linux-kernel - Re: [PATCH v2 1/1] [PATCH] mm/gup: avoid an unnecessary allocation call for FOLL

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Message-ID: <131cf9c8-ebc0-4cbb-b722-22fa8527bf3c@nvidia.com>
Date: Tue, 5 Nov 2024 13:31:01 -0800
From: John Hubbard <jhubbard@...dia.com>
To: David Hildenbrand <david@...hat.com>, Andrew Morton
	<akpm@...ux-foundation.org>
CC: LKML <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>, Vivek Kasireddy
	<vivek.kasireddy@...el.com>, Dave Airlie <airlied@...hat.com>, Gerd Hoffmann
	<kraxel@...hat.com>, Matthew Wilcox <willy@...radead.org>, Christoph Hellwig
	<hch@...radead.org>, Jason Gunthorpe <jgg@...dia.com>, Peter Xu
	<peterx@...hat.com>, Arnd Bergmann <arnd@...db.de>, Daniel Vetter
	<daniel.vetter@...ll.ch>, Dongwon Kim <dongwon.kim@...el.com>, Hugh Dickins
	<hughd@...gle.com>, Junxiao Chang <junxiao.chang@...el.com>, Mike Kravetz
	<mike.kravetz@...cle.com>, Oscar Salvador <osalvador@...e.de>,
	<linux-stable@...r.kernel.org>
Subject: Re: [PATCH v2 1/1] [PATCH] mm/gup: avoid an unnecessary allocation
 call for FOLL_LONGTERM cases

On 11/5/24 12:47 AM, David Hildenbrand wrote:
> On 05.11.24 04:29, John Hubbard wrote:
...
>>       return ret;
>>   }
>> +static long
>> +check_and_migrate_movable_pages_or_folios(struct pages_or_folios *pofs)
>> +{
>> +    LIST_HEAD(movable_folio_list);
>> +    unsigned long collected;
>> +
>> +    collected =
>> +        collect_longterm_unpinnable_folios(&movable_folio_list, pofs);
> 
> Nit: We're allowed to use more than 80 characters :)

Yes, I'm aware. Most of gup.c stays nicely within 80 cols, so it's nice
to keep that if not too awkward....

> 
> (I would prefer the old way it was split across more lines if we really want to split; this way here is less common)
> 

OK, if I need to respin I'll apply this, to restore the old way. If
not, maybe Andrew can fix it up please?

diff --git a/mm/gup.c b/mm/gup.c
index 0f5121ad0b9f..0a22f7def83c 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2435,8 +2435,8 @@ check_and_migrate_movable_pages_or_folios(struct pages_or_folios *pofs)
         LIST_HEAD(movable_folio_list);
         unsigned long collected;
  
-       collected =
-               collect_longterm_unpinnable_folios(&movable_folio_list, pofs);
+       collected = collect_longterm_unpinnable_folios(&movable_folio_list,
+                                                      pofs);
         if (!collected)
                 return 0;


> 
> Thanks!
> 
> Acked-by: David Hildenbrand <david@...hat.com>
> 

Appreciate the ack, and of course the idea and implementation as well! :)

thanks,
-- 
John Hubbard