linux-kernel - [PATCH mm-hotfixes-unstable] mm/zswap: invalidate duplicate entry when !zswap

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Date: Thu,  8 Feb 2024 02:32:54 +0000
From: chengming.zhou@...ux.dev
To: hannes@...xchg.org,
	yosryahmed@...gle.com,
	nphamcs@...il.com,
	akpm@...ux-foundation.org
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	chengming.zhou@...ux.dev,
	Chengming Zhou <zhouchengming@...edance.com>,
	stable@...r.kernel.org
Subject: [PATCH mm-hotfixes-unstable] mm/zswap: invalidate duplicate entry when !zswap_enabled

From: Chengming Zhou <zhouchengming@...edance.com>

We have to invalidate any duplicate entry even when !zswap_enabled
since zswap can be disabled anytime. If the folio store success before,
then got dirtied again but zswap disabled, we won't invalidate the old
duplicate entry in the zswap_store(). So later lru writeback may
overwrite the new data in swapfile.

Fixes: 42c06a0e8ebe ("mm: kill frontswap")
Cc: <stable@...r.kernel.org>
Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
---
 mm/zswap.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index fe7ee2640c69..32633d0597dc 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1516,7 +1516,7 @@ bool zswap_store(struct folio *folio)
 	if (folio_test_large(folio))
 		return false;
 
-	if (!zswap_enabled || !tree)
+	if (!tree)
 		return false;
 
 	/*
@@ -1531,6 +1531,10 @@ bool zswap_store(struct folio *folio)
 		zswap_invalidate_entry(tree, dupentry);
 	}
 	spin_unlock(&tree->lock);
+
+	if (!zswap_enabled)
+		return false;
+
 	objcg = get_obj_cgroup_from_folio(folio);
 	if (objcg && !obj_cgroup_may_zswap(objcg)) {
 		memcg = get_mem_cgroup_from_objcg(objcg);
-- 
2.40.1