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References: <20230217222130.85205-1-ilias.apalodimas@linaro.org> <20230221091458.7d026652@kernel.org>
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From:   Ilias Apalodimas <ilias.apalodimas@linaro.org>
Date:   Tue, 21 Feb 2023 19:21:58 +0200
Message-ID: <CAC_iWjJO6-C+v5dRHxqvpCy_miwhG7g6J2=o8YzfumfMHiKZ0Q@mail.gmail.com>
Subject: Re: [PATCH v3] page_pool: add a comment explaining the fragment
 counter usage
To:     Jakub Kicinski <kuba@kernel.org>
Cc:     netdev@vger.kernel.org, alexander.duyck@gmail.com,
        Alexander Duyck <alexanderduyck@fb.com>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>, linux-kernel@vger.kernel.org
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On Tue, 21 Feb 2023 at 19:15, Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Sat, 18 Feb 2023 00:21:30 +0200 Ilias Apalodimas wrote:
> > When reading the page_pool code the first impression is that keeping
> > two separate counters, one being the page refcnt and the other being
> > fragment pp_frag_count, is counter-intuitive.
> >
> > However without that fragment counter we don't know when to reliably
> > destroy or sync the outstanding DMA mappings.  So let's add a comment
> > explaining this part.
>
> I discussed with Paolo off-list, since it's just a comment change
> I'll push it in.

Fair enough. Thanks Jakub.

Regards
/Ilias