Re: [PATCH 1/2] mm/zswap: don't return LRU_SKIP if we have dropped lru lock

[Johannes Weiner]

On Fri, Jan 26, 2024 at 08:30:14AM +0000, chengming.zhou@xxxxxxxxx wrote:
> From: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
> 
> 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."?

> 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@xxxxxxxxxxxxx>

Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>