feat: align partition to minimum I/O size

Gather information about minimum/optimal I/O size for the disks and
align partitions to either physical block size or min i/o size,
whichever is bigger.

Signed-off-by: Andrey Smirnov <smirnov.andrey@gmail.com>

blockdevice/lba/lba.go

@@ -53,18 +53,27 @@ func (buf *Buffer) Bytes() []byte {
 type LBA struct {
 	PhysicalBlockSize int64
 	LogicalBlockSize  int64
-	TotalSectors      int64
+	MinimalIOSize     int64
+	OptimalIOSize     int64
+
+	TotalSectors int64
 
 	f *os.File
 }
 
 // AlignToPhysicalBlockSize aligns LBA value in LogicalBlockSize multiples to be aligned to PhysicalBlockSize.
 func (l *LBA) AlignToPhysicalBlockSize(lba uint64) uint64 {
 	physToLogical := uint64(l.PhysicalBlockSize / l.LogicalBlockSize)
+	minIOToLogical := uint64(l.MinimalIOSize / l.LogicalBlockSize)
+
+	ratio := physToLogical
+	if minIOToLogical > ratio {
+		ratio = minIOToLogical
+	}
 
-	if physToLogical <= 1 {
+	if ratio <= 1 {
 		return lba
 	}
 
-	return (lba + physToLogical - 1) / physToLogical * physToLogical
+	return (lba + ratio - 1) / ratio * ratio
 }

blockdevice/lba/lba_linux.go

@@ -13,6 +13,12 @@ import (
 	"golang.org/x/sys/unix"
 )
 
+// These newer ioctl magic values are not available from unix yet.
+const (
+	BLKIOMIN = 0x1278
+	BLKIOOPT = 0x1279
+)
+
 // NewLBA initializes and returns an `LBA`.
 func NewLBA(f *os.File) (lba *LBA, err error) {
 	st, err := f.Stat()
@@ -40,6 +46,34 @@ func NewLBA(f *os.File) (lba *LBA, err error) {
 		}
 	}
 
+	var minio int64
+	if _, _, errno := unix.Syscall(unix.SYS_IOCTL, f.Fd(), BLKIOMIN, uintptr(unsafe.Pointer(&minio))); errno != 0 {
+		if st.Mode().IsRegular() {
+			// Not supported, fail over to psize.
+			minio = psize
+		} else {
+			return nil, errors.New("BLKIOMIN failed")
+		}
+	}
+
+	if minio == 0 {
+		minio = psize
+	}
+
+	var optio int64
+	if _, _, errno := unix.Syscall(unix.SYS_IOCTL, f.Fd(), BLKIOOPT, uintptr(unsafe.Pointer(&optio))); errno != 0 {
+		if st.Mode().IsRegular() {
+			// Not supported, fail over to psize.
+			optio = minio
+		} else {
+			return nil, errors.New("BLKIOOPT failed")
+		}
+	}
+
+	if optio == 0 {
+		optio = minio
+	}
+
 	// Seek to the end to get the size.
 	size, err := f.Seek(0, 2)
 	if err != nil {
@@ -57,6 +91,8 @@ func NewLBA(f *os.File) (lba *LBA, err error) {
 	lba = &LBA{
 		PhysicalBlockSize: psize,
 		LogicalBlockSize:  lsize,
+		MinimalIOSize:     minio,
+		OptimalIOSize:     optio,
 		TotalSectors:      tsize,
 		f:                 f,
 	}

blockdevice/lba/lba_test.go

@@ -26,3 +26,20 @@ func TestAlignToPhysicalBlockSize(t *testing.T) {
 	assert.EqualValues(t, 8, l.AlignToPhysicalBlockSize(8))
 	assert.EqualValues(t, 16, l.AlignToPhysicalBlockSize(9))
 }
+
+func TestAlignToMinIOkSize(t *testing.T) {
+	l := lba.LBA{ //nolint: exhaustivestruct
+		MinimalIOSize:     262144,
+		PhysicalBlockSize: 512,
+		LogicalBlockSize:  512,
+	}
+
+	assert.EqualValues(t, 0, l.AlignToPhysicalBlockSize(0))
+	assert.EqualValues(t, 512, l.AlignToPhysicalBlockSize(1))
+	assert.EqualValues(t, 512, l.AlignToPhysicalBlockSize(2))
+	assert.EqualValues(t, 512, l.AlignToPhysicalBlockSize(3))
+	assert.EqualValues(t, 512, l.AlignToPhysicalBlockSize(4))
+	assert.EqualValues(t, 512, l.AlignToPhysicalBlockSize(8))
+	assert.EqualValues(t, 512, l.AlignToPhysicalBlockSize(512))
+	assert.EqualValues(t, 1024, l.AlignToPhysicalBlockSize(513))
+}