1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
|
// +build linux,amd64
package devmapper
import (
"fmt"
"github.com/dotcloud/docker/utils"
)
func stringToLoopName(src string) [LoNameSize]uint8 {
var dst [LoNameSize]uint8
copy(dst[:], src[:])
return dst
}
func getNextFreeLoopbackIndex() (int, error) {
f, err := osOpenFile("/dev/loop-control", osORdOnly, 0644)
if err != nil {
return 0, err
}
defer f.Close()
index, err := ioctlLoopCtlGetFree(f.Fd())
if index < 0 {
index = 0
}
return index, err
}
func openNextAvailableLoopback(index int, sparseFile *osFile) (loopFile *osFile, err error) {
// Start looking for a free /dev/loop
for {
target := fmt.Sprintf("/dev/loop%d", index)
index++
fi, err := osStat(target)
if err != nil {
if osIsNotExist(err) {
utils.Errorf("There are no more loopback device available.")
}
return nil, ErrAttachLoopbackDevice
}
if fi.Mode()&osModeDevice != osModeDevice {
utils.Errorf("Loopback device %s is not a block device.", target)
continue
}
// OpenFile adds O_CLOEXEC
loopFile, err = osOpenFile(target, osORdWr, 0644)
if err != nil {
utils.Errorf("Error openning loopback device: %s", err)
return nil, ErrAttachLoopbackDevice
}
// Try to attach to the loop file
if err := ioctlLoopSetFd(loopFile.Fd(), sparseFile.Fd()); err != nil {
loopFile.Close()
// If the error is EBUSY, then try the next loopback
if err != sysEBusy {
utils.Errorf("Cannot set up loopback device %s: %s", target, err)
return nil, ErrAttachLoopbackDevice
}
// Otherwise, we keep going with the loop
continue
}
// In case of success, we finished. Break the loop.
break
}
// This can't happen, but let's be sure
if loopFile == nil {
utils.Errorf("Unreachable code reached! Error attaching %s to a loopback device.", sparseFile.Name())
return nil, ErrAttachLoopbackDevice
}
return loopFile, nil
}
// attachLoopDevice attaches the given sparse file to the next
// available loopback device. It returns an opened *osFile.
func attachLoopDevice(sparseName string) (loop *osFile, err error) {
// Try to retrieve the next available loopback device via syscall.
// If it fails, we discard error and start loopking for a
// loopback from index 0.
startIndex, err := getNextFreeLoopbackIndex()
if err != nil {
utils.Debugf("Error retrieving the next available loopback: %s", err)
}
// OpenFile adds O_CLOEXEC
sparseFile, err := osOpenFile(sparseName, osORdWr, 0644)
if err != nil {
utils.Errorf("Error openning sparse file %s: %s", sparseName, err)
return nil, ErrAttachLoopbackDevice
}
defer sparseFile.Close()
loopFile, err := openNextAvailableLoopback(startIndex, sparseFile)
if err != nil {
return nil, err
}
// Set the status of the loopback device
loopInfo := &LoopInfo64{
loFileName: stringToLoopName(loopFile.Name()),
loOffset: 0,
loFlags: LoFlagsAutoClear,
}
if err := ioctlLoopSetStatus64(loopFile.Fd(), loopInfo); err != nil {
utils.Errorf("Cannot set up loopback device info: %s", err)
// If the call failed, then free the loopback device
if err := ioctlLoopClrFd(loopFile.Fd()); err != nil {
utils.Errorf("Error while cleaning up the loopback device")
}
loopFile.Close()
return nil, ErrAttachLoopbackDevice
}
return loopFile, nil
}
|
