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, 89 insertions, 0 deletions

diff --git a/integrationtests/cmd/ioworkload/scenario_truncate.go b/integrationtests/cmd/ioworkload/scenario_truncate.go
new file mode 100644
index 0000000..28be152
--- /dev/null
+++ b/integrationtests/cmd/ioworkload/scenario_truncate.go
@@ -0,0 +1,89 @@
+package main
+
+import (
+	"fmt"
+	"path/filepath"
+	"runtime"
+	"syscall"
+	"unsafe"
+)
+
+// truncateBasic opens a file, writes data, then truncates it via
+// syscall.Truncate which uses SYS_TRUNCATE directly on amd64 (path-based).
+func truncateBasic() error {
+	dir, cleanup, err := makeTempDir("truncate-basic")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	path := filepath.Join(dir, "truncfile.txt")
+	fd, err := syscall.Open(path, syscall.O_RDWR|syscall.O_CREAT, 0o644)
+	if err != nil {
+		return fmt.Errorf("open: %w", err)
+	}
+
+	if _, err := syscall.Write(fd, []byte("truncate this content")); err != nil {
+		syscall.Close(fd)
+		return fmt.Errorf("write: %w", err)
+	}
+	syscall.Close(fd)
+
+	return syscall.Truncate(path, 5)
+}
+
+// truncateFtruncate opens a file, writes data, then truncates it via
+// syscall.Ftruncate which uses SYS_FTRUNCATE directly on amd64 (fd-based).
+func truncateFtruncate() error {
+	dir, cleanup, err := makeTempDir("truncate-ftruncate")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	path := filepath.Join(dir, "ftruncfile.txt")
+	fd, err := syscall.Open(path, syscall.O_RDWR|syscall.O_CREAT, 0o644)
+	if err != nil {
+		return fmt.Errorf("open: %w", err)
+	}
+	defer syscall.Close(fd)
+
+	if _, err := syscall.Write(fd, []byte("ftruncate this content")); err != nil {
+		return fmt.Errorf("write: %w", err)
+	}
+	return syscall.Ftruncate(fd, 5)
+}
+
+// truncateEnoent attempts to truncate a nonexistent file via raw SYS_TRUNCATE.
+// The syscall fails with ENOENT, but ior captures the enter_truncate
+// tracepoint because the path is read on entry.
+func truncateEnoent() error {
+	dir, cleanup, err := makeTempDir("truncate-enoent")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	path := filepath.Join(dir, "truncate-enoent-missing.txt")
+	pathBytes, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return fmt.Errorf("path bytes: %w", err)
+	}
+	_, _, errno := syscall.Syscall(syscall.SYS_TRUNCATE, uintptr(unsafe.Pointer(pathBytes)), 0, 0)
+	runtime.KeepAlive(pathBytes)
+	if errno == 0 {
+		return fmt.Errorf("expected ENOENT, but truncate succeeded")
+	}
+	return nil
+}
+
+// truncateFtruncateEbadf calls raw SYS_FTRUNCATE on an invalid fd (99999).
+// The syscall fails with EBADF, but ior captures the enter_ftruncate
+// tracepoint because it is recorded on syscall entry.
+func truncateFtruncateEbadf() error {
+	_, _, errno := syscall.Syscall(syscall.SYS_FTRUNCATE, 99999, 0, 0)
+	if errno == 0 {
+		return fmt.Errorf("expected EBADF, but ftruncate succeeded")
+	}
+	return nil
+}