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[2620:137:e000::1:9]) by mx.google.com with ESMTPS id j7si45858wrv.370.2019.02.07.13.25.22 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 07 Feb 2019 13:25:22 -0800 (PST) Received-SPF: neutral (google.com: 2620:137:e000::1:9 is neither permitted nor denied by best guess record for domain of davem@davemloft.net) client-ip=2620:137:e000::1:9; Authentication-Results: mx.google.com; spf=neutral (google.com: 2620:137:e000::1:9 is neither permitted nor denied by best guess record for domain of davem@davemloft.net) smtp.mailfrom=davem@davemloft.net Received: from localhost (unknown [IPv6:2601:601:9f80:35cd::bf5]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id D7249146D8BE1; Thu, 7 Feb 2019 13:25:19 -0800 (PST) Date: Thu, 07 Feb 2019 13:25:19 -0800 (PST) Message-Id: <20190207.132519.1698007650891404763.davem@davemloft.net> To: ilias.apalodimas@linaro.org Cc: willy@infradead.org, brouer@redhat.com, tariqt@mellanox.com, toke@redhat.com, netdev@vger.kernel.org, mgorman@techsingularity.net, linux-mm@kvack.org Subject: Re: [RFC, PATCH] net: page_pool: Don't use page->private to store dma_addr_t From: David Miller In-Reply-To: <20190207152034.GA3295@apalos> References: <1549550196-25581-1-git-send-email-ilias.apalodimas@linaro.org> <20190207150745.GW21860@bombadil.infradead.org> <20190207152034.GA3295@apalos> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Thu, 07 Feb 2019 13:25:20 -0800 (PST) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Ilias Apalodimas Date: Thu, 7 Feb 2019 17:20:34 +0200 > Well updating struct page is the final goal, hence the comment. I am mostly > looking for opinions here since we are trying to store dma addresses which are > irrelevant to pages. Having dma_addr_t definitions in mm-related headers is a > bit controversial isn't it ? If we can add that, then yes the code would look > better I fundamentally disagree. One of the core operations performed on a page is mapping it so that a device and use it. Why have ancillary data structure support for this all over the place, rather than in the common spot which is the page. A page really is not just a 'mm' structure, it is a system structure.