Re: [nfs-utils PATCH] nfsdctl: tweak the version subcommand behavior

[Scott Mayhew <smayhew@redhat.com>]

On Thu, 09 Jan 2025, Jeff Layton wrote:

> On Wed, 2025-01-08 at 17:54 -0500, Scott Mayhew wrote:
> > The section for the 'nfsdctl version' subcommand on the man page states
> > that the minorversion is optional, and if omitted it will cause all
> > minorversions to be enabled/disabled, but it currently doesn't work that
> > way.
> > 
> > Make it work that way, with one exception.  If v4.0 is disabled, then
> > 'nfsdctl version +4' will not re-enable it; instead it must be
> > explicitly re-enabled via 'nfsdctl version +4.0'.  This mirrors the way
> > /proc/fs/nfsd/versions works.
> > 
> 
> The question is: do we want to mirror that particular quirk in the
> interface? I'm not sure if there was a logical reason for making +4
> work that way in the /proc interface, so it's not clear to me that we
> want to replicate that here.

Digging thru my email archive it seems that the reason for that was to
deal with really old kernels that understood +4/-4 but not +4.0/-4.0.
Since old kernels obviously won't have a netlink interface for nfsd it
seems we can drop this quirk at least.
> 
> Honestly, it may be better to just require explicit minorversions in
> this interface and not worry about trying to interpret what +4
> means. You'd need to specify "+4.1 +4.2" instead of just saying "+4",
> but that doesn't seem too onerous.
> 
> Thoughts?

It seems to me main alternatives are 

1. Drop the special handling for v4.0 but allow +4/-4 to always
enable/disable all minor versions, including v4.0.  So a small
adjustment to this patch.

2. Require the minor versions to be explicitly specified for v4.  So allow
+2/-2/+3/-3, but emit an error if +4/-4 is specified.  Maybe emit an error
if +2.0/-2.0/+3.0/-3.0 is specified.

3. Leave the code alone (so +4/-4 would be interpreted as +4.0/-4.1) and
just update the man page.

4. Make the 'nfsdctl version' behavior consistent with the nfs.conf option
handling in 'nfsdctl autostart'.  Currently thats:

        * vers4=y turns on all minor versions.  vers4.x=n on top of that
          will turn off those specific minor versions.
        * vers4=n turns off all minor versions.  vers4.x=y on top of
          that has no effect.

I don't really have a strong preference as long as the behavior matches
whatever the man page says it is.  If I had to vote I'd just say go with
option 3, but if it's important for the behaviors of the different
subcommands to be consistent, then we really don't have a choice and
have to go with option 4.

