[MTD] mtdpart: Make ecc_stats more realistic.

In the existing implementation, ecc_stats fields are incremented only by
one, regardless of master mtd errors number. For example, if there are N
errors were corrected by ECC, partition ecc_stats.corrected will be
incremented by one.

This commit changes simple increment to sum of old value and parent mtd
error count.

Signed-off-by: Yauhen Kharuzhy <jekhor@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/mtdpart.c

@@ -48,8 +48,11 @@ static int part_read(struct mtd_info *mtd, loff_t from, size_t len,
 		size_t *retlen, u_char *buf)
 {
 	struct mtd_part *part = PART(mtd);
+	struct mtd_ecc_stats stats;
 	int res;
 
+	stats = part->master->ecc_stats;
+
 	if (from >= mtd->size)
 		len = 0;
 	else if (from + len > mtd->size)
@@ -58,9 +61,9 @@ static int part_read(struct mtd_info *mtd, loff_t from, size_t len,
 				   len, retlen, buf);
 	if (unlikely(res)) {
 		if (res == -EUCLEAN)
-			mtd->ecc_stats.corrected++;
+			mtd->ecc_stats.corrected += part->master->ecc_stats.corrected - stats.corrected;
 		if (res == -EBADMSG)
-			mtd->ecc_stats.failed++;
+			mtd->ecc_stats.failed += part->master->ecc_stats.failed - stats.failed;
 	}
 	return res;
 }