SUNRPC: Add a helper to allow pNFS drivers to selectively cancel RPC calls

Add the helper rpc_cancel_tasks(), which uses a caller-defined selection
function to define a set of in-flight RPC calls to cancel. This is
mainly intended for pNFS drivers which are subject to a layout recall,
and which may therefore want to cancel all pending I/O using that layout
in order to redrive it after the layout recall has been satisfied.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

2 files changed, 48 insertions, 0 deletions

diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index a8c341e43510..57677517b474 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -873,6 +873,43 @@ void rpc_killall_tasks(struct rpc_clnt *clnt)
 }
 EXPORT_SYMBOL_GPL(rpc_killall_tasks);
 
+/**
+ * rpc_cancel_tasks - try to cancel a set of RPC tasks
+ * @clnt: Pointer to RPC client
+ * @error: RPC task error value to set
+ * @fnmatch: Pointer to selector function
+ * @data: User data
+ *
+ * Uses @fnmatch to define a set of RPC tasks that are to be cancelled.
+ * The argument @error must be a negative error value.
+ */
+unsigned long rpc_cancel_tasks(struct rpc_clnt *clnt, int error,
+			       bool (*fnmatch)(const struct rpc_task *,
+					       const void *),
+			       const void *data)
+{
+	struct rpc_task *task;
+	unsigned long count = 0;
+
+	if (list_empty(&clnt->cl_tasks))
+		return 0;
+	/*
+	 * Spin lock all_tasks to prevent changes...
+	 */
+	spin_lock(&clnt->cl_lock);
+	list_for_each_entry(task, &clnt->cl_tasks, tk_task) {
+		if (!RPC_IS_ACTIVATED(task))
+			continue;
+		if (!fnmatch(task, data))
+			continue;
+		rpc_task_try_cancel(task, error);
+		count++;
+	}
+	spin_unlock(&clnt->cl_lock);
+	return count;
+}
+EXPORT_SYMBOL_GPL(rpc_cancel_tasks);
+
 /*
  * Properly shut down an RPC client, terminating all outstanding
  * requests.
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index f388bfaf6ff0..de912e02371b 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -872,6 +872,17 @@ void rpc_signal_task(struct rpc_task *task)
 		rpc_wake_up_queued_task(queue, task);
 }
 
+void rpc_task_try_cancel(struct rpc_task *task, int error)
+{
+	struct rpc_wait_queue *queue;
+
+	if (!rpc_task_set_rpc_status(task, error))
+		return;
+	queue = READ_ONCE(task->tk_waitqueue);
+	if (queue)
+		rpc_wake_up_queued_task(queue, task);
+}
+
 void rpc_exit(struct rpc_task *task, int status)
 {
 	task->tk_status = status;