github.com/demonoid81/moby@v0.0.0-20200517203328-62dd8e17c460/pkg/loopback/ioctl.go (about) 1 // +build linux 2 3 package loopback // import "github.com/demonoid81/moby/pkg/loopback" 4 5 import ( 6 "unsafe" 7 8 "golang.org/x/sys/unix" 9 ) 10 11 func ioctlLoopCtlGetFree(fd uintptr) (int, error) { 12 // The ioctl interface for /dev/loop-control (since Linux 3.1) is a bit 13 // off compared to what you'd expect: instead of writing an integer to a 14 // parameter pointer like unix.IoctlGetInt() expects, it returns the first 15 // available loop device index directly. 16 ioctlReturn, _, err := unix.Syscall(unix.SYS_IOCTL, fd, LoopCtlGetFree, 0) 17 if err != 0 { 18 return 0, err 19 } 20 return int(ioctlReturn), nil 21 } 22 23 func ioctlLoopSetFd(loopFd, sparseFd uintptr) error { 24 return unix.IoctlSetInt(int(loopFd), unix.LOOP_SET_FD, int(sparseFd)) 25 } 26 27 func ioctlLoopSetStatus64(loopFd uintptr, loopInfo *unix.LoopInfo64) error { 28 if _, _, err := unix.Syscall(unix.SYS_IOCTL, loopFd, unix.LOOP_SET_STATUS64, uintptr(unsafe.Pointer(loopInfo))); err != 0 { 29 return err 30 } 31 return nil 32 } 33 34 func ioctlLoopClrFd(loopFd uintptr) error { 35 if _, _, err := unix.Syscall(unix.SYS_IOCTL, loopFd, unix.LOOP_CLR_FD, 0); err != 0 { 36 return err 37 } 38 return nil 39 } 40 41 func ioctlLoopGetStatus64(loopFd uintptr) (*unix.LoopInfo64, error) { 42 loopInfo := &unix.LoopInfo64{} 43 44 if _, _, err := unix.Syscall(unix.SYS_IOCTL, loopFd, unix.LOOP_GET_STATUS64, uintptr(unsafe.Pointer(loopInfo))); err != 0 { 45 return nil, err 46 } 47 return loopInfo, nil 48 } 49 50 func ioctlLoopSetCapacity(loopFd uintptr, value int) error { 51 return unix.IoctlSetInt(int(loopFd), unix.LOOP_SET_CAPACITY, value) 52 }