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Date:   Mon, 5 Jun 2023 11:44:05 -0400
From:   Johannes Weiner <hannes@cmpxchg.org>
To:     Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc:     vitaly.wool@konsulko.com, minchan@kernel.org,
        senozhatsky@chromium.org, yosryahmed@google.com,
        linux-mm@kvack.org, ddstreet@ieee.org, sjenning@redhat.com,
        nphamcs@gmail.com, akpm@linux-foundation.org,
        linux-kernel@vger.kernel.org, kernel-team@meta.com
Subject: Re: [RFC PATCH 6/7] mm: zswap: simplify writeback function
Message-ID: <20230605154405.GC221380@cmpxchg.org>
References: <20230605085419.44383-1-cerasuolodomenico@gmail.com>
 <20230605085419.44383-7-cerasuolodomenico@gmail.com>
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On Mon, Jun 05, 2023 at 10:54:18AM +0200, Domenico Cerasuolo wrote:
> @@ -1142,9 +1122,6 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
>  	zswap_written_back_pages++;
>  
>  	spin_lock(&tree->lock);
> -	/* drop local reference */
> -	zswap_entry_put(tree, entry);
> -
>  	/*
>  	* There are two possible situations for entry here:
>  	* (1) refcount is 1(normal case),  entry is valid and on the tree
> @@ -1152,7 +1129,7 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
>  	*     because invalidate happened during writeback
>  	*  search the tree and free the entry if find entry
>  	*/
> -	if (entry == zswap_rb_search(&tree->rbroot, offset))
> +	if (entry == zswap_rb_search(&tree->rbroot, swp_offset(swpentry)))
>  		zswap_entry_put(tree, entry);
>  	spin_unlock(&tree->lock);

This can be moved to zswap_shrink() as well. It already has a
post-writeback tree->lock section for lru putback and dropping its
local reference, it should do this as well.

Writeback is then is done after it bumped zswap_written_pages.