linux-kernel - Re: [PATCH v2 01/10] iommu/vt-d: add wrapper functions for page allocations

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Message-ID: <ZYinEGCdl8mZjmXi@casper.infradead.org>
Date: Sun, 24 Dec 2023 21:48:00 +0000
From: Matthew Wilcox <willy@...radead.org>
To: David Rientjes <rientjes@...gle.com>
Cc: Pasha Tatashin <pasha.tatashin@...een.com>,
	Andrew Morton <akpm@...ux-foundation.org>, alim.akhtar@...sung.com,
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Subject: Re: [PATCH v2 01/10] iommu/vt-d: add wrapper functions for page
 allocations

On Sun, Dec 24, 2023 at 01:30:50PM -0800, David Rientjes wrote:
> > > s/pages/page/ here and later in this file.
> > 
> > In this file, where there a page with an "order", I reference it with
> > "pages", when no order (i.e. order = 0), I reference it with "page"
> > 
> > I.e.: __iommu_alloc_page vs. __iommu_alloc_pages
> > 
> 
> Eh, the struct page points to a (potentially compound) page, not a set or 
> list of pages.  I won't bikeshed on it, but "struct page *pages" never 
> makes sense unless it's **pages or *pages[] :)

I'd suggest that 'pages' also makes sense when _not_ using __GFP_COMP,
as we do in fact allocate an array of pages in that case.

That said, we shouldn't encourage the use of non-compound allocations.
It would also be good for someone to define a memdesc for iommu memory
like we have already for slab.  We'll need it eventually, and it'll work
out better if someone who understands iommus (ie not me) does it.