linux-kernel - Re: [PATCH v5 1/3] net: introduce helper sendpage

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Message-ID: <20200818070010.GA2365@lst.de>
Date:   Tue, 18 Aug 2020 09:00:10 +0200
From:   Christoph Hellwig <hch@....de>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Christoph Hellwig <hch@....de>, Coly Li <colyli@...e.de>,
        linux-block@...r.kernel.org, linux-nvme@...ts.infradead.org,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        stable <stable@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Chaitanya Kulkarni <chaitanya.kulkarni@....com>,
        Hannes Reinecke <hare@...e.de>, Jan Kara <jack@...e.com>,
        Jens Axboe <axboe@...nel.dk>,
        Mikhail Skorzhinskii <mskorzhinskiy@...arflare.com>,
        Philipp Reisner <philipp.reisner@...bit.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Vlastimil Babka <vbabka@...e.com>
Subject: Re: [PATCH v5 1/3] net: introduce helper sendpage_ok() in
 include/linux/net.h

On Mon, Aug 17, 2020 at 12:12:12PM -0700, Cong Wang wrote:
> 
> So netdev people will have to understand and support PageSlab() or
> page_count()?

Yes.  As they came up with that contrived rule what is acceptable
for sendpage.  No one else really knows and other subsystems like the
block layer are perfectly fine with it.

> 
> If it is unusual even for mm people, how could netdev people suppose
> to understand this unusual mm bug? At least not any better.

It is not a mm bug, it is a networking quirk.