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Message-ID: <76b9e52a-9b51-4e4d-93ca-24a5aa3c4dca@linux.dev>
Date: Sat, 27 Jan 2024 22:33:49 +0800
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Subject: Re: [PATCH 1/2] mm/zswap: don't return LRU_SKIP if we have dropped
 lru lock
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To: Johannes Weiner <hannes@cmpxchg.org>
Cc: yosryahmed@google.com, nphamcs@gmail.com, akpm@linux-foundation.org,
 linux-mm@kvack.org, linux-kernel@vger.kernel.org,
 Chengming Zhou <zhouchengming@bytedance.com>
References: <20240126083015.3557006-1-chengming.zhou@linux.dev>
 <20240126142800.GF1567330@cmpxchg.org>
From: Chengming Zhou <chengming.zhou@linux.dev>
In-Reply-To: <20240126142800.GF1567330@cmpxchg.org>
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On 2024/1/26 22:28, Johannes Weiner wrote:
> On Fri, Jan 26, 2024 at 08:30:14AM +0000, chengming.zhou@linux.dev wrote:
>> From: Chengming Zhou <zhouchengming@bytedance.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.
> 
> Good catch. Can you mention the possible consequences in the log?
> 
> "Otherwise, the iteration might continue from a cursor position that
> was freed while the locks were dropped."?

Good, will do.

> 
>> 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@bytedance.com>
> 
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>

Thanks.