knfsd: add file to export stats about nfsd pools

Add /proc/fs/nfsd/pool_stats to export to userspace various
statistics about the operation of rpc server thread pools.

This patch is based on a forward-ported version of
knfsd-add-pool-thread-stats which has been shipping in the SGI
"Enhanced NFS" product since 2006 and which was previously
posted:

http://article.gmane.org/gmane.linux.nfs/10375

It has also been updated thus:

 * moved EXPORT_SYMBOL() to near the function it exports
 * made the new struct struct seq_operations const
 * used SEQ_START_TOKEN instead of ((void *)1)
 * merged fix from SGI PV 990526 "sunrpc: use dprintk instead of
   printk in svc_pool_stats_*()" by Harshula Jayasuriya.
 * merged fix from SGI PV 964001 "Crash reading pool_stats before
   nfsds are started".

Signed-off-by: Greg Banks <gnb@sgi.com>
Signed-off-by: Harshula Jayasuriya <harshula@sgi.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

1 files changed, 11 insertions, 0 deletions

diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 39ec186a492d..9f9f699dd469 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -24,6 +24,15 @@
  */
 typedef int             (*svc_thread_fn)(void *);
 
+/* statistics for svc_pool structures */
+struct svc_pool_stats {
+        unsigned long   packets;
+        unsigned long   sockets_queued;
+        unsigned long   threads_woken;
+        unsigned long   overloads_avoided;
+        unsigned long   threads_timedout;
+};
+
 /*
  *
  * RPC service thread pool.
@@ -42,6 +51,7 @@ struct svc_pool {
         unsigned int            sp_nrthreads;   /* # of threads in pool */
         struct list_head        sp_all_threads; /* all server threads */
         int                     sp_nwaking;     /* number of threads woken but not yet active */
+        struct svc_pool_stats   sp_stats;       /* statistics on pool operation */
 } ____cacheline_aligned_in_smp;
 
 /*
@@ -396,6 +406,7 @@ struct svc_serv *  svc_create_pooled(struct svc_program *, unsigned int,
                         sa_family_t, void (*shutdown)(struct svc_serv *),
                         svc_thread_fn, struct module *);
 int                svc_set_num_threads(struct svc_serv *, struct svc_pool *, int);
+int                svc_pool_stats_open(struct svc_serv *serv, struct file *file);
 void               svc_destroy(struct svc_serv *);
 int                svc_process(struct svc_rqst *);
 int                svc_register(const struct svc_serv *, const unsigned short,