ubi: Deal with interrupted erasures in WL

BugLink: http://bugs.launchpad.net/bugs/1637510

commit 23654188 upstream.

When Fastmap is used we can face here an -EBADMSG
since Fastmap cannot know about unmaps.
If the erasure was interrupted the PEB may show ECC
errors and UBI would go to ro-mode as it assumes
that the PEB was check during attach time, which is
not the case with Fastmap.

Fixes: dbb7d2a8 ("UBI: Add fastmap core")
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/mtd/ubi/wl.c

@@ -643,7 +643,7 @@ static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
 				int shutdown)
 {
 	int err, scrubbing = 0, torture = 0, protect = 0, erroneous = 0;
-	int vol_id = -1, lnum = -1;
+	int erase = 0, keep = 0, vol_id = -1, lnum = -1;
 #ifdef CONFIG_MTD_UBI_FASTMAP
 	int anchor = wrk->anchor;
 #endif
@@ -777,6 +777,16 @@ static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
 			       e1->pnum);
 			scrubbing = 1;
 			goto out_not_moved;
+		} else if (ubi->fast_attach && err == UBI_IO_BAD_HDR_EBADMSG) {
+			/*
+			 * While a full scan would detect interrupted erasures
+			 * at attach time we can face them here when attached from
+			 * Fastmap.
+			 */
+			dbg_wl("PEB %d has ECC errors, maybe from an interrupted erasure",
+			       e1->pnum);
+			erase = 1;
+			goto out_not_moved;
 		}
 
 		ubi_err(ubi, "error %d while reading VID header from PEB %d",
@@ -810,6 +820,7 @@ static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
 			 * Target PEB had bit-flips or write error - torture it.
 			 */
 			torture = 1;
+			keep = 1;
 			goto out_not_moved;
 		}
 
@@ -895,7 +906,7 @@ static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
 		ubi->erroneous_peb_count += 1;
 	} else if (scrubbing)
 		wl_tree_add(e1, &ubi->scrub);
-	else
+	else if (keep)
 		wl_tree_add(e1, &ubi->used);
 	ubi_assert(!ubi->move_to_put);
 	ubi->move_from = ubi->move_to = NULL;
@@ -907,6 +918,12 @@ static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
 	if (err)
 		goto out_ro;
 
+	if (erase) {
+		err = do_sync_erase(ubi, e1, vol_id, lnum, 1);
+		if (err)
+			goto out_ro;
+	}
+
 	mutex_unlock(&ubi->move_mutex);
 	return 0;