linux-kernel - Re: [PATCH 08/20] mm: zswap: further cleanup zswap

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Message-ID: <21f2bcba-a646-48b7-aa54-d763a490b216@bytedance.com>
Date: Tue, 30 Jan 2024 11:35:07 +0800
From: Chengming Zhou <zhouchengming@...edance.com>
To: Johannes Weiner <hannes@...xchg.org>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: Nhat Pham <nphamcs@...il.com>, Yosry Ahmed <yosryahmed@...gle.com>,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/20] mm: zswap: further cleanup zswap_store()

On 2024/1/30 09:36, Johannes Weiner wrote:
> - Remove dupentry, reusing entry works just fine.
> - Rename pool to shrink_pool, as this one actually is confusing.
> - Remove page, use folio_nid() and kmap_local_folio() directly.
> - Set entry->swpentry in a common path.
> - Move value and src to local scope of use.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

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

> ---
>  mm/zswap.c | 28 +++++++++++++---------------
>  1 file changed, 13 insertions(+), 15 deletions(-)
> 
> diff --git a/mm/zswap.c b/mm/zswap.c
> index f9b9494156ba..cde309c539b3 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -1542,14 +1542,11 @@ bool zswap_store(struct folio *folio)
>  {
>  	swp_entry_t swp = folio->swap;
>  	pgoff_t offset = swp_offset(swp);
> -	struct page *page = &folio->page;
>  	struct zswap_tree *tree = swap_zswap_tree(swp);
>  	struct zswap_entry *entry, *dupentry;
>  	struct obj_cgroup *objcg = NULL;
>  	struct mem_cgroup *memcg = NULL;
> -	struct zswap_pool *pool;
> -	unsigned long value;
> -	u8 *src;
> +	struct zswap_pool *shrink_pool;
>  
>  	VM_WARN_ON_ONCE(!folio_test_locked(folio));
>  	VM_WARN_ON_ONCE(!folio_test_swapcache(folio));
> @@ -1567,10 +1564,10 @@ bool zswap_store(struct folio *folio)
>  	 * the tree, and it might be written back overriding the new data.
>  	 */
>  	spin_lock(&tree->lock);
> -	dupentry = zswap_rb_search(&tree->rbroot, offset);
> -	if (dupentry) {
> +	entry = zswap_rb_search(&tree->rbroot, offset);
> +	if (entry) {
> +		zswap_invalidate_entry(tree, entry);
>  		zswap_duplicate_entry++;
> -		zswap_invalidate_entry(tree, dupentry);
>  	}
>  	spin_unlock(&tree->lock);
>  	objcg = get_obj_cgroup_from_folio(folio);
> @@ -1598,17 +1595,19 @@ bool zswap_store(struct folio *folio)
>  	}
>  
>  	/* allocate entry */
> -	entry = zswap_entry_cache_alloc(GFP_KERNEL, page_to_nid(page));
> +	entry = zswap_entry_cache_alloc(GFP_KERNEL, folio_nid(folio));
>  	if (!entry) {
>  		zswap_reject_kmemcache_fail++;
>  		goto reject;
>  	}
>  
>  	if (zswap_same_filled_pages_enabled) {
> -		src = kmap_local_page(page);
> +		unsigned long value;
> +		u8 *src;
> +
> +		src = kmap_local_folio(folio, 0);
>  		if (zswap_is_page_same_filled(src, &value)) {
>  			kunmap_local(src);
> -			entry->swpentry = swp;
>  			entry->length = 0;
>  			entry->value = value;
>  			atomic_inc(&zswap_same_filled_pages);
> @@ -1637,9 +1636,8 @@ bool zswap_store(struct folio *folio)
>  	if (!zswap_compress(folio, entry))
>  		goto put_pool;
>  
> -	entry->swpentry = swp;
> -
>  insert_entry:
> +	entry->swpentry = swp;
>  	entry->objcg = objcg;
>  	if (objcg) {
>  		obj_cgroup_charge_zswap(objcg, entry->length);
> @@ -1684,9 +1682,9 @@ bool zswap_store(struct folio *folio)
>  	return false;
>  
>  shrink:
> -	pool = zswap_pool_last_get();
> -	if (pool && !queue_work(shrink_wq, &pool->shrink_work))
> -		zswap_pool_put(pool);
> +	shrink_pool = zswap_pool_last_get();
> +	if (shrink_pool && !queue_work(shrink_wq, &shrink_pool->shrink_work))
> +		zswap_pool_put(shrink_pool);
>  	goto reject;
>  }
>