snapshotter: support "remap-ids" capability for overlayfs

Previously remapping of a snapshotter has been done using
recursive chown.

Commit
31a6449734 added a support
for "remap-ids" capability which allows snapshotter internals do
remappings in case of idmapped mounts support to avoid recursive
chown and creating a new remapped snapshot.

Signed-off-by: Ilya Hanov <ilya.hanov@huawei-partners.com>

snapshots/overlay/plugin/plugin.go

@@ -24,6 +24,11 @@ import (
 	"github.com/containerd/containerd/platforms"
 	"github.com/containerd/containerd/plugin"
 	"github.com/containerd/containerd/snapshots/overlay"
+	"github.com/containerd/containerd/snapshots/overlay/overlayutils"
+)
+
+const (
+	capaRemapIds = "remap-ids"
 )
 
 // Config represents configuration for the overlay plugin.
@@ -66,6 +71,10 @@ func init() {
 			if len(config.MountOptions) > 0 {
 				oOpts = append(oOpts, overlay.WithMountOptions(config.MountOptions))
 			}
+			if ok, err := overlayutils.SupportsIDMappedMounts(); err == nil && ok {
+				oOpts = append(oOpts, overlay.WithRemapIds)
+				ic.Meta.Capabilities = append(ic.Meta.Capabilities, capaRemapIds)
+			}
 
 			ic.Meta.Exports["root"] = root
 			return overlay.NewSnapshotter(root, oOpts...)