netdev - RE: [PATCH V2] net: ethernet: mellanox: correct page conversion

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Date:	Mon, 18 Apr 2016 14:39:36 +0000
From:	Eli Cohen <eli@...lanox.com>
To:	Christoph Hellwig <hch@...radead.org>
CC:	Sinan Kaya <okaya@...eaurora.org>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	"timur@...eaurora.org" <timur@...eaurora.org>,
	"cov@...eaurora.org" <cov@...eaurora.org>,
	Yishai Hadas <yishaih@...lanox.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH V2] net: ethernet: mellanox: correct page conversion

Right, I did not suggest this as a patch but just wanted to pinpoint the problematic issue which is that virt_to_page does not give you the correct pointer to the page.

-----Original Message-----
From: Christoph Hellwig [mailto:hch@...radead.org] 
Sent: Monday, April 18, 2016 9:33 AM
To: Eli Cohen <eli@...lanox.com>
Cc: Sinan Kaya <okaya@...eaurora.org>; linux-rdma@...r.kernel.org; timur@...eaurora.org; cov@...eaurora.org; Yishai Hadas <yishaih@...lanox.com>; netdev@...r.kernel.org; linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] net: ethernet: mellanox: correct page conversion

On Mon, Apr 18, 2016 at 09:54:47AM +0300, Eli Cohen wrote:
> Sinan,
> 
> if we get rid of the part this code:
> 
>                 if (BITS_PER_LONG == 64) {
>                         struct page **pages;
>                         pages = kmalloc(sizeof *pages * buf->nbufs, gfp);
>                         if (!pages)
>                                 goto err_free;
>                         ...
>                         ...
>                         if (!buf->direct.buf)
>                                 goto err_free;
>                 }
> 
> Does that solve the arm issue?

Not quite.  You still have code in mlx4_en_map_buffer that performs this mapping later if it it wasn't mapped in mlx4_buf_alloc.

You'll need to get rid of that by ensuring max_direct for all the cases currently using mlx4_en_map_buffer as well.