1 files changed, 17 insertions, 4 deletions

diff --git a/vm/page.c b/vm/page.c
index 2853497..98120e5 100644
--- a/vm/page.c
+++ b/vm/page.c
@@ -28,7 +28,7 @@ page_table_hash (const struct hash_elem *e, void *aux UNUSED)
   return hash_bytes (&pte->upage, sizeof pte->upage);
 }
 
-/* page table comperator needed by the hash table implementation
+/* page table comperator needed by the hash table implementation.
    returns true if A is less than B, or false if A is greater than
    or equal to B */
 static bool
@@ -55,7 +55,7 @@ page_table_entry_free (struct hash_elem *e, void *aux UNUSED)
   free (pte);
 }
 
-/* inserts a new entry into the page table
+/* inserts a new entry into the page table.
    returns false if entry is invalid or already in the table */
 static bool
 page_table_insert (struct hash *ht, struct page_table_entry *pte)
@@ -65,7 +65,7 @@ page_table_insert (struct hash *ht, struct page_table_entry *pte)
   return (hash_insert (ht, &pte->elem) == NULL);
 }
 
-/* inserts a new entry of type segment into the page table
+/* inserts a new entry of type segment into the page table.
    returns false if entry is invalid or already in the table */
 bool
 page_table_insert_segment (struct hash *ht, struct file *file, off_t ofs,
@@ -96,7 +96,20 @@ page_table_fetch (struct hash *ht, void *upage)
   return ((e != NULL) ? hash_entry (e, struct page_table_entry, elem) : NULL);
 }
 
-/* load the page referenced by the page table entry
+/* remove an entry from the page table. returns the element or NULL if not found.
+   the caller is responsible for freeing the element! */
+struct page_table_entry *
+page_table_remove (struct hash *ht, void *upage)
+{
+  struct page_table_entry pte;
+  struct hash_elem *e;
+
+  pte.upage = upage;
+  e = hash_delete (ht, &pte.elem);
+  return ((e != NULL) ? hash_entry (e, struct page_table_entry, elem) : NULL);
+}
+
+/* load the page referenced by the page table entry.
    returns true on success or already loaded, false otherwise */
 bool
 page_load (struct page_table_entry *pte)