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Date:   Mon, 12 Jul 2021 13:09:56 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Chuck Lever III <chuck.lever@oracle.com>
Cc:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        David Wysochanski <dwysocha@redhat.com>,
        Bruce Fields <bfields@fieldses.org>
Subject: Re: [PATCH v2 01/25] NFSD: Fix TP_printk() format specifier in
 trace_nfsd_dirent()
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On Mon, 12 Jul 2021 15:18:05 +0000
Chuck Lever III <chuck.lever@oracle.com> wrote:

> Hello Steven-
> 
> > On May 13, 2021, at 10:50 AM, Steven Rostedt <rostedt@goodmis.org> wrote:
> > 
> > On Wed, 12 May 2021 16:52:05 +0000
> > Chuck Lever III <chuck.lever@oracle.com> wrote:
> >   
> >> The underlying need is to support non-NUL-terminated C strings.
> >> 
> >> I assumed that since the commentary around 9a6944fee68e claims
> >> the proper way to trace C strings is to use __string and friends,
> >> and those do not support non-NUL-terminated strings, that such
> >> strings are really not first-class citizens. Thus I concluded
> >> that my use of '%.*s' was incorrect.
> >> 
> >> Having some __string-style helpers that can deal with such
> >> strings would be valuable.  
> > 
> > I guess the best I can do is a strncpy version, that will add the '\0' in
> > the ring buffer. That way we don't need to save the length as well (length
> > would need to be at least 4 bytes, where as '\0' is one).
> > 
> > Something like this?  
> 
> I don't see this change in v5.14-rc1.

Grumble.

I thought this thread was over with the bug fix that was sent, but
completely forgot about this change, as I never made it into a real commit.

I can add this now, kick off some tests, and grovel to Linus saying that
this is unused code, but other code will depend on this, and I want to get
it upstream so that it can.

-- Steve
> 
> 
> > I added "__string_len()" and "__assign_str_len()". You use them just like
> > __string() and __assign_str() but add a max length that you want to use
> > (although, it will always allocate "len" regardless if the string is
> > smaller). Then use __get_str() just like you use __string().
> > 
> > Would something like that work?
> > 
> > -- Steve
> >