Add support for anonymous volumes to `podman run -v`

Previously, when `podman run` encountered a volume mount without
separate source and destination (e.g. `-v /run`) we would assume
that both were the same - a bind mount of `/run` on the host to
`/run` in the container. However, this does not match Docker's
behavior - in Docker, this makes an anonymous named volume that
will be mounted at `/run`.

We already have (more limited) support for these anonymous
volumes in the form of image volumes. Extend this support to
allow it to be used with user-created volumes coming in from the
`-v` flag.

This change also affects how named volumes created by the
container but given names are treated by `podman run --rm` and
`podman rm -v`. Previously, they would be removed with the
container in these cases, but this did not match Docker's
behaviour. Docker only removed anonymous volumes. With this patch
we move to that model as well; `podman run -v testvol:/test` will
not have `testvol` survive the container being removed by `podman
rm -v`.

The sum total of these changes let us turn on volume removal in
`--rm` by default.

Fixes: #4276

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

1 files changed, 21 insertions, 10 deletions

diff --git a/libpod/runtime_ctr.go b/libpod/runtime_ctr.go
index 411264d25..2b214d572 100644
--- a/libpod/runtime_ctr.go
+++ b/libpod/runtime_ctr.go
@@ -295,21 +295,32 @@ func (r *Runtime) setupContainer(ctx context.Context, ctr *Container) (c *Contai
 	// Maintain an array of them - we need to lock them later.
 	ctrNamedVolumes := make([]*Volume, 0, len(ctr.config.NamedVolumes))
 	for _, vol := range ctr.config.NamedVolumes {
-		// Check if it exists already
-		dbVol, err := r.state.Volume(vol.Name)
-		if err == nil {
-			ctrNamedVolumes = append(ctrNamedVolumes, dbVol)
-			// The volume exists, we're good
-			continue
-		} else if errors.Cause(err) != define.ErrNoSuchVolume {
-			return nil, errors.Wrapf(err, "error retrieving named volume %s for new container", vol.Name)
+		isAnonymous := false
+		if vol.Name == "" {
+			// Anonymous volume. We'll need to create it.
+			// It needs a name first.
+			vol.Name = stringid.GenerateNonCryptoID()
+			isAnonymous = true
+		} else {
+			// Check if it exists already
+			dbVol, err := r.state.Volume(vol.Name)
+			if err == nil {
+				ctrNamedVolumes = append(ctrNamedVolumes, dbVol)
+				// The volume exists, we're good
+				continue
+			} else if errors.Cause(err) != define.ErrNoSuchVolume {
+				return nil, errors.Wrapf(err, "error retrieving named volume %s for new container", vol.Name)
+			}
 		}
 
 		logrus.Debugf("Creating new volume %s for container", vol.Name)
 
 		// The volume does not exist, so we need to create it.
-		newVol, err := r.newVolume(ctx, WithVolumeName(vol.Name), withSetCtrSpecific(),
-			WithVolumeUID(ctr.RootUID()), WithVolumeGID(ctr.RootGID()))
+		volOptions := []VolumeCreateOption{WithVolumeName(vol.Name), WithVolumeUID(ctr.RootUID()), WithVolumeGID(ctr.RootGID())}
+		if isAnonymous {
+			volOptions = append(volOptions, withSetCtrSpecific())
+		}
+		newVol, err := r.newVolume(ctx, volOptions...)
 		if err != nil {
 			return nil, errors.Wrapf(err, "error creating named volume %q", vol.Name)
 		}