patch-2.3.6 linux/mm/memory.c

• Lines: 121
• Date: Tue Jun 8 14:09:57 1999
• Orig file: v2.3.5/linux/mm/memory.c
• Orig date: Mon May 31 22:28:07 1999

diff -u --recursive --new-file v2.3.5/linux/mm/memory.c linux/mm/memory.c
@@ -543,19 +543,6 @@
 }
 
 /*
- * sanity-check function..
- */
-static void put_page(pte_t * page_table, pte_t pte)
-{
-	if (!pte_none(*page_table)) {
-		free_page_and_swap_cache(pte_page(pte));
-		return;
-	}
-/* no need for flush_tlb */
-	set_pte(page_table, pte);
-}
-
-/*
  * This routine is used to map in a page into an address space: needed by
  * execve() for the initial stack and environment pages.
  */
@@ -612,21 +599,15 @@
  * and potentially makes it more efficient.
  */
 static int do_wp_page(struct task_struct * tsk, struct vm_area_struct * vma,
-	unsigned long address, pte_t *page_table)
+	unsigned long address, pte_t *page_table, pte_t pte)
 {
-	pte_t pte;
 	unsigned long old_page, new_page;
 	struct page * page_map;
 	
-	pte = *page_table;
 	new_page = __get_free_page(GFP_USER);
-	/* Did someone else copy this page for us while we slept? */
+	/* Did swap_out() unmapped the protected page while we slept? */
 	if (pte_val(*page_table) != pte_val(pte))
 		goto end_wp_page;
-	if (!pte_present(pte))
-		goto end_wp_page;
-	if (pte_write(pte))
-		goto end_wp_page;
 	old_page = pte_page(pte);
 	if (MAP_NR(old_page) >= max_mapnr)
 		goto bad_wp_page;
@@ -650,36 +631,42 @@
 		delete_from_swap_cache(page_map);
 		/* FallThrough */
 	case 1:
-		/* We can release the kernel lock now.. */
-		unlock_kernel();
-
 		flush_cache_page(vma, address);
 		set_pte(page_table, pte_mkdirty(pte_mkwrite(pte)));
 		flush_tlb_page(vma, address);
 end_wp_page:
+		/*
+		 * We can release the kernel lock now.. Now swap_out will see
+		 * a dirty page and so won't get confused and flush_tlb_page
+		 * won't SMP race. -Andrea
+		 */
+		unlock_kernel();
+
 		if (new_page)
 			free_page(new_page);
 		return 1;
 	}
 		
-	unlock_kernel();
 	if (!new_page)
-		return 0;
+		goto no_new_page;
 
-	if (PageReserved(mem_map + MAP_NR(old_page)))
+	if (PageReserved(page_map))
 		++vma->vm_mm->rss;
 	copy_cow_page(old_page,new_page);
 	flush_page_to_ram(old_page);
 	flush_page_to_ram(new_page);
 	flush_cache_page(vma, address);
 	set_pte(page_table, pte_mkwrite(pte_mkdirty(mk_pte(new_page, vma->vm_page_prot))));
-	free_page(old_page);
 	flush_tlb_page(vma, address);
+	unlock_kernel();
+	__free_page(page_map);
 	return 1;
 
 bad_wp_page:
 	printk("do_wp_page: bogus page at address %08lx (%08lx)\n",address,old_page);
 	send_sig(SIGKILL, tsk, 1);
+no_new_page:
+	unlock_kernel();
 	if (new_page)
 		free_page(new_page);
 	return 0;
@@ -816,7 +803,7 @@
 		tsk->min_flt++;
 		flush_page_to_ram(page);
 	}
-	put_page(page_table, entry);
+	set_pte(page_table, entry);
 	return 1;
 }
 
@@ -874,7 +861,7 @@
 	} else if (atomic_read(&mem_map[MAP_NR(page)].count) > 1 &&
 		   !(vma->vm_flags & VM_SHARED))
 		entry = pte_wrprotect(entry);
-	put_page(page_table, entry);
+	set_pte(page_table, entry);
 	/* no need to invalidate: a not-present page shouldn't be cached */
 	return 1;
 }
@@ -908,7 +895,7 @@
 	flush_tlb_page(vma, address);
 	if (write_access) {
 		if (!pte_write(entry))
-			return do_wp_page(tsk, vma, address, pte);
+			return do_wp_page(tsk, vma, address, pte, entry);
 
 		entry = pte_mkdirty(entry);
 		set_pte(pte, entry);