From mboxrd@z Thu Jan  1 00:00:00 1970
From: 'Christoph Hellwig' <hch-jcswGhMUV9g@public.gmane.org>
Subject: Re: [PATCH 16/16] dma-mapping: use exact allocation in
	dma_alloc_contiguous
Date: Fri, 14 Jun 2019 17:05:58 +0200
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To: David Laight <David.Laight-ZS65k/vG3HxXrIkS9f7CXA@public.gmane.org>
Cc: Maxime Ripard <maxime.ripard-LDxbnhwyfcJBDgjK7y7TUQ@public.gmane.org>, Joonas Lahtinen <joonas.lahtinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>, "dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org" <dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org>, "linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org" <linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>, 'Christoph Hellwig' <hch-jcswGhMUV9g@public.gmane.org>, "devel-gWbeCf7V1WCQmaza687I9mD2FQJk+8+b@public.gmane.org" <devel-gWbeCf7V1WCQmaza687I9mD2FQJk+8+b@public.gmane.org>, "linux-s390-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-s390-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, David Airlie <airlied-cv59FeDIM0c@public.gmane.org>, "linux-media-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-media-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Intel Linux Wireless <linuxwifi-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, "intel-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org" <intel-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org>, Maarten Lankhorst <maarten.lankhorst-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>, Jani Nikula <jani.nikula-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>, Ian Abbott <abbotti-GUHe90Wt2aFaa/9Udqfwiw@public.gmane.org>, Rodrigo Vivi <rodrigo.vivi-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, Sean Paul <sean-p7yTbzM4H96eqtR555YLDQ@public.gmane.org>, "moderated list:ARM PORT" <linux-arm-kernel-IAPFreCvJWM1dQTEkxZZdg@public.gmane.org>
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On Fri, Jun 14, 2019 at 03:01:22PM +0000, David Laight wrote:
> I'm pretty sure there is a lot of code out there that makes that assumption.
> Without it many drivers will have to allocate almost double the
> amount of memory they actually need in order to get the required alignment.
> So instead of saving memory you'll actually make more be used.

That code would already be broken on a lot of Linux platforms.