iser: eliminate unnecessary memory allocations

Allocate `iser_pdu` from small allocation pool.
Lifecycle of `iscsi_in_pdu` is inside the function in iSER transport. Allocate
it on stack.

Signed-off-by: wanghonghao <wanghonghao@bytedance.com>

lib/iser.c

@@ -553,7 +553,7 @@ iscsi_iser_new_pdu(struct iscsi_context *iscsi, __attribute__((unused))size_t si
 	struct iscsi_pdu *pdu;
 	struct iser_pdu *iser_pdu;
 
-	iser_pdu = iscsi_zmalloc(iscsi, sizeof(*iser_pdu));
+	iser_pdu = iscsi_szmalloc(iscsi, sizeof(*iser_pdu));
 	pdu = &iser_pdu->iscsi_pdu;
 	pdu->indata.data = NULL;
 
@@ -596,7 +596,7 @@ iscsi_iser_free_pdu(struct iscsi_context *iscsi, struct iscsi_pdu *pdu)
 		iscsi->outqueue_current = NULL;
 	}
 
-	iscsi_free(iscsi, iser_pdu);
+	iscsi_sfree(iscsi, iser_pdu);
 }
 
 /**
@@ -1316,18 +1316,16 @@ static int
 iser_rcv_completion(struct iser_rx_desc *rx_desc,
 		    struct iser_conn *iser_conn)
 {
-	struct iscsi_in_pdu *in = NULL;
+	struct iscsi_in_pdu in;
 	int empty, err;
 	struct iscsi_context *iscsi = iser_conn->cma_id->context;
 
-	in = iscsi_malloc(iscsi, sizeof(*in));
+	in.hdr = (unsigned char*)rx_desc->iscsi_header;
+	in.data_pos = iscsi_get_pdu_data_size(&in.hdr[0]);
+	in.data = (unsigned char*)rx_desc->data;
 
-	in->hdr = (unsigned char*)rx_desc->iscsi_header;
+	enum iscsi_opcode opcode = in.hdr[0] & 0x3f;
-	in->data_pos = iscsi_get_pdu_data_size(&in->hdr[0]);
+	uint32_t itt = scsi_get_uint32(&in.hdr[16]);
-	in->data = (unsigned char*)rx_desc->data;
-
-	enum iscsi_opcode opcode = in->hdr[0] & 0x3f;
-	uint32_t itt = scsi_get_uint32(&in->hdr[16]);
 
 	if (opcode == ISCSI_PDU_NOP_IN && itt == 0xffffffff)
 		goto nop_target;
@@ -1375,34 +1373,26 @@ nop_target:
 		if (empty >= iser_conn->min_posted_rx) {
 			err = iser_post_recvm(iser_conn, empty);
 			if (err) {
-				err = -1;
+				return -1;
-				goto error;
 			}
 		}
 	} else if (iscsi->is_loggedin) {
 		if(iser_alloc_rx_descriptors(iser_conn, 255)) {
 			iscsi_set_error(iscsi, "iser_alloc_rx_descriptors Failed\n");
-			err = -1;
+			return -1;
-			goto error;
 		}
 		err = iser_post_recvm(iser_conn, ISER_MIN_POSTED_RX);
 		if (err) {
-			err = -1;
+			return -1;
-			goto error;
 		}
 	} else {
 		if (iser_post_recvl(iser_conn)) {
 			iscsi_set_error(iscsi, "Failed Post Recv login");
-			err = -1;
+			return -1;
-			goto error;
 		}
 	}
 
-	err = iscsi_process_pdu(iscsi, in);
+	return iscsi_process_pdu(iscsi, &in);
-
-error:
-	iscsi_free(iscsi, in);
-	return err;
 }
 
 /**
@@ -1749,6 +1739,11 @@ void iscsi_init_iser_transport(struct iscsi_context *iscsi)
 	/* Update iSCSI params as per iSER transport */
 	iscsi->initiator_max_recv_data_segment_length = ISCSI_DEF_MAX_RECV_SEG_LEN;
 	iscsi->target_max_recv_data_segment_length = ISCSI_DEF_MAX_RECV_SEG_LEN;
+
+	/* ensure smalloc_size is enough for iser_pdu */
+	while (iscsi->smalloc_size < sizeof(struct iser_pdu)) {
+		iscsi->smalloc_size <<= 1;
+	}
 }
 
 #endif