Fix some issues about mmp

index cebea4270817..12af6dc8457b 100644
@@ -122,6 +122,21 @@ void __dump_mmp_msg(struct super_block *sb, struct mmp_struct *mmp,
 		       (int)sizeof(mmp->mmp_bdevname), mmp->mmp_bdevname);
 }
 
+/*
+ * Get a random new sequence number but make sure it is not greater than
+ * EXT4_MMP_SEQ_MAX.
+ */
+static unsigned int mmp_new_seq(void)
+{
+	u32 new_seq;
+
+	do {
+		new_seq = prandom_u32();
+	} while (new_seq > EXT4_MMP_SEQ_MAX);
+
+	return new_seq;
+}
+
 /*
  * kmmpd will update the MMP sequence every s_mmp_update_interval seconds
  */

@@ -132,7 +147,7 @@ static int kmmpd(void *data)
 	struct buffer_head *bh = EXT4_SB(sb)->s_mmp_bh;
 	struct mmp_struct *mmp;
 	ext4_fsblk_t mmp_block;
-	u32 seq = 0;
+	u32 seq = mmp_new_seq();
 	unsigned long failed_writes = 0;
 	int mmp_update_interval = le16_to_cpu(es->s_mmp_update_interval);
 	unsigned mmp_check_interval;

@@ -258,21 +273,6 @@ void ext4_stop_mmpd(struct ext4_sb_info *sbi)
 	}
 }
 
-/*
- * Get a random new sequence number but make sure it is not greater than
- * EXT4_MMP_SEQ_MAX.
- */
-static unsigned int mmp_new_seq(void)
-{
-	u32 new_seq;
-
-	do {
-		new_seq = prandom_u32();
-	} while (new_seq > EXT4_MMP_SEQ_MAX);
-
-	return new_seq;
-}
-
 /*
  * Protect the filesystem from being mounted more than once.
  */

index 12af6dc8457b..89797f12a815 100644
@@ -152,6 +152,7 @@ static int kmmpd(void *data)
 	int mmp_update_interval = le16_to_cpu(es->s_mmp_update_interval);
 	unsigned mmp_check_interval;
 	unsigned long last_update_time;
+	unsigned long last_check_time;
 	unsigned long diff;
 	int retval = 0;
 

@@ -170,6 +171,7 @@ static int kmmpd(void *data)
 
 	memcpy(mmp->mmp_nodename, init_utsname()->nodename,
 	       sizeof(mmp->mmp_nodename));
+	last_update_time = jiffies;
 
 	while (!kthread_should_stop() && !sb_rdonly(sb)) {
 		if (!ext4_has_feature_mmp(sb)) {

@@ -198,17 +200,18 @@ static int kmmpd(void *data)
 		}
 
 		diff = jiffies - last_update_time;
-		if (diff < mmp_update_interval * HZ)
+		if (diff < mmp_update_interval * HZ) {
 			schedule_timeout_interruptible(mmp_update_interval *
 						       HZ - diff);
+			diff = jiffies - last_update_time;
+		}
 
 		/*
 		 * We need to make sure that more than mmp_check_interval
-		 * seconds have not passed since writing. If that has happened
-		 * we need to check if the MMP block is as we left it.
+		 * seconds have not passed since check. If that has happened
+		 * we need to check if the MMP block is as we write it.
 		 */
-		diff = jiffies - last_update_time;
-		if (diff > mmp_check_interval * HZ) {
+		if (jiffies - last_check_time > mmp_check_interval * HZ) {
 			struct buffer_head *bh_check = NULL;
 			struct mmp_struct *mmp_check;
 

@@ -234,6 +237,7 @@ static int kmmpd(void *data)
 				goto wait_to_exit;
 			}
 			put_bh(bh_check);
+			last_check_time = jiffies;
 		}
 
 		 /*

index 89797f12a815..0fe7b9ac9db6 100644
@@ -154,6 +154,7 @@ static int kmmpd(void *data)
 	unsigned long last_update_time;
 	unsigned long last_check_time;
 	unsigned long diff;
+	char nodename[64];
 	int retval = 0;
 
 	mmp_block = le64_to_cpu(es->s_mmp_block);

