs/odroidhc1'
> > > [   22.942638] NFSOP 'nolock=(null)'
> > > [   22.945772] NFSOP 'vers=4.2'
> > > [   22.948660] NFSOP 'addr=192.168.1.10'
> > > [   22.952350] NFSOP 'clientaddr=192.168.1.12'
> > > [   22.956831] NFS4: Couldn't follow remote path
> > 
> > Which accepts the "vers=4.2" parameter as there's no check that that
> > is
> > actually valid given the configuration, but then fails
> > later.  Secondly, it
> > does this:
> > 
> > > [   22.971001] NFSOP 'source=192.168.1.10:/srv/nfs/odroidhc1'
> > > [   22.975217] NFSOP 'nolock=(null)'
> > > [   22.978444] NFSOP 'vers=4'
> > > [   22.981265] NFSOP 'minorversion=1'
> > > [   22.984513] NFS: Value for 'minorversion' out of range
> > > mount.nfs4: Numerical result out of range
> > 
> > which fails because of the minorversion=1 specification, where the
> > kernel
> > config didn't enable NFS_V4_1.
> > 
> > It looks like it ought to have failed prior to these patches in the
> > same way:
> > 
> > 		case Opt_minorversion:
> > 			if (nfs_get_option_ul(args, &option))
> > 				goto out_invalid_value;
> > 			if (option > NFS4_MAX_MINOR_VERSION)
> > 				goto out_invalid_value;
> > 			mnt->minorversion = option;
> > 			break;
> > 
> 
> It looks like someone changed the return value from the old EINVAL to
> something else? The "Numerical result out of range" message above
> suggests it has been changed to EOVERFLOW, which probably is not
> supported by 'mount'.

It's returning ERANGE... and nope, mount.nfs doesn't support it (see
nfs_autonegotiate() in utils/mount/stropts.c).  Changing it to return
EINVAL fixes it:

diff --git a/fs/nfs/fs_context.c b/fs/nfs/fs_context.c
index 429315c011ae..74508ed9aeec 100644
--- a/fs/nfs/fs_context.c
+++ b/fs/nfs/fs_context.c
@@ -769,8 +769,7 @@ static int nfs_fs_context_parse_param(struct fs_context *fc,
 out_invalid_address:
        return nfs_invalf(fc, "NFS: Bad IP address specified");
 out_of_bounds:
-       nfs_invalf(fc, "NFS: Value for '%s' out of range", param->key);
-       return -ERANGE;
+       return nfs_invalf(fc, "NFS: Value for '%s' out of range", param->key);
 }
 
 /*


I think I may have been running a hacked up version of mount.nfs
before... because as soon as I updated my nfs-utils package it stopped
working for me too.

-Scott
> 
> -- 
> Trond Myklebust
> Linux NFS client maintainer, Hammerspace
> trond.myklebust@...merspace.com
> 
>