NFS: report how long an NFS file system has been mounted

Add a field in nfs_server to record a timestamp when a mount succeeds.
Report the number of seconds the file system has been mounted via
nfs_show_stats().

Test plan:
Mount an NFS file system, watch the mountstats reports and compare with
clock time.

Signed-off-by: Chuck Lever <cel@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index d65e69a06b72..65dec21af774 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -35,6 +35,7 @@ struct nfs_server {
         char *                  hostname;       /* remote hostname */
         struct nfs_fh           fh;
         struct sockaddr_in      addr;
+        unsigned long           mount_time;     /* when this fs was mounted */
 #ifdef CONFIG_NFS_V4
         /* Our own IP address, as a null-terminated string.
          * This is used to generate the clientid, and the callback address.