libceph: introduce alloc_watch_request()

ceph_osdc_alloc_messages() call will be moved out of
alloc_linger_request() in the next commit, which means that
ceph_osdc_watch() will need to call ceph_osdc_alloc_messages()
twice.  Add a helper for that.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

net/ceph/osd_client.c

@@ -4492,6 +4492,23 @@ alloc_linger_request(struct ceph_osd_linger_request *lreq)
 	return req;
 }
 
+static struct ceph_osd_request *
+alloc_watch_request(struct ceph_osd_linger_request *lreq, u8 watch_opcode)
+{
+	struct ceph_osd_request *req;
+
+	req = alloc_linger_request(lreq);
+	if (!req)
+		return NULL;
+
+	/*
+	 * Pass 0 for cookie because we don't know it yet, it will be
+	 * filled in by linger_submit().
+	 */
+	osd_req_op_watch_init(req, 0, 0, watch_opcode);
+	return req;
+}
+
 /*
  * Returns a handle, caller owns a ref.
  */
@@ -4521,25 +4538,18 @@ ceph_osdc_watch(struct ceph_osd_client *osdc,
 	lreq->t.flags = CEPH_OSD_FLAG_WRITE;
 	ktime_get_real_ts64(&lreq->mtime);
 
-	lreq->reg_req = alloc_linger_request(lreq);
+	lreq->reg_req = alloc_watch_request(lreq, CEPH_OSD_WATCH_OP_WATCH);
 	if (!lreq->reg_req) {
 		ret = -ENOMEM;
 		goto err_put_lreq;
 	}
 
-	lreq->ping_req = alloc_linger_request(lreq);
+	lreq->ping_req = alloc_watch_request(lreq, CEPH_OSD_WATCH_OP_PING);
 	if (!lreq->ping_req) {
 		ret = -ENOMEM;
 		goto err_put_lreq;
 	}
 
-	/*
-	 * Pass 0 for cookie because we don't know it yet, it will be
-	 * filled in by linger_submit().
-	 */
-	osd_req_op_watch_init(lreq->reg_req, 0, 0, CEPH_OSD_WATCH_OP_WATCH);
-	osd_req_op_watch_init(lreq->ping_req, 0, 0, CEPH_OSD_WATCH_OP_PING);
-
 	linger_submit(lreq);
 	ret = linger_reg_commit_wait(lreq);
 	if (ret) {