opts/mount: add tmpfs-specific options

added following options:

 * tmpfs-size
 * tmpfs-mode

Signed-off-by: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>

docs/reference/commandline/run.md

@@ -264,9 +264,9 @@ Docker daemon.
 
 For in-depth information about volumes, refer to [manage data in containers](https://docs.docker.com/engine/tutorials/dockervolumes/)
 
-### Add bin-mounts or volumes using the --mounts flag
+### Add bin-mounts or volumes using the --mount flag
 
-The `--mounts` flag allows you to mount volumes, host-directories and `tmpfs`
+The `--mount` flag allows you to mount volumes, host-directories and `tmpfs`
 mounts in a container.
 
 The `--mount` flag supports most options that are supported by the `-v` or the

docs/reference/commandline/service_create.md

@@ -172,6 +172,8 @@ or write from files or directories on other containers or the host operating
 system. These types are _data volumes_ (often referred to simply as volumes) and
 _bind-mounts_.
 
+Additionally, Docker also supports tmpfs mounts.
+
 A **bind-mount** makes a file or directory on the host available to the
 container it is mounted within. A bind-mount may be either read-only or
 read-write. For example, a container might share its host's DNS information by
@@ -188,6 +190,8 @@ shared between a container and the host machine, as well as between multiple
 containers. Docker uses a _volume driver_ to create, manage, and mount volumes.
 You can back up or restore volumes using Docker commands.
 
+A **tmpfs** mounts a tmpfs inside a container for volatile data.
+
 Consider a situation where your image starts a lightweight web server. You could
 use that image as a base image, copy in your website's HTML files, and package
 that into another image. Each time your website changed, you'd need to update
@@ -204,8 +208,8 @@ volumes in a service:
 
 | Option                                   | Required                  | Description
 |:-----------------------------------------|:--------------------------|:-----------------------------------------------------------------------------------------
-| **type**                                 |                           | The type of mount, can be either `volume`, or `bind`. Defaults to `volume` if no type is specified.<ul><li>`volume`: mounts a [managed volume](volume_create.md) into the container.</li><li>`bind`: bind-mounts a directory or file from the host into the container.</li></ul>
+| **type**                                 |                           | The type of mount, can be either `volume`, `bind`, or `tmpfs`. Defaults to `volume` if no type is specified.<ul><li>`volume`: mounts a [managed volume](volume_create.md) into the container.</li><li>`bind`: bind-mounts a directory or file from the host into the container.</li><li>`tmpfs`: mount a tmpfs in the container</li></ul>
-| **src** or **source**                    | for `type=bind`&nbsp;only | <ul><li>`type=volume`: `src` is an optional way to specify the name of the volume (for example, `src=my-volume`). If the named volume does not exist, it is automatically created. If no `src` is specified, the volume is assigned a random name which is guaranteed to be unique on the host, but may not be unique cluster-wide. A randomly-named volume has the same lifecycle as its container and is destroyed when the *container* is destroyed (which is upon `service update`, or when scaling or re-balancing the service).</li><li>`type=bind`: `src` is required, and specifies an absolute path to the file or directory to bind-mount (for example, `src=/path/on/host/`).  An error is produced if the file or directory does not exist.</li></ul>
+| **src** or **source**                    | for `type=bind`&nbsp;only | <ul><li>`type=volume`: `src` is an optional way to specify the name of the volume (for example, `src=my-volume`). If the named volume does not exist, it is automatically created. If no `src` is specified, the volume is assigned a random name which is guaranteed to be unique on the host, but may not be unique cluster-wide. A randomly-named volume has the same lifecycle as its container and is destroyed when the *container* is destroyed (which is upon `service update`, or when scaling or re-balancing the service).</li><li>`type=bind`: `src` is required, and specifies an absolute path to the file or directory to bind-mount (for example, `src=/path/on/host/`).  An error is produced if the file or directory does not exist.</li><li>`type=tmpfs`: `src` is not supported.</li></ul>
 | **dst** or **destination** or **target** | yes                       | Mount path inside the container, for example `/some/path/in/container/`. If the path does not exist in the container's filesystem, the Engine creates a directory at the specified location before mounting the volume or bind-mount.
 | **readonly** or **ro**                   |                           | The Engine mounts binds and volumes `read-write` unless `readonly` option is given when mounting the bind or volume.<br /><br /><ul><li>`true` or `1` or no value: Mounts the bind or volume read-only.</li><li>`false` or `0`: Mounts the bind or volume read-write.</li></ul>
 
@@ -256,6 +260,14 @@ The following options can only be used for named volumes (`type=volume`);
 | **volume-nocopy**     | By default, if you attach an empty volume to a container, and files or directories already existed at the mount-path in the container (`dst`), the Engine copies those files and directories into the volume, allowing the host to access them. Set `volume-nocopy` to disables copying files from the container's filesystem to the volume and mount the empty volume.<br /><br />A value is optional:<ul><li>`true` or `1`: Default if you do not provide a value. Disables copying.</li><li>`false` or `0`: Enables copying.</li></ul>
 | **volume-opt**        | Options specific to a given volume driver, which will be passed to the driver when creating the volume. Options are provided as a comma-separated list of key/value pairs, for example, `volume-opt=some-option=some-value,some-other-option=some-other-value`. For available options for a given driver, refer to that driver's documentation.
 
