[#142] Write data back to memory mapped file when eviction

src/userprog/process.c

@@ -218,7 +218,7 @@ process_exit (void)
     {
       struct process_mmap *mmap = list_entry (e, struct process_mmap, elem);
       e = list_next (e);
-      unmap_mmap_item (mmap);
+      mmap_unmap_item (mmap);
     }
 #endif
 
@@ -643,7 +643,7 @@ load_segment (struct file *file, off_t ofs, uint8_t *upage,
 
 #ifdef VM
       if (!suppl_pt_set_file (upage, file, ofs, page_read_bytes,
-                              page_zero_bytes, writable))
+                              page_zero_bytes, writable, false))
         return false;
 #else
       /* Get a page of memory. */

src/userprog/syscall.c

@@ -429,7 +429,8 @@ syscall_mmap (int fd, void *addr)
     {
       size_t read_bytes = (size_t) ofs + PGSIZE < size ? PGSIZE : size - ofs;
       size_t zero_bytes = PGSIZE - read_bytes;
-      if (!suppl_pt_set_file (addr + ofs, f, ofs, read_bytes, zero_bytes, true))
+      if (!suppl_pt_set_file (addr + ofs, f, ofs, read_bytes, zero_bytes,
+                              true, true))
         {
           fault_ofs = ofs;
           goto fail;
@@ -463,14 +464,27 @@ syscall_munmap (mapid_t mapping)
   struct process_mmap *mmap = process_get_mmap (mapping);
   if (mmap == NULL)
     return;
-  unmap_mmap_item (mmap);
+  mmap_unmap_item (mmap);
+}
+
+/* Wirtes data back to the original file with given offset. */
+off_t
+mmap_write_back (struct file *file, void *kpage, off_t ofs)
+{
+  lock_acquire (&filesys_lock);
+  file = file_reopen (file);
+  if (file == NULL)
+    return -1;
+  off_t writes_byte = file_write_at (file, kpage, PGSIZE, ofs);
+  lock_release (&filesys_lock);
+  return writes_byte;
 }
 
 /* Unmaps the mapping, which must be a mapping ID returned by
    a previous call to mmap by the same process that has not yet
    been unmapped. */
 void
-unmap_mmap_item (struct process_mmap *mmap)
+mmap_unmap_item (struct process_mmap *mmap)
 {
   ASSERT (pg_ofs (mmap->addr) == 0);
 

src/userprog/syscall.h

@@ -2,14 +2,16 @@
 #define USERPROG_SYSCALL_H
 
 #ifdef VM
-#include "process.h"
+#include "filesys/off_t.h"
+#include "userprog/process.h"
 #endif
 
 void syscall_init (void);
 void syscall_exit (int);
 
 #ifdef VM
-void unmap_mmap_item (struct process_mmap *);
+off_t mmap_write_back (struct file *, void *kpage, off_t);
+void mmap_unmap_item (struct process_mmap *);
 #endif
 
 #endif /* userprog/syscall.h */

src/vm/frame.c

@@ -178,6 +178,13 @@ frame_evict_and_get (void)
     case PAGE_FILE:
       if (!pte->writable)
         break;
+      if (pte->mmap)
+        {
+          if (!suppl_pt_update_dirty (pte))
+            break;
+          if (mmap_write_back (pte->file, pte->kpage, pte->ofs) == -1)
+            return NULL;
+        }
 
     case PAGE_ZERO:
       if (!suppl_pt_update_dirty (pte))

src/vm/page.c

@@ -63,7 +63,8 @@ suppl_pt_set_zero (void *upage)
    Note that this does not involve actual frame allocation. */
 bool
 suppl_pt_set_file (void *upage, struct file *file, off_t ofs,
-                   uint32_t read_bytes, uint32_t zero_bytes, bool writable)
+                   uint32_t read_bytes, uint32_t zero_bytes,
+                   bool writable, bool mmap)
 {
   if (suppl_pt_get_page (upage) != NULL)
     return false;
@@ -81,6 +82,7 @@ suppl_pt_set_file (void *upage, struct file *file, off_t ofs,
   pte->read_bytes = read_bytes;
   pte->zero_bytes = zero_bytes;
   pte->writable = writable;
+  pte->mmap = mmap;
 
   struct suppl_pt *pt = thread_current ()->suppl_pt;
   hash_insert (&pt->hash, &pte->elem);

src/vm/page.h

@@ -37,6 +37,7 @@ struct suppl_pte
             uint32_t read_bytes;    /* Read bytes. */
             uint32_t zero_bytes;    /* Zero bytes. */
             bool writable;          /* Writable flag. */
+            bool mmap;              /* Memory mapped file. */
           };
         struct                      /* Only for page type PAGE_SWAP. */
           {
@@ -52,7 +53,7 @@ void suppl_pt_destroy (struct suppl_pt *);
 
 bool suppl_pt_set_zero (void *upage);
 bool suppl_pt_set_file (void *upage, struct file *, off_t, uint32_t read_bytes,
-                        uint32_t zero_bytes, bool writable);
+                        uint32_t zero_bytes, bool writable, bool mmap);
 bool suppl_pt_load_page (void *upage);
 struct suppl_pte *suppl_pt_get_page (void *upage);
 void suppl_pt_clear_page (void *upage);