1package hcsshim
2
3import (
4	"sync"
5
6	"github.com/sirupsen/logrus"
7)
8
9var prepareLayerLock sync.Mutex
10
11// PrepareLayer finds a mounted read-write layer matching layerId and enables the
12// the filesystem filter for use on that layer.  This requires the paths to all
13// parent layers, and is necessary in order to view or interact with the layer
14// as an actual filesystem (reading and writing files, creating directories, etc).
15// Disabling the filter must be done via UnprepareLayer.
16func PrepareLayer(info DriverInfo, layerId string, parentLayerPaths []string) error {
17	title := "hcsshim::PrepareLayer "
18	logrus.Debugf(title+"flavour %d layerId %s", info.Flavour, layerId)
19
20	// Generate layer descriptors
21	layers, err := layerPathsToDescriptors(parentLayerPaths)
22	if err != nil {
23		return err
24	}
25
26	// Convert info to API calling convention
27	infop, err := convertDriverInfo(info)
28	if err != nil {
29		logrus.Error(err)
30		return err
31	}
32
33	// This lock is a temporary workaround for a Windows bug. Only allowing one
34	// call to prepareLayer at a time vastly reduces the chance of a timeout.
35	prepareLayerLock.Lock()
36	defer prepareLayerLock.Unlock()
37	err = prepareLayer(&infop, layerId, layers)
38	if err != nil {
39		err = makeErrorf(err, title, "layerId=%s flavour=%d", layerId, info.Flavour)
40		logrus.Error(err)
41		return err
42	}
43
44	logrus.Debugf(title+"succeeded flavour=%d layerId=%s", info.Flavour, layerId)
45	return nil
46}
47