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Date: Fri, 26 May 2023 17:50:02 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: David Howells <dhowells@redhat.com>
Cc: netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>, Eric
 Dumazet <edumazet@google.com>, Paolo Abeni <pabeni@redhat.com>, Willem de
 Bruijn <willemdebruijn.kernel@gmail.com>, David Ahern <dsahern@kernel.org>,
 Matthew Wilcox <willy@infradead.org>, Jens Axboe <axboe@kernel.dk>,
 linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jeroen de Borst
 <jeroendb@google.com>, Catherine Sullivan <csully@google.com>, Shailend
 Chand <shailend@google.com>, Felix Fietkau <nbd@nbd.name>, John Crispin
 <john@phrozen.org>, Sean Wang <sean.wang@mediatek.com>, Mark Lee
 <Mark-MC.Lee@mediatek.com>, Lorenzo Bianconi <lorenzo@kernel.org>, Matthias
 Brugger <matthias.bgg@gmail.com>, AngeloGioacchino Del Regno
 <angelogioacchino.delregno@collabora.com>, Keith Busch <kbusch@kernel.org>,
 Jens Axboe <axboe@fb.com>, Christoph Hellwig <hch@lst.de>, Sagi Grimberg
 <sagi@grimberg.me>, Chaitanya Kulkarni <kch@nvidia.com>, Andrew Morton
 <akpm@linux-foundation.org>, linux-arm-kernel@lists.infradead.org,
 linux-mediatek@lists.infradead.org, linux-nvme@lists.infradead.org
Subject: Re: [PATCH net-next 04/12] mm: Make the page_frag_cache allocator
 use multipage folios
Message-ID: <20230526175002.2591ccae@kernel.org>
In-Reply-To: <20230524153311.3625329-5-dhowells@redhat.com>
References: <20230524153311.3625329-1-dhowells@redhat.com>
	<20230524153311.3625329-5-dhowells@redhat.com>
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On Wed, 24 May 2023 16:33:03 +0100 David Howells wrote:
> -	offset = nc->offset - fragsz;
> -	if (unlikely(offset < 0)) {
> -		page = virt_to_page(nc->va);
> -
> -		if (page_ref_count(page) != nc->pagecnt_bias)
> +	offset = nc->offset;
> +	if (unlikely(fragsz > offset)) {
> +		/* Reuse the folio if everyone we gave it to has finished with
> +		 * it.
> +		 */
> +		if (!folio_ref_sub_and_test(folio, nc->pagecnt_bias)) {
> +			nc->folio = NULL;
>  			goto refill;
> +		}
> +
>  		if (unlikely(nc->pfmemalloc)) {
> -			page_ref_sub(page, nc->pagecnt_bias - 1);
> -			__free_pages(page, compound_order(page));
> +			__folio_put(folio);

This is not a pure 1:1 page -> folio conversion.
Why mix conversion with other code changes?