registry fails with 503, due to mkdir permission denied

I'm using gitlab 8.10 deployed with omnibus

my registry path is set to

gitlab_rails['registry_path'] = "/var/opt/git-repositories/registry/registry"

I then launch a gitlab reconfigure, the registry service is running, but when I tried to push an image I got

Error: Status 503 trying to push repository online-documentation/gitlab-ci-doc-uploader-docker: "{\"errors\":[{\"code\":\"UNAVAILABLE\",\"message\":\"service unavailable\",\"detail\":\"health check failed: please see /debug/health\"}]}\n"

After running the registry service with debug messages, I see the following error in the logs

ERRO[0026] response completed with error                 auth.user.name= environment=production err.code=unknown err.detail=filesystem: mkdir /var/opt/git-repositories/registry/registry: permission denied err.message=unknown error go.version=go1.5.4 http.request.host=localhost:5001 http.request.id=b4574e57-bc66-4394-83b8-56e2b9231da2 http.request.method=POST http.request.remoteaddr=127.0.0.1:56229 http.request.uri=/v2/online-documentation/gitlab-ci-doc-uploader-docker/blobs/uploads/ http.request.useragent=docker/1.12.0 go/go1.6.3 git-commit/8eab29e kernel/4.4.0-28-generic os/linux arch/amd64 UpstreamClient(Docker-Client/1.12.0 \(linux\)) http.response.contenttype=application/json; charset=utf-8 http.response.duration=5.276101ms http.response.status=500 http.response.written=174 instance.id=ac72465e-a42d-4dc0-b32f-42d5c6599d0c service=registry vars.name=online-documentation/gitlab-ci-doc-uploader-docker version=v2.4.1

with the important part

filesystem: mkdir /var/opt/git-repositories/registry/registry: permission denied

And indeed , If i connect to the server and do su registry -c 'mkdir /var/opt/git-repositories/registry/registry' I also got permission denied however it seems that gitlab reconfigure already take of setting the ""correct"" permissions as I can see

$ cd /var/opt/git-repositories/registry
$ ls -lha 

drwxr-x--- 2 registry git 4096 Aug 12 08:46 registry

What are the expected rights ?