linux-kernel - [PATCH 1/2] mm/zswap: don't return LRU

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Date: Fri, 26 Jan 2024 08:30:14 +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>
Subject: [PATCH 1/2] mm/zswap: don't return LRU_SKIP if we have dropped lru lock

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

LRU_SKIP can only be returned if we don't ever dropped lru lock, or
we need to return LRU_RETRY to restart from the head of lru list.

Actually we may need to introduce another LRU_STOP to really terminate
the ongoing shrinking scan process, when we encounter a warm page
already in the swap cache. The current list_lru implementation
doesn't have this function to early break from __list_lru_walk_one.

Fixes: b5ba474f3f51 ("zswap: shrink zswap pool based on memory pressure")
Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
---
 mm/zswap.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 00e90b9b5417..81cb3790e0dd 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -901,10 +901,8 @@ static enum lru_status shrink_memcg_cb(struct list_head *item, struct list_lru_o
 		 * into the warmer region. We should terminate shrinking (if we're in the dynamic
 		 * shrinker context).
 		 */
-		if (writeback_result == -EEXIST && encountered_page_in_swapcache) {
-			ret = LRU_SKIP;
+		if (writeback_result == -EEXIST && encountered_page_in_swapcache)
 			*encountered_page_in_swapcache = true;
-		}
 
 		goto put_unlock;
 	}
-- 
2.40.1