linux-kernel - Re: [PATCH 2/3] hugetlbfs: close race between MADV

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Date:   Mon, 02 Oct 2023 09:13:35 -0400
From:   Rik van Riel <riel@...riel.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     linux-kernel@...r.kernel.org, kernel-team@...a.com,
        linux-mm@...ck.org, akpm@...ux-foundation.org,
        muchun.song@...ux.dev, leit@...a.com, willy@...radead.org
Subject: Re: [PATCH 2/3] hugetlbfs: close race between MADV_DONTNEED and
 page fault

On Sun, 2023-10-01 at 21:39 -0700, Mike Kravetz wrote:
> 
> Looks like vma->vm_file is NULL and __hugetlb_zap_begin is trying to
> do
> i_mmap_lock_write(vma->vm_file->f_mapping).
> 
> Guess I did look closely. :)

Ugh. It looks like the fix for this bug ended up getting pulled
into patch 3, instead of patch 2.  I've had it in my code for a
while now :/

Let me move the fix for this thing into patch 2.

void __hugetlb_zap_begin(struct vm_area_struct *vma,
                         unsigned long *start, unsigned long *end)
{
        adjust_range_if_pmd_sharing_possible(vma, start, end);
        hugetlb_vma_lock_write(vma);
        if (vma->vm_file)
                i_mmap_lock_write(vma->vm_file->f_mapping);
}


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