better handling of memory areas duplication

fs/casio_smemfs/file.c

@@ -18,7 +18,8 @@ const struct file_operations smemfs_file_operations = {
 
 const struct mem_area_ops smemfs_mem_ops = {
 	.area_pagefault = smemfs_area_pagefault,
-	.area_release = smemfs_area_release
+	.area_release = smemfs_area_release,
+	.area_duplicate = smemfs_area_duplicate
 };
 
 
@@ -204,3 +205,10 @@ void smemfs_area_release(struct mem_area *area) {
 	// release the file, by closing it at vfs level?
 	vfs_close(area->file.filep);
 }
+
+
+int smemfs_area_duplicate(struct mem_area *orig, struct mem_area *copy) {
+	copy->file.filep->count++;
+	return 0;
+}
+

fs/casio_smemfs/file.h

@@ -32,5 +32,6 @@ int smemfs_area_resize(struct mem_area *area, const struct mem_area *new_area);
 
 void smemfs_area_release(struct mem_area *area);
 
+int smemfs_area_duplicate(struct mem_area *orig, struct mem_area *copy);
 
 #endif //_FS_SMEMFS_FILE_H

sys/mem_area.h

@@ -95,6 +95,11 @@ struct mem_area_ops {
 	 * Called when the area is no longer used.
 	 */
 	void (*area_release)(struct mem_area *area);
+
+	/**
+	 * Called when the area is duplicated, like during a fork.
+	 */
+	int (*area_duplicate)(struct mem_area *orig, struct mem_area *copy);
 };
 
 
@@ -181,6 +186,20 @@ extern inline void mem_area_release(struct mem_area *area) {
 int mem_area_resize(struct mem_area *area, size_t new_size, struct process *proc);
 
 
+/**
+ * Duplicate an area.
+ */
+extern inline struct mem_area *mem_area_clone(struct mem_area *area) {
+	struct mem_area *ret = mem_area_alloc();
+	if(ret != NULL) {
+		*ret = *area;
+		if(area->ops != NULL && area->ops->area_duplicate != NULL)
+			area->ops->area_duplicate(area, ret);
+	}
+	return ret;
+}
+
+
 /**
  * Helper for filesystem implementations, to handle MEM_AREA_PARTIAL.
  * Check for a given page to fill with 0 when needed, and return the number of

sys/process.c

@@ -279,15 +279,14 @@ pid_t sys_fork() {
 
 	// copy each memory area
 	struct list_head *area_list;
+	newproc->heap_area = NULL;
 
 	list_for_each(area_list, & cur->mem_areas) {
 		// duplicate it
-		// FIXME file should be duplicated? Or a counter need to be used?
 		struct mem_area *old_area = container_of(area_list, struct mem_area, list);
 		struct mem_area *new_area;
 		
-		new_area = mem_area_alloc();
-		*new_area = *old_area;
+		new_area = mem_area_clone(old_area);
 		mem_area_insert(newproc, new_area);
 
 		// check for heap, and translate to corresponding area