From: Christoph Hellwig <hch@infradead.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: joro@8bytes.org, linux-mm@kvack.org,
iommu@lists.linux-foundation.org, Roman Gushchin <guro@fb.com>
Subject: Re: [PATCH] iommu/dma: Remove broken huge page handling
Date: Thu, 3 Sep 2020 17:38:56 +0100 [thread overview]
Message-ID: <20200903163856.GA20737@infradead.org> (raw)
In-Reply-To: <e287dbe69aa0933abafd97c80631940fd188ddd1.1599132844.git.robin.murphy@arm.com>
On Thu, Sep 03, 2020 at 12:34:04PM +0100, Robin Murphy wrote:
> The attempt to handle huge page allocations was originally added since
> the comments around stripping __GFP_COMP in other implementations were
> nonsensical, and we naively assumed that split_huge_page() could simply
> be called equivalently to split_page(). It turns out that this doesn't
> actually work correctly, so just get rid of it - there's little point
> going to the effort of allocating huge pages if we're only going to
> split them anyway.
>
> Reported-by: Roman Gushchin <guro@fb.com>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
This looks sensibe. We really need to clear it in generic code, but
last time I checked there were one or two buggy drivers that assumed
__GFP_COMP works and actually gives a compound page (iirc legacy
drm stuff). All that stuff really needs fixing..
Reviewed-by: Christoph Hellwig <hch@lst.de>
next prev parent reply other threads:[~2020-09-03 16:39 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-03 11:34 Robin Murphy
2020-09-03 16:38 ` Christoph Hellwig [this message]
2020-09-04 9:55 ` Joerg Roedel
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