linux-kernel - [PATCH 1/4] mm/zswap: remove unnecessary dlen writes for incompressible pages

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Message-Id: <20251003203851.43128-2-sj@kernel.org>
Date: Fri,  3 Oct 2025 13:38:48 -0700
From: SeongJae Park <sj@...nel.org>
To: 
Cc: SeongJae Park <sj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Chengming Zhou <chengming.zhou@...ux.dev>,
	Johannes Weiner <hannes@...xchg.org>,
	Nhat Pham <nphamcs@...il.com>,
	Yosry Ahmed <yosry.ahmed@...ux.dev>,
	kernel-team@...a.com,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [PATCH 1/4] mm/zswap: remove unnecessary dlen writes for incompressible pages

Incompressible pages handling logic in zswap_compress() is setting
'dlen' as PAGE_SIZE twice.  Once before deciding whether to save the
content as is, and once again after it is decided to save it as is.
But the value of 'dlen' is used only if it is decided to save the
content as is, so the first write is unnecessary.  It is not causing
real user issues, but making code confusing to read.  Remove the
unnecessary write operation.

Signed-off-by: SeongJae Park <sj@...nel.org>
---
 mm/zswap.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index c1af782e54ec..80619c8589a7 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -894,7 +894,6 @@ static bool zswap_compress(struct page *page, struct zswap_entry *entry,
 	 * to the active LRU list in the case.
 	 */
 	if (comp_ret || !dlen || dlen >= PAGE_SIZE) {
-		dlen = PAGE_SIZE;
 		if (!mem_cgroup_zswap_writeback_enabled(
 					folio_memcg(page_folio(page)))) {
 			comp_ret = comp_ret ? comp_ret : -EINVAL;
-- 
2.39.5