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Subject: Re: [PATCH v2] hugetlb: don't delete vma_lock in hugetlb
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From:   Nadav Amit <nadav.amit@gmail.com>
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Date:   Sun, 30 Oct 2022 11:52:52 -0700
Cc:     Mike Kravetz <mike.kravetz@oracle.com>,
        Linux-MM <linux-mm@kvack.org>,
        kernel list <linux-kernel@vger.kernel.org>,
        Naoya Horiguchi <naoya.horiguchi@linux.dev>,
        David Hildenbrand <david@redhat.com>,
        Axel Rasmussen <axelrasmussen@google.com>,
        Mina Almasry <almasrymina@google.com>,
        Rik van Riel <riel@surriel.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Matthew Wilcox <willy@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Wei Chen <harperchen1110@gmail.com>,
        "# 5 . 10+" <stable@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
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To:     Peter Xu <peterx@redhat.com>
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On Oct 30, 2022, at 11:43 AM, Peter Xu <peterx@redhat.com> wrote:

> The loop comes from 7e027b14d53e ("vm: simplify unmap_vmas() calling
> convention", 2012-05-06), where zap_page_range() was used to replace a call
> to unmap_vmas() because the patch wanted to eliminate the zap details
> pointer for unmap_vmas(), which makes sense.
> 
> I didn't check the old code, but from what I can tell (and also as Mike
> pointed out) I don't think zap_page_range() in the lastest code base is
> ever used on multi-vma at all.  Otherwise the mmu notifier is already
> broken - see mmu_notifier_range_init() where the vma pointer is also part
> of the notification.
> 
> Perhaps we should just remove the loop?

There is already zap_page_range_single() that does exactly that. Just need
to export it.