linux-kernel - [PATCH v2 5/5] mm/zswap: use postorder iteration when destroying rbtree

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Message-Id: <1375125570-9401-6-git-send-email-cody@linux.vnet.ibm.com>
Date:	Mon, 29 Jul 2013 12:19:30 -0700
From:	Cody P Schafer <cody@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, Linux MM <linux-mm@...ck.org>,
	David Woodhouse <David.Woodhouse@...el.com>,
	Rik van Riel <riel@...hat.com>,
	Michel Lespinasse <walken@...gle.com>,
	Seth Jennings <sjenning@...ux.vnet.ibm.com>,
	Cody P Schafer <cody@...ux.vnet.ibm.com>
Subject: [PATCH v2 5/5] mm/zswap: use postorder iteration when destroying rbtree

Signed-off-by: Cody P Schafer <cody@...ux.vnet.ibm.com>
Reviewed-by: Seth Jennings <sjenning@...ux.vnet.ibm.com>
---
 mm/zswap.c | 16 ++--------------
 1 file changed, 2 insertions(+), 14 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index deda2b6..5c853b2 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -790,26 +790,14 @@ static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
 static void zswap_frontswap_invalidate_area(unsigned type)
 {
 	struct zswap_tree *tree = zswap_trees[type];
-	struct rb_node *node;
-	struct zswap_entry *entry;
+	struct zswap_entry *entry, *n;
 
 	if (!tree)
 		return;
 
 	/* walk the tree and free everything */
 	spin_lock(&tree->lock);
-	/*
-	 * TODO: Even though this code should not be executed because
-	 * the try_to_unuse() in swapoff should have emptied the tree,
-	 * it is very wasteful to rebalance the tree after every
-	 * removal when we are freeing the whole tree.
-	 *
-	 * If post-order traversal code is ever added to the rbtree
-	 * implementation, it should be used here.
-	 */
-	while ((node = rb_first(&tree->rbroot))) {
-		entry = rb_entry(node, struct zswap_entry, rbnode);
-		rb_erase(&entry->rbnode, &tree->rbroot);
+	rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode) {
 		zbud_free(tree->pool, entry->handle);
 		zswap_entry_cache_free(entry);
 		atomic_dec(&zswap_stored_pages);
-- 
1.8.3.4

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