linux-kernel - Re: [PATCH v2 19/37] mm/gup: remove record

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Message-ID: <815cbde4-a56d-446d-b517-c63e12e473de@redhat.com>
Date: Sat, 6 Sep 2025 09:00:54 +0200
From: David Hildenbrand <david@...hat.com>
To: John Hubbard <jhubbard@...dia.com>, linux-kernel@...r.kernel.org
Cc: Alexander Potapenko <glider@...gle.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Brendan Jackman <jackmanb@...gle.com>, Christoph Lameter <cl@...two.org>,
 Dennis Zhou <dennis@...nel.org>, Dmitry Vyukov <dvyukov@...gle.com>,
 dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
 iommu@...ts.linux.dev, io-uring@...r.kernel.org,
 Jason Gunthorpe <jgg@...dia.com>, Jens Axboe <axboe@...nel.dk>,
 Johannes Weiner <hannes@...xchg.org>, kasan-dev@...glegroups.com,
 kvm@...r.kernel.org, "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Linus Torvalds <torvalds@...ux-foundation.org>, linux-arm-kernel@...s.com,
 linux-arm-kernel@...ts.infradead.org, linux-crypto@...r.kernel.org,
 linux-ide@...r.kernel.org, linux-kselftest@...r.kernel.org,
 linux-mips@...r.kernel.org, linux-mmc@...r.kernel.org, linux-mm@...ck.org,
 linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
 linux-scsi@...r.kernel.org, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
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 Michal Hocko <mhocko@...e.com>, Mike Rapoport <rppt@...nel.org>,
 Muchun Song <muchun.song@...ux.dev>, netdev@...r.kernel.org,
 Oscar Salvador <osalvador@...e.de>, Peter Xu <peterx@...hat.com>,
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 Tejun Heo <tj@...nel.org>, virtualization@...ts.linux.dev,
 Vlastimil Babka <vbabka@...e.cz>, wireguard@...ts.zx2c4.com, x86@...nel.org,
 Zi Yan <ziy@...dia.com>
Subject: Re: [PATCH v2 19/37] mm/gup: remove record_subpages()

>    	pmdp = pmd_offset_lockless(pudp, pud, addr);
> @@ -3046,23 +3041,21 @@ static int gup_fast_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr,
>    
>    		next = pmd_addr_end(addr, end);
>    		if (!pmd_present(pmd))
> -			return 0;
> +			break;
>    
> -		if (unlikely(pmd_leaf(pmd))) {
> -			/* See gup_fast_pte_range() */
> -			if (pmd_protnone(pmd))
> -				return 0;
> +		if (unlikely(pmd_leaf(pmd)))
> +			cur_nr_pages = gup_fast_pmd_leaf(pmd, pmdp, addr, next, flags, pages);
> +		else
> +			cur_nr_pages = gup_fast_pte_range(pmd, pmdp, addr, next, flags, pages);
>    
> -			if (!gup_fast_pmd_leaf(pmd, pmdp, addr, next, flags,
> -				pages, nr))
> -				return 0;
> +		nr_pages += cur_nr_pages;
> +		pages += cur_nr_pages;
>    
> -		} else if (!gup_fast_pte_range(pmd, pmdp, addr, next, flags,
> -					       pages, nr))
> -			return 0;
> +		if (nr_pages != (next - addr) >> PAGE_SIZE)
> +			break;

^ cur_nr_pages. Open for suggestions on how to make that thing here even 
better.

-- 
Cheers

David / dhildenb