Commit 3a194f3f authored by Naoya Horiguchi's avatar Naoya Horiguchi Committed by Andrew Morton
Browse files

mm/hugetlb: make pud_huge() and follow_huge_pud() aware of non-present pud entry 

follow_pud_mask() does not support non-present pud entry now.  As long as
I tested on x86_64 server, follow_pud_mask() still simply returns
no_page_table() for non-present_pud_entry() due to pud_bad(), so no severe
user-visible effect should happen.  But generally we should call
follow_huge_pud() for non-present pud entry for 1GB hugetlb page.

Update pud_huge() and follow_huge_pud() to handle non-present pud entries.
The changes are similar to previous works for pud entries commit
e66f17ff ("mm/hugetlb: take page table lock in follow_huge_pmd()") and
commit cbef8478 ("mm/hugetlb: pmd_huge() returns true for non-present
hugepage").

Link: https://lkml.kernel.org/r/20220714042420.1847125-3-naoya.horiguchi@linux.dev


Signed-off-by: default avatarNaoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: default avatarMiaohe Lin <linmiaohe@huawei.com>
Reviewed-by: default avatarMike Kravetz <mike.kravetz@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Liu Shixin <liushixin2@huawei.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent c0531714

arch/x86/mm/hugetlbpage.c

+7 −1
Original line number Diff line number Diff line
@@ -30,9 +30,15 @@ int pmd_huge(pmd_t pmd) 
		(pmd_val(pmd) & (_PAGE_PRESENT|_PAGE_PSE)) != _PAGE_PRESENT;

}



/*

 * pud_huge() returns 1 if @pud is hugetlb related entry, that is normal

 * hugetlb entry or non-present (migration or hwpoisoned) hugetlb entry.

 * Otherwise, returns 0.

 */

int pud_huge(pud_t pud)

{

	return !!(pud_val(pud) & _PAGE_PSE);

	return !pud_none(pud) &&

		(pud_val(pud) & (_PAGE_PRESENT|_PAGE_PSE)) != _PAGE_PRESENT;

}



#ifdef CONFIG_HUGETLB_PAGE

mm/hugetlb.c

+30 −2
Original line number Diff line number Diff line
@@ -6985,10 +6985,38 @@ struct page * __weak 
follow_huge_pud(struct mm_struct *mm, unsigned long address,

		pud_t *pud, int flags)

{

	if (flags & (FOLL_GET | FOLL_PIN))

	struct page *page = NULL;

	spinlock_t *ptl;

	pte_t pte;



	if (WARN_ON_ONCE(flags & FOLL_PIN))

		return NULL;



	return pte_page(*(pte_t *)pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);

retry:

	ptl = huge_pte_lock(hstate_sizelog(PUD_SHIFT), mm, (pte_t *)pud);

	if (!pud_huge(*pud))

		goto out;

	pte = huge_ptep_get((pte_t *)pud);

	if (pte_present(pte)) {

		page = pud_page(*pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);

		if (WARN_ON_ONCE(!try_grab_page(page, flags))) {

			page = NULL;

			goto out;

		}

	} else {

		if (is_hugetlb_entry_migration(pte)) {

			spin_unlock(ptl);

			__migration_entry_wait(mm, (pte_t *)pud, ptl);

			goto retry;

		}

		/*

		 * hwpoisoned entry is treated as no_page_table in

		 * follow_page_mask().

		 */

	}

out:

	spin_unlock(ptl);

	return page;

}



struct page * __weak