Re: [nfs-utils PATCH] mount.nfs: improve handling of bg, fg, and sloppy in nfsmount.conf

[Scott Mayhew <smayhew@redhat.com>]

On Thu, 15 Aug 2013, Chuck Lever wrote:

> Hi Scott-
> 
> On Aug 15, 2013, at 9:58 AM, Scott Mayhew <smayhew@redhat.com> wrote:
> 
> > This patch makes 2 small improvements to the parsing of the bg, fg, and
> > sloppy mount options in nfsmount.conf.
> > 
> > 1. "bg" and "fg" negate should each other.  "Background=True" should
> > mean "bg" and "Background=False" should mean "fg".  The same applies to
> > "Foreground".
> 
> This looks OK.
> 
> > 2. Once we see "Sloppy=False" while parsing the configuration file we
> > should ignore subsequent occurrences of the sloppy option.  This will
> > preserve the "right-most setting wins" behavior for the sloppy mount
> > option.
> 
> Here, I'm confused.  The "right-most wins" rule goes:
> 
>   1.  mount options are parsed in order from left (closest to the command-line prompt) to right (closest to the carriage return)
> 
>   2.  the last instance of an option (the right-most instance) is the setting that takes effect 
> 
> As I understand it, this applies to config file settings in the following way:  config file settings are specified in order from "whole system" to "server" to "mount point", then the command line options are appended to the end of that.

conf_get_mntopts parses the mountpoint specific options first, then the
server-specific options, and finally global options, inserting each
option at the head of a list as it goes.  It then walks the list and
appends each option to the string that it ultimately returns to the
caller.  So the order that options appear in the list is reversed from
how they appear in the string.
> 
> Then, "Right-most wins" means the last occurrence of "Sloppy=true" should override any previous occurrence of "Sloppy=False", right?  Or did I misunderstand again?

Yes, this is what it does.
> 
> It seems like you can just walk the appropriate sections of the config file, and set the sloppiness in each section that has such a setting.  The last section you walked with a sloppiness setting wins.  After you are done walking, append (or don't) a "sloppy" option, then pass that on to the mount.nfs command.
> 
> IIUC if the last config file setting is "Sloppy=True" there is no way for command-line options to disable "sloppy".

That's true with the existing code as well though.  I don't see any way
around that besides adding another nfs mount option to the kernel... but
what is the likelihood that someone would specify sloppy=true in their
config file and then want to override it from the command line?

-Scott
> 
> 
> > Signed-off-by: Scott Mayhew <smayhew@redhat.com>
> > ---
> > utils/mount/configfile.c | 11 +++++++++++
> > 1 file changed, 11 insertions(+)
> > 
> > diff --git a/utils/mount/configfile.c b/utils/mount/configfile.c
> > index 1f1b6e7..68b9f93 100644
> > --- a/utils/mount/configfile.c
> > +++ b/utils/mount/configfile.c
> > @@ -73,6 +73,8 @@ struct mnt_alias {
> > };
> > int mnt_alias_sz = (sizeof(mnt_alias_tab)/sizeof(mnt_alias_tab[0]));
> > 
> > +static int strict;
> > +
> > /*
> >  * See if the option is an alias, if so return the 
> >  * real mount option along with the argument type.
> > @@ -310,7 +312,15 @@ conf_parse_mntopts(char *section, char *arg, char *opts)
> > 		if (strcasecmp(value, "false") == 0) {
> > 			if (argtype != MNT_NOARG)
> > 				snprintf(buf, BUFSIZ, "no%s", field);
> > +			else if (strcasecmp(field, "bg") == 0)
> > +				snprintf(buf, BUFSIZ, "fg");
> > +			else if (strcasecmp(field, "fg") == 0)
> > +				snprintf(buf, BUFSIZ, "bg");
> > +			else if (strcasecmp(field, "sloppy") == 0)
> > +				strict = 1;
> > 		} else if (strcasecmp(value, "true") == 0) {
> > +			if ((strcasecmp(field, "sloppy") == 0) && strict)
> > +				continue;
> > 			snprintf(buf, BUFSIZ, "%s", field);
> > 		} else {
> > 			nvalue = strdup(value);
> > @@ -345,6 +355,7 @@ char *conf_get_mntopts(char *spec, char *mount_point,
> > 	char *ptr, *server, *config_opts;
> > 	int optlen = 0;
> > 
> > +	strict = 0;
> > 	SLIST_INIT(&head);
> > 	list_size = 0;
> > 	/*
> > -- 
> > 1.7.11.7
> > 
> > --
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> 
> -- 
> Chuck Lever
> chuck[dot]lever[at]oracle[dot]com
> 
> 
> 
>