diff -urN oldtree/include/linux/pagemap.h newtree/include/linux/pagemap.h
--- oldtree/include/linux/pagemap.h	2006-08-02 07:14:22.000000000 -0700
+++ newtree/include/linux/pagemap.h	2006-08-04 07:34:52.000000000 -0700
@@ -132,14 +132,29 @@
 }
 
 extern void FASTCALL(__lock_page(struct page *page));
+extern void FASTCALL(__lock_page_nosync(struct page *page));
 extern void FASTCALL(unlock_page(struct page *page));
 
+/*
+ * lock_page may only be called if we have the page's inode pinned.
+ */
 static inline void lock_page(struct page *page)
 {
 	might_sleep();
 	if (TestSetPageLocked(page))
 		__lock_page(page);
 }
+
+/*
+ * lock_page_nosync should only be used if we can't pin the page's inode.
+ * Doesn't play quite so well with block device plugging.
+ */
+static inline void lock_page_nosync(struct page *page)
+{
+	might_sleep();
+	if (TestSetPageLocked(page))
+		__lock_page_nosync(page);
+}
 	
 /*
  * This is exported only for wait_on_page_locked/wait_on_page_writeback.
diff -urN oldtree/mm/filemap.c newtree/mm/filemap.c
--- oldtree/mm/filemap.c	2006-08-02 07:14:23.000000000 -0700
+++ newtree/mm/filemap.c	2006-08-04 07:34:52.000000000 -0700
@@ -497,6 +497,12 @@
 EXPORT_SYMBOL(page_cache_alloc_cold);
 #endif
 
+static int __sleep_on_page_lock(void *word)
+{
+	io_schedule();
+	return 0;
+}
+
 /*
  * In order to wait for pages to become available there must be
  * waitqueues associated with pages. By using a hash table of
@@ -568,6 +574,17 @@
 }
 EXPORT_SYMBOL(end_page_writeback);
 
+/*
+ * Variant of lock_page that does not require the caller to hold a reference
+ * on the page's mapping.
+ */
+void fastcall __lock_page_nosync(struct page *page)
+{
+	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
+	__wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock,
+							TASK_UNINTERRUPTIBLE);
+}
+
 /**
  * __lock_page - get a lock on the page, assuming we need to sleep to get it
  * @page: the page to lock
diff -urN oldtree/mm/page-writeback.c newtree/mm/page-writeback.c
--- oldtree/mm/page-writeback.c	2006-08-02 07:14:23.000000000 -0700
+++ newtree/mm/page-writeback.c	2006-08-04 07:34:53.000000000 -0700
@@ -701,7 +701,7 @@
 {
 	int ret;
 
-	lock_page(page);
+	lock_page_nosync(page);
 	ret = set_page_dirty(page);
 	unlock_page(page);
 	return ret;