Split ioworkload scenarios.go into per-category files

Split the 2494-line scenarios.go monolith into 14 focused files by
syscall category: open, readwrite, close, dup, fcntl, rename, link,
unlink, dir, stat, sync, truncate, iouring, plus the slimmed-down
scenarios.go containing only the registry map, makeTempDir, and crash.

Extracted rawLink, rawSymlink, rawReadlink helpers in scenario_link.go
to reduce code duplication in linkBasic.

Task: #349 (Go best practices: split oversized scenarios file)
Amp-Thread-ID: https://ampcode.com/threads/T-019c81c6-e1b6-747a-9144-40f6be997e60
Co-authored-by: Amp <amp@ampcode.com>

1 files changed, 129 insertions, 0 deletions

diff --git a/integrationtests/cmd/ioworkload/scenario_iouring.go b/integrationtests/cmd/ioworkload/scenario_iouring.go
new file mode 100644
index 0000000..b1aac4e
--- /dev/null
+++ b/integrationtests/cmd/ioworkload/scenario_iouring.go
@@ -0,0 +1,129 @@
+package main
+
+import (
+	"fmt"
+	"runtime"
+	"syscall"
+	"unsafe"
+)
+
+const (
+	sysIoUringSetup    = 425
+	sysIoUringEnter    = 426
+	sysIoUringRegister = 427
+
+	// io_uring_params struct size: 10 x uint32 + io_sqring_offsets(40) + io_cqring_offsets(40) = 120 bytes.
+	ioUringParamsSize = 120
+
+	ioringRegisterProbe = 8 // IORING_REGISTER_PROBE
+)
+
+// iouringSetup creates an io_uring instance via io_uring_setup(2) and closes the fd.
+func iouringSetup() error {
+	fd, err := ioUringSetupRing(1)
+	if err != nil {
+		return err
+	}
+	return syscall.Close(fd)
+}
+
+// iouringEnter creates an io_uring instance, then calls io_uring_enter(2)
+// with zero submissions/completions to exercise the enter tracepoint.
+func iouringEnter() error {
+	fd, err := ioUringSetupRing(1)
+	if err != nil {
+		return err
+	}
+	defer syscall.Close(fd)
+
+	_, _, errno := syscall.Syscall6(
+		sysIoUringEnter,
+		uintptr(fd),
+		0, // to_submit
+		0, // min_complete
+		0, // flags
+		0, // sig
+		0, // sz
+	)
+	if errno != 0 {
+		return fmt.Errorf("io_uring_enter: %w", errno)
+	}
+	return nil
+}
+
+// iouringRegister creates an io_uring instance, then calls io_uring_register(2)
+// with IORING_REGISTER_PROBE to exercise the register tracepoint.
+func iouringRegister() error {
+	fd, err := ioUringSetupRing(1)
+	if err != nil {
+		return err
+	}
+	defer syscall.Close(fd)
+
+	// io_uring_probe header is 16 bytes; we don't need probe_op entries.
+	var probeBuf [16]byte
+	_, _, errno := syscall.Syscall6(
+		sysIoUringRegister,
+		uintptr(fd),
+		ioringRegisterProbe,
+		uintptr(unsafe.Pointer(&probeBuf[0])),
+		0, // nr_args (0 ops requested)
+		0, 0,
+	)
+	runtime.KeepAlive(probeBuf)
+	if errno != 0 {
+		return fmt.Errorf("io_uring_register: %w", errno)
+	}
+	return nil
+}
+
+// iouringEnterEbadf calls io_uring_enter on an invalid fd.
+// The syscall fails with EBADF, but ior captures the enter_io_uring_enter tracepoint.
+func iouringEnterEbadf() error {
+	_, _, errno := syscall.Syscall6(
+		sysIoUringEnter,
+		99999, // invalid fd
+		0,     // to_submit
+		0,     // min_complete
+		0,     // flags
+		0,     // sig
+		0,     // sz
+	)
+	if errno == 0 {
+		return fmt.Errorf("expected EBADF, but io_uring_enter succeeded")
+	}
+	return nil
+}
+
+// iouringRegisterEbadf calls io_uring_register on an invalid fd.
+// The syscall fails with EBADF, but ior captures the enter_io_uring_register tracepoint.
+func iouringRegisterEbadf() error {
+	_, _, errno := syscall.Syscall6(
+		sysIoUringRegister,
+		99999, // invalid fd
+		ioringRegisterProbe,
+		0, // arg (NULL)
+		0, // nr_args
+		0, 0,
+	)
+	if errno == 0 {
+		return fmt.Errorf("expected EBADF, but io_uring_register succeeded")
+	}
+	return nil
+}
+
+// ioUringSetupRing calls io_uring_setup(2) and returns the ring fd.
+func ioUringSetupRing(entries uint32) (int, error) {
+	var params [ioUringParamsSize]byte
+	fd, _, errno := syscall.Syscall(
+		sysIoUringSetup,
+		uintptr(entries),
+		uintptr(unsafe.Pointer(&params[0])),
+		0,
+	)
+	runtime.KeepAlive(params)
+	if errno != 0 {
+		return 0, fmt.Errorf("io_uring_setup: %w", errno)
+	}
+	return int(fd), nil
+}