> 
> > Link: https://issues.redhat.com/browse/RHEL-72477
> > Signed-off-by: Scott Mayhew <smayhew@redhat.com>
> > ---
> >  utils/nfsdctl/nfsdctl.8    |  9 ++++--
> >  utils/nfsdctl/nfsdctl.adoc |  5 +++-
> >  utils/nfsdctl/nfsdctl.c    | 58 +++++++++++++++++++++++++++++++++++---
> >  3 files changed, 64 insertions(+), 8 deletions(-)
> > 
> > diff --git a/utils/nfsdctl/nfsdctl.8 b/utils/nfsdctl/nfsdctl.8
> > index b08fe803..835d60b4 100644
> > --- a/utils/nfsdctl/nfsdctl.8
> > +++ b/utils/nfsdctl/nfsdctl.8
> > @@ -2,12 +2,12 @@
> >  .\"     Title: nfsdctl
> >  .\"    Author: Jeff Layton
> >  .\" Generator: Asciidoctor 2.0.20
> > -.\"      Date: 2024-12-30
> > +.\"      Date: 2025-01-08
> >  .\"    Manual: \ \&
> >  .\"    Source: \ \&
> >  .\"  Language: English
> >  .\"
> > -.TH "NFSDCTL" "8" "2024-12-30" "\ \&" "\ \&"
> > +.TH "NFSDCTL" "8" "2025-01-08" "\ \&" "\ \&"
> >  .ie \n(.g .ds Aq \(aq
> >  .el       .ds Aq '
> >  .ss \n[.ss] 0
> > @@ -172,7 +172,10 @@ MINOR: the minor version integer value
> >  .nf
> >  .fam C
> >  The minorversion field is optional. If not given, it will disable or enable
> > -all minorversions for that major version.
> > +all minorversions for that major version.  Note however that if NFSv4.0 was
> > +previously disabled, it can only be re\-enabled by explicitly specifying the
> > +minorversion (this mirrors the behavior of the /proc/fs/nfsd/versions
> > +interface).
> >  .fam
> >  .fi
> >  .if n .RE
> > diff --git a/utils/nfsdctl/nfsdctl.adoc b/utils/nfsdctl/nfsdctl.adoc
> > index c5921458..20e9bf8e 100644
> > --- a/utils/nfsdctl/nfsdctl.adoc
> > +++ b/utils/nfsdctl/nfsdctl.adoc
> > @@ -91,7 +91,10 @@ Each subcommand can also accept its own set of options and arguments. The
> >      MINOR: the minor version integer value
> >  
> >    The minorversion field is optional. If not given, it will disable or enable
> > -  all minorversions for that major version.
> > +  all minorversions for that major version.  Note however that if NFSv4.0 was
> > +  previously disabled, it can only be re-enabled by explicitly specifying the
> > +  minorversion (this mirrors the behavior of the /proc/fs/nfsd/versions
> > +  interface).
> >  
> >    Note that versions can only be set when there are no nfsd threads running.
> >  
> > diff --git a/utils/nfsdctl/nfsdctl.c b/utils/nfsdctl/nfsdctl.c
> > index 722bf4a0..d86ff80e 100644
> > --- a/utils/nfsdctl/nfsdctl.c
> > +++ b/utils/nfsdctl/nfsdctl.c
> > @@ -761,6 +761,32 @@ static int update_nfsd_version(int major, int minor, bool enabled)
> >  	return -EINVAL;
> >  }
> >  
> > +static bool v40_is_disabled(void)
> > +{
> > +	int i;
> > +
> > +	for (i = 0; i < MAX_NFS_VERSIONS; ++i) {
> > +		if (nfsd_versions[i].major == 0)
> > +			break;
> > +		if (nfsd_versions[i].major == 4 && nfsd_versions[i].minor == 0)
> > +			return !nfsd_versions[i].enabled;
> > +	}
> > +	return false;
> > +}
> > +
> > +static int get_max_minorversion(void)
> > +{
> > +	int i, max = 0;
> > +
> > +	for (i = 0; i < MAX_NFS_VERSIONS; ++i) {
> > +		if (nfsd_versions[i].major == 0)
> > +			break;
> > +		if (nfsd_versions[i].major == 4 && nfsd_versions[i].minor > max)
> > +			max = nfsd_versions[i].minor;
> > +	}
> > +	return max;
> > +}
> > +
> >  static void version_usage(void)
> >  {
> >  	printf("Usage: %s version { {+,-}major.minor } ...\n", taskname);
> > @@ -778,7 +804,8 @@ static void version_usage(void)
> >  
> >  static int version_func(struct nl_sock *sock, int argc, char ** argv)
> >  {
> > -	int ret, i;
> > +	int ret, i, j, max_minor;
> > +	bool v40_disabled;
> >  
> >  	/* help is only valid as first argument after command */
> >  	if (argc > 1 &&
> > @@ -792,6 +819,9 @@ static int version_func(struct nl_sock *sock, int argc, char ** argv)
> >  		return ret;
> >  
> >  	if (argc > 1) {
> > +		v40_disabled = v40_is_disabled();
> > +		max_minor = get_max_minorversion();
> > +
> >  		for (i = 1; i < argc; ++i) {
> >  			int ret, major, minor = 0;
> >  			char sign = '\0', *str = argv[i];
> > @@ -815,9 +845,29 @@ static int version_func(struct nl_sock *sock, int argc, char ** argv)
> >  				return -EINVAL;
> >  			}
> >  
> > -			ret = update_nfsd_version(major, minor, enabled);
> > -			if (ret)
> > -				return ret;
> > +			/*
> > +			 * The minorversion field is optional. If omitted, it should
> > +			 * cause all the minor versions for that major version to be
> > +			 * enabled/disabled.
> > +			 *
> > +			 * HOWEVER, we do not enable v4.0 in this manner if it was
> > +			 * previously disabled - it has to be explicitly enabled
> > +			 * instead.  This is to retain the behavior of the old
> > +			 * /proc/fs/nfsd/versions interface.
> > +			 */
> > +			if (major == 4 && ret == 2) {
> > +				for (j = 0; j <= max_minor; ++j) {
> > +					if (j == 0 && enabled && v40_disabled)
> > +						continue;
> > +					ret = update_nfsd_version(major, j, enabled);
> > +					if (ret)
> > +						return ret;
> > +				}
> > +			} else {
> > +				ret = update_nfsd_version(major, minor, enabled);
> > +				if (ret)
> > +					return ret;
> > +			}
> >  		}
> >  		return set_nfsd_versions(sock);
> >  	}
> 
> -- 
> Jeff Layton <jlayton@kernel.org>
>