linux-kernel - Re: [PATCH v2 2/2] mm: zswap: remove unnecessary trees cleanups in zswap

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Message-ID: <305078e5-b31e-43ed-825d-7b634c9c9f58@bytedance.com>
Date: Wed, 24 Jan 2024 15:34:05 +0800
From: Chengming Zhou <zhouchengming@...edance.com>
To: Yosry Ahmed <yosryahmed@...gle.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: Johannes Weiner <hannes@...xchg.org>, Nhat Pham <nphamcs@...il.com>,
 Chris Li <chrisl@...nel.org>, Huang Ying <ying.huang@...el.com>,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] mm: zswap: remove unnecessary trees cleanups in
 zswap_swapoff()

On 2024/1/24 12:51, Yosry Ahmed wrote:
> During swapoff, try_to_unuse() makes sure that zswap_invalidate() is
> called for all swap entries before zswap_swapoff() is called. This means
> that all zswap entries should already be removed from the tree. Simplify
> zswap_swapoff() by removing the trees cleanup code, and leave an
> assertion in its place.
> 
> Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com>

Looks good to me, thanks!

Reviewed-by: Chengming Zhou <zhouchengming@...edance.com>

> ---
>  mm/zswap.c | 16 +++-------------
>  1 file changed, 3 insertions(+), 13 deletions(-)
> 
> diff --git a/mm/zswap.c b/mm/zswap.c
> index dcdd5ecfedb09..78df16d307aa8 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -1808,19 +1808,9 @@ void zswap_swapoff(int type)
>  	if (!trees)
>  		return;
>  
> -	for (i = 0; i < nr_zswap_trees[type]; i++) {
> -		struct zswap_tree *tree = trees + i;
> -		struct zswap_entry *entry, *n;
> -
> -		/* walk the tree and free everything */
> -		spin_lock(&tree->lock);
> -		rbtree_postorder_for_each_entry_safe(entry, n,
> -						     &tree->rbroot,
> -						     rbnode)
> -			zswap_free_entry(entry);
> -		tree->rbroot = RB_ROOT;
> -		spin_unlock(&tree->lock);
> -	}
> +	/* try_to_unuse() invalidated all the entries already */
> +	for (i = 0; i < nr_zswap_trees[type]; i++)
> +		WARN_ON_ONCE(!RB_EMPTY_ROOT(&trees[i].rbroot));
>  
>  	kvfree(trees);
>  	nr_zswap_trees[type] = 0;