UBI: modify ubi_wl_flush function to clear work queue for a lnum

This patch modifies ubi_wl_flush to force the erasure of
particular volume id / logical eraseblock number pairs. Previous functionality
is preserved when passing UBI_ALL for both values. The locations where ubi_wl_flush
were called are appropriately changed: ubi_leb_erase only flushes for the
erased LEB, and ubi_create_volume forces only flushing for its volume id.
External code can call this new feature via the new function ubi_flush() added
to kapi.c, which simply passes through to ubi_wl_flush().

This was tested by disabling the call to do_work in ubi thread, which results
in the work queue remaining unless explicitly called to remove. UBIFS was
changed to call ubifs_leb_change 50 times for four different LEBs. Then the
new function was called to clear the queue: passing wrong volume ids / lnum,
correct ones, and finally UBI_ALL for both to ensure it was finally all
cleard. The work queue was dumped each time and the selective removal
of the particular LEB numbers was observed. Extra checks were enabled and
ubifs's integck was also run. Finally, the drive was repeatedly filled and
emptied to ensure that the queue was cleared normally.

Artem: amended the patch.

Signed-off-by: Joel Reardon <[e-mail]>
Signed-off-by: Artem Bityutskiy <[e-mail]>

drivers/mtd/ubi/cdev.c

···
 		if (err)
 			break;
 
-		err = ubi_wl_flush(ubi);
+		err = ubi_wl_flush(ubi, UBI_ALL, UBI_ALL);
 		break;
 	}
 

drivers/mtd/ubi/kapi.c

···
 	if (err)
 		return err;
 
-	return ubi_wl_flush(ubi);
+	return ubi_wl_flush(ubi, vol->vol_id, lnum);
 }
 EXPORT_SYMBOL_GPL(ubi_leb_erase);
 
···
 	return 0;
 }
 EXPORT_SYMBOL_GPL(ubi_sync);
+
+/**
+ * ubi_flush - flush UBI work queue.
+ * @ubi_num: UBI device to flush work queue
+ * @vol_id: volume id to flush for
+ * @lnum: logical eraseblock number to flush for
+ *
+ * This function executes all pending works for a particular volume id / logical
+ * eraseblock number pair. If either value is set to %UBI_ALL, then it acts as
+ * a wildcard for all of the corresponding volume numbers or logical
+ * eraseblock numbers. It returns zero in case of success and a negative error
+ * code in case of failure.
+ */
+int ubi_flush(int ubi_num, int vol_id, int lnum)
+{
+	struct ubi_device *ubi;
+	int err = 0;
+
+	ubi = ubi_get_device(ubi_num);
+	if (!ubi)
+		return -ENODEV;
+
+	err = ubi_wl_flush(ubi, vol_id, lnum);
+	ubi_put_device(ubi);
+	return err;
+}
+EXPORT_SYMBOL_GPL(ubi_flush);
 
 BLOCKING_NOTIFIER_HEAD(ubi_notifiers);
 

drivers/mtd/ubi/ubi.h

···
 int ubi_wl_get_peb(struct ubi_device *ubi);
 int ubi_wl_put_peb(struct ubi_device *ubi, int vol_id, int lnum,
 		   int pnum, int torture);
-int ubi_wl_flush(struct ubi_device *ubi);
+int ubi_wl_flush(struct ubi_device *ubi, int vol_id, int lnum);
 int ubi_wl_scrub_peb(struct ubi_device *ubi, int pnum);
 int ubi_wl_init(struct ubi_device *ubi, struct ubi_attach_info *ai);
 void ubi_wl_close(struct ubi_device *ubi);

drivers/mtd/ubi/upd.c

···
 	}
 
 	if (bytes == 0) {
-		err = ubi_wl_flush(ubi);
+		err = ubi_wl_flush(ubi, UBI_ALL, UBI_ALL);
 		if (err)
 			return err;
 
···
 
 	ubi_assert(vol->upd_received <= vol->upd_bytes);
 	if (vol->upd_received == vol->upd_bytes) {
-		err = ubi_wl_flush(ubi);
+		err = ubi_wl_flush(ubi, UBI_ALL, UBI_ALL);
 		if (err)
 			return err;
 		/* The update is finished, clear the update marker */

drivers/mtd/ubi/vmt.c

···
 	 * Finish all pending erases because there may be some LEBs belonging
 	 * to the same volume ID.
 	 */
-	err = ubi_wl_flush(ubi);
+	err = ubi_wl_flush(ubi, vol_id, UBI_ALL);
 	if (err)
 		goto out_acc;
 

drivers/mtd/ubi/wl.c

···
 /**
  * ubi_wl_flush - flush all pending works.
  * @ubi: UBI device description object
+ * @vol_id: the volume id to flush for
+ * @lnum: the logical eraseblock number to flush for
  *
- * This function returns zero in case of success and a negative error code in
- * case of failure.
+ * This function executes all pending works for a particular volume id /
+ * logical eraseblock number pair. If either value is set to %UBI_ALL, then it
+ * acts as a wildcard for all of the corresponding volume numbers or logical
+ * eraseblock numbers. It returns zero in case of success and a negative error
+ * code in case of failure.
  */
-int ubi_wl_flush(struct ubi_device *ubi)
+int ubi_wl_flush(struct ubi_device *ubi, int vol_id, int lnum)
 {
-	int err;
+	int err = 0;
+	int found = 1;
 
 	/*
 	 * Erase while the pending works queue is not empty, but not more than
 	 * the number of currently pending works.
 	 */
-	dbg_wl("flush (%d pending works)", ubi->works_count);
-	while (ubi->works_count) {
-		err = do_work(ubi);
-		if (err)
-			return err;
-	}
+	dbg_wl("flush pending work for LEB %d:%d (%d pending works)",
+	       vol_id, lnum, ubi->works_count);
 
-	/*
-	 * Make sure all the works which have been done in parallel are
-	 * finished.
-	 */
 	down_write(&ubi->work_sem);
-	up_write(&ubi->work_sem);
+	while (found) {
+		struct ubi_work *wrk;
+		found = 0;
 
-	/*
-	 * And in case last was the WL worker and it canceled the LEB
-	 * movement, flush again.
-	 */
-	while (ubi->works_count) {
-		dbg_wl("flush more (%d pending works)", ubi->works_count);
-		err = do_work(ubi);
-		if (err)
-			return err;
+		spin_lock(&ubi->wl_lock);
+		list_for_each_entry(wrk, &ubi->works, list) {
+			if ((vol_id == UBI_ALL || wrk->vol_id == vol_id) &&
+			    (lnum == UBI_ALL || wrk->lnum == lnum)) {
+				list_del(&wrk->list);
+				ubi->works_count -= 1;
+				ubi_assert(ubi->works_count >= 0);
+				spin_unlock(&ubi->wl_lock);
+
+				err = wrk->func(ubi, wrk, 0);
+				if (err)
+					goto out;
+				spin_lock(&ubi->wl_lock);
+				found = 1;
+				break;
+			}
+		}
+		spin_unlock(&ubi->wl_lock);
 	}
 
-	return 0;
+out:
+	up_write(&ubi->work_sem);
+	return err;
 }
 
 /**

include/linux/mtd/ubi.h

···
 int ubi_leb_map(struct ubi_volume_desc *desc, int lnum);
 int ubi_is_mapped(struct ubi_volume_desc *desc, int lnum);
 int ubi_sync(int ubi_num);
+int ubi_flush(int ubi_num, int vol_id, int lnum);
 
 /*
  * This function is the same as the 'ubi_leb_read()' function, but it does not