Function StartAsyncPagesFileLoad

pkg/sentry/pgalloc/save_restore.go:1321–1353

StartAsyncPagesFileLoad constructs asynchronous loading state for the pages file ar. It takes ownership of ar, even if it returns a non-nil error.

(ar stateio.AsyncReader, doneCallback func(error), timeline *timing.Timeline)

// StartAsyncPagesFileLoad constructs asynchronous loading state for the pages
// file ar. It takes ownership of ar, even if it returns a non-nil error.
func StartAsyncPagesFileLoad(ar stateio.AsyncReader, doneCallback func(error), timeline *timing.Timeline) (*AsyncPagesFileLoad, error) {
	maxReadBytes := hostarch.PageRoundDown(ar.MaxReadBytes())
	if maxReadBytes <= 0 {
		ar.Close()
		return nil, fmt.Errorf("stateio.AsyncReader.MaxReadBytes() (%d) must be at least one page)", ar.MaxReadBytes())
	}
	// Cap maxParallel due to the uint32 range of bitmap.Bitmap.
	maxParallel := min(ar.MaxParallel(), 1<<30)
	apfl := &AsyncPagesFileLoad{
		timeStartWaiters: math.MaxInt64,
		timeline:         timeline.Fork("async page loading"),
		doneCallback:     doneCallback,
		ar:               ar,
		maxReadBytes:     maxReadBytes,
		qavail:           maxParallel,
		opsBusy:          bitmap.New(uint32(maxParallel)),
		ops:              make([]aplOp, maxParallel),
	}
	// Mark ops in opsBusy that don't actually exist as permanently busy.
	for i, n := maxParallel, apfl.opsBusy.Size(); i < n; i++ {
		apfl.opsBusy.Add(uint32(i))
	}
	// Pre-allocate slices in ops.
	maxRanges := ar.MaxRanges()
	for i := range apfl.ops {
		op := &apfl.ops[i]
		op.frs = make([]memmap.FileRange, 0, maxRanges)
		op.iovecs = make([]unix.Iovec, 0, maxRanges)
	}
	apfl.lfStatus.Init()
	go apfl.main()
	return apfl, nil
}

// MemoryFilesDone must be called after calling LoadFrom() for all MemoryFiles
// loading from apfl. MemoryFilesDone may be called multiple times; subsequent