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, 385 insertions, 0 deletions

diff --git a/integrationtests/cmd/ioworkload/scenario_link.go b/integrationtests/cmd/ioworkload/scenario_link.go
new file mode 100644
index 0000000..bb16984
--- /dev/null
+++ b/integrationtests/cmd/ioworkload/scenario_link.go
@@ -0,0 +1,385 @@
+package main
+
+import (
+	"fmt"
+	"path/filepath"
+	"runtime"
+	"syscall"
+	"unsafe"
+)
+
+// linkBasic creates a file, hard links it via link(2), symlinks it via
+// symlink(2), and reads the symlink via readlink(2).
+// Uses raw SYS_LINK, SYS_SYMLINK, SYS_READLINK because Go's syscall wrappers
+// delegate to linkat/symlinkat/readlinkat on amd64.
+func linkBasic() error {
+	dir, cleanup, err := makeTempDir("link-basic")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	origPath := filepath.Join(dir, "original.txt")
+	fd, err := syscall.Open(origPath, syscall.O_RDWR|syscall.O_CREAT, 0o644)
+	if err != nil {
+		return fmt.Errorf("open: %w", err)
+	}
+	if err := syscall.Close(fd); err != nil {
+		return fmt.Errorf("close: %w", err)
+	}
+
+	if err := rawLink(origPath, filepath.Join(dir, "hardlink.txt")); err != nil {
+		return err
+	}
+
+	symPath := filepath.Join(dir, "symlink.txt")
+	if err := rawSymlink(origPath, symPath); err != nil {
+		return err
+	}
+
+	return rawReadlink(symPath)
+}
+
+// linkLinkat creates a file and hard links it via linkat(2).
+func linkLinkat() error {
+	dir, cleanup, err := makeTempDir("link-linkat")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	origName := "linkat-original.txt"
+	origPath := filepath.Join(dir, origName)
+	fd, err := syscall.Open(origPath, syscall.O_RDWR|syscall.O_CREAT, 0o644)
+	if err != nil {
+		return fmt.Errorf("open: %w", err)
+	}
+	if err := syscall.Close(fd); err != nil {
+		return fmt.Errorf("close: %w", err)
+	}
+
+	dirFD, err := syscall.Open(dir, syscall.O_RDONLY|syscall.O_DIRECTORY, 0)
+	if err != nil {
+		return fmt.Errorf("open dir: %w", err)
+	}
+	defer syscall.Close(dirFD)
+
+	hardName := "linkat-hard.txt"
+	oldBytes, err := syscall.BytePtrFromString(origName)
+	if err != nil {
+		return fmt.Errorf("old name bytes: %w", err)
+	}
+	newBytes, err := syscall.BytePtrFromString(hardName)
+	if err != nil {
+		return fmt.Errorf("new name bytes: %w", err)
+	}
+
+	_, _, errno := syscall.Syscall6(
+		syscall.SYS_LINKAT,
+		uintptr(dirFD),
+		uintptr(unsafe.Pointer(oldBytes)),
+		uintptr(dirFD),
+		uintptr(unsafe.Pointer(newBytes)),
+		0, // flags
+		0,
+	)
+	runtime.KeepAlive(oldBytes)
+	runtime.KeepAlive(newBytes)
+	if errno != 0 {
+		return fmt.Errorf("linkat: %w", errno)
+	}
+	return nil
+}
+
+// linkSymlinkat creates a symlink via symlinkat(2).
+func linkSymlinkat() error {
+	dir, cleanup, err := makeTempDir("link-symlinkat")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	origPath := filepath.Join(dir, "symlinkat-original.txt")
+	fd, err := syscall.Open(origPath, syscall.O_RDWR|syscall.O_CREAT, 0o644)
+	if err != nil {
+		return fmt.Errorf("open: %w", err)
+	}
+	if err := syscall.Close(fd); err != nil {
+		return fmt.Errorf("close: %w", err)
+	}
+
+	dirFD, err := syscall.Open(dir, syscall.O_RDONLY|syscall.O_DIRECTORY, 0)
+	if err != nil {
+		return fmt.Errorf("open dir: %w", err)
+	}
+	defer syscall.Close(dirFD)
+
+	targetBytes, err := syscall.BytePtrFromString(origPath)
+	if err != nil {
+		return fmt.Errorf("target bytes: %w", err)
+	}
+	linkName := "symlinkat-link.txt"
+	linkBytes, err := syscall.BytePtrFromString(linkName)
+	if err != nil {
+		return fmt.Errorf("link name bytes: %w", err)
+	}
+
+	_, _, errno := syscall.Syscall(
+		syscall.SYS_SYMLINKAT,
+		uintptr(unsafe.Pointer(targetBytes)),
+		uintptr(dirFD),
+		uintptr(unsafe.Pointer(linkBytes)),
+	)
+	runtime.KeepAlive(targetBytes)
+	runtime.KeepAlive(linkBytes)
+	if errno != 0 {
+		return fmt.Errorf("symlinkat: %w", errno)
+	}
+	return nil
+}
+
+// linkReadlinkat creates a symlink, then reads it via readlinkat(2).
