1 files changed, 20 insertions, 8 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 0aee2f3ae15c..e070b8593b37 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5241,6 +5241,21 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma,
 	VM_BUG_ON(unshare && (flags & FOLL_WRITE));
 	VM_BUG_ON(!unshare && !(flags & FOLL_WRITE));
 
+	/*
+	 * hugetlb does not support FOLL_FORCE-style write faults that keep the
+	 * PTE mapped R/O such as maybe_mkwrite() would do.
+	 */
+	if (WARN_ON_ONCE(!unshare && !(vma->vm_flags & VM_WRITE)))
+		return VM_FAULT_SIGSEGV;
+
+	/* Let's take out MAP_SHARED mappings first. */
+	if (vma->vm_flags & VM_MAYSHARE) {
+		if (unlikely(unshare))
+			return 0;
+		set_huge_ptep_writable(vma, haddr, ptep);
+		return 0;
+	}
+
 	pte = huge_ptep_get(ptep);
 	old_page = pte_page(pte);
 
@@ -5781,12 +5796,11 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	 * If we are going to COW/unshare the mapping later, we examine the
 	 * pending reservations for this page now. This will ensure that any
 	 * allocations necessary to record that reservation occur outside the
-	 * spinlock. For private mappings, we also lookup the pagecache
-	 * page now as it is used to determine if a reservation has been
-	 * consumed.
+	 * spinlock. Also lookup the pagecache page now as it is used to
+	 * determine if a reservation has been consumed.
 	 */
 	if ((flags & (FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE)) &&
-	    !huge_pte_write(entry)) {
+	    !(vma->vm_flags & VM_MAYSHARE) && !huge_pte_write(entry)) {
 		if (vma_needs_reservation(h, vma, haddr) < 0) {
 			ret = VM_FAULT_OOM;
 			goto out_mutex;
@@ -5794,9 +5808,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 		/* Just decrements count, does not deallocate */
 		vma_end_reservation(h, vma, haddr);
 
-		if (!(vma->vm_flags & VM_MAYSHARE))
-			pagecache_page = hugetlbfs_pagecache_page(h,
-								vma, haddr);
+		pagecache_page = hugetlbfs_pagecache_page(h, vma, haddr);
 	}
 
 	ptl = huge_pte_lock(h, mm, ptep);
@@ -6029,7 +6041,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
 	if (!huge_pte_none_mostly(huge_ptep_get(dst_pte)))
 		goto out_release_unlock;
 
-	if (vm_shared) {
+	if (page_in_pagecache) {
 		page_dup_file_rmap(page, true);
 	} else {
 		ClearHPageRestoreReserve(page);