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@@ -69,7 +69,10 @@ func getFreeLoopDev() (uint32, error) {
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return uint32(num), nil
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return uint32(num), nil
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}
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}
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-func setupLoopDev(backingFile, loopDev string, param LoopParams) error {
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+// setupLoopDev attaches the backing file to the loop device and returns
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+// the file handle for the loop device. The caller is responsible for
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+// closing the file handle.
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+func setupLoopDev(backingFile, loopDev string, param LoopParams) (_ *os.File, retErr error) {
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// 1. Open backing file and loop device
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// 1. Open backing file and loop device
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flags := os.O_RDWR
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flags := os.O_RDWR
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if param.Readonly {
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if param.Readonly {
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@@ -78,19 +81,23 @@ func setupLoopDev(backingFile, loopDev string, param LoopParams) error {
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back, err := os.OpenFile(backingFile, flags, 0)
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back, err := os.OpenFile(backingFile, flags, 0)
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if err != nil {
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if err != nil {
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- return errors.Wrapf(err, "could not open backing file: %s", backingFile)
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+ return nil, errors.Wrapf(err, "could not open backing file: %s", backingFile)
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}
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}
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defer back.Close()
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defer back.Close()
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loop, err := os.OpenFile(loopDev, flags, 0)
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loop, err := os.OpenFile(loopDev, flags, 0)
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if err != nil {
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if err != nil {
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- return errors.Wrapf(err, "could not open loop device: %s", loopDev)
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+ return nil, errors.Wrapf(err, "could not open loop device: %s", loopDev)
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}
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}
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- defer loop.Close()
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+ defer func() {
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+ if retErr != nil {
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+ loop.Close()
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+ }
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+ }()
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// 2. Set FD
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// 2. Set FD
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if _, _, err = ioctl(loop.Fd(), unix.LOOP_SET_FD, back.Fd()); err != nil {
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if _, _, err = ioctl(loop.Fd(), unix.LOOP_SET_FD, back.Fd()); err != nil {
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- return errors.Wrapf(err, "could not set loop fd for device: %s", loopDev)
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+ return nil, errors.Wrapf(err, "could not set loop fd for device: %s", loopDev)
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}
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}
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// 3. Set Info
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// 3. Set Info
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@@ -110,7 +117,7 @@ func setupLoopDev(backingFile, loopDev string, param LoopParams) error {
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_, _, err = ioctl(loop.Fd(), unix.LOOP_SET_STATUS64, uintptr(unsafe.Pointer(&info)))
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_, _, err = ioctl(loop.Fd(), unix.LOOP_SET_STATUS64, uintptr(unsafe.Pointer(&info)))
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if err == nil {
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if err == nil {
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- return nil
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+ return loop, nil
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}
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}
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if param.Direct {
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if param.Direct {
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@@ -119,13 +126,12 @@ func setupLoopDev(backingFile, loopDev string, param LoopParams) error {
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info.Flags &= ^(uint32(unix.LO_FLAGS_DIRECT_IO))
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info.Flags &= ^(uint32(unix.LO_FLAGS_DIRECT_IO))
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_, _, err = ioctl(loop.Fd(), unix.LOOP_SET_STATUS64, uintptr(unsafe.Pointer(&info)))
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_, _, err = ioctl(loop.Fd(), unix.LOOP_SET_STATUS64, uintptr(unsafe.Pointer(&info)))
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if err == nil {
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if err == nil {
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- return nil
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+ return loop, nil
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}
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}
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}
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}
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- // Cleanup loop fd and return error
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_, _, _ = ioctl(loop.Fd(), unix.LOOP_CLR_FD, 0)
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_, _, _ = ioctl(loop.Fd(), unix.LOOP_CLR_FD, 0)
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- return errors.Errorf("failed to set loop device info: %v", err)
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+ return nil, errors.Errorf("failed to set loop device info: %v", err)
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}
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}
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// setupLoop looks for (and possibly creates) a free loop device, and
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// setupLoop looks for (and possibly creates) a free loop device, and
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@@ -142,15 +148,16 @@ func setupLoopDev(backingFile, loopDev string, param LoopParams) error {
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// the loop device when done with it.
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// the loop device when done with it.
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//
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//
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// Upon success, the file handle to the loop device is returned.
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// Upon success, the file handle to the loop device is returned.
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-func setupLoop(backingFile string, param LoopParams) (string, error) {
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+func setupLoop(backingFile string, param LoopParams) (*os.File, error) {
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for retry := 1; retry < 100; retry++ {
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for retry := 1; retry < 100; retry++ {
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num, err := getFreeLoopDev()
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num, err := getFreeLoopDev()
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if err != nil {
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if err != nil {
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- return "", err
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+ return nil, err
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}
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}
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loopDev := fmt.Sprintf(loopDevFormat, num)
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loopDev := fmt.Sprintf(loopDevFormat, num)
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- if err := setupLoopDev(backingFile, loopDev, param); err != nil {
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+ file, err := setupLoopDev(backingFile, loopDev, param)
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+ if err != nil {
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// Per util-linux/sys-utils/losetup.c:create_loop(),
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// Per util-linux/sys-utils/losetup.c:create_loop(),
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// free loop device can race and we end up failing
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// free loop device can race and we end up failing
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// with EBUSY when trying to set it up.
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// with EBUSY when trying to set it up.
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@@ -159,13 +166,13 @@ func setupLoop(backingFile string, param LoopParams) (string, error) {
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time.Sleep(time.Millisecond * time.Duration(rand.Intn(retry*10)))
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time.Sleep(time.Millisecond * time.Duration(rand.Intn(retry*10)))
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continue
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continue
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}
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}
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- return "", err
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+ return nil, err
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}
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}
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- return loopDev, nil
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+ return file, nil
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}
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}
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- return "", errors.New("timeout creating new loopback device")
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+ return nil, errors.New("timeout creating new loopback device")
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}
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}
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func removeLoop(loopdev string) error {
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func removeLoop(loopdev string) error {
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@@ -179,12 +186,17 @@ func removeLoop(loopdev string) error {
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return err
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return err
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}
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}
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-// Attach a specified backing file to a loop device
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+// AttachLoopDevice attaches a specified backing file to a loop device
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func AttachLoopDevice(backingFile string) (string, error) {
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func AttachLoopDevice(backingFile string) (string, error) {
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- return setupLoop(backingFile, LoopParams{})
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+ file, err := setupLoop(backingFile, LoopParams{})
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+ if err != nil {
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+ return "", err
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+ }
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+ defer file.Close()
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+ return file.Name(), nil
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}
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}
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-// Detach a loop device
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+// DetachLoopDevice detaches the provided loop devices
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func DetachLoopDevice(devices ...string) error {
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func DetachLoopDevice(devices ...string) error {
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for _, dev := range devices {
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for _, dev := range devices {
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if err := removeLoop(dev); err != nil {
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if err := removeLoop(dev); err != nil {
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