+func linkReadlinkat() error {
+	dir, cleanup, err := makeTempDir("link-readlinkat")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	origPath := filepath.Join(dir, "readlinkat-original.txt")
+	fd, err := syscall.Open(origPath, syscall.O_RDWR|syscall.O_CREAT, 0o644)
+	if err != nil {
+		return fmt.Errorf("open: %w", err)
+	}
+	if err := syscall.Close(fd); err != nil {
+		return fmt.Errorf("close: %w", err)
+	}
+
+	// Create symlink using raw SYS_SYMLINK so we don't mix tracepoints.
+	linkPath := filepath.Join(dir, "readlinkat-link.txt")
+	if err := rawSymlink(origPath, linkPath); err != nil {
+		return err
+	}
+
+	// Read via readlinkat(2).
+	dirFD, err := syscall.Open(dir, syscall.O_RDONLY|syscall.O_DIRECTORY, 0)
+	if err != nil {
+		return fmt.Errorf("open dir: %w", err)
+	}
+	defer syscall.Close(dirFD)
+
+	linkName := "readlinkat-link.txt"
+	nameBytes, err := syscall.BytePtrFromString(linkName)
+	if err != nil {
+		return fmt.Errorf("link name bytes: %w", err)
+	}
+	buf := make([]byte, 256)
+	_, _, errno := syscall.Syscall6(
+		syscall.SYS_READLINKAT,
+		uintptr(dirFD),
+		uintptr(unsafe.Pointer(nameBytes)),
+		uintptr(unsafe.Pointer(&buf[0])),
+		uintptr(len(buf)),
+		0, 0,
+	)
+	runtime.KeepAlive(nameBytes)
+	runtime.KeepAlive(buf)
+	if errno != 0 {
+		return fmt.Errorf("readlinkat: %w", errno)
+	}
+	return nil
+}
+
+// linkEnoent attempts to hard link a nonexistent source via raw SYS_LINK.
+// The syscall fails with ENOENT, but ior captures the enter_link tracepoint
+// because arguments are read on syscall entry.
+func linkEnoent() error {
+	dir, cleanup, err := makeTempDir("link-enoent")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	srcPath := filepath.Join(dir, "link-enoent-missing.txt")
+	dstPath := filepath.Join(dir, "link-enoent-dst.txt")
+
+	srcBytes, err := syscall.BytePtrFromString(srcPath)
+	if err != nil {
+		return fmt.Errorf("src path bytes: %w", err)
+	}
+	dstBytes, err := syscall.BytePtrFromString(dstPath)
+	if err != nil {
+		return fmt.Errorf("dst path bytes: %w", err)
+	}
+
+	_, _, errno := syscall.Syscall(
+		syscall.SYS_LINK,
+		uintptr(unsafe.Pointer(srcBytes)),
+		uintptr(unsafe.Pointer(dstBytes)),
+		0,
+	)
+	runtime.KeepAlive(srcBytes)
+	runtime.KeepAlive(dstBytes)
+	if errno == 0 {
+		return fmt.Errorf("expected ENOENT, but link succeeded")
+	}
+	return nil
+}
+
+// linkSymlinkEexist creates a regular file, then attempts to create a symlink
+// at the same path via raw SYS_SYMLINK. The syscall fails with EEXIST because
+// the link path already exists, but ior captures the enter_symlink tracepoint.
+func linkSymlinkEexist() error {
+	dir, cleanup, err := makeTempDir("link-symlink-eexist")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	existingPath := filepath.Join(dir, "symlink-eexist.txt")
+	fd, err := syscall.Open(existingPath, syscall.O_RDWR|syscall.O_CREAT, 0o644)
+	if err != nil {
+		return fmt.Errorf("open: %w", err)
+	}
+	if err := syscall.Close(fd); err != nil {
+		return fmt.Errorf("close: %w", err)
+	}
+
+	targetBytes, err := syscall.BytePtrFromString("/tmp/dummy-target")
+	if err != nil {
+		return fmt.Errorf("target bytes: %w", err)
+	}
+	linkBytes, err := syscall.BytePtrFromString(existingPath)
+	if err != nil {
+		return fmt.Errorf("link path bytes: %w", err)
+	}
+
+	_, _, errno := syscall.Syscall(
+		syscall.SYS_SYMLINK,
+		uintptr(unsafe.Pointer(targetBytes)),
+		uintptr(unsafe.Pointer(linkBytes)),
+		0,
+	)
+	runtime.KeepAlive(targetBytes)
+	runtime.KeepAlive(linkBytes)
+	if errno == 0 {
+		return fmt.Errorf("expected EEXIST, but symlink succeeded")
+	}
+	return nil
+}
+
+// linkReadlinkatEinval creates a regular file and calls readlinkat(2) on it.
