SUNRPC: track length of RPC wait queues

RPC wait queue length will eventually be exported to userland via the RPC
iostats interface.

Test plan:
Compile kernel with CONFIG_NFS enabled.

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

2 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h
index a390c9b8a01e..6c23f73a799a 100644
--- a/include/linux/sunrpc/sched.h
+++ b/include/linux/sunrpc/sched.h
@@ -203,6 +203,7 @@ struct rpc_wait_queue {
         unsigned char           priority;               /* current priority */
         unsigned char           count;                  /* # task groups remaining serviced so far */
         unsigned char           nr;                     /* # tasks remaining for cookie */
+        unsigned short          qlen;                   /* total # tasks waiting in queue */
 #ifdef RPC_DEBUG
         const char *            name;
 #endif
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index 1b74420d1603..aa0449dcd8e5 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -181,6 +181,7 @@ static void __rpc_add_wait_queue(struct rpc_wait_queue *queue, struct rpc_task *
         else
                 list_add_tail(&task->u.tk_wait.list, &queue->tasks[0]);
         task->u.tk_wait.rpc_waitq = queue;
+        queue->qlen++;
         rpc_set_queued(task);
 
         dprintk("RPC: %4d added to queue %p \"%s\"\n",
@@ -215,6 +216,7 @@ static void __rpc_remove_wait_queue(struct rpc_task *task)
                 __rpc_remove_wait_queue_priority(task);
         else
                 list_del(&task->u.tk_wait.list);
+        queue->qlen--;
         dprintk("RPC: %4d removed from queue %p \"%s\"\n",
                                 task->tk_pid, queue, rpc_qname(queue));
 }