+#### Options for tmpfs
+The following options can only be used for tmpfs mounts (`type=tmpfs`);
+
+| Option                | Description
+|:----------------------|:--------------------------------------------------------------------------------------------------------------------
+| **tmpfs-size**        | Size of the tmpfs mount in bytes. Unlimited by default in Linux.
+| **tmpfs-mode**        | File mode of the tmpfs in octal. (e.g. `"700"` or `"0700"`.) Defaults to ``"1777"`` in Linux.
+
 #### Differences between "--mount" and "--volume"
 
 The `--mount` flag supports most options that are supported by the `-v`

opts/mount.go

@@ -3,10 +3,12 @@ package opts
 import (
 	"encoding/csv"
 	"fmt"
+	"os"
 	"strconv"
 	"strings"
 
 	mounttypes "github.com/docker/docker/api/types/mount"
+	"github.com/docker/go-units"
 )
 
 // MountOpt is a Value type for parsing mounts
@@ -43,6 +45,13 @@ func (m *MountOpt) Set(value string) error {
 		return mount.BindOptions
 	}
 
+	tmpfsOptions := func() *mounttypes.TmpfsOptions {
+		if mount.TmpfsOptions == nil {
+			mount.TmpfsOptions = new(mounttypes.TmpfsOptions)
+		}
+		return mount.TmpfsOptions
+	}
+
 	setValueOnMap := func(target map[string]string, value string) {
 		parts := strings.SplitN(value, "=", 2)
 		if len(parts) == 1 {
@@ -102,6 +111,18 @@ func (m *MountOpt) Set(value string) error {
 				volumeOptions().DriverConfig.Options = make(map[string]string)
 			}
 			setValueOnMap(volumeOptions().DriverConfig.Options, value)
+		case "tmpfs-size":
+			sizeBytes, err := units.RAMInBytes(value)
+			if err != nil {
+				return fmt.Errorf("invalid value for %s: %s", key, value)
+			}
+			tmpfsOptions().SizeBytes = sizeBytes
+		case "tmpfs-mode":
+			ui64, err := strconv.ParseUint(value, 8, 32)
+			if err != nil {
+				return fmt.Errorf("invalid value for %s: %s", key, value)
+			}
+			tmpfsOptions().Mode = os.FileMode(ui64)
 		default:
 			return fmt.Errorf("unexpected key '%s' in '%s'", key, field)
 		}
@@ -115,11 +136,14 @@ func (m *MountOpt) Set(value string) error {
 		return fmt.Errorf("target is required")
 	}
 
-	if mount.Type == mounttypes.TypeBind && mount.VolumeOptions != nil {
+	if mount.VolumeOptions != nil && mount.Type != mounttypes.TypeVolume {
-		return fmt.Errorf("cannot mix 'volume-*' options with mount type '%s'", mounttypes.TypeBind)
+		return fmt.Errorf("cannot mix 'volume-*' options with mount type '%s'", mount.Type)
 	}
-	if mount.Type == mounttypes.TypeVolume && mount.BindOptions != nil {
+	if mount.BindOptions != nil && mount.Type != mounttypes.TypeBind {
-		return fmt.Errorf("cannot mix 'bind-*' options with mount type '%s'", mounttypes.TypeVolume)
+		return fmt.Errorf("cannot mix 'bind-*' options with mount type '%s'", mount.Type)
+	}
+	if mount.TmpfsOptions != nil && mount.Type != mounttypes.TypeTmpfs {
+		return fmt.Errorf("cannot mix 'tmpfs-*' options with mount type '%s'", mount.Type)
 	}
 
 	m.values = append(m.values, mount)

opts/mount_test.go

@@ -1,6 +1,7 @@
 package opts
 
 import (
+	"os"
 	"testing"
 
 	mounttypes "github.com/docker/docker/api/types/mount"
@@ -151,3 +152,33 @@ func TestMountOptTypeConflict(t *testing.T) {
 	assert.Error(t, m.Set("type=bind,target=/foo,source=/foo,volume-nocopy=true"), "cannot mix")
 	assert.Error(t, m.Set("type=volume,target=/foo,source=/foo,bind-propagation=rprivate"), "cannot mix")
 }
+
+func TestMountOptSetTmpfsNoError(t *testing.T) {
+	for _, testcase := range []string{
+		// tests several aliases that should have same result.
+		"type=tmpfs,target=/target,tmpfs-size=1m,tmpfs-mode=0700",
+		"type=tmpfs,target=/target,tmpfs-size=1MB,tmpfs-mode=700",
+	} {
+		var mount MountOpt
+
+		assert.NilError(t, mount.Set(testcase))
+
+		mounts := mount.Value()
+		assert.Equal(t, len(mounts), 1)
+		assert.DeepEqual(t, mounts[0], mounttypes.Mount{
+			Type:   mounttypes.TypeTmpfs,
+			Target: "/target",
+			TmpfsOptions: &mounttypes.TmpfsOptions{
+				SizeBytes: 1024 * 1024, // not 1000 * 1000
+				Mode:      os.FileMode(0700),
+			},
+		})
+	}
+}
+
+func TestMountOptSetTmpfsError(t *testing.T) {
+	var m MountOpt
+	assert.Error(t, m.Set("type=tmpfs,target=/foo,tmpfs-size=foo"), "invalid value for tmpfs-size")
+	assert.Error(t, m.Set("type=tmpfs,target=/foo,tmpfs-mode=foo"), "invalid value for tmpfs-mode")
+	assert.Error(t, m.Set("type=tmpfs"), "target is required")
+}