Add a mmap destroy function to cleanup all mmap hash table entries upon thread exit

src/threads/thread.c

@@ -397,6 +397,8 @@ thread_exit (void)
   process_exit ();
 #endif
 
+  mmap_destroy ();
+
   /* Remove thread from all threads list, set our status to dying,
      and schedule another process.  That process will destroy us
      when it calls thread_schedule_tail(). */

src/vm/mmap.c

@@ -33,3 +33,21 @@ mmap_less (const struct hash_elem *a_, const struct hash_elem *b_,
 
   return a->mapping < b->mapping;
 }
+
+/* Cleans up the mmap table for the current thread. Frees the memory allocated
+   for the mmap entry. */
+static void
+mmap_cleanup (struct hash_elem *e, void *aux UNUSED)
+{
+  struct mmap_entry *mmap = hash_entry (e, struct mmap_entry, elem);
+  file_close (mmap->file);
+  free (mmap);
+}
+
+/* Destroys the mmap table for the current thread. Frees all the memory
+   allocated for the mmap entries. */
+void
+mmap_destroy (void)
+{
+  hash_destroy (&thread_current ()->mmap_files, mmap_cleanup);
+}

src/vm/mmap.h

@@ -3,6 +3,7 @@
 
 #include <hash.h>
 #include "threads/thread.h"
+#include "filesys/file.h"
 
 /* A mapping identifier type. */
 typedef unsigned mapid_t;
@@ -17,5 +18,6 @@ struct mmap_entry {
 };
 
 bool mmap_init (void);
+void mmap_destroy (void);
 
 #endif /* vm/mmap.h */