hugetlb: add lockdep check for i_mmap_rwsem held in huge_pmd_share

 * !shared pmd case because we can allocate the pmd later as well, it makes the

 * code much cleaner.

 *

 * This routine must be called with i_mmap_rwsem held in at least read mode.

 * For hugetlbfs, this prevents removal of any page table entries associated

 * with the address space.  This is important as we are setting up sharing

 * based on existing page table entries (mappings).

 * This routine must be called with i_mmap_rwsem held in at least read mode if

 * sharing is possible.  For hugetlbfs, this prevents removal of any page

 * table entries associated with the address space.  This is important as we

 * are setting up sharing based on existing page table entries (mappings).

 *

 * NOTE: This routine is only called from huge_pte_alloc.  Some callers of

 * huge_pte_alloc know that sharing is not possible and do not take

 * i_mmap_rwsem as a performance optimization.  This is handled by the

 * if !vma_shareable check at the beginning of the routine. i_mmap_rwsem is

 * only required for subsequent processing.

 */

pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)

{

	if (!vma_shareable(vma, addr))

		return (pte_t *)pmd_alloc(mm, pud, addr);

	i_mmap_assert_locked(mapping);

	vma_interval_tree_foreach(svma, &mapping->i_mmap, idx, idx) {

		if (svma == vma)

			continue;