linux-kernel - [PATCH v2 2/2] mm: zswap: remove unnecessary trees cleanups in zswap

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Message-ID: <20240124045113.415378-3-yosryahmed@google.com>
Date: Wed, 24 Jan 2024 04:51:12 +0000
From: Yosry Ahmed <yosryahmed@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Johannes Weiner <hannes@...xchg.org>, Nhat Pham <nphamcs@...il.com>, Chris Li <chrisl@...nel.org>, 
	Chengming Zhou <zhouchengming@...edance.com>, Huang Ying <ying.huang@...el.com>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, Yosry Ahmed <yosryahmed@...gle.com>
Subject: [PATCH v2 2/2] mm: zswap: remove unnecessary trees cleanups in zswap_swapoff()

During swapoff, try_to_unuse() makes sure that zswap_invalidate() is
called for all swap entries before zswap_swapoff() is called. This means
that all zswap entries should already be removed from the tree. Simplify
zswap_swapoff() by removing the trees cleanup code, and leave an
assertion in its place.

Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com>
---
 mm/zswap.c | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index dcdd5ecfedb09..78df16d307aa8 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1808,19 +1808,9 @@ void zswap_swapoff(int type)
 	if (!trees)
 		return;
 
-	for (i = 0; i < nr_zswap_trees[type]; i++) {
-		struct zswap_tree *tree = trees + i;
-		struct zswap_entry *entry, *n;
-
-		/* walk the tree and free everything */
-		spin_lock(&tree->lock);
-		rbtree_postorder_for_each_entry_safe(entry, n,
-						     &tree->rbroot,
-						     rbnode)
-			zswap_free_entry(entry);
-		tree->rbroot = RB_ROOT;
-		spin_unlock(&tree->lock);
-	}
+	/* try_to_unuse() invalidated all the entries already */
+	for (i = 0; i < nr_zswap_trees[type]; i++)
+		WARN_ON_ONCE(!RB_EMPTY_ROOT(&trees[i].rbroot));
 
 	kvfree(trees);
 	nr_zswap_trees[type] = 0;
-- 
2.43.0.429.g432eaa2c6b-goog