Re: [PATCH 10/10] mm/hugetlb: Introduce hugetlb_walk()

[Eric Biggers]

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