Author: markj
Date: Mon Sep  2 21:52:18 2019
New Revision: 351726
URL: https://svnweb.freebsd.org/changeset/base/351726

Log:
  MFC r351518:
  Fix a few nits in vm_pqbatch_process_page().

Modified:
  stable/12/sys/vm/vm_page.c
Directory Properties:
  stable/12/   (props changed)

Modified: stable/12/sys/vm/vm_page.c
==============================================================================
--- stable/12/sys/vm/vm_page.c  Mon Sep  2 19:04:02 2019        (r351725)
+++ stable/12/sys/vm/vm_page.c  Mon Sep  2 21:52:18 2019        (r351726)
@@ -3104,9 +3104,10 @@ vm_pqbatch_process_page(struct vm_pagequeue *pq, vm_pa
         * the page queue lock held.  In this case it is about to free the page,
         * which must not have any queue state.
         */
-       qflags = atomic_load_8(&m->aflags) & PGA_QUEUE_STATE_MASK;
-       KASSERT(pq == vm_page_pagequeue(m) || qflags == 0,
-           ("page %p doesn't belong to queue %p but has queue state %#x",
+       qflags = atomic_load_8(&m->aflags);
+       KASSERT(pq == vm_page_pagequeue(m) ||
+           (qflags & PGA_QUEUE_STATE_MASK) == 0,
+           ("page %p doesn't belong to queue %p but has aflags %#x",
            m, pq, qflags));
 
        if ((qflags & PGA_DEQUEUE) != 0) {
@@ -3120,6 +3121,13 @@ vm_pqbatch_process_page(struct vm_pagequeue *pq, vm_pa
                        vm_pagequeue_cnt_inc(pq);
                        vm_page_aflag_set(m, PGA_ENQUEUED);
                }
+
+               /*
+                * Give PGA_REQUEUE_HEAD precedence over PGA_REQUEUE.
+                * In particular, if both flags are set in close succession,
+                * only PGA_REQUEUE_HEAD will be applied, even if it was set
+                * first.
+                */
                if ((qflags & PGA_REQUEUE_HEAD) != 0) {
                        KASSERT(m->queue == PQ_INACTIVE,
                            ("head enqueue not supported for page %p", m));
@@ -3128,12 +3136,8 @@ vm_pqbatch_process_page(struct vm_pagequeue *pq, vm_pa
                } else
                        TAILQ_INSERT_TAIL(&pq->pq_pl, m, plinks.q);
 
-               /*
-                * PGA_REQUEUE and PGA_REQUEUE_HEAD must be cleared after
-                * setting PGA_ENQUEUED in order to synchronize with the
-                * page daemon.
-                */
-               vm_page_aflag_clear(m, PGA_REQUEUE | PGA_REQUEUE_HEAD);
+               vm_page_aflag_clear(m, qflags & (PGA_REQUEUE |
+                   PGA_REQUEUE_HEAD));
        }
 }
 
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