===================================================================
--- linux-2.6.orig/mm/filemap.c	2007-01-22 20:10:30.000000000 +0100
+++ linux-2.6/mm/filemap.c	2007-01-22 20:11:03.000000000 +0100
@@ -596,15 +596,31 @@ void fastcall __lock_page_nosync(struct 
  * Is there a pagecache struct page at the given (mapping, offset) tuple?
  * If yes, increment its refcount and return it; if no, return NULL.
  */
-struct page * find_get_page(struct address_space *mapping, unsigned long offset)
+struct page *find_get_page(struct address_space *mapping, unsigned long offset)
 {
+	void **pagep;
 	struct page *page;
 
-	read_lock_irq(&mapping->tree_lock);
-	page = radix_tree_lookup(&mapping->page_tree, offset);
-	if (page)
-		page_cache_get(page);
-	read_unlock_irq(&mapping->tree_lock);
+	rcu_read_lock();
+repeat:
+	page = NULL;
+	pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
+	if (pagep) {
+		page = radix_tree_deref_slot(pagep);
+		if (unlikely(!page || page == RADIX_TREE_RETRY))
+			goto repeat;
+
+		if (!page_cache_get_speculative(page))
+			goto repeat;
+
+		/* Has the page moved? */
+		if (unlikely(page != *pagep)) {
+			page_cache_release(page);
+			goto repeat;
+		}
+	}
+	rcu_read_unlock();
+
 	return page;
 }
 EXPORT_SYMBOL(find_get_page);
@@ -644,26 +660,19 @@ struct page *find_lock_page(struct addre
 {
 	struct page *page;
 
-	read_lock_irq(&mapping->tree_lock);
 repeat:
-	page = radix_tree_lookup(&mapping->page_tree, offset);
+	page = find_get_page(mapping, offset);
 	if (page) {
-		page_cache_get(page);
-		if (TestSetPageLocked(page)) {
-			read_unlock_irq(&mapping->tree_lock);
-			__lock_page(page);
-			read_lock_irq(&mapping->tree_lock);
-
-			/* Has the page been truncated while we slept? */
-			if (unlikely(page->mapping != mapping ||
-				     page->index != offset)) {
-				unlock_page(page);
-				page_cache_release(page);
-				goto repeat;
-			}
+		lock_page(page);
+		/* Has the page been truncated? */
+		if (unlikely(page->mapping != mapping
+				|| page->index != offset)) {
+			unlock_page(page);
+			page_cache_release(page);
+			goto repeat;
 		}
 	}
-	read_unlock_irq(&mapping->tree_lock);
+
 	return page;
 }
 EXPORT_SYMBOL(find_lock_page);
@@ -733,13 +742,39 @@ unsigned find_get_pages(struct address_s
 {
 	unsigned int i;
 	unsigned int ret;
+	unsigned int nr_found;
 
-	read_lock_irq(&mapping->tree_lock);
-	ret = radix_tree_gang_lookup(&mapping->page_tree,
-				(void **)pages, start, nr_pages);
-	for (i = 0; i < ret; i++)
-		page_cache_get(pages[i]);
-	read_unlock_irq(&mapping->tree_lock);
+	rcu_read_lock();
+restart:
+	nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
+				(void ***)pages, start, nr_pages);
+	ret = 0;
+	for (i = 0; i < nr_found; i++) {
+		struct page *page;
+repeat:
+		page = radix_tree_deref_slot((void **)pages[i]);
+		if (unlikely(!page))
+			continue;
+		/*
+		 * this can only trigger if nr_found == 1, making livelock
+		 * a non issue.
+		 */
+		if (unlikely(page == RADIX_TREE_RETRY))
+			goto restart;
+
+		if (!page_cache_get_speculative(page))
+			goto repeat;
+
+		/* Has the page moved? */
+		if (unlikely(page != *((void **)pages[i]))) {
+			page_cache_release(page);
+			goto repeat;
+		}
+
+		pages[ret] = page;
+		ret++;
+	}
+	rcu_read_unlock();
 	return ret;
 }
 
