Re: [PATCH] mm: split vm_normal_pages for LRU and non-LRU handling

From: David Hildenbrand <david@redhat.com>
To: Felix Kuehling <felix.kuehling@amd.com>,
	Alex Sierra <alex.sierra@amd.com>,
	jgg@nvidia.com
Cc: rcampbell@nvidia.com, willy@infradead.org, apopple@nvidia.com,
	dri-devel@lists.freedesktop.org, linux-xfs@vger.kernel.org,
	linux-mm@kvack.org, jglisse@redhat.com,
	amd-gfx@lists.freedesktop.org, akpm@linux-foundation.org,
	linux-ext4@vger.kernel.org, hch@lst.de
Subject: Re: [PATCH] mm: split vm_normal_pages for LRU and non-LRU handling
Date: Tue, 1 Mar 2022 17:32:24 +0100	[thread overview]
Message-ID: <85a68c56-7cce-ef98-7aa6-c68eabf3fa0b@redhat.com> (raw)
In-Reply-To: <353c7bbd-b20e-8a7a-029a-cda9b531e5e8@amd.com>

On 01.03.22 17:30, Felix Kuehling wrote:
> Am 2022-03-01 um 11:22 schrieb David Hildenbrand:
>>>>>    		if (PageReserved(page))
>>>>> diff --git a/mm/migrate.c b/mm/migrate.c
>>>>> index c31d04b46a5e..17d049311b78 100644
>>>>> --- a/mm/migrate.c
>>>>> +++ b/mm/migrate.c
>>>>> @@ -1614,7 +1614,7 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
>>>>>    		goto out;
>>>>>    
>>>>>    	/* FOLL_DUMP to ignore special (like zero) pages */
>>>>> -	follflags = FOLL_GET | FOLL_DUMP;
>>>>> +	follflags = FOLL_GET | FOLL_DUMP | FOLL_LRU;
>>>>>    	page = follow_page(vma, addr, follflags);
>>>> Why wouldn't we want to dump DEVICE_COHERENT pages? This looks wrong.
>>> This function later calls isolate_lru_page, which is something you can't
>>> do with a device page.
>>>
>> Then, that code might require care instead. We most certainly don't want
>> to have random memory holes in a dump just because some anonymous memory
>> was migrated to DEVICE_COHERENT.
> I don't think this code is for core dumps. The call chain I see is
> 
> SYSCALL_DEFINE6(move_pages, ...) -> kernel_move_pages -> do_pages_move 
> -> add_page_for_migration
> 

Ah, sorry, I got mislead by FOLL_DUMP and thought we'd be in
get_dump_page() . As you said, nothing to do.

-- 
Thanks,

David / dhildenb