RDMA/rxe: Cleanup rxe_mcast.c

Finish adding subroutine comment headers to subroutines in
rxe_mcast.c. Make minor api change cleanups.

Link: https://lore.kernel.org/r/20220223230706.50332-5-rpearsonhpe@gmail.com
Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/sw/rxe/rxe_mcast.c

@@ -1,12 +1,33 @@
 // SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
 /*
+ * Copyright (c) 2022 Hewlett Packard Enterprise, Inc. All rights reserved.
  * Copyright (c) 2016 Mellanox Technologies Ltd. All rights reserved.
  * Copyright (c) 2015 System Fabric Works, Inc. All rights reserved.
  */
 
-#include "rxe.h"
-#include "rxe_loc.h"
+/*
+ * rxe_mcast.c implements driver support for multicast transport.
+ * It is based on two data structures struct rxe_mcg ('mcg') and
+ * struct rxe_mca ('mca'). An mcg is allocated each time a qp is
+ * attached to a new mgid for the first time. These are indexed by
+ * a red-black tree using the mgid. This data structure is searched
+ * for the mcg when a multicast packet is received and when another
+ * qp is attached to the same mgid. It is cleaned up when the last qp
+ * is detached from the mcg. Each time a qp is attached to an mcg an
+ * mca is created. It holds a pointer to the qp and is added to a list
+ * of qp's that are attached to the mcg. The qp_list is used to replicate
+ * mcast packets in the rxe receive path.
+ */
 
+#include "rxe.h"
+
+/**
+ * rxe_mcast_add - add multicast address to rxe device
+ * @rxe: rxe device object
+ * @mgid: multicast address as a gid
+ *
+ * Returns 0 on success else an error
+ */
 static int rxe_mcast_add(struct rxe_dev *rxe, union ib_gid *mgid)
 {
 	unsigned char ll_addr[ETH_ALEN];
@@ -16,6 +37,13 @@ static int rxe_mcast_add(struct rxe_dev *rxe, union ib_gid *mgid)
 	return dev_mc_add(rxe->ndev, ll_addr);
 }
 
+/**
+ * rxe_mcast_delete - delete multicast address from rxe device
+ * @rxe: rxe device object
+ * @mgid: multicast address as a gid
+ *
+ * Returns 0 on success else an error
+ */
 static int rxe_mcast_delete(struct rxe_dev *rxe, union ib_gid *mgid)
 {
 	unsigned char ll_addr[ETH_ALEN];
@@ -216,7 +244,7 @@ err_dec:
 
 /**
  * rxe_cleanup_mcg - cleanup mcg for kref_put
- * @kref:
+ * @kref: struct kref embnedded in mcg
  */
 void rxe_cleanup_mcg(struct kref *kref)
 {
@@ -299,9 +327,17 @@ static int __rxe_init_mca(struct rxe_qp *qp, struct rxe_mcg *mcg,
 	return 0;
 }
 
-static int rxe_attach_mcg(struct rxe_dev *rxe, struct rxe_qp *qp,
-				  struct rxe_mcg *mcg)
+/**
+ * rxe_attach_mcg - attach qp to mcg if not already attached
+ * @qp: qp object
+ * @mcg: mcg object
+ *
+ * Context: caller must hold reference on qp and mcg.
+ * Returns: 0 on success else an error
+ */
+static int rxe_attach_mcg(struct rxe_mcg *mcg, struct rxe_qp *qp)
 {
+	struct rxe_dev *rxe = mcg->rxe;
 	struct rxe_mca *mca, *tmp;
 	unsigned long flags;
 	int err;
@@ -358,17 +394,19 @@ static void __rxe_cleanup_mca(struct rxe_mca *mca, struct rxe_mcg *mcg)
 	kfree(mca);
 }
 
