patch-2.4.4 linux/mm/swap_state.c

• Lines: 113
• Date: Wed Apr 25 14:46:21 2001
• Orig file: v2.4.3/linux/mm/swap_state.c
• Orig date: Fri Dec 29 15:04:27 2000

diff -u --recursive --new-file v2.4.3/linux/mm/swap_state.c linux/mm/swap_state.c
@@ -17,9 +17,24 @@
 
 #include <asm/pgtable.h>
 
+/*
+ * We may have stale swap cache pages in memory: notice
+ * them here and get rid of the unnecessary final write.
+ */
 static int swap_writepage(struct page *page)
 {
-	rw_swap_page(WRITE, page, 0);
+	/* One for the page cache, one for this user, one for page->buffers */
+	if (page_count(page) > 2 + !!page->buffers)
+		goto in_use;
+	if (swap_count(page) > 1)
+		goto in_use;
+
+	/* We could remove it here, but page_launder will do it anyway */
+	UnlockPage(page);
+	return 0;
+
+in_use:
+	rw_swap_page(WRITE, page);
 	return 0;
 }
 
@@ -130,26 +145,6 @@
 	UnlockPage(page);
 }
 
-/* 
- * Perform a free_page(), also freeing any swap cache associated with
- * this page if it is the last user of the page. Can not do a lock_page,
- * as we are holding the page_table_lock spinlock.
- */
-void free_page_and_swap_cache(struct page *page)
-{
-	/* 
-	 * If we are the only user, then try to free up the swap cache. 
-	 */
-	if (PageSwapCache(page) && !TryLockPage(page)) {
-		if (!is_page_shared(page)) {
-			delete_from_swap_cache_nolock(page);
-		}
-		UnlockPage(page);
-	}
-	page_cache_release(page);
-}
-
-
 /*
  * Lookup a swap entry in the swap cache. A found page will be returned
  * unlocked and with its refcount incremented - we rely on the kernel
@@ -168,37 +163,18 @@
 		/*
 		 * Right now the pagecache is 32-bit only.  But it's a 32 bit index. =)
 		 */
-repeat:
-		found = find_lock_page(&swapper_space, entry.val);
+		found = find_get_swapcache_page(&swapper_space, entry.val);
 		if (!found)
 			return 0;
-		/*
-		 * Though the "found" page was in the swap cache an instant
-		 * earlier, it might have been removed by refill_inactive etc.
-		 * Re search ... Since find_lock_page grabs a reference on
-		 * the page, it can not be reused for anything else, namely
-		 * it can not be associated with another swaphandle, so it
-		 * is enough to check whether the page is still in the scache.
-		 */
-		if (!PageSwapCache(found)) {
-			UnlockPage(found);
-			page_cache_release(found);
-			goto repeat;
-		}
+		if (!PageSwapCache(found))
+			BUG();
 		if (found->mapping != &swapper_space)
-			goto out_bad;
+			BUG();
 #ifdef SWAP_CACHE_INFO
 		swap_cache_find_success++;
 #endif
-		UnlockPage(found);
 		return found;
 	}
-
-out_bad:
-	printk (KERN_ERR "VM: Found a non-swapper swap page!\n");
-	UnlockPage(found);
-	page_cache_release(found);
-	return 0;
 }
 
 /* 
@@ -210,7 +186,7 @@
  * the swap entry is no longer in use.
  */
 
-struct page * read_swap_cache_async(swp_entry_t entry, int wait)
+struct page * read_swap_cache_async(swp_entry_t entry)
 {
 	struct page *found_page = 0, *new_page;
 	unsigned long new_page_addr;
@@ -243,7 +219,7 @@
 	 */
 	lock_page(new_page);
 	add_to_swap_cache(new_page, entry);
-	rw_swap_page(READ, new_page, wait);
+	rw_swap_page(READ, new_page);
 	return new_page;
 
 out_free_page: