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

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Date: Fri, 12 Apr 2024 11:37:00 +1000
From: Alistair Popple <apopple@...dia.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-mm@...ck.org, 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


David Hildenbrand <david@...hat.com> writes:

> 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 :)

Thanks. Rebasing was the other thing I meant to add as a TODO in the
cover letter :)

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