libceph: wait_request_timeout()

The unwatch timeout is currently implemented in rbd.  With
watch/unwatch code moving into libceph, we are going to need
a ceph_osdc_wait_request() variant with a timeout.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

net/ceph/osd_client.c

@@ -2668,28 +2668,36 @@ void ceph_osdc_cancel_request(struct ceph_osd_request *req)
 EXPORT_SYMBOL(ceph_osdc_cancel_request);
 
 /*
- * wait for a request to complete
+ * @timeout: in jiffies, 0 means "wait forever"
  */
-int ceph_osdc_wait_request(struct ceph_osd_client *osdc,
-			   struct ceph_osd_request *req)
+static int wait_request_timeout(struct ceph_osd_request *req,
+				unsigned long timeout)
 {
-	int rc;
-
-	dout("%s %p tid %llu\n", __func__, req, req->r_tid);
+	long left;
 
-	rc = wait_for_completion_interruptible(&req->r_completion);
-	if (rc < 0) {
-		dout("%s %p tid %llu interrupted\n", __func__, req, req->r_tid);
+	dout("%s req %p tid %llu\n", __func__, req, req->r_tid);
+	left = wait_for_completion_interruptible_timeout(&req->r_completion,
+						ceph_timeout_jiffies(timeout));
+	if (left <= 0) {
+		left = left ?: -ETIMEDOUT;
 		ceph_osdc_cancel_request(req);
 
 		/* kludge - need to to wake ceph_osdc_sync() */
 		complete_all(&req->r_safe_completion);
-		return rc;
+	} else {
+		left = req->r_result; /* completed */
 	}
 
-	dout("%s %p tid %llu result %d\n", __func__, req, req->r_tid,
-	     req->r_result);
-	return req->r_result;
+	return left;
+}
+
+/*
+ * wait for a request to complete
+ */
+int ceph_osdc_wait_request(struct ceph_osd_client *osdc,
+			   struct ceph_osd_request *req)
+{
+	return wait_request_timeout(req, 0);
 }
 EXPORT_SYMBOL(ceph_osdc_wait_request);