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devmapper: Add option for specifying an lvm2 created thin-pool device

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Ideally lvm2 would be used to create/manage the thin-pool volume that is
then handed to docker to exclusively create/manage the thin and thin
snapshot volumes needed for it's containers.  Managing the thin-pool
outside of docker makes for the most feature-rich method of having
docker utilize device mapper thin provisioning as the backing storage
for docker's containers.  lvm2-based thin-pool management feature
highlights include: automatic or interactive thin-pool resize support,
dynamically change thin-pool features, automatic thinp metadata checking
when lvm2 activates the thin-pool, etc.

Docker will not activate/deactivate the specified thin-pool device but
it will exclusively manage/create thin and thin snapshot volumes in it.

Docker will not take ownership of the specified thin-pool device unless
it has 0 data blocks used and a transaction id of 0.  This should help
guard against using a thin-pool that is already in use.

Also fix typos in setupBaseImage() relative to the thin volume type of
the base image.

Docker-DCO-1.1-Signed-off-by: Mike Snitzer <snitzer@redhat.com> (github: snitm)
This commit is contained in:
Mike Snitzer 2014-10-24 19:25:24 -04:00
parent ad6467f9e1
commit 2b10749cdd
2 changed files with 49 additions and 7 deletions
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19
daemon/graphdriver/devmapper/README.md
View file

@ -100,6 +100,25 @@ Here is the list of supported options:
``docker -d --storage-opt dm.mountopt=nodiscard``
* `dm.thinpooldev`
Specifies a custom blockdevice to use for the thin pool.
If using a block device for device mapper storage, ideally lvm2
would be used to create/manage the thin-pool volume that is then
handed to docker to exclusively create/manage the thin and thin
snapshot volumes needed for it's containers. Managing the thin-pool
outside of docker makes for the most feature-rich method of having
docker utilize device mapper thin provisioning as the backing
storage for docker's containers. lvm2-based thin-pool management
feature highlights include: automatic or interactive thin-pool
resize support, dynamically change thin-pool features, automatic
thinp metadata checking when lvm2 activates the thin-pool, etc.
Example use:
``docker -d --storage-opt dm.thinpooldev=/dev/mapper/thin-pool``
* `dm.datadev`
Specifies a custom blockdevice to use for data for the thin pool.

37
daemon/graphdriver/devmapper/deviceset.go
View file

@ -84,6 +84,7 @@ type DeviceSet struct {
metadataDevice string
doBlkDiscard bool
thinpBlockSize uint32
thinPoolDevice string
}
type DiskUsage struct {
@ -150,7 +151,11 @@ func (devices *DeviceSet) oldMetadataFile() string {
}
func (devices *DeviceSet) getPoolName() string {
return devices.devicePrefix + "-pool"
if devices.thinPoolDevice == "" {
return devices.devicePrefix + "-pool"
} else {
return devices.thinPoolDevice
}
}
func (devices *DeviceSet) getPoolDevName() string {
@ -411,7 +416,21 @@ func (devices *DeviceSet) setupBaseImage() error {
}
}
log.Debugf("Initializing base device-manager snapshot")
if devices.thinPoolDevice != "" && oldInfo == nil {
if _, transactionId, dataUsed, _, _, _, err := devices.poolStatus(); err != nil {
return err
} else {
if dataUsed != 0 {
return fmt.Errorf("Unable to take ownership of thin-pool (%s) that already has used data blocks",
devices.thinPoolDevice)
} else if transactionId != 0 {
return fmt.Errorf("Unable to take ownership of thin-pool (%s) with non-zero transaction Id",
devices.thinPoolDevice)
}
}
}
log.Debugf("Initializing base device-mapper thin volume")
id := devices.NextDeviceId
@ -430,7 +449,7 @@ func (devices *DeviceSet) setupBaseImage() error {
return err
}
log.Debugf("Creating filesystem on base device-manager snapshot")
log.Debugf("Creating filesystem on base device-mapper thin volume")
if err = devices.activateDeviceIfNeeded(info); err != nil {
return err
@ -605,7 +624,7 @@ func (devices *DeviceSet) initDevmapper(doInit bool) error {
devices.devicePrefix = fmt.Sprintf("docker-%d:%d-%d", major(sysSt.Dev), minor(sysSt.Dev), sysSt.Ino)
log.Debugf("Generated prefix: %s", devices.devicePrefix)
// Check for the existence of the device <prefix>-pool
// Check for the existence of the thin-pool device
log.Debugf("Checking for existence of the pool '%s'", devices.getPoolName())
info, err := devicemapper.GetInfo(devices.getPoolName())
if info == nil {
@ -624,7 +643,7 @@ func (devices *DeviceSet) initDevmapper(doInit bool) error {
createdLoopback := false
// If the pool doesn't exist, create it
if info.Exists == 0 {
if info.Exists == 0 && devices.thinPoolDevice == "" {
log.Debugf("Pool doesn't exist. Creating it.")
var (
@ -988,8 +1007,10 @@ func (devices *DeviceSet) Shutdown() error {
}
devices.Lock()
if err := devices.deactivatePool(); err != nil {
log.Debugf("Shutdown deactivate pool , error: %s", err)
if devices.thinPoolDevice == "" {
if err := devices.deactivatePool(); err != nil {
log.Debugf("Shutdown deactivate pool , error: %s", err)
}
}
devices.saveDeviceSetMetaData()
@ -1275,6 +1296,8 @@ func NewDeviceSet(root string, doInit bool, options []string) (*DeviceSet, error
devices.metadataDevice = val
case "dm.datadev":
devices.dataDevice = val
case "dm.thinpooldev":
devices.thinPoolDevice = strings.TrimPrefix(val, "/dev/mapper/")
case "dm.blkdiscard":
foundBlkDiscard = true
devices.doBlkDiscard, err = strconv.ParseBool(val)