linux-kernel - Re: [PATCH v2 1/2] mm/gup: Remove dead pgmap refcounting code

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Message-ID: <1ffb22b9-98e2-4073-8399-217f4ed4d9d9@nvidia.com>
Date: Fri, 5 Sep 2025 20:27:00 -0700
From: John Hubbard <jhubbard@...dia.com>
To: Alistair Popple <apopple@...dia.com>, linux-mm@...ck.org,
 akpm@...ux-foundation.org
Cc: david@...hat.com, osalvador@...e.de, jgg@...pe.ca, peterx@...hat.com,
 linux-kernel@...r.kernel.org, dan.j.williams@...el.com,
 Jason Gunthorpe <jgg@...dia.com>
Subject: Re: [PATCH v2 1/2] mm/gup: Remove dead pgmap refcounting code

On 9/5/25 5:56 PM, John Hubbard wrote:
...> Maybe I'll post a quick follow-up, in fact, to remove page_mask
> as well. No need to pass that around all over the place, I think
> it can instead be computed by the single place that actually
> consumes it.
> 

Almost, but not quite. The problem is in the -EEXIST return code
case for follow_page_mask(). In that case, we also need folio
size (PMD, PUD, or normal) to be returned. The page_mask argument
does that now, and as long as we are in C, it's awkward to do
anything else. 

oh well.

thanks,
-- 
John Hubbard