linux-ext4 - Re: [RFC 01/10] mm/gup.c: Remove redundant check for PCI P2PDMA page

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Date: Thu, 11 Apr 2024 15:47:17 +0200
From: David Hildenbrand <david@...hat.com>
To: Alistair Popple <apopple@...dia.com>, linux-mm@...ck.org
Cc: david@...morbit.com, dan.j.williams@...el.com, jhubbard@...dia.com,
 rcampbell@...dia.com, willy@...radead.org, jgg@...dia.com,
 linux-fsdevel@...r.kernel.org, jack@...e.cz, djwong@...nel.org, hch@....de,
 ruansy.fnst@...itsu.com, nvdimm@...ts.linux.dev, linux-xfs@...r.kernel.org,
 linux-ext4@...r.kernel.org, jglisse@...hat.com
Subject: Re: [RFC 01/10] mm/gup.c: Remove redundant check for PCI P2PDMA page

On 11.04.24 02:57, Alistair Popple wrote:
> PCI P2PDMA pages are not mapped with pXX_devmap PTEs therefore the
> check in __gup_device_huge() is redundant. Remove it
> 
> Signed-off-by: Alistair Popple <apopple@...dia.com>
> ---
>   mm/gup.c | 5 -----
>   1 file changed, 5 deletions(-)
> 
> diff --git a/mm/gup.c b/mm/gup.c
> index 2f8a2d8..a9c8a09 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -2683,11 +2683,6 @@ static int __gup_device_huge(unsigned long pfn, unsigned long addr,
>   			break;
>   		}
>   
> -		if (!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)) {
> -			undo_dev_pagemap(nr, nr_start, flags, pages);
> -			break;
> -		}
> -
>   		SetPageReferenced(page);
>   		pages[*nr] = page;
>   		if (unlikely(try_grab_page(page, flags))) {

Rebasing on mm-unstable, you'll notice some minor conflicts, but nothing 
earth shattering :)

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

-- 
Cheers,

David / dhildenb