github.com/reds/docker@v1.11.2-rc1/pkg/loopback/loopback.go (about)

     1  // +build linux
     2  
     3  package loopback
     4  
     5  import (
     6  	"fmt"
     7  	"os"
     8  	"syscall"
     9  
    10  	"github.com/Sirupsen/logrus"
    11  )
    12  
    13  func getLoopbackBackingFile(file *os.File) (uint64, uint64, error) {
    14  	loopInfo, err := ioctlLoopGetStatus64(file.Fd())
    15  	if err != nil {
    16  		logrus.Errorf("Error get loopback backing file: %s", err)
    17  		return 0, 0, ErrGetLoopbackBackingFile
    18  	}
    19  	return loopInfo.loDevice, loopInfo.loInode, nil
    20  }
    21  
    22  // SetCapacity reloads the size for the loopback device.
    23  func SetCapacity(file *os.File) error {
    24  	if err := ioctlLoopSetCapacity(file.Fd(), 0); err != nil {
    25  		logrus.Errorf("Error loopbackSetCapacity: %s", err)
    26  		return ErrSetCapacity
    27  	}
    28  	return nil
    29  }
    30  
    31  // FindLoopDeviceFor returns a loopback device file for the specified file which
    32  // is backing file of a loop back device.
    33  func FindLoopDeviceFor(file *os.File) *os.File {
    34  	stat, err := file.Stat()
    35  	if err != nil {
    36  		return nil
    37  	}
    38  	targetInode := stat.Sys().(*syscall.Stat_t).Ino
    39  	targetDevice := stat.Sys().(*syscall.Stat_t).Dev
    40  
    41  	for i := 0; true; i++ {
    42  		path := fmt.Sprintf("/dev/loop%d", i)
    43  
    44  		file, err := os.OpenFile(path, os.O_RDWR, 0)
    45  		if err != nil {
    46  			if os.IsNotExist(err) {
    47  				return nil
    48  			}
    49  
    50  			// Ignore all errors until the first not-exist
    51  			// we want to continue looking for the file
    52  			continue
    53  		}
    54  
    55  		dev, inode, err := getLoopbackBackingFile(file)
    56  		if err == nil && dev == targetDevice && inode == targetInode {
    57  			return file
    58  		}
    59  		file.Close()
    60  	}
    61  
    62  	return nil
    63  }