linux-kernel - Re: [PATCH v2 1/3] mm/zswap: don't return LRU

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Message-ID: <Zbg-INqi9oMUqJaW@google.com>
Date: Tue, 30 Jan 2024 00:09:04 +0000
From: Yosry Ahmed <yosryahmed@...gle.com>
To: Chengming Zhou <zhouchengming@...edance.com>
Cc: Johannes Weiner <hannes@...xchg.org>, Nhat Pham <nphamcs@...il.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Chris Li <chriscli@...gle.com>, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 1/3] mm/zswap: don't return LRU_SKIP if we have dropped
 lru lock

On Sun, Jan 28, 2024 at 01:28:49PM +0000, Chengming Zhou wrote:
> 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.
> 
> Otherwise, the iteration might continue from a cursor position that
> was freed while the locks were dropped.

Does this warrant a stable backport?

> 
> 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")
> Acked-by: Johannes Weiner <hannes@...xchg.org>
> Reviewed-by: Nhat Pham <nphamcs@...il.com>
> Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>

Acked-by: Yosry Ahmed <yosryahmed@...gle.com>