ext4: miscellaneous error checks and coding cleanups for mballoc

ext4_mb_seq_history_open(): check if sbi->s_mb_history is NULL

ext4_mb_history_init(): replace kmalloc and memset with kzalloc

ext4_mb_init_backend(): remove memset since kzalloc is used

ext4_mb_init(): the return value of ext4_mb_init_backend is int,
	but i is unsigned, replace it with a new int variable.
Signed-off-by: NShen Feng <shen@cn.fujitsu.com>
Reviewed-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NMingming Cao <cmm@us.ibm.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

fs/ext4/mballoc.c

@@ -1985,6 +1985,8 @@ static int ext4_mb_seq_history_open(struct inode *inode, struct file *file)
 	int rc;
 	int size;
 
+	if (unlikely(sbi->s_mb_history == NULL))
+		return -ENOMEM;
 	s = kmalloc(sizeof(*s), GFP_KERNEL);
 	if (s == NULL)
 		return -ENOMEM;
@@ -2187,9 +2189,7 @@ static void ext4_mb_history_init(struct super_block *sb)
 	sbi->s_mb_history_cur = 0;
 	spin_lock_init(&sbi->s_mb_history_lock);
 	i = sbi->s_mb_history_max * sizeof(struct ext4_mb_history);
-	sbi->s_mb_history = kmalloc(i, GFP_KERNEL);
-	if (likely(sbi->s_mb_history != NULL))
-		memset(sbi->s_mb_history, 0, i);
+	sbi->s_mb_history = kzalloc(i, GFP_KERNEL);
 	/* if we can't allocate history, then we simple won't use it */
 }
 
@@ -2303,7 +2303,6 @@ static int ext4_mb_init_backend(struct super_block *sb)
 			i++;
 			goto err_freebuddy;
 		}
-		memset(meta_group_info[j], 0, len);
 		set_bit(EXT4_GROUP_INFO_NEED_INIT_BIT,
 			&(meta_group_info[j]->bb_state));
 
@@ -2358,6 +2357,7 @@ int ext4_mb_init(struct super_block *sb, int needs_recovery)
 	unsigned i;
 	unsigned offset;
 	unsigned max;
+	int ret;
 
 	if (!test_opt(sb, MBALLOC))
 		return 0;
@@ -2392,12 +2392,12 @@ int ext4_mb_init(struct super_block *sb, int needs_recovery)
 	} while (i <= sb->s_blocksize_bits + 1);
 
 	/* init file for buddy data */
-	i = ext4_mb_init_backend(sb);
-	if (i) {
+	ret = ext4_mb_init_backend(sb);
+	if (ret != 0) {
 		clear_opt(sbi->s_mount_opt, MBALLOC);
 		kfree(sbi->s_mb_offsets);
 		kfree(sbi->s_mb_maxs);
-		return i;
+		return ret;
 	}
 
 	spin_lock_init(&sbi->s_md_lock);