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Date:   Tue, 29 Nov 2022 21:18:08 -0800
From:   Eric Biggers <ebiggers@kernel.org>
To:     Peter Xu <peterx@redhat.com>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        James Houghton <jthoughton@google.com>,
        Jann Horn <jannh@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Rik van Riel <riel@surriel.com>,
        Nadav Amit <nadav.amit@gmail.com>,
        Miaohe Lin <linmiaohe@huawei.com>,
        Muchun Song <songmuchun@bytedance.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH 10/10] mm/hugetlb: Introduce hugetlb_walk()
Message-ID: <Y4bnkO3ikp5bu44x@sol.localdomain>
References: <20221129193526.3588187-1-peterx@redhat.com>
 <20221129193526.3588187-11-peterx@redhat.com>
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On Tue, Nov 29, 2022 at 02:35:26PM -0500, Peter Xu wrote:
> +static inline pte_t *
> +hugetlb_walk(struct vm_area_struct *vma, unsigned long addr, unsigned long sz)
> +{
> +#if defined(CONFIG_ARCH_WANT_HUGE_PMD_SHARE) && defined(CONFIG_LOCKDEP)
> +	struct hugetlb_vma_lock *vma_lock = vma->vm_private_data;
> +
> +	/*
> +	 * If pmd sharing possible, locking needed to safely walk the
> +	 * hugetlb pgtables.  More information can be found at the comment
> +	 * above huge_pte_offset() in the same file.
> +	 *
> +	 * NOTE: lockdep_is_held() is only defined with CONFIG_LOCKDEP.
> +	 */
> +	if (__vma_shareable_flags_pmd(vma))
> +		WARN_ON_ONCE(!lockdep_is_held(&vma_lock->rw_sema) &&
> +			     !lockdep_is_held(
> +				 &vma->vm_file->f_mapping->i_mmap_rwsem));
> +#endif

FYI, in next-20221130 there is a compile error here due to this commit:

    In file included from security/commoncap.c:19:
    ./include/linux/hugetlb.h:1262:42: error: incomplete definition of type 'struct hugetlb_vma_lock'
                    WARN_ON_ONCE(!lockdep_is_held(&vma_lock->rw_sema) &&
                                                   ~~~~~~~~^
    ./include/linux/lockdep.h:286:47: note: expanded from macro 'lockdep_is_held'
    #define lockdep_is_held(lock)           lock_is_held(&(lock)->dep_map)
                                                           ^~~~

- Eric