IB/rxe: Refactor lookup memory function

Consolidate all error checks under single if() condition and use helper
unlikely() macro for them, in addition drop unneeded goto labels.

rxe_pool_get_index() already provides RB tree based efficient lookup.
Avoid doing extra checks for error cases which are rare and already
covered by rxe_pool_get_index().
Signed-off-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Daniel Jurgens <danielj@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/sw/rxe/rxe_mr.c

@@ -573,33 +573,20 @@ struct rxe_mem *lookup_mem(struct rxe_pd *pd, int access, u32 key,
 	struct rxe_dev *rxe = to_rdev(pd->ibpd.device);
 	int index = key >> 8;
 
-	if (index >= RXE_MIN_MR_INDEX && index <= RXE_MAX_MR_INDEX) {
 	mem = rxe_pool_get_index(&rxe->mr_pool, index);
 	if (!mem)
-			goto err1;
-	} else {
-		goto err1;
-	}
-
-	if ((type == lookup_local && mem->lkey != key) ||
-	    (type == lookup_remote && mem->rkey != key))
-		goto err2;
-
-	if (mem->pd != pd)
-		goto err2;
-
-	if (access && !(access & mem->access))
-		goto err2;
+		return NULL;
 
-	if (mem->state != RXE_MEM_STATE_VALID)
-		goto err2;
+	if (unlikely((type == lookup_local && mem->lkey != key) ||
+		     (type == lookup_remote && mem->rkey != key) ||
+		     mem->pd != pd ||
+		     (access && !(access & mem->access)) ||
+		     mem->state != RXE_MEM_STATE_VALID)) {
+		rxe_drop_ref(mem);
+		mem = NULL;
+	}
 
 	return mem;
-
-err2:
-	rxe_drop_ref(mem);
-err1:
-	return NULL;
 }
 
 int rxe_mem_map_pages(struct rxe_dev *rxe, struct rxe_mem *mem,