udf: Provide function for calculating dir entry length

Provide function for calculating directory entry length and use to
reduce code duplication.

Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/udf/udfdecl.h b/fs/udf/udfdecl.h
index bae311b..ed890bc 100644
--- a/fs/udf/udfdecl.h
+++ b/fs/udf/udfdecl.h
@@ -132,6 +132,12 @@ struct inode *udf_find_metadata_inode_efe(struct super_block *sb,
 extern int udf_write_fi(struct inode *inode, struct fileIdentDesc *,
 			struct fileIdentDesc *, struct udf_fileident_bh *,
 			uint8_t *, uint8_t *);
+static inline unsigned int udf_dir_entry_len(struct fileIdentDesc *cfi)
+{
+	return ALIGN(sizeof(struct fileIdentDesc) +
+		le16_to_cpu(cfi->lengthOfImpUse) + cfi->lengthFileIdent,
+		UDF_NAME_PAD);
+}
 
 /* file.c */
 extern long udf_ioctl(struct file *, unsigned int, unsigned long);