Add --force to podman umount to force the unmounting of the rootfs

podman umount will currently only unmount file system if not other
process is using it, otherwise the umount decrements the container
storage to indicate that the caller is no longer using the mount
point, once the count gets to 0, the file system is actually unmounted.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

Closes: #1184
Approved by: TomSweeneyRedHat

cmd/podman/umount.go

@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 
+	"github.com/containers/storage"
 	"github.com/pkg/errors"
 	"github.com/projectatomic/libpod/cmd/podman/libpodruntime"
 	"github.com/projectatomic/libpod/libpod"
@@ -16,13 +17,24 @@ var (
 			Name:  "all, a",
 			Usage: "umount all of the currently mounted containers",
 		},
+		cli.BoolFlag{
+			Name:  "force, f",
+			Usage: "force the complete umount all of the currently mounted containers",
+		},
 	}
 
+	description = `
+Container storage increments a mount counter each time a container is mounted.
+When a container is unmounted, the mount counter is decremented and the
+container's root filesystem is physically unmounted only when the mount
+counter reaches zero indicating no other processes are using the mount.
+An unmount can be forced with the --force flag.
+`
 	umountCommand = cli.Command{
 		Name:        "umount",
 		Aliases:     []string{"unmount"},
 		Usage:       "Unmounts working container's root filesystem",
-		Description: "Unmounts working container's root filesystem",
+		Description: description,
 		Flags:       umountFlags,
 		Action:      umountCmd,
 		ArgsUsage:   "CONTAINER-NAME-OR-ID",
@@ -36,6 +48,7 @@ func umountCmd(c *cli.Context) error {
 	}
 	defer runtime.Shutdown(false)
 
+	force := c.Bool("force")
 	umountAll := c.Bool("all")
 	args := c.Args()
 	if len(args) == 0 && !umountAll {
@@ -58,7 +71,7 @@ func umountCmd(c *cli.Context) error {
 				continue
 			}
 
-			if err = ctr.Unmount(); err != nil {
+			if err = ctr.Unmount(force); err != nil {
 				if lastError != nil {
 					logrus.Error(lastError)
 				}
@@ -78,7 +91,10 @@ func umountCmd(c *cli.Context) error {
 				continue
 			}
 
-			if err = ctr.Unmount(); err != nil {
+			if err = ctr.Unmount(force); err != nil {
+				if umountAll && errors.Cause(err) == storage.ErrLayerNotMounted {
+					continue
+				}
 				if lastError != nil {
 					logrus.Error(lastError)
 				}

completions/bash/podman

@@ -1358,6 +1358,8 @@ _podman_umount() {
     local boolean_options="
     --all
     -a
+    --force
+    -f
     --help
     -h
  "

docs/podman-umount.1.md

@@ -7,13 +7,28 @@ podman\-umount - Unmount the specified working containers' root file system.
 **podman umount** *container* ...
 
 ## DESCRIPTION
-Unmounts the specified containers' root file system.
+Unmounts the specified containers' root file system, if no other processes
+are using it.
+
+Container storage increments a mount counter each time a container is mounted.
+When a container is unmounted, the mount counter is decremented and the
+container's root filesystem is physically unmounted only when the mount
+counter reaches zero indicating no other processes are using the mount.
+An unmount can be forced with the --force flag.
 
 ## OPTIONS
 **--all, -a**
 
 All of the currently mounted containers will be unmounted.
 
+**--force, -f**
+
+Force the unmounting of specified containers' root file system, even if other
+processes have mounted it.
+
+Note: This could cause other processes that are using the file system to fail,
+as the mount point could be removed without their knowledge.
+
 ## EXAMPLE
 
 podman umount containerID

libpod/container_api.go

@@ -441,7 +441,7 @@ func (c *Container) Mount() (string, error) {
 }
 
 // Unmount unmounts a container's filesystem on the host
-func (c *Container) Unmount() error {
+func (c *Container) Unmount(force bool) error {
 	if !c.batched {
 		c.lock.Lock()
 		defer c.lock.Unlock()
@@ -469,7 +469,7 @@ func (c *Container) Unmount() error {
 			return errors.Wrapf(err, "can't unmount %s last mount, it is still in use", c.ID())
 		}
 	}
-	return c.unmount()
+	return c.unmount(force)
 }
 
 // Pause pauses a container

libpod/container_internal.go

@@ -839,7 +839,7 @@ func (c *Container) cleanupStorage() error {
 		return nil
 	}
 
-	if err := c.unmount(); err != nil {
+	if err := c.unmount(false); err != nil {
 		// If the container has already been removed, warn but don't
 		// error
 		// We still want to be able to kick the container out of the
@@ -1338,9 +1338,9 @@ func (c *Container) mount() (string, error) {
 }
 
 // unmount unmounts the container's root filesystem
-func (c *Container) unmount() error {
+func (c *Container) unmount(force bool) error {
 	// Also unmount storage
-	if _, err := c.runtime.storageService.UnmountContainerImage(c.ID()); err != nil {
+	if _, err := c.runtime.storageService.UnmountContainerImage(c.ID(), force); err != nil {
 		return errors.Wrapf(err, "error unmounting container %s root filesystem", c.ID())
 	}
 

libpod/storage.go

@@ -231,7 +231,7 @@ func (r *storageService) MountContainerImage(idOrName string) (string, error) {
 	return mountPoint, nil
 }
 
-func (r *storageService) UnmountContainerImage(idOrName string) (bool, error) {
+func (r *storageService) UnmountContainerImage(idOrName string, force bool) (bool, error) {
 	if idOrName == "" {
 		return false, ErrEmptyID
 	}
@@ -239,7 +239,17 @@ func (r *storageService) UnmountContainerImage(idOrName string) (bool, error) {
 	if err != nil {
 		return false, err
 	}
-	mounted, err := r.store.Unmount(container.ID, false)
+
+	if !force {
+		mounted, err := r.store.Mounted(container.ID)
+		if err != nil {
+			return false, err
+		}
+		if mounted == 0 {
+			return false, storage.ErrLayerNotMounted
+		}
+	}
+	mounted, err := r.store.Unmount(container.ID, force)
 	if err != nil {
 		logrus.Debugf("failed to unmount container %q: %v", container.ID, err)
 		return false, err