Re: [PATCH] rpc.nfsd: mount up nfsdfs is it doesn't appear to be mounted yet (try #2)

[Steve Dickson <SteveD@redhat.com>]

On 09/16/2010 07:32 AM, Jeff Layton wrote:
> On Thu, 16 Sep 2010 07:06:20 -0400
> Steve Dickson <SteveD@redhat.com> wrote:
> 
>>>> +
>>>> +	/*
>>>> +	 * this call can return an error if modprobe is set up to automatically
>>>> +	 * mount nfsdfs when nfsd.ko is plugged in. So, ignore the return
>>>> +	 * code from it and just check for the "threads" file afterward.
>>>> +	 */
>>>> +	system("/bin/mount -t nfsd nfsd " NFSD_FS_DIR " >/dev/null 2>&1");
>>>> +
>>>> +	err = stat(NFSD_THREAD_FILE, &statbuf);
>>>> +	if (err == 0)
>>>> +		return;
>>>> +
>>>> +	xlog(L_ERROR, "Unable to access " NFSD_FS_DIR " errno %d (%m)." 
>>>> +		"\nPlease try, as root, 'mount -t nfsd nfsd " NFSD_FS_DIR 
>>>> +		"' and then restart %s to correct the problem", errno, progname);
>>>> +
>>>
>>> A few of problems with that log message...
>>>
>>> First, it looks like something failed, but nfsd will probably end up
>>> getting started anyway. We recommend starting nfsd to correct the
>>> problem, but it's not clear what the problem actually is. nfsd got
>>> started right?
>> Hmm... I was thinking this part of the message
>>     "Unable to access " NFSD_FS_DIR " errno %d (%m)."
>> made it clear as to what the problem is. 
>>
>> We are making note of a non fatal error... and since
>> the message is being written to stderr, instead if 
>> syslog()-ed, the actual message look more like a note 
>> then an error since the 'ERROR' string is not be added.
>> We could change the message to a L_WARNING... 
>>
> 
> L_WARNING would be more appropriate I think. But the typical user is
> going to "huh?" with this error message. It says something about a
> "problem" but we're not being clear as to what the problem is. After
> all, nfsd got started so it's not likely to be immediately clear to the
> uninitiated person.
L_WARNING it is...

> 
>>>
>>> Second, it says to restart nfsd to correct the problem, but restarting
>>> nfsd isn't exactly straightforward (you need to run "nfsd 0" and then
>>> nfsd <some positive int>).
>> Well I'm making the assumption that people who do see this
>> message did not use the normal init-script way of starting rpc.nfsd,
>> because if they did they would not be seeing this message. So,
>> again I'm assuming, that these same people are starting rpc.nfsd
>> my hand, which means they know how to restart rpc.nfsd.
>>
> 
> That depends very much on the init script. We know that Fedora and
> RHEL, and probably others too, will plug in nfsd.ko before running
> rpc.nfsd. Based on the report by Tetsuo a couple of months ago, I think
> it's safe to assume that at least some Debian userspace doesn't do
> that. By extension, that probably means that Ubuntu doesn't either. It's
> also quite plausible that many smaller, distros (OpenWRT, for instance)
> won't. Personally, I expect that once we do this we're going to find
> that a large number of distros will need to fix their init scripts.
Agreed...

> 
>>>
>>> Third, there could be other problems than just the fact that nfsdfs
>>> didn't get mounted. Maybe there was some weird SELinux permissions
>>> problem? In that case, trying to mount nfsdfs won't help anything and
>>> that message will just confuse the issue.
>> If its an SELinux error or some issue that causing either the stat()
>> and mount() to fail, hopefully those type of issues will be logged. 
>> Plus having them try the mount by hand could possibly lead them in the 
>> right direction.
>>
> 
> Fair enough.
> 
>>>
>>> I think it's going to be really difficult to explain the problem and
>>> solution in a terse xlog message. My expectation was mainly that we
>>> should pop up a message to give the user a heads up that "something" is
>>> wrong. I think it's tough to offer specific solutions in such a message
>>> though.
>> All I'm trying to is log an non-fatal error,  give a reason
>> as to why the error happen and a possible resolution to that error.
>> Since were are not logging the fact the system() call failed, I
>> thought it was a fairly reasonable thing to do....
>>
> 
> It is. The main issue is that we have a somewhat complex situation here
> if the mount ended up not working. I attempted to deal with it by being
> somewhat vague. That said...we're getting into bikeshed paint colors
> here. If it helps move things along, let's go with your version and
> call it a day...
Cool... thanks taking the time...

steved.