UBIFS: clean up free space checking

recovery.c has 'is_empty()' helper and it is better to use
this helper instead of re-implementing it in several places.
This patch does this and removes some amount of unneeded code.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Reviewed-by: Adrian Hunter <Adrian.Hunter@nokia.com>

fs/ubifs/recovery.c

@@ -357,11 +357,7 @@ static int is_last_write(const struct ubifs_info *c, void *buf, int offs)
 	empty_offs = ALIGN(offs + 1, c->min_io_size);
 	check_len = c->leb_size - empty_offs;
 	p = buf + empty_offs - offs;
-
-	for (; check_len > 0; check_len--)
-		if (*p++ != 0xff)
-			return 0;
-	return 1;
+	return is_empty(p, check_len);
 }
 
 /**
@@ -814,7 +810,7 @@ struct ubifs_scan_leb *ubifs_recover_log_leb(struct ubifs_info *c, int lnum,
 static int recover_head(const struct ubifs_info *c, int lnum, int offs,
 			void *sbuf)
 {
-	int len, err, need_clean = 0;
+	int len, err;
 
 	if (c->min_io_size > 1)
 		len = c->min_io_size;
@@ -828,19 +824,7 @@ static int recover_head(const struct ubifs_info *c, int lnum, int offs,
 
 	/* Read at the head location and check it is empty flash */
 	err = ubi_read(c->ubi, lnum, sbuf, offs, len);
-	if (err)
-		need_clean = 1;
-	else {
-		uint8_t *p = sbuf;
-
-		while (len--)
-			if (*p++ != 0xff) {
-				need_clean = 1;
-				break;
-			}
-	}
-
-	if (need_clean) {
+	if (err || !is_empty(sbuf, len)) {
 		dbg_rcvry("cleaning head at %d:%d", lnum, offs);
 		if (offs == 0)
 			return ubifs_leb_unmap(c, lnum);