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>
diff --git a/net/rds/message.c b/net/rds/message.c
index bbecb8c..071a261 100644
--- a/net/rds/message.c
+++ b/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) {