Add daemon option --default-shm-size

This fix fixes issue raised in 29492 where it was not
possible to specify a default `--default-shm-size` in daemon
configuration for each `docker run``.

The flag `--default-shm-size` which is reloadable, has been
added to the daemon configuation.
Related docs has been updated.

This fix fixes 29492.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

command/service/opts.go

@@ -11,7 +11,6 @@ import (
 	"github.com/docker/docker/opts"
 	runconfigopts "github.com/docker/docker/runconfig/opts"
 	"github.com/docker/go-connections/nat"
-	units "github.com/docker/go-units"
 	"github.com/spf13/cobra"
 )
 
@@ -19,26 +18,6 @@ type int64Value interface {
 	Value() int64
 }
 
-type memBytes int64
-
-func (m *memBytes) String() string {
-	return units.BytesSize(float64(m.Value()))
-}
-
-func (m *memBytes) Set(value string) error {
-	val, err := units.RAMInBytes(value)
-	*m = memBytes(val)
-	return err
-}
-
-func (m *memBytes) Type() string {
-	return "bytes"
-}
-
-func (m *memBytes) Value() int64 {
-	return int64(*m)
-}
-
 // PositiveDurationOpt is an option type for time.Duration that uses a pointer.
 // It bahave similarly to DurationOpt but only allows positive duration values.
 type PositiveDurationOpt struct {
@@ -149,9 +128,9 @@ type updateOptions struct {
 
 type resourceOptions struct {
 	limitCPU      opts.NanoCPUs
-	limitMemBytes memBytes
+	limitMemBytes opts.MemBytes
 	resCPU        opts.NanoCPUs
-	resMemBytes   memBytes
+	resMemBytes   opts.MemBytes
 }
 
 func (r *resourceOptions) ToResourceRequirements() *swarm.ResourceRequirements {

command/service/opts_test.go

@@ -11,12 +11,12 @@ import (
 )
 
 func TestMemBytesString(t *testing.T) {
-	var mem memBytes = 1048576
+	var mem opts.MemBytes = 1048576
 	assert.Equal(t, mem.String(), "1 MiB")
 }
 
 func TestMemBytesSetAndValue(t *testing.T) {
-	var mem memBytes
+	var mem opts.MemBytes
 	assert.NilError(t, mem.Set("5kb"))
 	assert.Equal(t, mem.Value(), int64(5120))
 }