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package wclayer
import (
"context"
"strings"
"sync"
"github.com/Microsoft/hcsshim/internal/hcserror"
"github.com/Microsoft/hcsshim/internal/oc"
"go.opencensus.io/trace"
)
var prepareLayerLock sync.Mutex
// PrepareLayer finds a mounted read-write layer matching path and enables the
// the filesystem filter for use on that layer. This requires the paths to all
// parent layers, and is necessary in order to view or interact with the layer
// as an actual filesystem (reading and writing files, creating directories, etc).
// Disabling the filter must be done via UnprepareLayer.
func PrepareLayer(ctx context.Context, path string, parentLayerPaths []string) (err error) {
title := "hcsshim::PrepareLayer"
ctx, span := trace.StartSpan(ctx, title)
defer span.End()
defer func() { oc.SetSpanStatus(span, err) }()
span.AddAttributes(
trace.StringAttribute("path", path),
trace.StringAttribute("parentLayerPaths", strings.Join(parentLayerPaths, ", ")))
// Generate layer descriptors
layers, err := layerPathsToDescriptors(ctx, parentLayerPaths)
if err != nil {
return err
}
// This lock is a temporary workaround for a Windows bug. Only allowing one
// call to prepareLayer at a time vastly reduces the chance of a timeout.
prepareLayerLock.Lock()
defer prepareLayerLock.Unlock()
err = prepareLayer(&stdDriverInfo, path, layers)
if err != nil {
return hcserror.New(err, title, "")
}
return nil
}
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