Re: [PATCH v2 1/1] nfsd4: Expose the callback address and state of each NFS4 client

[Trond Myklebust <trondmy@hammerspace.com>]

On Tue, 2021-05-25 at 16:58 -0400, Bruce Fields wrote:
> When I run trace-cmd report I get output like:
> 
>   [nfsd:nfsd_cb_state] function cb_state2str not defined
>   [nfsd:nfsd_cb_shutdown] function cb_state2str not defined
>   [nfsd:nfsd_cb_probe] function cb_state2str not defined
>   [nfsd:nfsd_cb_lost] function cb_state2str not defined
> 
> I don't know how this is supposed to work.  Is it OK for tracepoint
> definitions
> to reference kernel functions if they're defined in the right way
> somehow?  If
> not, I don't know what the solution would be for sharing this--define
> a macro
> that expands to the array literal and use that in both places?  Or
> maybe just
> live with the the redundancy.
> 

You need to store the string in the TP_fast_assign() section if you
want to be able to display it. Otherwise 'perf' tries (and fails) to
find the cb_state2str function so it can invoke it.

> --b.
> 
> On Mon, May 17, 2021 at 04:29:45PM -0400, Dave Wysochanski wrote:
> > In addition to the client's address, display the callback channel
> > state and address in the 'info' file.  Define and use a common
> > function for this information that can be used by both callback
> > trace events and the NFS4 client 'info' file.
> > 
> > Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
> > ---
> >  fs/nfsd/nfs4state.c |  2 ++
> >  fs/nfsd/trace.c     | 15 +++++++++++++++
> >  fs/nfsd/trace.h     |  9 ++-------
> >  3 files changed, 19 insertions(+), 7 deletions(-)
> > 
> > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > index b2573d3ecd3c..f3b8221bb543 100644
> > --- a/fs/nfsd/nfs4state.c
> > +++ b/fs/nfsd/nfs4state.c
> > @@ -2385,6 +2385,8 @@ static int client_info_show(struct seq_file
> > *m, void *v)
> >                 seq_printf(m, "\nImplementation time: [%lld,
> > %ld]\n",
> >                         clp->cl_nii_time.tv_sec, clp-
> > >cl_nii_time.tv_nsec);
> >         }
> > +       seq_printf(m, "callback state: %s\n", cb_state2str(clp-
> > >cl_cb_state));
> > +       seq_printf(m, "callback address: %pISpc\n", &clp-
> > >cl_cb_conn.cb_addr);
> >         drop_client(clp);
> >  
> >         return 0;
> > diff --git a/fs/nfsd/trace.c b/fs/nfsd/trace.c
> > index f008b95ceec2..6291b5d10824 100644
> > --- a/fs/nfsd/trace.c
> > +++ b/fs/nfsd/trace.c
> > @@ -2,3 +2,18 @@
> >  
> >  #define CREATE_TRACE_POINTS
> >  #include "trace.h"
> > +
> > +const char *cb_state2str(const int state)
> > +{
> > +       switch (state) {
> > +       case NFSD4_CB_UP:
> > +               return "UP";
> > +       case NFSD4_CB_UNKNOWN:
> > +               return "UNKNOWN";
> > +       case NFSD4_CB_DOWN:
> > +               return "DOWN";
> > +       case NFSD4_CB_FAULT:
> > +               return "FAULT";
> > +       }
> > +       return "UNDEFINED";
> > +}
> > diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
> > index 10cc3aaf1089..8908d48b2aa6 100644
> > --- a/fs/nfsd/trace.h
> > +++ b/fs/nfsd/trace.h
> > @@ -876,12 +876,7 @@
> >         TP_printk("client %08x:%08x", __entry->cl_boot, __entry-
> > >cl_id)
> >  )
> >  
> > -#define
> > show_cb_state(val)                                             \
> > -
> >        __print_symbolic(val,                                        
> >    \
> > -               { NFSD4_CB_UP,          "UP"
> > },                         \
> > -               { NFSD4_CB_UNKNOWN,     "UNKNOWN"
> > },                    \
> > -               { NFSD4_CB_DOWN,        "DOWN"
> > },                       \
> > -               { NFSD4_CB_FAULT,       "FAULT"})
> > +const char *cb_state2str(const int state);
> >  
> >  DECLARE_EVENT_CLASS(nfsd_cb_class,
> >         TP_PROTO(const struct nfs4_client *clp),
> > @@ -901,7 +896,7 @@
> >         ),
> >         TP_printk("addr=%pISpc client %08x:%08x state=%s",
> >                 __entry->addr, __entry->cl_boot, __entry->cl_id,
> > -               show_cb_state(__entry->state))
> > +               cb_state2str(__entry->state))
> >  );
> >  
> >  #define DEFINE_NFSD_CB_EVENT(name)                     \
> > -- 
> > 1.8.3.1

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com