+// The syscall fails with EINVAL because the path is not a symlink, but ior
+// captures the enter_readlinkat tracepoint on syscall entry.
+func linkReadlinkatEinval() error {
+	dir, cleanup, err := makeTempDir("link-readlinkat-einval")
+	if err != nil {
+		return err
+	}
+	defer cleanup()
+
+	regularFile := "readlinkat-einval.txt"
+	regularPath := filepath.Join(dir, regularFile)
+	fd, err := syscall.Open(regularPath, syscall.O_RDWR|syscall.O_CREAT, 0o644)
+	if err != nil {
+		return fmt.Errorf("open: %w", err)
+	}
+	if err := syscall.Close(fd); err != nil {
+		return fmt.Errorf("close: %w", err)
+	}
+
+	dirFD, err := syscall.Open(dir, syscall.O_RDONLY|syscall.O_DIRECTORY, 0)
+	if err != nil {
+		return fmt.Errorf("open dir: %w", err)
+	}
+	defer syscall.Close(dirFD)
+
+	nameBytes, err := syscall.BytePtrFromString(regularFile)
+	if err != nil {
+		return fmt.Errorf("name bytes: %w", err)
+	}
+	buf := make([]byte, 256)
+	_, _, errno := syscall.Syscall6(
+		syscall.SYS_READLINKAT,
+		uintptr(dirFD),
+		uintptr(unsafe.Pointer(nameBytes)),
+		uintptr(unsafe.Pointer(&buf[0])),
+		uintptr(len(buf)),
+		0, 0,
+	)
+	runtime.KeepAlive(nameBytes)
+	runtime.KeepAlive(buf)
+	if errno == 0 {
+		return fmt.Errorf("expected EINVAL, but readlinkat succeeded")
+	}
+	return nil
+}
+
+// rawLink calls link(2) via raw SYS_LINK.
+func rawLink(oldPath, newPath string) error {
+	oldBytes, err := syscall.BytePtrFromString(oldPath)
+	if err != nil {
+		return fmt.Errorf("old path bytes: %w", err)
+	}
+	newBytes, err := syscall.BytePtrFromString(newPath)
+	if err != nil {
+		return fmt.Errorf("new path bytes: %w", err)
+	}
+	_, _, errno := syscall.Syscall(
+		syscall.SYS_LINK,
+		uintptr(unsafe.Pointer(oldBytes)),
+		uintptr(unsafe.Pointer(newBytes)),
+		0,
+	)
+	runtime.KeepAlive(oldBytes)
+	runtime.KeepAlive(newBytes)
+	if errno != 0 {
+		return fmt.Errorf("link: %w", errno)
+	}
+	return nil
+}
+
+// rawSymlink calls symlink(2) via raw SYS_SYMLINK.
+func rawSymlink(target, linkPath string) error {
+	targetBytes, err := syscall.BytePtrFromString(target)
+	if err != nil {
+		return fmt.Errorf("target path bytes: %w", err)
+	}
+	linkBytes, err := syscall.BytePtrFromString(linkPath)
+	if err != nil {
+		return fmt.Errorf("link path bytes: %w", err)
+	}
+	_, _, errno := syscall.Syscall(
+		syscall.SYS_SYMLINK,
+		uintptr(unsafe.Pointer(targetBytes)),
+		uintptr(unsafe.Pointer(linkBytes)),
+		0,
+	)
+	runtime.KeepAlive(targetBytes)
+	runtime.KeepAlive(linkBytes)
+	if errno != 0 {
+		return fmt.Errorf("symlink: %w", errno)
+	}
+	return nil
+}
+
+// rawReadlink calls readlink(2) via raw SYS_READLINK.
+func rawReadlink(path string) error {
+	pathBytes, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return fmt.Errorf("path bytes: %w", err)
+	}
+	buf := make([]byte, 256)
+	_, _, errno := syscall.Syscall(
+		syscall.SYS_READLINK,
+		uintptr(unsafe.Pointer(pathBytes)),
+		uintptr(unsafe.Pointer(&buf[0])),
+		uintptr(len(buf)),
+	)
+	runtime.KeepAlive(pathBytes)
+	runtime.KeepAlive(buf)
+	if errno != 0 {
+		return fmt.Errorf("readlink: %w", errno)
+	}
+	return nil
+}