rbd: rbd-nbd logging the ceph-CSI way

- One logfile per device/volume
- Add ability to customize the logdir, default: /var/log/ceph

Note: if user customizes the hostpath to something else other than default
/var/log/ceph, then it is his responsibility to update the `cephLogDir`
in storageclass to reflect the same with daemon:

```
cephLogDir: "/var/log/mynewpath"
```

Signed-off-by: Prasanna Kumar Kalever <prasanna.kalever@redhat.com>

examples/rbd/storageclass.yaml

@@ -69,6 +69,12 @@ parameters:
    # on supported nodes
    # mounter: rbd-nbd
 
+   # (optional) ceph client log location, eg: rbd-nbd
+   # By default host-path /var/log/ceph of node is bind-mounted into
+   # csi-rbdplugin pod at /var/log/ceph mount path. See docs/rbd-nbd.md
+   # for available configuration options.
+   # cephLogDir: /var/log/ceph
+
    # (optional) Prefix to use for naming RBD images.
    # If omitted, defaults to "csi-vol-".
    # volumeNamePrefix: "foo-bar-"

internal/rbd/nodeserver.go

@@ -274,6 +274,7 @@ func (ns *NodeServer) NodeStageVolume(
 	volOptions.MapOptions = req.GetVolumeContext()["mapOptions"]
 	volOptions.UnmapOptions = req.GetVolumeContext()["unmapOptions"]
 	volOptions.Mounter = req.GetVolumeContext()["mounter"]
+	volOptions.LogDir = req.GetVolumeContext()["cephLogDir"]
 
 	err = volOptions.Connect(cr)
 	if err != nil {

internal/rbd/rbd_attach.go

@@ -296,6 +296,14 @@ func createPath(ctx context.Context, volOpt *rbdVolume, device string, cr *util.
 		util.WarningLog(ctx, "failed to detect if image %q is thick-provisioned: %v", volOpt, err)
 	}
 
+	if isNbd {
+		if volOpt.LogDir == "" {
+			volOpt.LogDir = defaultLogDir
+		}
+		mapArgs = append(mapArgs, "--log-file",
+			getCephClientLogFileName(volOpt.VolID, volOpt.LogDir, "rbd-nbd"))
+	}
+
 	cli := rbd
 	if device != "" {
 		// TODO: use rbd cli for attach/detach in the future

internal/rbd/rbd_util.go

@@ -50,6 +50,7 @@ const (
 	rbdImageWatcherSteps     = 10
 	rbdDefaultMounter        = "rbd"
 	rbdNbdMounter            = "rbd-nbd"
+	defaultLogDir            = "/var/log/ceph"
 
 	// Output strings returned during invocation of "ceph rbd task add remove <imagespec>" when
 	// command is not supported by ceph manager. Used to check errors and recover when the command
@@ -136,6 +137,7 @@ type rbdVolume struct {
 	ReservedID         string
 	MapOptions         string
 	UnmapOptions       string
+	LogDir             string
 	VolName            string `json:"volName"`
 	MonValueFromSecret string `json:"monValueFromSecret"`
 	VolSize            int64  `json:"volSize"`
@@ -2002,3 +2004,16 @@ func (ri *rbdImage) addSnapshotScheduling(
 
 	return nil
 }
+
+// getCephClientLogFileName compiles the complete log file path based on inputs.
+func getCephClientLogFileName(id, logDir, prefix string) string {
+	if prefix == "" {
+		prefix = "ceph"
+	}
+
+	if logDir == "" {
+		logDir = defaultLogDir
+	}
+
+	return fmt.Sprintf("%s/%s-%s.log", logDir, prefix, id)
+}