linux-ext4 - Re: [RFC 09/10] mm/khugepage.c: Warn if trying to scan devmap pmd

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Date: Thu, 11 Apr 2024 15:45:57 +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 09/10] mm/khugepage.c: Warn if trying to scan devmap pmd

On 11.04.24 02:57, Alistair Popple wrote:
> The only user of devmap PTEs is FS DAX, and khugepaged should not be
> scanning these VMAs. This is checked by calling
> hugepage_vma_check. Therefore khugepaged should never encounter a
> devmap PTE. Warn if this occurs.
> 
> Signed-off-by: Alistair Popple <apopple@...dia.com>
> 
> ---
> 
> Note this is a transitory patch to test the above assumption both at
> runtime and during review. I will likely remove it as the whole thing
> gets deleted when pXX_devmap is removed.

Yes, doesn't make sense for this patch to exist if it would go upstream 
along with the next patch that removes that completely.

-- 
Cheers,

David / dhildenb