Merge branch 'akpm'

* akpm:
  mm: madvise(MADV_DODUMP): allow hugetlbfs pages
  ocfs2: fix locking for res->tracking and dlm->tracking_list
  mm/vmscan.c: fix int overflow in callers of do_shrink_slab()
  mm/vmstat.c: skip NR_TLB_REMOTE_FLUSH* properly
  mm/vmstat.c: fix outdated vmstat_text
  proc: restrict kernel stack dumps to root
  mm/hugetlb: add mmap() encodings for 32MB and 512MB page sizes
  mm/migrate.c: split only transparent huge pages when allocation fails
  ipc/shm.c: use ERR_CAST() for shm_lock() error return
  mm/gup_benchmark: fix unsigned comparison to zero in __gup_benchmark_ioctl
  mm, thp: fix mlocking THP page with migration enabled
  ocfs2: fix crash in ocfs2_duplicate_clusters_by_page()
  hugetlb: take PMD sharing into account when flushing tlb/caches
  mm: migration: fix migration of huge PMD shared pages

1 files changed, 79 insertions, 11 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3c21775f196b..5c390f5a5207 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3326,8 +3326,8 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
 	struct page *page;
 	struct hstate *h = hstate_vma(vma);
 	unsigned long sz = huge_page_size(h);
-	const unsigned long mmun_start = start;	/* For mmu_notifiers */
-	const unsigned long mmun_end   = end;	/* For mmu_notifiers */
+	unsigned long mmun_start = start;	/* For mmu_notifiers */
+	unsigned long mmun_end   = end;		/* For mmu_notifiers */
 
 	WARN_ON(!is_vm_hugetlb_page(vma));
 	BUG_ON(start & ~huge_page_mask(h));
@@ -3339,6 +3339,11 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
 	 */
 	tlb_remove_check_page_size_change(tlb, sz);
 	tlb_start_vma(tlb, vma);
+
+	/*
+	 * If sharing possible, alert mmu notifiers of worst case.
+	 */
+	adjust_range_if_pmd_sharing_possible(vma, &mmun_start, &mmun_end);
 	mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
 	address = start;
 	for (; address < end; address += sz) {
@@ -3349,6 +3354,10 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
 		ptl = huge_pte_lock(h, mm, ptep);
 		if (huge_pmd_unshare(mm, &address, ptep)) {
 			spin_unlock(ptl);
+			/*
+			 * We just unmapped a page of PMDs by clearing a PUD.
+			 * The caller's TLB flush range should cover this area.
+			 */
 			continue;
 		}
 
@@ -3431,12 +3440,23 @@ void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 {
 	struct mm_struct *mm;
 	struct mmu_gather tlb;
+	unsigned long tlb_start = start;
+	unsigned long tlb_end = end;
+
+	/*
+	 * If shared PMDs were possibly used within this vma range, adjust
+	 * start/end for worst case tlb flushing.
+	 * Note that we can not be sure if PMDs are shared until we try to
+	 * unmap pages.  However, we want to make sure TLB flushing covers
+	 * the largest possible range.
+	 */
+	adjust_range_if_pmd_sharing_possible(vma, &tlb_start, &tlb_end);
 
 	mm = vma->vm_mm;
 
-	tlb_gather_mmu(&tlb, mm, start, end);
+	tlb_gather_mmu(&tlb, mm, tlb_start, tlb_end);
 	__unmap_hugepage_range(&tlb, vma, start, end, ref_page);
-	tlb_finish_mmu(&tlb, start, end);
+	tlb_finish_mmu(&tlb, tlb_start, tlb_end);
 }
 
 /*
@@ -4298,11 +4318,21 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
 	pte_t pte;
 	struct hstate *h = hstate_vma(vma);
 	unsigned long pages = 0;
+	unsigned long f_start = start;
+	unsigned long f_end = end;
+	bool shared_pmd = false;
+
+	/*
+	 * In the case of shared PMDs, the area to flush could be beyond
+	 * start/end.  Set f_start/f_end to cover the maximum possible
+	 * range if PMD sharing is possible.
+	 */
+	adjust_range_if_pmd_sharing_possible(vma, &f_start, &f_end);
 
