mmap_private opens the file for reading, not for writing

mmap.h

@@ -15,7 +15,7 @@ const char* mmap_read(const char *filename,size_t* filesize);
 /* like mmap_read but use openat instead of open */
 const char* mmap_readat(const char *filename,size_t* filesize,int dirfd);
 
-/* open file for writing, mmap whole file privately (copy on write),
+/* open file for reading, mmap whole file privately (copy on write),
  * close file, write length of map in filesize and return pointer to
  * map. */
 char* mmap_private(const char *filename,size_t* filesize);