mmap locking API: convert mmap_sem API comments

Convert comments that reference old mmap_sem APIs to reference
corresponding new mmap locking APIs instead.

Signed-off-by: Michel Lespinasse <walken@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Davidlohr Bueso <dbueso@suse.de>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Liam Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ying Han <yinghan@google.com>
Link: http://lkml.kernel.org/r/20200520052908.204642-12-walken@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memory.c b/mm/memory.c
index 823982a..4e2e17b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3323,10 +3323,10 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
 	 * pte_offset_map() on pmds where a huge pmd might be created
 	 * from a different thread.
 	 *
-	 * pte_alloc_map() is safe to use under down_write(mmap_sem) or when
+	 * pte_alloc_map() is safe to use under mmap_write_lock(mm) or when
 	 * parallel threads are excluded by other means.
 	 *
-	 * Here we only have down_read(mmap_sem).
+	 * Here we only have mmap_read_lock(mm).
 	 */
 	if (pte_alloc(vma->vm_mm, vmf->pmd))
 		return VM_FAULT_OOM;