pstree: Move struct pid to pstree.h

I believe this make sense to keep this structure
in pstree.h where pstree related data lives.

Also I've added some comments on struct pid members.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/crtools.h

@@ -221,12 +221,6 @@ struct rst_info {
 	struct list_head	tty_slaves;
 };
 
-struct pid
-{
-	pid_t real;		/* used to peek/poke tasks during dump stage */
-	pid_t virt;		/* used all over in the images and saved after restore */
-};
-
 static inline int in_vma_area(struct vma_area *vma, unsigned long addr)
 {
 	return addr >= (unsigned long)vma->vma.start &&

include/namespaces.h

@@ -2,6 +2,7 @@
 #define __CR_NS_H__
 
 #include "crtools.h"
+#include "pstree.h"
 
 int dump_namespaces(struct pid *pid, unsigned int ns_flags);
 int prepare_namespace(int pid, unsigned long clone_flags);

include/pstree.h

@@ -3,6 +3,22 @@
 #include "list.h"
 #include "crtools.h"
 
+struct pid {
+	/*
+	 * The @real pid is used to fetch tasks during dumping stage,
+	 * This is a global pid seen from the context where the dumping
+	 * is running.
+	 */
+	pid_t real;
+
+	/*
+	 * The @virt pid is one which used in the image itself and keeps
+	 * the pid value to be restored. This pid fetched from the
+	 * dumpee context, because the dumpee might have own pid namespace.
+	 */
+	pid_t virt;
+};
+
 struct pstree_item {
 	struct pstree_item	*parent;
 	struct list_head	children;	/* list of my children */

parasite-syscall.c

@@ -12,6 +12,7 @@
 #include "parasite.h"
 #include "crtools.h"
 #include "namespaces.h"
+#include "pstree.h"
 
 #include "protobuf.h"
 #include "protobuf/sa.pb-c.h"