init: wait untill btrfs multidevice gets assembled

And only after that proceed with mounting

Fixes #194

init/ioctl.go

@@ -0,0 +1,57 @@
+package main
+
+import (
+	"fmt"
+
+	"golang.org/x/sys/unix"
+)
+
+const (
+	directionNone  = 0
+	directionWrite = 1
+	directionRead  = 2
+
+	numberBits    = 8
+	typeBits      = 8
+	sizeBits      = 14
+	directionBits = 2
+
+	numberMask    = (1 << numberBits) - 1
+	typeMask      = (1 << typeBits) - 1
+	sizeMask      = (1 << sizeBits) - 1
+	directionMask = (1 << directionBits) - 1
+
+	numberShift    = 0
+	typeShift      = numberShift + numberBits
+	sizeShift      = typeShift + typeBits
+	directionShift = sizeShift + sizeBits
+)
+
+// ioc calculates the ioctl command for the specified direction, type, number and size
+func ioc(dir, t, nr, size uintptr) uintptr {
+	return (dir << directionShift) | (t << typeShift) | (nr << numberShift) | (size << sizeShift)
+}
+
+// ior calculates the ioctl command for a read-ioctl of the specified type, number and size
+func ior(t, nr, size uintptr) uintptr {
+	return ioc(directionRead, t, nr, size)
+}
+
+// iow calculates the ioctl command for a write-ioctl of the specified type, number and size
+func iow(t, nr, size uintptr) uintptr {
+	return ioc(directionWrite, t, nr, size)
+}
+
+// iowr calculates the ioctl command for a read/write-ioctl of the specified type, number and size
+func iowr(t, nr, size uintptr) uintptr {
+	return ioc(directionWrite|directionRead, t, nr, size)
+}
+
+// ioctl executes an ioctl command on the specified file descriptor
+func ioctl(fd, cmd, ptr uintptr) error {
+	_, _, errno := unix.Syscall(unix.SYS_IOCTL, fd, cmd, ptr)
+	if errno != 0 {
+		return fmt.Errorf("ioctl(0x%x): %v", cmd, errno)
+	}
+	return nil
+}

init/main.go

@@ -14,6 +14,7 @@ import (
 	"sync"
 	"sync/atomic"
 	"time"
+	"unsafe"
 
 	"github.com/yookoala/realpath"
 	"golang.org/x/sys/unix"
@@ -372,6 +373,12 @@ func mountRootFs(dev, fstype string) error {
 	wg := loadModules(fstype)
 	wg.Wait()
 
+	if fstype == "btrfs" {
+		if err := waitForBtrfsDevicesReady(dev); err != nil {
+			return err
+		}
+	}
+
 	if err := fsck(dev); err != nil {
 		return err
 	}
@@ -386,6 +393,29 @@ func mountRootFs(dev, fstype string) error {
 	return nil
 }
 
+// Wait until all devices of a multiple-device filesystem are scanned and registered within the kernel module
+func waitForBtrfsDevicesReady(dev string) error {
+	controlFile, err := os.OpenFile("/dev/btrfs-control", os.O_RDWR, 0)
+	if err != nil {
+		return err
+	}
+	defer controlFile.Close()
+
+	/* this should be 4k */
+	var btrfsIoctlVolArgs struct {
+		fs   int64
+		name [4088]uint8
+	}
+
+	warning("!!!!!!! BTRFS_IOC_DEVICES_READY for %s", dev)
+
+	copy(btrfsIoctlVolArgs.name[:], dev)
+
+	var BTRFS_IOCTL_MAGIC uintptr = 0x94
+	BTRFS_IOC_DEVICES_READY := ior(BTRFS_IOCTL_MAGIC, 39, unsafe.Sizeof(btrfsIoctlVolArgs))
+	return ioctl(controlFile.Fd(), BTRFS_IOC_DEVICES_READY, uintptr(unsafe.Pointer(&btrfsIoctlVolArgs)))
+}
+
 func mountFlags() (uintptr, string) {
 	rootMountFlags, options := sunderMountFlags(rootFlags, rootAutodiscoveryMountFlags)
 	if rootRo {

tests/assets.go

@@ -29,6 +29,7 @@ var assetGenerators = map[string]assetGenerator{
 	"lvm.img":                   {"lvm.sh", []string{"FS_UUID=74c9e30c-506f-4106-9f61-a608466ef29c", "FS_LABEL=lvmr00t"}},
 	"mdraid_raid1.img":          {"mdraid_raid1.sh", []string{"FS_UUID=98b1a905-3c72-42f0-957a-6c23b303b1fd", "FS_LABEL=boosmdraid"}},
 	"mdraid_raid5.img":          {"mdraid_raid5.sh", []string{"FS_UUID=e62c7dc0-5728-4571-b475-7745de2eef1e", "FS_LABEL=boosmdraid"}},
+	"btrfs_raid0.img":           {"btrfs_raid0.sh", []string{"FS_UUID=5eaa0c1c-e1dc-4be7-9b03-9f1ed5a87289"}},
 	"archlinux.ext4.raw":        {"archlinux_ext4.sh", nil},
 	"archlinux.btrfs.raw":       {"archlinux_btrfs.sh", []string{"LUKS_PASSWORD=hello"}},
 	"voidlinux.img":             {"voidlinux.sh", nil},

tests/btrfs_test.go

@@ -0,0 +1,18 @@
+package tests
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestBtrfsRaid0(t *testing.T) {
+	vm, err := buildVmInstance(t, Opts{
+		disk:       "assets/btrfs_raid0.img",
+		kernelArgs: []string{"root=UUID=5eaa0c1c-e1dc-4be7-9b03-9f1ed5a87289"},
+	})
+	require.NoError(t, err)
+	defer vm.Shutdown()
+
+	require.NoError(t, vm.ConsoleExpect("Hello, booster!"))
+}

tests/generators/btrfs_raid0.sh

@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+
+trap 'quit' EXIT ERR
+
+quit() {
+  set +o errexit
+  sudo umount "${dir}"
+  rm -r "${dir}"
+}
+
+truncate --size 650M "${OUTPUT}"
+lodev=$(sudo losetup -f -P --show "${OUTPUT}")
+# create 2 partitions equal size
+sudo fdisk "${lodev}" <<< "g
+n
+
+
++300M
+t
+
+29
+n
+
+
++300M
+t
+
+29
+w
+"
+
+sudo mkfs.btrfs --uuid=$FS_UUID -d raid0 "${lodev}p1" "${lodev}p2"
+dir=$(mktemp -d)
+sudo mount "${lodev}p1" "${dir}"
+sudo chown "${USER}" "${dir}"
+mkdir "${dir}/sbin"
+cp assets/init "${dir}/sbin/init"