@@ -169,8 +170,8 @@ static int kmmpd(void *data)
 	BUILD_BUG_ON(sizeof(mmp->mmp_bdevname) < BDEVNAME_SIZE);
 	bdevname(bh->b_bdev, mmp->mmp_bdevname);
 
-	memcpy(mmp->mmp_nodename, init_utsname()->nodename,
-	       sizeof(mmp->mmp_nodename));
+	memcpy(nodename, init_utsname()->nodename, sizeof(nodename));
+	memcpy(mmp->mmp_nodename, nodename, sizeof(mmp->mmp_nodename));
 	last_update_time = jiffies;
 
 	while (!kthread_should_stop() && !sb_rdonly(sb)) {

@@ -224,8 +225,8 @@ static int kmmpd(void *data)
 			}
 
 			mmp_check = (struct mmp_struct *)(bh_check->b_data);
-			if (mmp->mmp_seq != mmp_check->mmp_seq ||
-			    memcmp(mmp->mmp_nodename, mmp_check->mmp_nodename,
+			if (seq != mmp_check->mmp_seq ||
+			    memcmp(nodename, mmp_check->mmp_nodename,
 				   sizeof(mmp->mmp_nodename))) {
 				dump_mmp_msg(sb, mmp_check,
 					     "Error while updating MMP info. "

index 0fe7b9ac9db6..2a1473e4a9de 100644
@@ -213,10 +213,7 @@ static int kmmpd(void *data)
 		 * we need to check if the MMP block is as we write it.
 		 */
 		if (jiffies - last_check_time > mmp_check_interval * HZ) {
-			struct buffer_head *bh_check = NULL;
-			struct mmp_struct *mmp_check;
-
-			retval = read_mmp_block(sb, &bh_check, mmp_block);
+			retval = read_mmp_block(sb, &bh, mmp_block);
 			if (retval) {
 				ext4_error_err(sb, -retval,
 					       "error reading MMP data: %d",

@@ -224,20 +221,18 @@ static int kmmpd(void *data)
 				goto wait_to_exit;
 			}
 
-			mmp_check = (struct mmp_struct *)(bh_check->b_data);
-			if (seq != mmp_check->mmp_seq ||
-			    memcmp(nodename, mmp_check->mmp_nodename,
-				   sizeof(mmp->mmp_nodename))) {
-				dump_mmp_msg(sb, mmp_check,
+			mmp = (struct mmp_struct *)(bh->b_data);
+			if (seq != le32_to_cpu(mmp->mmp_seq) ||
+			    memcmp(nodename, mmp->mmp_nodename,
+				    sizeof(nodename))) {
+				dump_mmp_msg(sb, mmp,
 					     "Error while updating MMP info. "
 					     "The filesystem seems to have been"
 					     " multiply mounted.");
 				ext4_error_err(sb, EBUSY, "abort");
-				put_bh(bh_check);
 				retval = -EBUSY;
 				goto wait_to_exit;
 			}
-			put_bh(bh_check);
 			last_check_time = jiffies;
 		}
 

index 2a1473e4a9de..eed854bb6194 100644
@@ -218,6 +218,7 @@ static int kmmpd(void *data)
 				ext4_error_err(sb, -retval,
 					       "error reading MMP data: %d",
 					       retval);
+				EXT4_SB(sb)->s_mmp_bh = NULL;
 				goto wait_to_exit;
 			}
 

index eed854bb6194..41c0a03019db 100644
@@ -205,6 +205,14 @@ static int kmmpd(void *data)
 			schedule_timeout_interruptible(mmp_update_interval *
 						       HZ - diff);
 			diff = jiffies - last_update_time;
+			/* If 'diff' little 'than mmp_update_interval * HZ', it
+			 * means someone call ext4_stop_mmpd to stop kmmpd
+			 * kthread. We don't need to update mmp_check_interval
+			 * any more, as 'diff' is not exact value.
+			 */
+			if (unlikely(diff < mmp_update_interval * HZ &&
+			    kthread_should_stop()))
+				break;
 		}
 
 		/*