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Switch from symlinks to block devices for raw block devices #469

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0c8c3de
Switch from symlinks to block devices for raw block devices
datamattsson Oct 24, 2025
0acbac0
Switch from symlink to block devices for raw block devices
datamattsson Oct 31, 2025
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2 changes: 1 addition & 1 deletion go.mod
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@ require (
github.com/stretchr/testify v1.10.0
golang.org/x/mod v0.24.0
golang.org/x/net v0.38.0
golang.org/x/sys v0.33.0
google.golang.org/grpc v1.71.1
k8s.io/api v0.29.0
k8s.io/apimachinery v0.29.0
Expand Down Expand Up @@ -78,7 +79,6 @@ require (
go.uber.org/zap v1.27.0 // indirect
golang.org/x/crypto v0.38.0 // indirect
golang.org/x/oauth2 v0.25.0 // indirect
golang.org/x/sys v0.33.0 // indirect
golang.org/x/term v0.32.0 // indirect
golang.org/x/text v0.25.0 // indirect
golang.org/x/time v0.5.0 // indirect
Expand Down
59 changes: 39 additions & 20 deletions pkg/driver/node_server.go
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@ import (

"github.com/container-storage-interface/spec/lib/go/csi"
"golang.org/x/net/context"
"golang.org/x/sys/unix"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/status"
"k8s.io/apimachinery/pkg/api/resource"
Expand Down Expand Up @@ -1029,31 +1030,49 @@ func (driver *Driver) nodePublishVolume(

// If Block, then stage the volume for raw block device access
if volAccessType.String() == model.BlockType.String() {
log.Tracef("Publishing the volume for raw block access (create symlink), devicePath: %s, targetPath: %v",
log.Tracef("Publishing the volume for raw block access (create block device), devicePath: %s, targetPath: %v",
stagingDev.Device.AltFullPathName, targetPath)

// Check if target path symlink to the device already exists
exists, symlink, _ := util.IsFileSymlink(targetPath)
if symlink {
errMsg := fmt.Sprintf("Target path %s already published as symlink to the device %s", targetPath, stagingDev.Device.AltFullPathName)
// Check if target path block device to the mpath device already exists
exists, blockDevice, _ := util.IsFileBlockDevice(targetPath)
if blockDevice {
errMsg := fmt.Sprintf("Target path %s already published as block device to the mpath device %s", targetPath, stagingDev.Device.AltFullPathName)
log.Error("Error: ", errMsg)
return status.Error(codes.Internal, errMsg)
}
if exists {
// Remove the target path before creating the symlink
log.Tracef("Removing the target path %s before creating symlink to the device", targetPath)
log.Tracef("Removing the target block device %s before creating block device to the mpath device", targetPath)
if err := util.FileDelete(targetPath); err != nil {
return status.Error(codes.Internal,
fmt.Sprintf("Error removing the target path %s before creating symlink to the device, err: %s",
fmt.Sprintf("Error removing the target block device %s before creating block device to the mpath device, err: %s",
targetPath, err.Error()))
}
}

// Note: Bind-mount is not allowed for raw block device as there is no filesystem on it.
// So, we create softlink to the device file. TODO: mknode() instead ???
// Ex: ln -s /dev/mpathbm <targetPath>
if err := os.Symlink(stagingDev.Device.AltFullPathName, targetPath); err != nil {
errMsg := fmt.Sprintf("Failed to create symlink %s to the device path %s, err: %v",
rawDeviceMinor, err := strconv.Atoi(stagingDev.Device.Minor)
if err != nil {
errMsg := fmt.Sprintf("Failed to retrieve device minor to create %s from the mpath device path %s, err: %v",
targetPath, stagingDev.Device.AltFullPathName, err.Error())
log.Error("Error: ", errMsg)
return status.Error(codes.Internal, errMsg)
}

rawDeviceMajor, err := strconv.Atoi(stagingDev.Device.Major)
if err != nil {
errMsg := fmt.Sprintf("Failed to retrieve device major to create %s from the mpath device path %s, err: %v",
targetPath, stagingDev.Device.AltFullPathName, err.Error())
log.Error("Error: ", errMsg)
return status.Error(codes.Internal, errMsg)
}

rawDeviceMode := uint32(unix.S_IFBLK | 0660)
rawDeviceMM := int(unix.Mkdev(uint32(rawDeviceMajor), uint32(rawDeviceMinor)))

// Create block device
if err := unix.Mknod(targetPath, rawDeviceMode, rawDeviceMM); err != nil {
errMsg := fmt.Sprintf("Failed to create block device %s to the mpath device path %s, err: %v",
targetPath, stagingDev.Device.AltFullPathName, err.Error())
log.Error("Error: ", errMsg)
return status.Error(codes.Internal, errMsg)
Expand Down Expand Up @@ -1456,10 +1475,10 @@ func (driver *Driver) isVolumePublished(
return false, nil // Not published yet as targetPath does not exists
}

// Check if target path is the symlink to the device
_, symlink, _ := util.IsFileSymlink(targetPath)
if !symlink {
log.Tracef("Target path %s is not symlink to the device %s", targetPath, stagingDev.Device.AltFullPathName)
// Check if target path is a block device
_, blockDevice, _ := util.IsFileBlockDevice(targetPath)
if !blockDevice {
log.Tracef("Target path %s is not a block device to the mpath device %s", targetPath, stagingDev.Device.AltFullPathName)
return false, nil // Not published yet as symlink does not exists
}

Expand Down Expand Up @@ -1732,13 +1751,13 @@ func (driver *Driver) nodeUnpublishVolume(targetPath string) error {
defer log.Trace("<<<<< nodeUnpublishVolume")

// Block volume: Check for symlink and remove it
_, symlink, _ := util.IsFileSymlink(targetPath)
if symlink {
// Remove the symlink
log.Tracef("Removing the symlink from target path %s", targetPath)
_, blockDevice, _ := util.IsFileBlockDevice(targetPath)
if blockDevice {
// Remove the block device
log.Tracef("Removing the block device from mpath device %s", targetPath)
if err := util.FileDelete(targetPath); err != nil {
return status.Error(codes.Internal,
fmt.Sprintf("Error removing the symlink target path %s, err: %s",
fmt.Sprintf("Error removing the block device target path%s, err: %s",
targetPath, err.Error()))
}
return nil
Expand Down