daemon.getSourceMount(): fix for / mount point

A recent optimization in getSourceMount() made it return an error
in case when the found mount point is "/". This prevented bind-mounted
volumes from working in such cases.

A (rather trivial but adeqate) unit test case is added.

Fixes: 871c957242 ("getSourceMount(): simplify")
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/daemon/oci_linux_test.go b/daemon/oci_linux_test.go
index 5f2731b8d6..e28fac004e 100644
--- a/daemon/oci_linux_test.go
+++ b/daemon/oci_linux_test.go
@@ -1,6 +1,7 @@
 package daemon // import "github.com/docker/docker/daemon"
 
 import (
+	"os"
 	"testing"
 
 	containertypes "github.com/docker/docker/api/types/container"
@@ -86,3 +87,16 @@ func TestIpcPrivateVsReadonly(t *testing.T) {
 		assert.Check(t, is.Equal(false, inSlice(m.Options, "ro")))
 	}
 }
+
+func TestGetSourceMount(t *testing.T) {
+	// must be able to find source mount for /
+	mnt, _, err := getSourceMount("/")
+	assert.NilError(t, err)
+	assert.Equal(t, mnt, "/")
+
+	// must be able to find source mount for current directory
+	cwd, err := os.Getwd()
+	assert.NilError(t, err)
+	_, _, err = getSourceMount(cwd)
+	assert.NilError(t, err)
+}