linux-kernel - Re: [PATCH net-next 05/12] mm: Make the page_frag_cache allocator handle __GFP

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Date:   Fri, 26 May 2023 17:57:36 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     David Howells <dhowells@...hat.com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        David Ahern <dsahern@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Jens Axboe <axboe@...nel.dk>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Jeroen de Borst <jeroendb@...gle.com>,
        Catherine Sullivan <csully@...gle.com>,
        Shailend Chand <shailend@...gle.com>,
        Felix Fietkau <nbd@....name>, John Crispin <john@...ozen.org>,
        Sean Wang <sean.wang@...iatek.com>,
        Mark Lee <Mark-MC.Lee@...iatek.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...com>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        Chaitanya Kulkarni <kch@...dia.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-nvme@...ts.infradead.org,
        Alexander Duyck <alexander.duyck@...il.com>
Subject: Re: [PATCH net-next 05/12] mm: Make the page_frag_cache allocator
 handle __GFP_ZERO itself

On Wed, 24 May 2023 16:33:04 +0100 David Howells wrote:
> Make the page_frag_cache allocator handle __GFP_ZERO itself rather than
> passing it off to the page allocator.  There may be a mix of callers, some
> specifying __GFP_ZERO and some not - and even if all specify __GFP_ZERO, we
> might refurbish the page, in which case the returned memory doesn't get
> cleared.

I think it's pretty clear that page frag allocator was never supposed
to support GFP_ZERO, as we don't need it in networking.. So maybe
you're better off adding the memset() in nvme?

CCing Alex, who I think would say something along those lines :)
IDK how much we still care given that most networking drivers are
migrating to page_poll these days.