[PATCH] mm/zswap: invalidate duplicate entry when !zswap_enabled

[chengming.zhou@linux.dev]

From: Chengming Zhou <zhouchengming@bytedance.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.

Link: https://lkml.kernel.org/r/20240208023254.3873823-1-chengming.zhou@linux.dev
Fixes: 42c06a0e8ebe ("mm: kill frontswap")
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 678e54d4bb9a4822f8ae99690ac131c5d490cdb1)
---
 mm/zswap.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 37d2b1cb2ecb..63fb94d68e10 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1215,7 +1215,7 @@ bool zswap_store(struct folio *folio)
 	if (folio_test_large(folio))
 		return false;
 
-	if (!zswap_enabled || !tree)
+	if (!tree)
 		return false;
 
 	/*
@@ -1231,6 +1231,9 @@ bool zswap_store(struct folio *folio)
 	}
 	spin_unlock(&tree->lock);
 
+	if (!zswap_enabled)
+		return false;
+
 	/*
 	 * XXX: zswap reclaim does not work with cgroups yet. Without a
 	 * cgroup-aware entry LRU, we will push out entries system-wide based on
-- 
2.40.1