linux-kernel - Re: [PATCH v9 2/3] hugetlb: remove duplicate mmu notifications

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Message-ID: <cfb2e9de-3bf8-6380-f336-dc3d7a5ecc29@redhat.com>
Date:   Mon, 14 Nov 2022 10:06:18 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Peter Xu <peterx@...hat.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Rik van Riel <riel@...riel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Wei Chen <harperchen1110@...il.com>, stable@...r.kernel.org
Subject: Re: [PATCH v9 2/3] hugetlb: remove duplicate mmu notifications

On 12.11.22 00:26, Mike Kravetz wrote:
> The common hugetlb unmap routine __unmap_hugepage_range performs mmu
> notification calls.  However, in the case where __unmap_hugepage_range
> is called via __unmap_hugepage_range_final, mmu notification calls are
> performed earlier in other calling routines.
> 
> Remove mmu notification calls from __unmap_hugepage_range.  Add
> notification calls to the only other caller: unmap_hugepage_range.
> unmap_hugepage_range is called for truncation and hole punch, so
> change notification type from UNMAP to CLEAR as this is more appropriate.
> 
> Fixes: 90e7e7f5ef3f ("mm: enable MADV_DONTNEED for hugetlb mappings")
> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
> Reported-by: Wei Chen <harperchen1110@...il.com>
> Cc: <stable@...r.kernel.org>

Why exactly do we care about stable backports here? What's the 
user-visible impact?

-- 
Thanks,

David / dhildenb