github.com/kaisenlinux/docker.io@v0.0.0-20230510090727-ea55db55fac7/engine/pkg/loopback/ioctl.go (about)

     1  //go:build linux
     2  // +build linux
     3  
     4  package loopback // import "github.com/docker/docker/pkg/loopback"
     5  
     6  import (
     7  	"unsafe"
     8  
     9  	"golang.org/x/sys/unix"
    10  )
    11  
    12  func ioctlLoopCtlGetFree(fd uintptr) (int, error) {
    13  	// The ioctl interface for /dev/loop-control (since Linux 3.1) is a bit
    14  	// off compared to what you'd expect: instead of writing an integer to a
    15  	// parameter pointer like unix.IoctlGetInt() expects, it returns the first
    16  	// available loop device index directly.
    17  	ioctlReturn, _, err := unix.Syscall(unix.SYS_IOCTL, fd, LoopCtlGetFree, 0)
    18  	if err != 0 {
    19  		return 0, err
    20  	}
    21  	return int(ioctlReturn), nil
    22  }
    23  
    24  func ioctlLoopSetFd(loopFd, sparseFd uintptr) error {
    25  	return unix.IoctlSetInt(int(loopFd), unix.LOOP_SET_FD, int(sparseFd))
    26  }
    27  
    28  func ioctlLoopSetStatus64(loopFd uintptr, loopInfo *unix.LoopInfo64) error {
    29  	if _, _, err := unix.Syscall(unix.SYS_IOCTL, loopFd, unix.LOOP_SET_STATUS64, uintptr(unsafe.Pointer(loopInfo))); err != 0 {
    30  		return err
    31  	}
    32  	return nil
    33  }
    34  
    35  func ioctlLoopClrFd(loopFd uintptr) error {
    36  	if _, _, err := unix.Syscall(unix.SYS_IOCTL, loopFd, unix.LOOP_CLR_FD, 0); err != 0 {
    37  		return err
    38  	}
    39  	return nil
    40  }
    41  
    42  func ioctlLoopGetStatus64(loopFd uintptr) (*unix.LoopInfo64, error) {
    43  	loopInfo := &unix.LoopInfo64{}
    44  
    45  	if _, _, err := unix.Syscall(unix.SYS_IOCTL, loopFd, unix.LOOP_GET_STATUS64, uintptr(unsafe.Pointer(loopInfo))); err != 0 {
    46  		return nil, err
    47  	}
    48  	return loopInfo, nil
    49  }
    50  
    51  func ioctlLoopSetCapacity(loopFd uintptr, value int) error {
    52  	return unix.IoctlSetInt(int(loopFd), unix.LOOP_SET_CAPACITY, value)
    53  }