linux-kernel - Re: [PATCH v4.4-rc8 v3] dmaengine: ioatdma: Squelch framesize warnings

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Date:	Fri, 8 Jan 2016 11:41:23 -0800
From:	Dan Williams <dan.j.williams@...el.com>
To:	Tim Gardner <tim.gardner@...onical.com>
Cc:	"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Vinod Koul <vinod.koul@...el.com>,
	Dave Jiang <dave.jiang@...el.com>,
	Prarit Bhargava <prarit@...hat.com>,
	Nicholas Mc Guire <der.herr@...r.at>,
	Jarkko Nikula <jarkko.nikula@...ux.intel.com>
Subject: Re: [PATCH v4.4-rc8 v3] dmaengine: ioatdma: Squelch framesize warnings

On Fri, Jan 8, 2016 at 11:25 AM,  <tim.gardner@...onical.com> wrote:
> From: Tim Gardner <tim.gardner@...onical.com>
>
>   CC [M]  drivers/dma/ioat/prep.o
> drivers/dma/ioat/prep.c: In function 'ioat_prep_pqxor':
> drivers/dma/ioat/prep.c:682:1: warning: the frame size of 1048 bytes is larger than 1024 bytes [-Wframe-larger-than=]
>  }
>  ^
> drivers/dma/ioat/prep.c: In function 'ioat_prep_pqxor_val':
> drivers/dma/ioat/prep.c:714:1: warning: the frame size of 1048 bytes is larger than 1024 bytes [-Wframe-larger-than=]
>  }
>
> gcc version 5.3.1 20151219 (Ubuntu 5.3.1-4ubuntu1)
>
> Cc: Vinod Koul <vinod.koul@...el.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Dave Jiang <dave.jiang@...el.com>
> Cc: Prarit Bhargava <prarit@...hat.com>
> Cc: Nicholas Mc Guire <der.herr@...r.at>
> Cc: Jarkko Nikula <jarkko.nikula@...ux.intel.com>
> Signed-off-by: Tim Gardner <tim.gardner@...onical.com>
> ---
>
> v2 - use per CPU static buffers instead of dynamically allocating memory.
> v3 - Use get_cpu_var/put_cpu_var which implicitly control preeemption. Drop
>      the wrapper function that no longer serves any purpose.
>
>  drivers/dma/ioat/prep.c | 29 +++++++++++++++++++++++++----
>  1 file changed, 25 insertions(+), 4 deletions(-)

Looks good to me... but now that I think about it, why is MAX_SCF set
to 1024 in the first place?  Certainly it can't be bigger than the
maximum number of sources in a single operation which is 8 to 16.
Even md raid can only support up to 256 devices in an array.  So I
think that contstant is bogus.

If we set it to 16 we may not even need the percpu change.

Dave?