netdev - Re: [RFC, PATCH] net: page_pool: Don't use page->private to store dma_addr

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Message-ID: <20190207214237.GA10676@Iliass-MBP.lan>
Date:   Thu, 7 Feb 2019 23:42:37 +0200
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     David Miller <davem@...emloft.net>, brouer@...hat.com,
        tariqt@...lanox.com, toke@...hat.com, netdev@...r.kernel.org,
        mgorman@...hsingularity.net, linux-mm@...ck.org
Subject: Re: [RFC, PATCH] net: page_pool: Don't use page->private to store
 dma_addr_t

Hi Matthew,

On Thu, Feb 07, 2019 at 01:34:00PM -0800, Matthew Wilcox wrote:
> On Thu, Feb 07, 2019 at 01:25:19PM -0800, David Miller wrote:
> > From: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> > 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.
> 
> +1
> 
> The fundamental point of computing is to do I/O.
Ok, great that should sort it out then.
I'll use your proposal and base the patch on that. 

Thanks for taking the time with this

/Ilias