UBIFS: small amendments in the LEB scanning code

This patch fixes few minor things I've spotted while going through
code:

1. Better document return codes
2. If 'ubifs_scan_a_node()' returns some thing we do not expect,
   treat this as an error.
3. Try to do recovery only when 'ubifs_scan()' returns %-EUCLEAN,
   not on any error.
4. If empty space starts at a non-aligned address, print a message.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Reviewed-by: Adrian Hunter <Adrian.Hunter@nokia.com>

fs/ubifs/recovery.c

@@ -543,8 +543,8 @@ static int drop_incomplete_group(struct ubifs_scan_leb *sleb, int *offs)
  *
  * This function does a scan of a LEB, but caters for errors that might have
  * been caused by the unclean unmount from which we are attempting to recover.
- *
- * This function returns %0 on success and a negative error code on failure.
+ * Returns %0 in case of success, %-EUCLEAN if an unrecoverable corruption is
+ * found, and a negative error code in case of failure.
  */
 struct ubifs_scan_leb *ubifs_recover_leb(struct ubifs_info *c, int lnum,
 					 int offs, void *sbuf, int grouped)
@@ -643,7 +643,8 @@ struct ubifs_scan_leb *ubifs_recover_leb(struct ubifs_info *c, int lnum,
 			goto corrupted;
 		default:
 			dbg_err("unknown");
-			goto corrupted;
+			err = -EINVAL;
+			goto error;
 		}
 	}
 

fs/ubifs/replay.c

@@ -837,9 +837,10 @@ static int replay_log_leb(struct ubifs_info *c, int lnum, int offs, void *sbuf)
 
 	dbg_mnt("replay log LEB %d:%d", lnum, offs);
 	sleb = ubifs_scan(c, lnum, offs, sbuf);
-	if (IS_ERR(sleb)) {
-		if (c->need_recovery)
-			sleb = ubifs_recover_log_leb(c, lnum, offs, sbuf);
+	if (IS_ERR(sleb) ) {
+		if (PTR_ERR(sleb) != -EUCLEAN || !c->need_recovery)
+			return PTR_ERR(sleb);
+		sleb = ubifs_recover_log_leb(c, lnum, offs, sbuf);
 		if (IS_ERR(sleb))
 			return PTR_ERR(sleb);
 	}

fs/ubifs/scan.c

@@ -256,7 +256,9 @@ void ubifs_scanned_corruption(const struct ubifs_info *c, int lnum, int offs,
  * @sbuf: scan buffer (must be c->leb_size)
  *
  * This function scans LEB number @lnum and returns complete information about
- * its contents. Returns an error code in case of failure.
+ * its contents. Returns the scaned information in case of success and,
+ * %-EUCLEAN if the LEB neads recovery, and other negative error codes in case
+ * of failure.
  */
 struct ubifs_scan_leb *ubifs_scan(const struct ubifs_info *c, int lnum,
 				  int offs, void *sbuf)
@@ -279,7 +281,6 @@ struct ubifs_scan_leb *ubifs_scan(const struct ubifs_info *c, int lnum,
 		cond_resched();
 
 		ret = ubifs_scan_a_node(c, buf, len, lnum, offs, 0);
-
 		if (ret > 0) {
 			/* Padding bytes or a valid padding node */
 			offs += ret;
@@ -304,7 +305,8 @@ struct ubifs_scan_leb *ubifs_scan(const struct ubifs_info *c, int lnum,
 			goto corrupted;
 		default:
 			dbg_err("unknown");
-			goto corrupted;
+			err = -EINVAL;
+			goto error;
 		}
 
 		err = ubifs_add_snod(c, sleb, buf, offs);
@@ -317,8 +319,10 @@ struct ubifs_scan_leb *ubifs_scan(const struct ubifs_info *c, int lnum,
 		len -= node_len;
 	}
 
-	if (offs % c->min_io_size)
-		goto corrupted;
+	if (offs % c->min_io_size) {
+		ubifs_err("empty space starts at non-aligned offset %d", offs);
+		goto corrupted;;
+	}
 
 	ubifs_end_scan(c, sleb, lnum, offs);