ext4: MMP: fix error message rate-limiting logic in kmmpd

Current logic would print an error message only once, and then
'failed_writes' would stay at 1.  Rework the loop to increment
'failed_writes' and print the error message every
s_mmp_update_interval * 60 seconds, as intended according to the
comment.

Signed-off-by: Nikitas Angelinas <nikitas_angelinas@xyratex.com>
Signed-off-by: Andrew Perepechko <andrew_perepechko@xyratex.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Acked-by: Andreas Dilger <adilger@dilger.ca>

fs/ext4/mmp.c

@@ -125,8 +125,9 @@ static int kmmpd(void *data)
 		 * Don't spew too many error messages. Print one every
 		 * (s_mmp_update_interval * 60) seconds.
 		 */
-		if (retval && (failed_writes % 60) == 0) {
-			ext4_error(sb, "Error writing to MMP block");
+		if (retval) {
+			if ((failed_writes % 60) == 0)
+				ext4_error(sb, "Error writing to MMP block");
 			failed_writes++;
 		}