Build fails to export image with "failed calculating diff pairs for exported snapshot"

[msg555]

Steps to reproduce:

First, due to a separate issue (containerd/containerd#3238), we need to push registry.access.redhat.com/rhel7/rhel:7.3 to a local registry. Let's suppose that image is called localhost:5000/rhel7:7.3. Then the below setup is what I'm using

Dockerfile:

FROM localhost:5000/rhel7:7.3
RUN rm -rf /usr/lib/python2.7/site-packages/subscription_manager

Build command:
buildctl build --frontend dockerfile.v0 --local dockerfile=. --local context=. --output type=image,name=myimage

The client gets the error

error: failed to solve: rpc error: code = Unknown desc = failed calculating diff pairs for exported snapshot: mount callback failed on /tmp/containerd-mount622803746: mount callback failed on /tmp/containerd-mount457946649: failed to open writer: ref buildkit/1/r7hengy3nchk411du0q39x1g8 locked: unavailable

On the daemon side we see

ERRO[2558] /moby.buildkit.v1.Control/Solve returned error: unavailable
github.com/containerd/containerd/errdefs.init.ializers
	/src/vendor/github.com/containerd/containerd/errdefs/errors.go:44
runtime.main
	/usr/local/go/src/runtime/proc.go:188
runtime.goexit
	/usr/local/go/src/runtime/asm_amd64.s:1337
ref buildkit/1/r7hengy3nchk411du0q39x1g8 locked
github.com/containerd/containerd/content/local.tryLock
	/src/vendor/github.com/containerd/containerd/content/local/locks.go:39
github.com/containerd/containerd/content/local.(*store).Writer
	/src/vendor/github.com/containerd/containerd/content/local/store.go:455
github.com/containerd/containerd/metadata.(*contentStore).Writer.func1
	/src/vendor/github.com/containerd/containerd/metadata/content.go:462
go.etcd.io/bbolt.(*DB).Update
	/src/vendor/go.etcd.io/bbolt/db.go:688
github.com/containerd/containerd/metadata.(*DB).Update
	/src/vendor/github.com/containerd/containerd/metadata/db.go:238
github.com/containerd/containerd/metadata.update
	/src/vendor/github.com/containerd/containerd/metadata/bolt.go:56
github.com/containerd/containerd/metadata.(*contentStore).Writer
	/src/vendor/github.com/containerd/containerd/metadata/content.go:385
github.com/moby/buildkit/snapshot/containerd.(*nsContent).writer
	/src/snapshot/containerd/content.go:89
github.com/moby/buildkit/snapshot/containerd.(*nsContent).Writer
	/src/snapshot/containerd/content.go:75
github.com/moby/buildkit/snapshot/containerd.(*noGCContentStore).Writer
	/src/snapshot/containerd/content.go:114
github.com/containerd/containerd/diff/walking.(*walkingDiff).Compare.func1.1
	/src/vendor/github.com/containerd/containerd/diff/walking/differ.go:90
github.com/containerd/containerd/mount.WithTempMount
	/src/vendor/github.com/containerd/containerd/mount/temp.go:65
github.com/containerd/containerd/diff/walking.(*walkingDiff).Compare.func1
	/src/vendor/github.com/containerd/containerd/diff/walking/differ.go:83
github.com/containerd/containerd/mount.WithTempMount
	/src/vendor/github.com/containerd/containerd/mount/temp.go:65
github.com/containerd/containerd/diff/walking.(*walkingDiff).Compare
	/src/vendor/github.com/containerd/containerd/diff/walking/differ.go:82
github.com/moby/buildkit/util/winlayers.(*winDiffer).Compare
	/src/util/winlayers/differ.go:49
github.com/moby/buildkit/cache/blobs.getDiffPairs.func2.1
	/src/cache/blobs/blobs.go:102