@@ -760,19 +795,44 @@ unsigned find_get_pages_contig(struct ad
 {
 	unsigned int i;
 	unsigned int ret;
+	unsigned int nr_found;
 
-	read_lock_irq(&mapping->tree_lock);
-	ret = radix_tree_gang_lookup(&mapping->page_tree,
-				(void **)pages, index, nr_pages);
-	for (i = 0; i < ret; i++) {
-		if (pages[i]->mapping == NULL || pages[i]->index != index)
+	rcu_read_lock();
+restart:
+	nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
+				(void ***)pages, index, nr_pages);
+	ret = 0;
+	for (i = 0; i < nr_found; i++) {
+		struct page *page;
+repeat:
+		page = radix_tree_deref_slot((void **)pages[i]);
+		if (unlikely(!page))
+			continue;
+		/*
+		 * this can only trigger if nr_found == 1, making livelock
+		 * a non issue.
+		 */
+		if (unlikely(page == RADIX_TREE_RETRY))
+			goto restart;
+
+		if (page->mapping == NULL || page->index != index)
 			break;
 
-		page_cache_get(pages[i]);
+		if (!page_cache_get_speculative(page))
+			goto repeat;
+
+		/* Has the page moved? */
+		if (unlikely(page != *((void **)pages[i]))) {
+			page_cache_release(page);
+			goto repeat;
+		}
+
+		pages[ret] = page;
+		ret++;
 		index++;
 	}
-	read_unlock_irq(&mapping->tree_lock);
-	return i;
+	rcu_read_unlock();
+	return ret;
 }
 
 /**
@@ -793,6 +853,7 @@ unsigned find_get_pages_tag(struct addre
 	unsigned int ret;
 
 	read_lock_irq(&mapping->tree_lock);
+	/* TODO: implement lookup_tag_slot and make this lockless */
 	ret = radix_tree_gang_lookup_tag(&mapping->page_tree,
 				(void **)pages, *index, nr_pages, tag);
 	for (i = 0; i < ret; i++)
Index: linux-2.6/mm/readahead.c
===================================================================
--- linux-2.6.orig/mm/readahead.c	2007-01-13 21:04:13.000000000 +0100
+++ linux-2.6/mm/readahead.c	2007-01-22 20:11:03.000000000 +0100
@@ -281,27 +281,25 @@ __do_page_cache_readahead(struct address
 	/*
 	 * Preallocate as many pages as we will need.
 	 */
-	read_lock_irq(&mapping->tree_lock);
 	for (page_idx = 0; page_idx < nr_to_read; page_idx++) {
 		pgoff_t page_offset = offset + page_idx;
 		
 		if (page_offset > end_index)
 			break;
 
+		rcu_read_lock();
 		page = radix_tree_lookup(&mapping->page_tree, page_offset);
+		rcu_read_unlock();
 		if (page)
 			continue;
 
-		read_unlock_irq(&mapping->tree_lock);
 		page = page_cache_alloc_cold(mapping);
-		read_lock_irq(&mapping->tree_lock);
 		if (!page)
 			break;
 		page->index = page_offset;
 		list_add(&page->lru, &page_pool);
 		ret++;
 	}
-	read_unlock_irq(&mapping->tree_lock);
 
 	/*
 	 * Now start the IO.  We ignore I/O errors - if the page is not
Index: linux-2.6/mm/page-writeback.c
===================================================================
--- linux-2.6.orig/mm/page-writeback.c	2007-01-22 17:29:38.000000000 +0100
+++ linux-2.6/mm/page-writeback.c	2007-01-22 20:11:03.000000000 +0100
@@ -959,12 +959,11 @@ EXPORT_SYMBOL(test_set_page_writeback);
  */
 int mapping_tagged(struct address_space *mapping, int tag)
 {
-	unsigned long flags;
 	int ret;
 
-	read_lock_irqsave(&mapping->tree_lock, flags);
+	rcu_read_lock();
 	ret = radix_tree_tagged(&mapping->page_tree, tag);
-	read_unlock_irqrestore(&mapping->tree_lock, flags);
+	rcu_read_unlock();
 	return ret;
 }
 EXPORT_SYMBOL(mapping_tagged);

