linux-kernel - Re: [PATCH 1/2] hugetlbfs: extend hugetlb_vma

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Date:   Wed, 20 Sep 2023 00:09:41 -0400
From:   Rik van Riel <riel@...riel.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     linux-kernel@...r.kernel.org, kernel-team@...a.com,
        linux-mm@...ck.org, akpm@...ux-foundation.org,
        muchun.song@...ux.dev, mike.kravetz@...cle.com, leit@...a.com
Subject: Re: [PATCH 1/2] hugetlbfs: extend hugetlb_vma_lock to private VMAs

On Wed, 2023-09-20 at 04:57 +0100, Matthew Wilcox wrote:
> On Tue, Sep 19, 2023 at 10:16:09PM -0400, riel@...riel.com wrote:
> > From: Rik van Riel <riel@...riel.com>
> > 
> > Extend the locking scheme used to protect shared hugetlb mappings
> > from truncate vs page fault races, in order to protect private
> > hugetlb mappings (with resv_map) against MADV_DONTNEED.
> > 
> > Add a read-write semaphore to the resv_map data structure, and
> > use that from the hugetlb_vma_(un)lock_* functions, in preparation
> > for closing the race between MADV_DONTNEED and page faults.
> 
> This feels an awful lot like the invalidate_lock in struct
> address_space
> which was recently added by Jan Kara.
> 
Indeed it does.

It might be even nicer if we could replace the hugetlb_vma_lock
special logic with the invalidate_lock for hugetlbfs.

Mike, can you think of any reason why the hugetlb_vma_lock logic
should not be replaced with the invalidate_lock?

If not, I'd be happy to implement that.

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