io_uring: Add .errdetails to parse CQ status

Background
 - fio normally prints out the strerr and errno value when facing
   errors.  In case of io_uring_cmd ioengine with --cmd_type=nvme,
   io_u->error represents the CQ entry status code type and status
   code which should be parsed as a NVMe error value rather than
   errno.

In io_u error failure condition, it prints out parsed CQ entry error
status values with SCT(Status Code Type) and SC(Status Code).  The print
will be like the following example:

  fio: io_uring_cmd: /dev/ng0n1: cq entry status (sct=0x00; sc=0x04)

If --cmd_type!=nvme, it prints out generic status code like below:

  fio: io_uring_cmd: /dev/<devnode>: status=0x4

Signed-off-by: Minwoo Im <minwoo.im@samsung.com>

engines/io_uring.c

@@ -554,6 +554,39 @@ static struct io_u *fio_ioring_cmd_event(struct thread_data *td, int event)
 	return io_u;
 }
 
+static char *fio_ioring_cmd_errdetails(struct thread_data *td,
+				       struct io_u *io_u)
+{
+	struct ioring_options *o = td->eo;
+	unsigned int sct = (io_u->error >> 8) & 0x7;
+	unsigned int sc = io_u->error & 0xff;
+#define MAXERRDETAIL 1024
+#define MAXMSGCHUNK 128
+	char *msg, msgchunk[MAXMSGCHUNK];
+
+	msg = calloc(1, MAXERRDETAIL);
+	strcpy(msg, "io_uring_cmd: ");
+
+	snprintf(msgchunk, MAXMSGCHUNK, "%s: ", io_u->file->file_name);
+	strlcat(msg, msgchunk, MAXERRDETAIL);
+
+	if (o->cmd_type == FIO_URING_CMD_NVME) {
+		strlcat(msg, "cq entry status (", MAXERRDETAIL);
+
+		snprintf(msgchunk, MAXMSGCHUNK, "sct=0x%02x; ", sct);
+		strlcat(msg, msgchunk, MAXERRDETAIL);
+
+		snprintf(msgchunk, MAXMSGCHUNK, "sc=0x%02x)", sc);
+		strlcat(msg, msgchunk, MAXERRDETAIL);
+	} else {
+		/* Print status code in generic */
+		snprintf(msgchunk, MAXMSGCHUNK, "status=0x%x", io_u->error);
+		strlcat(msg, msgchunk, MAXERRDETAIL);
+	}
+
+	return msg;
+}
+
 static int fio_ioring_cqring_reap(struct thread_data *td, unsigned int events,
 				   unsigned int max)
 {
@@ -1590,6 +1623,7 @@ static struct ioengine_ops ioengine_uring_cmd = {
 	.commit			= fio_ioring_commit,
 	.getevents		= fio_ioring_getevents,
 	.event			= fio_ioring_cmd_event,
+	.errdetails		= fio_ioring_cmd_errdetails,
 	.cleanup		= fio_ioring_cleanup,
 	.open_file		= fio_ioring_cmd_open_file,
 	.close_file		= fio_ioring_cmd_close_file,