Simplify swappiness check

As suggested in https://github.com/docker/docker/pull/14004/files#r34022527

The concern there is we can't differentiate whether user explicitly
asked for an invalid value of -1 or he did not specify anything.

I don't think this would be a problem, because:
 - like all other default values like zero, we can't differentiate
   user specify it or not, most of which, zeros are also invalid, so
   default is default, we show these default values in help info,
   so users would know if they set value as default, it'll be like
   they set nothing.
 - we can't do this kind of string check in REST api request, so
   it'll make the behave different from docker command and RESTapi.

Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>

docs/reference/run.md

@@ -617,7 +617,8 @@ and require killing system processes to free memory.
 By default, a container's kernel can swap out a percentage of anonymous pages.
 To set this percentage for a container, specify a `--memory-swappiness` value
 between 0 and 100. A value of 0 turns off anonymous page swapping. A value of
-100 sets all anonymous pages as swappable.
+100 sets all anonymous pages as swappable. By default, if you are not using
+`--memory-swappiness`, memory swappiness value will be inherited from the parent.
 
 For example, you can set:
 

integration-cli/docker_cli_run_test.go

@@ -75,11 +75,6 @@ func (s *DockerSuite) TestRunWithSwappinessInvalid(c *check.C) {
 	if err == nil {
 		c.Fatalf("failed. test was able to set invalid value, output: %q", out)
 	}
-	runCmd = exec.Command(dockerBinary, "run", "--memory-swappiness", "-1", "busybox", "true")
-	out, _, err = runCommandWithOutput(runCmd)
-	if err == nil {
-		c.Fatalf("failed. test was able to set invalid value, output: %q", out)
-	}
 }
 
 // "test" should be printed

runconfig/parse.go

@@ -73,7 +73,6 @@ func Parse(cmd *flag.FlagSet, args []string) (*Config, *HostConfig, *flag.FlagSe
 		flStdin           = cmd.Bool([]string{"i", "-interactive"}, false, "Keep STDIN open even if not attached")
 		flTty             = cmd.Bool([]string{"t", "-tty"}, false, "Allocate a pseudo-TTY")
 		flOomKillDisable  = cmd.Bool([]string{"-oom-kill-disable"}, false, "Disable OOM Killer")
-		flSwappinessStr   = cmd.String([]string{"-memory-swappiness"}, "", "Tuning container memory swappiness (0 to 100)")
 		flContainerIDFile = cmd.String([]string{"#cidfile", "-cidfile"}, "", "Write the container ID to the file")
 		flEntrypoint      = cmd.String([]string{"#entrypoint", "-entrypoint"}, "", "Overwrite the default ENTRYPOINT of the image")
 		flHostname        = cmd.String([]string{"h", "-hostname"}, "", "Container host name")
@@ -87,6 +86,7 @@ func Parse(cmd *flag.FlagSet, args []string) (*Config, *HostConfig, *flag.FlagSe
 		flCpusetCpus      = cmd.String([]string{"#-cpuset", "-cpuset-cpus"}, "", "CPUs in which to allow execution (0-3, 0,1)")
 		flCpusetMems      = cmd.String([]string{"-cpuset-mems"}, "", "MEMs in which to allow execution (0-3, 0,1)")
 		flBlkioWeight     = cmd.Int64([]string{"-blkio-weight"}, 0, "Block IO (relative weight), between 10 and 1000")
+		flSwappiness      = cmd.Int64([]string{"-memory-swappiness"}, -1, "Tuning container memory swappiness (0 to 100)")
 		flNetMode         = cmd.String([]string{"-net"}, "default", "Set the Network mode for the container")
 		flMacAddress      = cmd.String([]string{"-mac-address"}, "", "Container MAC address (e.g. 92:d0:c6:0a:29:33)")
 		flIpcMode         = cmd.String([]string{"-ipc"}, "", "IPC namespace to use")
@@ -190,17 +190,9 @@ func Parse(cmd *flag.FlagSet, args []string) (*Config, *HostConfig, *flag.FlagSe
 		}
 	}
 
-	var parsedSwappiness int64
-	var flSwappiness int64
-
-	if *flSwappinessStr != "" {
-		parsedSwappiness, err = strconv.ParseInt(*flSwappinessStr, 10, 64)
-		if err != nil || parsedSwappiness < 0 || parsedSwappiness > 100 {
-			return nil, nil, cmd, fmt.Errorf("invalid value:%s. valid memory swappiness range is 0-100", *flSwappinessStr)
-		}
-		flSwappiness = parsedSwappiness
-	} else {
-		flSwappiness = -1
+	swappiness := *flSwappiness
+	if swappiness != -1 && (swappiness < 0 || swappiness > 100) {
+		return nil, nil, cmd, fmt.Errorf("Invalid value: %d. Valid memory swappiness range is 0-100", swappiness)
 	}
 
 	var binds []string
@@ -355,7 +347,7 @@ func Parse(cmd *flag.FlagSet, args []string) (*Config, *HostConfig, *flag.FlagSe
 		CpuQuota:         *flCpuQuota,
 		BlkioWeight:      *flBlkioWeight,
 		OomKillDisable:   *flOomKillDisable,
-		MemorySwappiness: flSwappiness,
+		MemorySwappiness: swappiness,
 		Privileged:       *flPrivileged,
 		PortBindings:     portBindings,
 		Links:            flLinks.GetAll(),