net/rds: Use ERR_PTR for rds_message_alloc_sgs()

Returning the error code via a 'int *ret' when the function returns a
pointer is very un-kernely and causes gcc 10's static analysis to choke:

net/rds/message.c: In function ‘rds_message_map_pages’:
net/rds/message.c:358:10: warning: ‘ret’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  358 |   return ERR_PTR(ret);

Use a typical ERR_PTR return instead.
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/rds/message.c

@@ -308,26 +308,20 @@ struct rds_message *rds_message_alloc(unsigned int extra_len, gfp_t gfp)
 /*
  * RDS ops use this to grab SG entries from the rm's sg pool.
  */
-struct scatterlist *rds_message_alloc_sgs(struct rds_message *rm, int nents,
-					  int *ret)
+struct scatterlist *rds_message_alloc_sgs(struct rds_message *rm, int nents)
 {
 	struct scatterlist *sg_first = (struct scatterlist *) &rm[1];
 	struct scatterlist *sg_ret;
 
-	if (WARN_ON(!ret))
-		return NULL;
-
 	if (nents <= 0) {
 		pr_warn("rds: alloc sgs failed! nents <= 0\n");
-		*ret = -EINVAL;
-		return NULL;
+		return ERR_PTR(-EINVAL);
 	}
 
 	if (rm->m_used_sgs + nents > rm->m_total_sgs) {
 		pr_warn("rds: alloc sgs failed! total %d used %d nents %d\n",
 			rm->m_total_sgs, rm->m_used_sgs, nents);
-		*ret = -ENOMEM;
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 	}
 
 	sg_ret = &sg_first[rm->m_used_sgs];
@@ -343,7 +337,6 @@ struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned in
 	unsigned int i;
 	int num_sgs = DIV_ROUND_UP(total_len, PAGE_SIZE);
 	int extra_bytes = num_sgs * sizeof(struct scatterlist);
-	int ret;
 
 	rm = rds_message_alloc(extra_bytes, GFP_NOWAIT);
 	if (!rm)
@@ -352,10 +345,10 @@ struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned in
 	set_bit(RDS_MSG_PAGEVEC, &rm->m_flags);
 	rm->m_inc.i_hdr.h_len = cpu_to_be32(total_len);
 	rm->data.op_nents = DIV_ROUND_UP(total_len, PAGE_SIZE);
-	rm->data.op_sg = rds_message_alloc_sgs(rm, num_sgs, &ret);
-	if (!rm->data.op_sg) {
+	rm->data.op_sg = rds_message_alloc_sgs(rm, num_sgs);
+	if (IS_ERR(rm->data.op_sg)) {
 		rds_message_put(rm);
-		return ERR_PTR(ret);
+		return ERR_CAST(rm->data.op_sg);
 	}
 
 	for (i = 0; i < rm->data.op_nents; ++i) {

net/rds/rdma.c

@@ -665,9 +665,11 @@ int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
 	op->op_odp_mr = NULL;
 
 	WARN_ON(!nr_pages);
-	op->op_sg = rds_message_alloc_sgs(rm, nr_pages, &ret);
-	if (!op->op_sg)
+	op->op_sg = rds_message_alloc_sgs(rm, nr_pages);
+	if (IS_ERR(op->op_sg)) {
+		ret = PTR_ERR(op->op_sg);
 		goto out_pages;
+	}
 
 	if (op->op_notify || op->op_recverr) {
 		/* We allocate an uninitialized notifier here, because
@@ -906,9 +908,11 @@ int rds_cmsg_atomic(struct rds_sock *rs, struct rds_message *rm,
 	rm->atomic.op_silent = !!(args->flags & RDS_RDMA_SILENT);
 	rm->atomic.op_active = 1;
 	rm->atomic.op_recverr = rs->rs_recverr;
-	rm->atomic.op_sg = rds_message_alloc_sgs(rm, 1, &ret);
-	if (!rm->atomic.op_sg)
+	rm->atomic.op_sg = rds_message_alloc_sgs(rm, 1);
+	if (IS_ERR(rm->atomic.op_sg)) {
+		ret = PTR_ERR(rm->atomic.op_sg);
 		goto err;
+	}
 
 	/* verify 8 byte-aligned */
 	if (args->local_addr & 0x7) {

net/rds/rds.h

@@ -844,8 +844,7 @@ rds_conn_connecting(struct rds_connection *conn)
 
 /* message.c */
 struct rds_message *rds_message_alloc(unsigned int nents, gfp_t gfp);
-struct scatterlist *rds_message_alloc_sgs(struct rds_message *rm, int nents,
-					  int *ret);
+struct scatterlist *rds_message_alloc_sgs(struct rds_message *rm, int nents);
 int rds_message_copy_from_user(struct rds_message *rm, struct iov_iter *from,
 			       bool zcopy);
 struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned int total_len);

net/rds/send.c

@@ -1274,9 +1274,11 @@ int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len)
 
 	/* Attach data to the rm */
 	if (payload_len) {
-		rm->data.op_sg = rds_message_alloc_sgs(rm, num_sgs, &ret);
-		if (!rm->data.op_sg)
+		rm->data.op_sg = rds_message_alloc_sgs(rm, num_sgs);
+		if (IS_ERR(rm->data.op_sg)) {
+			ret = PTR_ERR(rm->data.op_sg);
 			goto out;
+		}
 		ret = rds_message_copy_from_user(rm, &msg->msg_iter, zcopy);
 		if (ret)
 			goto out;