io_uring: Add IO_U_F_DEVICE_ERROR to identify error types

__io_u_log_error expects a positive value of io_u->error parsing it with
strerror() expecting it to be an errno.  io_uring_cmd (cmd_type=nvme),
for example, has returned errno value as a positive value and
device-specific CQE status type and code as well.

Commit 78831c6 ("io_uring: Fix the flip to negative of CQE status")
has put the abs() to the cqe->res, and it caused confusions between the
actual CQE stauts and the system error value (errno).  Now we have
Commit 2a13699 ("io_uring: Add .errdetails to parse CQ status"),
meaning that io_uring_cmd ioengines will parse the actual value of
io_u->error value as CQE status value, so we should know if the value is
for CQE status or errno.

This patch added a flag IO_U_F_DEVICE_ERROR to io_u to represent if
io_u->error has device-specific error value, otherwise it's errno.

Signed-off-by: Minwoo Im <minwoo.im.dev@gmail.com>
Link: https://lore.kernel.org/r/20240926004134.26004-1-minwoo.im.dev@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

engines/io_uring.c

@@ -528,12 +528,9 @@ static struct io_u *fio_ioring_cmd_event(struct thread_data *td, int event)
 	cqe = &ld->cq_ring.cqes[index];
 	io_u = (struct io_u *) (uintptr_t) cqe->user_data;
 
-	if (cqe->res != 0) {
-		io_u->error = abs(cqe->res);
-		return io_u;
-	} else {
-		io_u->error = 0;
-	}
+	io_u->error = cqe->res;
+	if (io_u->error != 0)
+		goto ret;
 
 	if (o->cmd_type == FIO_URING_CMD_NVME) {
 		data = FILE_ENG_DATA(io_u->file);
@@ -544,6 +541,16 @@ static struct io_u *fio_ioring_cmd_event(struct thread_data *td, int event)
 		}
 	}
 
+ret:
+	/*
+	 * If IO_U_F_DEVICE_ERROR is not set, io_u->error will be parsed as an
+	 * errno, otherwise device-specific error value (status value in CQE).
+	 */
+	if ((int)io_u->error > 0)
+		io_u_set(td, io_u, IO_U_F_DEVICE_ERROR);
+	else
+		io_u_clear(td, io_u, IO_U_F_DEVICE_ERROR);
+	io_u->error = abs(io_u->error);
 	return io_u;
 }
 
@@ -557,6 +564,9 @@ static char *fio_ioring_cmd_errdetails(struct thread_data *td,
 #define MAXMSGCHUNK 128
 	char *msg, msgchunk[MAXMSGCHUNK];
 
+	if (!(io_u->flags & IO_U_F_DEVICE_ERROR))
+		return NULL;
+
 	msg = calloc(1, MAXERRDETAIL);
 	strcpy(msg, "io_uring_cmd: ");
 

io_u.c

@@ -1956,7 +1956,8 @@ static void __io_u_log_error(struct thread_data *td, struct io_u *io_u)
 	log_err("fio: io_u error%s%s: %s: %s offset=%llu, buflen=%llu\n",
 		io_u->file ? " on file " : "",
 		io_u->file ? io_u->file->file_name : "",
-		strerror(io_u->error),
+		(io_u->flags & IO_U_F_DEVICE_ERROR) ?
+			"Device-specific error" : strerror(io_u->error),
 		io_ddir_name(io_u->ddir),
 		io_u->offset, io_u->xfer_buflen);
 
@@ -1965,8 +1966,10 @@ static void __io_u_log_error(struct thread_data *td, struct io_u *io_u)
 	if (td->io_ops->errdetails) {
 		char *err = td->io_ops->errdetails(td, io_u);
 
-		log_err("fio: %s\n", err);
-		free(err);
+		if (err) {
+			log_err("fio: %s\n", err);
+			free(err);
+		}
 	}
 
 	if (!td->error)

io_u.h

@@ -22,6 +22,7 @@ enum {
 	IO_U_F_BARRIER		= 1 << 6,
 	IO_U_F_VER_LIST		= 1 << 7,
 	IO_U_F_PATTERN_DONE	= 1 << 8,
+	IO_U_F_DEVICE_ERROR	= 1 << 9,
 };
 
 /*