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//go:build linux
package dmflakey
import (
"fmt"
"os"
"os/exec"
"time"
"unsafe"
"golang.org/x/sys/unix"
)
// newFlakeyDevice creates flakey device.
//
// REF: https://docs.kernel.org/admin-guide/device-mapper/dm-flakey.html
func newFlakeyDevice(flakeyDevice, loopDevice string, interval time.Duration) error {
loopSize, err := getBlkSize(loopDevice)
if err != nil {
return fmt.Errorf("failed to get the size of the loop device %s: %w", loopDevice, err)
}
// The flakey device will be available in interval.Seconds().
table := fmt.Sprintf("0 %d flakey %s 0 %d 0",
loopSize, loopDevice, int(interval.Seconds()))
args := []string{"create", flakeyDevice, "--table", table}
output, err := exec.Command("dmsetup", args...).CombinedOutput()
if err != nil {
return fmt.Errorf("failed to create flakey device %s with table %s (out: %s): %w",
flakeyDevice, table, string(output), err)
}
return nil
}
// reloadFlakeyDevice reloads the flakey device with feature table.
func reloadFlakeyDevice(flakeyDevice string, syncFS bool, table string) (retErr error) {
args := []string{"suspend", "--nolockfs", flakeyDevice}
if syncFS {
args[1] = flakeyDevice
args = args[:len(args)-1]
}
output, err := exec.Command("dmsetup", args...).CombinedOutput()
if err != nil {
return fmt.Errorf("failed to suspend flakey device %s (out: %s): %w",
flakeyDevice, string(output), err)
}
defer func() {
output, derr := exec.Command("dmsetup", "resume", flakeyDevice).CombinedOutput()
if derr != nil {
derr = fmt.Errorf("failed to resume flakey device %s (out: %s): %w",
flakeyDevice, string(output), derr)
}
if retErr == nil {
retErr = derr
}
}()
output, err = exec.Command("dmsetup", "load", flakeyDevice, "--table", table).CombinedOutput()
if err != nil {
return fmt.Errorf("failed to reload flakey device %s with table (%s) (out: %s): %w",
flakeyDevice, table, string(output), err)
}
return nil
}
// removeFlakeyDevice removes flakey device.
func deleteFlakeyDevice(flakeyDevice string) error {
output, err := exec.Command("dmsetup", "remove", flakeyDevice).CombinedOutput()
if err != nil {
return fmt.Errorf("failed to remove flakey device %s (out: %s): %w",
flakeyDevice, string(output), err)
}
return nil
}
// getBlkSize64 gets device size in bytes (BLKGETSIZE64).
//
// REF: https://man7.org/linux/man-pages/man8/blockdev.8.html
func getBlkSize64(device string) (int64, error) {
deviceFd, err := os.Open(device)
if err != nil {
return 0, fmt.Errorf("failed to open device %s: %w", device, err)
}
defer deviceFd.Close()
var size int64
if _, _, err := unix.Syscall(unix.SYS_IOCTL, deviceFd.Fd(), unix.BLKGETSIZE64, uintptr(unsafe.Pointer(&size))); err != 0 {
return 0, fmt.Errorf("failed to get block size: %w", err)
}
return size, nil
}
// getBlkSize gets size in 512-byte sectors (BLKGETSIZE64 / 512).
//
// REF: https://man7.org/linux/man-pages/man8/blockdev.8.html
func getBlkSize(device string) (int64, error) {
size, err := getBlkSize64(device)
return size / 512, err
}
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