Different consumers of the struct vm_page abuse pageq member to keep

additional information, when the page is guaranteed to not belong to a
paging queue.  Usually, this results in a lot of type casts which make
reasoning about the code correctness harder.

Sometimes m->object is used instead of pageq, which could cause real
and confusing bugs if non-NULL m->object is leaked.  See r141955 and
r253140 for examples.

Change the pageq member into a union containing explicitly-typed
members.  Use them instead of type-punning or abusing m->object in x86
pmaps, uma and vm_page_alloc_contig().

Requested and reviewed by:	alc
Sponsored by:	The FreeBSD Foundation

1 files changed, 2 insertions, 2 deletions

diff --git a/sys/vm/device_pager.c b/sys/vm/device_pager.c
index ba193e9..8113f03 100644
--- a/sys/vm/device_pager.c
+++ b/sys/vm/device_pager.c
@@ -226,7 +226,7 @@ dev_pager_free_page(vm_object_t object, vm_page_t m)
 	KASSERT((object->type == OBJT_DEVICE &&
 	    (m->oflags & VPO_UNMANAGED) != 0),
 	    ("Managed device or page obj %p m %p", object, m));
-	TAILQ_REMOVE(&object->un_pager.devp.devp_pglist, m, pageq);
+	TAILQ_REMOVE(&object->un_pager.devp.devp_pglist, m, plinks.q);
 	vm_page_putfake(m);
 }
 
@@ -281,7 +281,7 @@ dev_pager_getpages(vm_object_t object, vm_page_t *ma, int count, int reqpage)
 		    ("Wrong page type %p %p", ma[reqpage], object));
 		if (object->type == OBJT_DEVICE) {
 			TAILQ_INSERT_TAIL(&object->un_pager.devp.devp_pglist,
-			    ma[reqpage], pageq);
+			    ma[reqpage], plinks.q);
 		}
 	}