 	BUG_ON(address >= end);
-	flush_cache_range(vma, address, end);
+	flush_cache_range(vma, f_start, f_end);
 
-	mmu_notifier_invalidate_range_start(mm, start, end);
+	mmu_notifier_invalidate_range_start(mm, f_start, f_end);
 	i_mmap_lock_write(vma->vm_file->f_mapping);
 	for (; address < end; address += huge_page_size(h)) {
 		spinlock_t *ptl;
@@ -4313,6 +4343,7 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
 		if (huge_pmd_unshare(mm, &address, ptep)) {
 			pages++;
 			spin_unlock(ptl);
+			shared_pmd = true;
 			continue;
 		}
 		pte = huge_ptep_get(ptep);
@@ -4348,9 +4379,13 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
 	 * Must flush TLB before releasing i_mmap_rwsem: x86's huge_pmd_unshare
 	 * may have cleared our pud entry and done put_page on the page table:
 	 * once we release i_mmap_rwsem, another task can do the final put_page
-	 * and that page table be reused and filled with junk.
+	 * and that page table be reused and filled with junk.  If we actually
+	 * did unshare a page of pmds, flush the range corresponding to the pud.
 	 */
-	flush_hugetlb_tlb_range(vma, start, end);
+	if (shared_pmd)
+		flush_hugetlb_tlb_range(vma, f_start, f_end);
+	else
+		flush_hugetlb_tlb_range(vma, start, end);
 	/*
 	 * No need to call mmu_notifier_invalidate_range() we are downgrading
 	 * page table protection not changing it to point to a new page.
@@ -4358,7 +4393,7 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
 	 * See Documentation/vm/mmu_notifier.rst
 	 */
 	i_mmap_unlock_write(vma->vm_file->f_mapping);
-	mmu_notifier_invalidate_range_end(mm, start, end);
+	mmu_notifier_invalidate_range_end(mm, f_start, f_end);
 
 	return pages << h->order;
 }
@@ -4545,13 +4580,41 @@ static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr)
 	/*
 	 * check on proper vm_flags and page table alignment
 	 */
-	if (vma->vm_flags & VM_MAYSHARE &&
-	    vma->vm_start <= base && end <= vma->vm_end)
+	if (vma->vm_flags & VM_MAYSHARE && range_in_vma(vma, base, end))
 		return true;
 	return false;
 }
 
 /*
+ * Determine if start,end range within vma could be mapped by shared pmd.
+ * If yes, adjust start and end to cover range associated with possible
+ * shared pmd mappings.
+ */
+void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
+				unsigned long *start, unsigned long *end)
+{
+	unsigned long check_addr = *start;
+
+	if (!(vma->vm_flags & VM_MAYSHARE))
+		return;
+
+	for (check_addr = *start; check_addr < *end; check_addr += PUD_SIZE) {
+		unsigned long a_start = check_addr & PUD_MASK;
+		unsigned long a_end = a_start + PUD_SIZE;
+
+		/*
+		 * If sharing is possible, adjust start/end if necessary.
+		 */
+		if (range_in_vma(vma, a_start, a_end)) {
+			if (a_start < *start)
+				*start = a_start;
+			if (a_end > *end)
+				*end = a_end;
+		}
+	}
+}
+
+/*
  * Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc()
  * and returns the corresponding pte. While this is not necessary for the
  * !shared pmd case because we can allocate the pmd later as well, it makes the
@@ -4648,6 +4711,11 @@ int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
 {
 	return 0;
 }
+
+void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
+				unsigned long *start, unsigned long *end)
+{
+}
 #define want_pmd_share()	(0)
 #endif /* CONFIG_ARCH_WANT_HUGE_PMD_SHARE */