mm: fixup documentation regarding pte_numa() and PROT_NUMA

pte_numa() no longer exists -- replaced by pte_protnone() -- and PROT_NUMA
probably never existed: MM_CP_PROT_NUMA also ends up using PROT_NONE.

Let's fixup the doc.

Link: https://lkml.kernel.org/r/20220825164659.89824-4-david@redhat.comSigned-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/mm_types.h

@@ -614,22 +614,22 @@ struct mm_struct {
 #endif
 #ifdef CONFIG_NUMA_BALANCING
 		/*
-		 * numa_next_scan is the next time that the PTEs will be marked
-		 * pte_numa. NUMA hinting faults will gather statistics and
-		 * migrate pages to new nodes if necessary.
+		 * numa_next_scan is the next time that PTEs will be remapped
+		 * PROT_NONE to trigger NUMA hinting faults; such faults gather
+		 * statistics and migrate pages to new nodes if necessary.
 		 */
 		unsigned long numa_next_scan;
 
-		/* Restart point for scanning and setting pte_numa */
+		/* Restart point for scanning and remapping PTEs. */
 		unsigned long numa_scan_offset;
 
-		/* numa_scan_seq prevents two threads setting pte_numa */
+		/* numa_scan_seq prevents two threads remapping PTEs. */
 		int numa_scan_seq;
 #endif
 		/*
 		 * An operation with batched TLB flushing is going on. Anything
 		 * that can move process memory needs to flush the TLB when
-		 * moving a PROT_NONE or PROT_NUMA mapped page.
+		 * moving a PROT_NONE mapped page.
 		 */
 		atomic_t tlb_flush_pending;
 #ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH