mm: rmap: use flush_cache_range() to flush cache for hugetlb pages

Now we will use flush_cache_page() to flush cache for anonymous hugetlb
pages when unmapping or migrating a hugetlb page mapping, but the
flush_cache_page() only handles a PAGE_SIZE range on some architectures
(like arm32, arc and so on), which will cause potential cache issues. 
Thus change to use flush_cache_range() to cover the whole size of a
hugetlb page.

Link: https://lkml.kernel.org/r/dc903b378d1e2d26bbbe85409ab9d009631f175c.1651056365.git.baolin.wang@linux.alibaba.comSigned-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/rmap.c

@@ -1525,13 +1525,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
 		anon_exclusive = folio_test_anon(folio) &&
 				 PageAnonExclusive(subpage);
 
-		if (folio_test_hugetlb(folio) && !folio_test_anon(folio)) {
-			/*
-			 * To call huge_pmd_unshare, i_mmap_rwsem must be
-			 * held in write mode.  Caller needs to explicitly
-			 * do this outside rmap routines.
-			 */
-			VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
+		if (folio_test_hugetlb(folio)) {
 			/*
 			 * huge_pmd_unshare may unmap an entire PMD page.
 			 * There is no way of knowing exactly which PMDs may
@@ -1541,6 +1535,14 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
 			 */
 			flush_cache_range(vma, range.start, range.end);
 
+			if (!folio_test_anon(folio)) {
+				/*
+				 * To call huge_pmd_unshare, i_mmap_rwsem must be
+				 * held in write mode.  Caller needs to explicitly
+				 * do this outside rmap routines.
+				 */
+				VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
+
 				if (huge_pmd_unshare(mm, vma, &address, pvmw.pte)) {
 					flush_tlb_range(vma, range.start, range.end);
 					mmu_notifier_invalidate_range(mm, range.start,
@@ -1558,6 +1560,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
 					page_vma_mapped_walk_done(&pvmw);
 					break;
 				}
+			}
 		} else {
 			flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
 		}
@@ -1879,13 +1882,7 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
 		anon_exclusive = folio_test_anon(folio) &&
 				 PageAnonExclusive(subpage);
 
-		if (folio_test_hugetlb(folio) && !folio_test_anon(folio)) {
-			/*
-			 * To call huge_pmd_unshare, i_mmap_rwsem must be
-			 * held in write mode.  Caller needs to explicitly
-			 * do this outside rmap routines.
-			 */
-			VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
+		if (folio_test_hugetlb(folio)) {
 			/*
 			 * huge_pmd_unshare may unmap an entire PMD page.
 			 * There is no way of knowing exactly which PMDs may
@@ -1895,6 +1892,14 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
 			 */
 			flush_cache_range(vma, range.start, range.end);
 
+			if (!folio_test_anon(folio)) {
+				/*
+				 * To call huge_pmd_unshare, i_mmap_rwsem must be
+				 * held in write mode.  Caller needs to explicitly
+				 * do this outside rmap routines.
+				 */
+				VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
+
 				if (huge_pmd_unshare(mm, vma, &address, pvmw.pte)) {
 					flush_tlb_range(vma, range.start, range.end);
 					mmu_notifier_invalidate_range(mm, range.start,
@@ -1912,6 +1917,7 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
 					page_vma_mapped_walk_done(&pvmw);
 					break;
 				}
+			}
 		} else {
 			flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
 		}