vm_page: Explain which we clear modify on migration of a non-dirty page

1 files changed, 2 insertions, 0 deletions

diff --git a/vm/vm_page.c b/vm/vm_page.c
index 4fde0759..00edb3c6 100644
--- a/vm/vm_page.c
+++ b/vm/vm_page.c
@@ -1027,6 +1027,8 @@ vm_page_seg_balance_page(struct vm_page_seg *seg,
     vm_page_copy(src, dest);
 
     if (!src->dirty) {
+        /* Avoid spuriously thinking the page is now dirty just because we have
+         * copied the data into it just above.  */
         pmap_clear_modify(dest->phys_addr);
     }