netdev - use exact allocation for dma coherent memory

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Message-Id: <20190614134726.3827-1-hch@lst.de>
Date:   Fri, 14 Jun 2019 15:47:10 +0200
From:   Christoph Hellwig <hch@....de>
To:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Ian Abbott <abbotti@....co.uk>,
        H Hartley Sweeten <hsweeten@...ionengravers.com>
Cc:     Intel Linux Wireless <linuxwifi@...el.com>,
        linux-arm-kernel@...ts.infradead.org (moderated list:ARM PORT),
        dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
        linux-rdma@...r.kernel.org, linux-media@...r.kernel.org,
        netdev@...r.kernel.org, linux-wireless@...r.kernel.org,
        linux-s390@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: use exact allocation for dma coherent memory

Hi all,

various architectures have used exact memory allocations for dma
allocations for a long time, but x86 and thus the common code based
on it kept using our normal power of two allocator, which tends to
waste a lot of memory for certain allocations.

Switching to a slightly cleaned up alloc_pages_exact is pretty easy,
but it turns out that because we didn't filter valid gfp_t flags
on the DMA allocator, a bunch of drivers were passing __GFP_COMP
to it, which is rather bogus in too many ways to explain.  Arm has
been filtering it for a while, but this series instead tries to fix
the drivers and warn when __GFP_COMP is passed, which makes it much
larger than just adding the functionality.