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From:   James Houghton <jthoughton@google.com>
Date:   Tue, 10 Jan 2023 15:04:14 -0500
Message-ID: <CADrL8HUvugKN15=XBkELCa=rhd3vjRiwUDsY5cFKkWHO1x5Nyg@mail.gmail.com>
Subject: Re: [PATCH 35/46] hugetlb: add MADV_COLLAPSE for hugetlb
To:     Mike Kravetz <mike.kravetz@oracle.com>,
        Muchun Song <songmuchun@bytedance.com>,
        Peter Xu <peterx@redhat.com>
Cc:     David Hildenbrand <david@redhat.com>,
        David Rientjes <rientjes@google.com>,
        Axel Rasmussen <axelrasmussen@google.com>,
        Mina Almasry <almasrymina@google.com>,
        "Zach O'Keefe" <zokeefe@google.com>,
        Manish Mishra <manish.mishra@nutanix.com>,
        Naoya Horiguchi <naoya.horiguchi@nec.com>,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Baolin Wang <baolin.wang@linux.alibaba.com>,
        Miaohe Lin <linmiaohe@huawei.com>,
        Yang Shi <shy828301@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
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> +
> +               if (curr < end) {
> +                       /* Don't hold the VMA lock for too long. */
> +                       hugetlb_vma_unlock_write(vma);
> +                       cond_resched();
> +                       hugetlb_vma_lock_write(vma);

I need to drop/reacquire the mapping lock here too (missed this when I
added the bits to grab the mapping lock in this function).