f2fs: move mnt_want_write_file after arguments checking

It's needless of mnt_want_write_file for arguments checking.
Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/file.c

@@ -2037,45 +2037,37 @@ static int f2fs_ioc_defragment(struct file *filp, unsigned long arg)
 	if (!S_ISREG(inode->i_mode))
 		return -EINVAL;
 
-	err = mnt_want_write_file(filp);
-	if (err)
-		return err;
-
-	if (f2fs_readonly(sbi->sb)) {
-		err = -EROFS;
-		goto out;
-	}
+	if (f2fs_readonly(sbi->sb))
+		return -EROFS;
 
 	if (copy_from_user(&range, (struct f2fs_defragment __user *)arg,
-							sizeof(range))) {
-		err = -EFAULT;
-		goto out;
-	}
+							sizeof(range)))
+		return -EFAULT;
 
 	/* verify alignment of offset & size */
-	if (range.start & (F2FS_BLKSIZE - 1) ||
-		range.len & (F2FS_BLKSIZE - 1)) {
-		err = -EINVAL;
-		goto out;
-	}
+	if (range.start & (F2FS_BLKSIZE - 1) || range.len & (F2FS_BLKSIZE - 1))
+		return -EINVAL;
 
 	if (unlikely((range.start + range.len) >> PAGE_SHIFT >
-					sbi->max_file_blocks)) {
-		err = -EINVAL;
-		goto out;
-	}
+					sbi->max_file_blocks))
+		return -EINVAL;
+
+	err = mnt_want_write_file(filp);
+	if (err)
+		return err;
 
 	err = f2fs_defragment_range(sbi, filp, &range);
+	mnt_drop_write_file(filp);
+
 	f2fs_update_time(sbi, REQ_TIME);
 	if (err < 0)
-		goto out;
+		return err;
 
 	if (copy_to_user((struct f2fs_defragment __user *)arg, &range,
 							sizeof(range)))
-		err = -EFAULT;
-out:
-	mnt_drop_write_file(filp);
-	return err;
+		return -EFAULT;
+
+	return 0;
 }
 
 static int f2fs_move_file_range(struct file *file_in, loff_t pos_in,