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Devmapper: Mount images readonly when calculating changes

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There is no need to have this be writable, and there is a chance
that e.g. atime updates will cause writes to the image which is
bad for disk use wrt sharing between all containers.
This commit is contained in:
Alexander Larsson 2013-10-17 16:14:53 +02:00
parent ad2fbd9e87
commit a14496ce89
2 changed files with 12 additions and 6 deletions
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12
devmapper/deviceset_devmapper.go
View file

@ -650,7 +650,7 @@ func (devices *DeviceSetDM) Shutdown() error {
return nil return nil
} }
func (devices *DeviceSetDM) MountDevice(hash, path string) error { func (devices *DeviceSetDM) MountDevice(hash, path string, readOnly bool) error {
devices.Lock() devices.Lock()
defer devices.Unlock() defer devices.Unlock()
@ -666,9 +666,15 @@ func (devices *DeviceSetDM) MountDevice(hash, path string) error {
info := devices.Devices[hash] info := devices.Devices[hash]
err := syscall.Mount(info.DevName(), path, "ext4", syscall.MS_MGC_VAL, "discard") var flags uintptr = syscall.MS_MGC_VAL
if readOnly {
flags = flags | syscall.MS_RDONLY
}
err := syscall.Mount(info.DevName(), path, "ext4", flags, "discard")
if err != nil && err == syscall.EINVAL { if err != nil && err == syscall.EINVAL {
err = syscall.Mount(info.DevName(), path, "ext4", syscall.MS_MGC_VAL, "") err = syscall.Mount(info.DevName(), path, "ext4", flags, "")
} }
if err != nil { if err != nil {
utils.Debugf("\n--->Err: %s\n", err) utils.Debugf("\n--->Err: %s\n", err)

6
image.go
View file

@ -384,7 +384,7 @@ func (image *Image) ensureImageDevice(devices *devmapper.DeviceSetDM) error {
return err return err
} }
if err := devices.MountDevice(image.ID, mountDir); err != nil { if err := devices.MountDevice(image.ID, mountDir, false); err != nil {
utils.Debugf("Error mounting device: %s", err) utils.Debugf("Error mounting device: %s", err)
devices.RemoveDevice(image.ID) devices.RemoveDevice(image.ID)
return err return err
@ -467,7 +467,7 @@ func (image *Image) Mount(runtime *Runtime, root, rw string, id string) error {
} }
utils.Debugf("Mounting container %s at %s for container", id, root) utils.Debugf("Mounting container %s at %s for container", id, root)
if err := devices.MountDevice(id, root); err != nil { if err := devices.MountDevice(id, root, false); err != nil {
return err return err
} }
@ -509,7 +509,7 @@ func (image *Image) Changes(runtime *Runtime, root, rw, id string) ([]Change, er
// We re-use rw for the temporary mount of the base image as its // We re-use rw for the temporary mount of the base image as its
// not used by device-mapper otherwise // not used by device-mapper otherwise
err = devices.MountDevice(image.ID, rw) err = devices.MountDevice(image.ID, rw, true)
if err != nil { if err != nil {
return nil, err return nil, err
} }