fs/proc/task_mmu: hold PTL in pagemap_hugetlb_range and gather_hugetlb_stats

Hold PTL in pagemap_hugetlb_range() and gather_hugetlb_stats() to avoid
operating on stale page, as pagemap_pmd_range() and gather_pte_stats()
have done.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Jinjiang Tu <[e-mail]>
Acked-by: David Hildenbrand <[e-mail]>
Cc: Andrei Vagin <[e-mail]>
Cc: Andrii Nakryiko <[e-mail]>
Cc: Baolin Wang <[e-mail]>
Cc: Brahmajit Das <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: Christophe Leroy <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: Dev Jain <[e-mail]>
Cc: Hugh Dickins <[e-mail]>
Cc: Joern Engel <[e-mail]>
Cc: Kefeng Wang <[e-mail]>
Cc: Lorenzo Stoakes <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Ryan Roberts <[e-mail]>
Cc: Thiago Jung Bauermann <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

fs/proc/task_mmu.c

···
 	struct pagemapread *pm = walk->private;
 	struct vm_area_struct *vma = walk->vma;
 	u64 flags = 0, frame = 0;
+	spinlock_t *ptl;
 	int err = 0;
 	pte_t pte;
 
 	if (vma->vm_flags & VM_SOFTDIRTY)
 		flags |= PM_SOFT_DIRTY;
 
+	ptl = huge_pte_lock(hstate_vma(vma), walk->mm, ptep);
 	pte = huge_ptep_get(walk->mm, addr, ptep);
 	if (pte_present(pte)) {
 		struct folio *folio = page_folio(pte_page(pte));
···
 
 		err = add_to_pagemap(&pme, pm);
 		if (err)
-			return err;
+			break;
 		if (pm->show_pfn && (flags & PM_PRESENT))
 			frame++;
 	}
 
+	spin_unlock(ptl);
 	cond_resched();
 
 	return err;
···
 static int gather_hugetlb_stats(pte_t *pte, unsigned long hmask,
 		unsigned long addr, unsigned long end, struct mm_walk *walk)
 {
-	pte_t huge_pte = huge_ptep_get(walk->mm, addr, pte);
+	pte_t huge_pte;
 	struct numa_maps *md;
 	struct page *page;
+	spinlock_t *ptl;
 
+	ptl = huge_pte_lock(hstate_vma(walk->vma), walk->mm, pte);
+	huge_pte = huge_ptep_get(walk->mm, addr, pte);
 	if (!pte_present(huge_pte))
-		return 0;
+		goto out;
 
 	page = pte_page(huge_pte);
 
 	md = walk->private;
 	gather_stats(page, md, pte_dirty(huge_pte), 1);
+out:
+	spin_unlock(ptl);
 	return 0;
 }