'docker cp' can't copy file into container after 'docker exec' operation.

[davidchen8319]

Description
'docker cp' can't copy file into container after 'docker exec' operation.

Steps to reproduce

chy@ubuntu:~$ docker run -d   --tmpfs /myapp --name gvisor-analysis  --runtime=runsc gcc:4.9 sleep 360000
8f089e62ecd1882df28a7b583e8eabf95279e1c9cd14c732e23e835d59ac194e
chy@ubuntu:~$ docker cp gvisor_analysis/experiments/execute/write_throughput/write gvisor-analysis:/write
chy@ubuntu:~$ docker cp gvisor_analysis/experiments/execute/write_throughput/write gvisor-analysis:/write2
chy@ubuntu:~$ docker exec -it gvisor-analysis ls /
bin  boot  dev	etc  home  lib	lib64  media  mnt  myapp  opt  proc  root  run	sbin  srv  sys	tmp  usr  var  write  write2

note: 'write write2' is listed. continue next step.

chy@ubuntu:~$ docker cp gvisor_analysis/experiments/execute/write_throughput/write gvisor-analysis:/write3
chy@ubuntu:~$ docker exec -it gvisor-analysis ls /
bin  boot  dev	etc  home  lib	lib64  media  mnt  myapp  opt  proc  root  run	sbin  srv  sys	tmp  usr  var  write  write2

note: write3 is missing.

Environment

Please include the following details of your environment:

• runsc -v
  runsc version release-20200622.1-59-g6c099d830091-dirty
  spec: 1.0.1-dev

• docker version or docker info (if available)
  Client: Docker Engine - Community
  Version: 19.03.12
  API version: 1.40
  Go version: go1.13.10
  Git commit: 48a66213fe
  Built: Mon Jun 22 15:45:36 2020
  OS/Arch: linux/amd64
  Experimental: false

Server: Docker Engine - Community
Engine:
Version: 19.03.12
API version: 1.40 (minimum version 1.12)
Go version: go1.13.10
Git commit: 48a66213fe
Built: Mon Jun 22 15:44:07 2020
OS/Arch: linux/amd64
Experimental: false
containerd:
Version: 1.2.13
GitCommit: 7ad184331fa3e55e52b890ea95e65ba581ae3429
runc:
Version: 1.0.0-rc10
GitCommit: dc9208a3303feef5b3839f4323d9beb36df0a9dd
docker-init:
Version: 0.18.0
GitCommit: fec3683

• uname -a
  Linux ubuntu 5.3.0-61-generic runsc runtime not working with centos 7.5 #55~18.04.1-Ubuntu SMP Mon Jun 22 16:40:20 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

• git describe (if built from source)
  release-20200622.1-59-g6c099d830

• runsc debug logs (if available)

[ianlewis]

This is a duplicate of #4

See: https://gvisor.dev/docs/user_guide/FAQ/#fs-cache