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, 12 insertions, 0 deletions

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 3d93b2064ce5..4adebb6312c4 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -60,6 +60,7 @@ enum {
         NFSD_FO_UnlockFS,
         NFSD_Threads,
         NFSD_Pool_Threads,
+        NFSD_Pool_Stats,
         NFSD_Versions,
         NFSD_Ports,
         NFSD_MaxBlkSize,
@@ -172,6 +173,16 @@ static const struct file_operations exports_operations = {
         .owner          = THIS_MODULE,
 };
 
+extern int nfsd_pool_stats_open(struct inode *inode, struct file *file);
+
+static struct file_operations pool_stats_operations = {
+        .open           = nfsd_pool_stats_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = seq_release,
+        .owner          = THIS_MODULE,
+};
+
 /*----------------------------------------------------------------------------*/
 /*
  * payload - write methods
@@ -1246,6 +1257,7 @@ static int nfsd_fill_super(struct super_block * sb, void * data, int silent)
                 [NFSD_Fh] = {"filehandle", &transaction_ops, S_IWUSR|S_IRUSR},
                 [NFSD_Threads] = {"threads", &transaction_ops, S_IWUSR|S_IRUSR},
                 [NFSD_Pool_Threads] = {"pool_threads", &transaction_ops, S_IWUSR|S_IRUSR},
+                [NFSD_Pool_Stats] = {"pool_stats", &pool_stats_operations, S_IRUGO},
                 [NFSD_Versions] = {"versions", &transaction_ops, S_IWUSR|S_IRUSR},
                 [NFSD_Ports] = {"portlist", &transaction_ops, S_IWUSR|S_IRUGO},
                 [NFSD_MaxBlkSize] = {"max_block_size", &transaction_ops, S_IWUSR|S_IRUGO},