github.com/moby/buildkit/util/flightcontrol.(*call).run
	/src/util/flightcontrol/flightcontrol.go:116
sync.(*Once).Do
	/usr/local/go/src/sync/once.go:44
runtime.goexit
	/usr/local/go/src/runtime/asm_amd64.s:1337
failed to open writer
github.com/containerd/containerd/diff/walking.(*walkingDiff).Compare.func1.1
	/src/vendor/github.com/containerd/containerd/diff/walking/differ.go:96
github.com/containerd/containerd/mount.WithTempMount
	/src/vendor/github.com/containerd/containerd/mount/temp.go:65
github.com/containerd/containerd/diff/walking.(*walkingDiff).Compare.func1
	/src/vendor/github.com/containerd/containerd/diff/walking/differ.go:83
github.com/containerd/containerd/mount.WithTempMount
	/src/vendor/github.com/containerd/containerd/mount/temp.go:65
github.com/containerd/containerd/diff/walking.(*walkingDiff).Compare
	/src/vendor/github.com/containerd/containerd/diff/walking/differ.go:82
github.com/moby/buildkit/util/winlayers.(*winDiffer).Compare
	/src/util/winlayers/differ.go:49
github.com/moby/buildkit/cache/blobs.getDiffPairs.func2.1
	/src/cache/blobs/blobs.go:102
github.com/moby/buildkit/util/flightcontrol.(*call).run
	/src/util/flightcontrol/flightcontrol.go:116
sync.(*Once).Do
	/usr/local/go/src/sync/once.go:44
runtime.goexit
	/usr/local/go/src/runtime/asm_amd64.s:1337
mount callback failed on /tmp/containerd-mount055207063
github.com/containerd/containerd/mount.WithTempMount
	/src/vendor/github.com/containerd/containerd/mount/temp.go:65
github.com/containerd/containerd/diff/walking.(*walkingDiff).Compare.func1
	/src/vendor/github.com/containerd/containerd/diff/walking/differ.go:83
github.com/containerd/containerd/mount.WithTempMount
	/src/vendor/github.com/containerd/containerd/mount/temp.go:65
github.com/containerd/containerd/diff/walking.(*walkingDiff).Compare
	/src/vendor/github.com/containerd/containerd/diff/walking/differ.go:82
github.com/moby/buildkit/util/winlayers.(*winDiffer).Compare
	/src/util/winlayers/differ.go:49
github.com/moby/buildkit/cache/blobs.getDiffPairs.func2.1
	/src/cache/blobs/blobs.go:102
github.com/moby/buildkit/util/flightcontrol.(*call).run
	/src/util/flightcontrol/flightcontrol.go:116
sync.(*Once).Do
	/usr/local/go/src/sync/once.go:44
runtime.goexit
	/usr/local/go/src/runtime/asm_amd64.s:1337
mount callback failed on /tmp/containerd-mount440148504
github.com/containerd/containerd/mount.WithTempMount
	/src/vendor/github.com/containerd/containerd/mount/temp.go:65
github.com/containerd/containerd/diff/walking.(*walkingDiff).Compare
	/src/vendor/github.com/containerd/containerd/diff/walking/differ.go:82
github.com/moby/buildkit/util/winlayers.(*winDiffer).Compare
	/src/util/winlayers/differ.go:49
github.com/moby/buildkit/cache/blobs.getDiffPairs.func2.1
	/src/cache/blobs/blobs.go:102
github.com/moby/buildkit/util/flightcontrol.(*call).run
	/src/util/flightcontrol/flightcontrol.go:116
sync.(*Once).Do
	/usr/local/go/src/sync/once.go:44
runtime.goexit
	/usr/local/go/src/runtime/asm_amd64.s:1337
failed calculating diff pairs for exported snapshot
github.com/moby/buildkit/exporter/containerimage.(*ImageWriter).exportLayers.func1.1
	/src/exporter/containerimage/writer.go:161
golang.org/x/sync/errgroup.(*Group).Go.func1
	/src/vendor/golang.org/x/sync/errgroup/errgroup.go:58
runtime.goexit
	/usr/local/go/src/runtime/asm_amd64.s:1337