diff --git a/src/userprog/syscall.c b/src/userprog/syscall.c
index 2a32cd3..2078c9f 100644
--- a/src/userprog/syscall.c
+++ b/src/userprog/syscall.c
@@ -466,35 +466,12 @@ syscall_munmap (mapid_t mapping)
   /* Get the mmap entry from the mapping identifier. */
   struct mmap_entry *mmap = mmap_get (mapping);
 
-  /* Free all the pages associated with the mapping, writing back to the file
-     if necessary. */
-  off_t length = file_length (mmap->file);
-  for (off_t ofs = 0; ofs < length; ofs += PGSIZE)
-    {
-      void *upage = mmap->upage + ofs;
-
-      /* Get the SPT page entry for this page. */
-      struct page_entry *page = page_get(upage);
-      if (page == NULL)
-        continue;
-
-      /* Write the page back to the file if it is dirty. */
-      if (pagedir_is_dirty (thread_current ()->pagedir, upage))
-        {
-          lock_acquire (&filesys_lock);
-          file_write_at (mmap->file, upage, page->read_bytes, ofs);
-          lock_release (&filesys_lock);
-        }
-
-      /* Remove the page from the supplemental page table. */
-      hash_delete (&thread_current ()->pages, &page->elem);
-    }
-
-  /* Remove the mapping from the mmap table. Close the file and free the mmap
-     entry. */
+  /* Delete the mmap entry from the hash table. */
   hash_delete (&thread_current ()->mmap_files, &mmap->elem);
-  file_close (mmap->file);
-  free(mmap);
+
+  /* Unmap the mmap entry: free the pages and write back to the file if
+     necessary. NOTE. freeing and cleaning up is also handled by mmap_unmap. */
+  mmap_unmap (mmap);
 }
 
 /* Hashing function needed for the open_file table. Returns a hash for an entry,
diff --git a/src/vm/mmap.c b/src/vm/mmap.c
index b3b16db..c34991d 100644
--- a/src/vm/mmap.c
+++ b/src/vm/mmap.c
@@ -4,6 +4,7 @@
 #include "threads/malloc.h"
 #include "userprog/syscall.h"
 #include "userprog/pagedir.h"
+#include <stdio.h>
 
 static unsigned mmap_hash (const struct hash_elem *e, void *aux);
 static bool mmap_less (const struct hash_elem *a_, const struct hash_elem *b_,
@@ -85,11 +86,8 @@ mmap_unmap (struct mmap_entry *mmap)
     hash_delete (&thread_current ()->pages, &page->elem);
   }
 
-  /* Remove the mapping from the mmap table. Close the file and free the mmap
-     entry. */
-  hash_delete (&thread_current ()->mmap_files, &mmap->elem);
   file_close (mmap->file);
-  free(mmap);
+  free (mmap);
 }
 
 /* Destroys the mmap table for the current thread. Frees all the memory
@@ -120,14 +118,13 @@ 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. */
+/* Cleans up the mmap table for the current thread. Implicitly unmaps the mmap
+   entry, freeing pages and writing back to the file if necessary. */
 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);
+  mmap_unmap (mmap);
 }
 
 /* Updates the 'owner' thread's page table entry for virtual address 'upage'
diff --git a/src/vm/mmap.h b/src/vm/mmap.h
index 593e070..cba21fc 100644
--- a/src/vm/mmap.h
+++ b/src/vm/mmap.h
@@ -21,6 +21,7 @@ bool mmap_init (struct thread *t);
 struct mmap_entry *mmap_get (mapid_t mapping);
 struct mmap_entry *mmap_insert (struct file *file, void *upage);
 void mmap_unmap (struct mmap_entry *mmap);
+void mmap_umap_all (void);
 void mmap_destroy (void);
 
 #endif /* vm/mmap.h */
diff --git a/src/vm/page.c b/src/vm/page.c
index 18f718e..c75fdcc 100644
--- a/src/vm/page.c
+++ b/src/vm/page.c
@@ -59,7 +59,6 @@ page_get (void *upage)
 
   struct hash_elem *e
     = hash_find (&thread_current ()->pages, &fake_page_entry.elem);
-
   if (e == NULL)
       return NULL;