UBI: prepare attach and detach functions

Prepare the attach and detach functions to by used outside of
module initialization:

* detach function checks reference count before detaching
* it kills the background thread as well
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

drivers/mtd/ubi/ubi.h

@@ -404,6 +404,7 @@ extern struct file_operations ubi_ctrl_cdev_operations;
 extern struct file_operations ubi_cdev_operations;
 extern struct file_operations ubi_vol_cdev_operations;
 extern struct class *ubi_class;
+extern struct mutex ubi_devices_mutex;
 
 /* vtbl.c */
 int ubi_change_vtbl_record(struct ubi_device *ubi, int idx,
@@ -462,6 +463,7 @@ int ubi_wl_flush(struct ubi_device *ubi);
 int ubi_wl_scrub_peb(struct ubi_device *ubi, int pnum);
 int ubi_wl_init_scan(struct ubi_device *ubi, struct ubi_scan_info *si);
 void ubi_wl_close(struct ubi_device *ubi);
+int ubi_thread(void *u);
 
 /* io.c */
 int ubi_io_read(const struct ubi_device *ubi, void *buf, int pnum, int offset,
@@ -481,6 +483,9 @@ int ubi_io_write_vid_hdr(struct ubi_device *ubi, int pnum,
 			 struct ubi_vid_hdr *vid_hdr);
 
 /* build.c */
+int ubi_attach_mtd_dev(struct mtd_info *mtd, int vid_hdr_offset,
+		       int data_offset);
+int ubi_detach_mtd_dev(int ubi_num, int anyway);
 struct ubi_device *ubi_get_device(int ubi_num);
 void ubi_put_device(struct ubi_device *ubi);
 struct ubi_device *ubi_get_by_major(int major);

drivers/mtd/ubi/wl.c

@@ -1356,7 +1356,7 @@ static void tree_destroy(struct rb_root *root)
  * ubi_thread - UBI background thread.
  * @u: the UBI device description object pointer
  */
-static int ubi_thread(void *u)
+int ubi_thread(void *u)
 {
 	int failures = 0;
 	struct ubi_device *ubi = u;
@@ -1454,18 +1454,10 @@ int ubi_wl_init_scan(struct ubi_device *ubi, struct ubi_scan_info *si)
 
 	sprintf(ubi->bgt_name, UBI_BGT_NAME_PATTERN, ubi->ubi_num);
 
-	ubi->bgt_thread = kthread_create(ubi_thread, ubi, ubi->bgt_name);
-	if (IS_ERR(ubi->bgt_thread)) {
-		err = PTR_ERR(ubi->bgt_thread);
-		ubi_err("cannot spawn \"%s\", error %d", ubi->bgt_name,
-			err);
-		return err;
-	}
-
 	err = -ENOMEM;
 	ubi->lookuptbl = kzalloc(ubi->peb_count * sizeof(void *), GFP_KERNEL);
 	if (!ubi->lookuptbl)
-		goto out_free;
+		return err;
 
 	list_for_each_entry_safe(seb, tmp, &si->erase, u.list) {
 		cond_resched();
@@ -1598,10 +1590,6 @@ static void protection_trees_destroy(struct ubi_device *ubi)
  */
 void ubi_wl_close(struct ubi_device *ubi)
 {
-	dbg_wl("disable \"%s\"", ubi->bgt_name);
-	if (ubi->bgt_thread)
-		kthread_stop(ubi->bgt_thread);
-
 	dbg_wl("close the UBI wear-leveling unit");
 
 	cancel_pending(ubi);