DLPX-77532 The iscsi estat script needs to be fixed so it reports data correctly (#69)

Author: brad-lewis

bpf/estat/iscsi.c

@@ -4,6 +4,24 @@
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
+/* 
+ * This tracer provides latency and througphput data for the iscsi target 
+ * read and writes. The latency is measured from entering 
+ * iscsit_process_scsi_cmd() to exiting iscsit_target_response(). The
+ * thread that enters iscsi_process_scsi_cmd() will put an entry on the
+ * request task queue. This entry will be removed from the queue and
+ * processed by another thread which calls iscsi_target_response.
+ * The tracing is performed by three probe functions.
+ * 1. iscsi_target_start - This function saves a timestamp of the entry
+ *    into iscsit_process_scsi_cmd() hashed by a pointer to the iscssi_cmd.
+ * 2. iscsi_target_response - This function serves the purpose of moving
+ *    the timestamp saved by iscsi_target_start to a thread id based hash.
+ *    Also the size and direction are stored in the hash since kretprobes
+ *    do not have access to parameters.
+ * 3. iscsi_target_end - This function retrieves the hashed base data by
+ *    thread id and performs the data aggregation.
+ */
+
 #include <uapi/linux/ptrace.h>
 #include <linux/bpf_common.h>
 #include <uapi/linux/bpf.h>
@@ -20,20 +38,20 @@
 typedef struct {
 	u64 ts;
 	u64 size;
+	u32 direction;
 } iscsi_data_t;
 
 
-BPF_HASH(iscsi_base_data, u64, iscsi_data_t);
+BPF_HASH(iscsi_start_ts, u64, u64);
+BPF_HASH(iscsi_base_data, u32, iscsi_data_t);
 
 // @@ kprobe|iscsit_process_scsi_cmd|iscsi_target_start
 int
 iscsi_target_start(struct pt_regs *ctx, struct iscsi_conn *conn,
     struct iscsi_cmd *cmd, struct iscsi_scsi_req *hdr)
 {
-	iscsi_data_t data = {};
-	data.ts = bpf_ktime_get_ns();
-	data.size = hdr->data_length;
-	iscsi_base_data.update((u64 *) &cmd, &data);
+	u64 ts = bpf_ktime_get_ns();
+	iscsi_start_ts.update((u64 *) &cmd, &ts);
 
 	return (0);
 }
@@ -53,25 +71,48 @@ aggregate_data(iscsi_data_t *data, u64 ts, char *opstr)
 	return (0);
 }
 
-// @@ kprobe|iscsit_build_rsp_pdu|iscsi_target_end
-// @@ kprobe|iscsit_build_datain_pdu|iscsi_target_end
+
+
+// @@ kprobe|iscsit_response_queue|iscsi_target_response
 int
-iscsi_target_end(struct pt_regs *ctx, struct iscsi_cmd *cmd)
+iscsi_target_response(struct pt_regs *ctx, struct iscsi_conn *conn, struct iscsi_cmd *cmd, int state)
+{
+	u32 tid = bpf_get_current_pid_tgid();
+	iscsi_data_t data = {};
+
+	u64 *tsp = iscsi_start_ts.lookup((u64 *) &cmd);
+	if (tsp == 0) {
+		return (0);   // missed issue
+	}
+
+	data.ts = *tsp;
+	data.size = cmd->se_cmd.data_length;
+	data.direction = cmd->data_direction;
+
+	iscsi_base_data.update(&tid, &data);
+	iscsi_start_ts.delete((u64 *) &cmd);
+
+	return (0);
+}
+
+// @@ kretprobe|iscsit_response_queue|iscsi_target_end
+int
+iscsi_target_end(struct pt_regs *ctx)
 {
 	u64 ts = bpf_ktime_get_ns();
-	iscsi_data_t *data = iscsi_base_data.lookup((u64 *) &cmd);
-	u64 delta;
+	u32 tid = bpf_get_current_pid_tgid();
+	iscsi_data_t *data = iscsi_base_data.lookup(&tid);
 
 	if (data == 0) {
 		return (0);   // missed issue
 	}
 
-	if (cmd->data_direction == DMA_FROM_DEVICE) {
+	if (data->direction == DMA_FROM_DEVICE) {
 		aggregate_data(data, ts, READ_STR);
-	} else if (cmd->data_direction & DMA_TO_DEVICE) {
+	} else if (data->direction == DMA_TO_DEVICE) {
 		aggregate_data(data, ts, WRITE_STR);
 	}
-	iscsi_base_data.delete((u64 *) &cmd);
+	iscsi_base_data.delete(&tid);
 
 	return (0);
 }