feat(mmap-go): make fallocate work on both linux and darwin

src/mmap-go-prototype/mac_falloc.go → src/mmap-go-prototype/fallocate_darwin.go

@@ -1,3 +1,6 @@
+//go:build darwin
+// +build darwin
+
 package main
 
 import (
@@ -7,22 +10,22 @@ import (
 )
 
 // based on https://github.com/coilhq/tigerbeetle/blob/7e12fccc4859f035cd26af29b8e9f9749a0899a3/src/storage.zig#L430
-func MacFallocate(file *os.File, offset int64, length int64) error {
+func fallocate(fd int, _mode uint32, offset int64, length int64) error {
 	store := syscall.Fstore_t{
 		Flags:      syscall.F_ALLOCATECONTIG | syscall.F_ALLOCATEALL,
 		Posmode:    syscall.F_PEOFPOSMODE,
 		Offset:     0,
 		Length:     offset + length,
 		Bytesalloc: 0,
 	}
-	_, _, err := syscall.Syscall(syscall.SYS_FCNTL, file.Fd(), syscall.F_PREALLOCATE, uintptr(unsafe.Pointer(&store)))
+	_, _, err := syscall.Syscall(syscall.SYS_FCNTL, fd, syscall.F_PREALLOCATE, uintptr(unsafe.Pointer(&store)))
 	if err != 0 {
 		store.Flags = syscall.F_ALLOCATEALL
-		_, _, err = syscall.Syscall(syscall.SYS_FCNTL, file.Fd(), syscall.F_PREALLOCATE, uintptr(unsafe.Pointer(&store)))
+		_, _, err = syscall.Syscall(syscall.SYS_FCNTL, fd, syscall.F_PREALLOCATE, uintptr(unsafe.Pointer(&store)))
 		if err != 0 {
 			return err
 		}
 	}
 
-	return syscall.Ftruncate(int(file.Fd()), store.Length)
+	return syscall.Ftruncate(fd, store.Length)
 }

src/mmap-go-prototype/fallocate_linux.go

@@ -0,0 +1,12 @@
+//go:build linux
+// +build linux
+
+package main
+
+import (
+	"syscall"
+)
+
+func fallocate(fd int, mode uint32, offset int64, length int64) error {
+	return syscall.Fallocate(fd, mode, offset, length)
+}

src/mmap-go-prototype/go.mod

@@ -0,0 +1,3 @@
+module github.com/symbiont-io/detsys-testkit/src/mmap-go-prototype
+
+go 1.16

src/mmap-go-prototype/mmap.go → src/mmap-go-prototype/main.go

@@ -25,10 +25,9 @@ func NewMmap(f string) *Mmap {
 
 	// XXX: Passing `FALLOC_FL_ZERO_RANGE` as mode would zero the file, but
 	// I couldn't find this constant in `syscall`...
-	// mode := uint32(0) // syscall.F_PREALLOCATE
+	mode := uint32(0) // syscall.F_PREALLOCATE
 
-	//if err := syscall.Fallocate(int(file.Fd()), mode, 0, int64(pageSize)); err != nil {
-	if err := MacFallocate(file, 0, int64(pageSize)); err != nil {
+	if err := fallocate(int(file.Fd()), mode, 0, int64(pageSize)); err != nil {
 		panic(err)
 	}