knfsd: Replace lock_kernel with a mutex in nfsd pool stats.

lock_kernel() in knfsd was replaced with a mutex. The later
commit 03cf6c9f49a8fea953d38648d016e3f46e814991 ("knfsd:
add file to export stats about nfsd pools") did not follow
that change. This patch fixes the issue.

Also move the get and put of nfsd_serv to the open and close methods
(instead of start and stop methods) to allow atomic check and increment
of reference count in the open method (where we can still return an
error).

Signed-off-by: Ryusei Yamaguchi <mandel59@gmail.com>
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Cc: Greg Banks <gnb@fmeh.org>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index b764d7d..00388d2 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -174,12 +174,13 @@
 };
 
 extern int nfsd_pool_stats_open(struct inode *inode, struct file *file);
+extern int nfsd_pool_stats_release(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,
+	.release	= nfsd_pool_stats_release,
 	.owner		= THIS_MODULE,
 };