diff --git a/fs/udf/file.c b/fs/udf/file.c
index 6834509a7e5a..ccab8b78e363 100644
--- a/fs/udf/file.c
+++ b/fs/udf/file.c
@@ -120,36 +120,11 @@ static ssize_t udf_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	ssize_t retval;
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file_inode(file);
-	int err, pos;
 	size_t count = iov_iter_count(from);
 	struct udf_inode_info *iinfo = UDF_I(inode);
+	int err;
 
 	mutex_lock(&inode->i_mutex);
-	down_write(&iinfo->i_data_sem);
-	if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
-		if (file->f_flags & O_APPEND)
-			pos = inode->i_size;
-		else
-			pos = iocb->ki_pos;
-
-		if (inode->i_sb->s_blocksize <
-				(udf_file_entry_alloc_offset(inode) +
-						pos + count)) {
-			err = udf_expand_file_adinicb(inode);
-			if (err) {
-				mutex_unlock(&inode->i_mutex);
-				udf_debug("udf_expand_adinicb: err=%d\n", err);
-				return err;
-			}
-		} else {
-			if (pos + count > inode->i_size)
-				iinfo->i_lenAlloc = pos + count;
-			else
-				iinfo->i_lenAlloc = inode->i_size;
-			up_write(&iinfo->i_data_sem);
-		}
-	} else
-		up_write(&iinfo->i_data_sem);
 
 	retval = generic_write_checks(file, &iocb->ki_pos, &count);
 	if (retval)
@@ -160,6 +135,25 @@ static ssize_t udf_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 
 	iov_iter_truncate(from, count);
 
+	down_write(&iinfo->i_data_sem);
+	if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
+		loff_t end = iocb->ki_pos + iov_iter_count(from);
+
+		if (inode->i_sb->s_blocksize <
+				(udf_file_entry_alloc_offset(inode) + end)) {
+			err = udf_expand_file_adinicb(inode);
+			if (err) {
+				mutex_unlock(&inode->i_mutex);
+				udf_debug("udf_expand_adinicb: err=%d\n", err);
+				return err;
+			}
+		} else {
+			iinfo->i_lenAlloc = max(end, inode->i_size);
+			up_write(&iinfo->i_data_sem);
+		}
+	} else
+		up_write(&iinfo->i_data_sem);
+
 	retval = __generic_file_write_iter(iocb, from);
 out:
 	mutex_unlock(&inode->i_mutex);