UBI: fix missing scrub when there is a bit-flip

Under some cases, when scrubbing the PEB if we did not get the lock on
the PEB it fails to scrub. Add that PEB again to the scrub list

Artem: minor amendments.

Cc: stable@kernel.org [2.6.31+]
Signed-off-by: Bhavesh Parekh <bparekh@nvidia.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

drivers/mtd/ubi/eba.c

@@ -1028,12 +1028,14 @@ int ubi_eba_copy_leb(struct ubi_device *ubi, int from, int to,
 	 * 'ubi_wl_put_peb()' function on the @ubi->move_mutex. In turn, we are
 	 * holding @ubi->move_mutex and go sleep on the LEB lock. So, if the
 	 * LEB is already locked, we just do not move it and return
-	 * %MOVE_CANCEL_RACE, which means that UBI will re-try, but later.
+	 * %MOVE_RETRY. Note, we do not return %MOVE_CANCEL_RACE here because
+	 * we do not know the reasons of the contention - it may be just a
+	 * normal I/O on this LEB, so we want to re-try.
 	 */
 	err = leb_write_trylock(ubi, vol_id, lnum);
 	if (err) {
 		dbg_wl("contention on LEB %d:%d, cancel", vol_id, lnum);
-		return MOVE_CANCEL_RACE;
+		return MOVE_RETRY;
 	}
 
 	/*

drivers/mtd/ubi/ubi.h

@@ -120,13 +120,15 @@ enum {
  *                     PEB
  * MOVE_CANCEL_BITFLIPS: canceled because a bit-flip was detected in the
  *                       target PEB
+ * MOVE_RETRY: retry scrubbing the PEB
  */
 enum {
 	MOVE_CANCEL_RACE = 1,
 	MOVE_SOURCE_RD_ERR,
 	MOVE_TARGET_RD_ERR,
 	MOVE_TARGET_WR_ERR,
 	MOVE_CANCEL_BITFLIPS,
+	MOVE_RETRY,
 };
 
 /**

drivers/mtd/ubi/wl.c

@@ -795,7 +795,10 @@ static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
 			protect = 1;
 			goto out_not_moved;
 		}
-
+		if (err == MOVE_RETRY) {
+			scrubbing = 1;
+			goto out_not_moved;
+		}
 		if (err == MOVE_CANCEL_BITFLIPS || err == MOVE_TARGET_WR_ERR ||
 		    err == MOVE_TARGET_RD_ERR) {
 			/*