-static int rxe_detach_mcg(struct rxe_dev *rxe, struct rxe_qp *qp,
-				   union ib_gid *mgid)
+/**
+ * rxe_detach_mcg - detach qp from mcg
+ * @mcg: mcg object
+ * @qp: qp object
+ *
+ * Returns: 0 on success else an error if qp is not attached.
+ */
+static int rxe_detach_mcg(struct rxe_mcg *mcg, struct rxe_qp *qp)
 {
-	struct rxe_mcg *mcg;
+	struct rxe_dev *rxe = mcg->rxe;
 	struct rxe_mca *mca, *tmp;
 	unsigned long flags;
 
-	mcg = rxe_lookup_mcg(rxe, mgid);
-	if (!mcg)
-		return -EINVAL;
-
 	spin_lock_irqsave(&rxe->mcg_lock, flags);
 	list_for_each_entry_safe(mca, tmp, &mcg->qp_list, qp_list) {
 		if (mca->qp == qp) {
@@ -378,16 +416,11 @@ static int rxe_detach_mcg(struct rxe_dev *rxe, struct rxe_qp *qp,
 			 * mcast group falls to zero go ahead and
 			 * tear it down. This will not free the
 			 * object since we are still holding a ref
-			 * from the get key above
+			 * from the caller
 			 */
 			if (atomic_read(&mcg->qp_num) <= 0)
 				__rxe_destroy_mcg(mcg);
 
-			/* drop the ref from get key. This will free the
-			 * object if qp_num is zero.
-			 */
-			kref_put(&mcg->ref_cnt, rxe_cleanup_mcg);
-
 			spin_unlock_irqrestore(&rxe->mcg_lock, flags);
 			return 0;
 		}
@@ -398,6 +431,14 @@ static int rxe_detach_mcg(struct rxe_dev *rxe, struct rxe_qp *qp,
 	return -EINVAL;
 }
 
+/**
+ * rxe_attach_mcast - attach qp to multicast group (see IBA-11.3.1)
+ * @ibqp: (IB) qp object
+ * @mgid: multicast IP address
+ * @mlid: multicast LID, ignored for RoCEv2 (see IBA-A17.5.6)
+ *
+ * Returns: 0 on success else an errno
+ */
 int rxe_attach_mcast(struct ib_qp *ibqp, union ib_gid *mgid, u16 mlid)
 {
 	int err;
@@ -410,20 +451,38 @@ int rxe_attach_mcast(struct ib_qp *ibqp, union ib_gid *mgid, u16 mlid)
 	if (IS_ERR(mcg))
 		return PTR_ERR(mcg);
 
-	err = rxe_attach_mcg(rxe, qp, mcg);
+	err = rxe_attach_mcg(mcg, qp);
 
 	/* if we failed to attach the first qp to mcg tear it down */
 	if (atomic_read(&mcg->qp_num) == 0)
 		rxe_destroy_mcg(mcg);
 
 	kref_put(&mcg->ref_cnt, rxe_cleanup_mcg);
+
 	return err;
 }
 
+/**
+ * rxe_detach_mcast - detach qp from multicast group (see IBA-11.3.2)
+ * @ibqp: address of (IB) qp object
+ * @mgid: multicast IP address
+ * @mlid: multicast LID, ignored for RoCEv2 (see IBA-A17.5.6)
+ *
+ * Returns: 0 on success else an errno
+ */
 int rxe_detach_mcast(struct ib_qp *ibqp, union ib_gid *mgid, u16 mlid)
 {
 	struct rxe_dev *rxe = to_rdev(ibqp->device);
 	struct rxe_qp *qp = to_rqp(ibqp);
+	struct rxe_mcg *mcg;
+	int err;
 
-	return rxe_detach_mcg(rxe, qp, mgid);
+	mcg = rxe_lookup_mcg(rxe, mgid);
+	if (!mcg)
+		return -EINVAL;
+
+	err = rxe_detach_mcg(mcg, qp);
+	kref_put(&mcg->ref_cnt, rxe_cleanup_mcg);
+
+	return err;
 }