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Index: head/sys/vm/vm_page.c
===================================================================
--- head/sys/vm/vm_page.c
+++ head/sys/vm/vm_page.c
@@ -3462,27 +3462,58 @@
vm_page_swapqueue(vm_page_t m, uint8_t oldq, uint8_t newq)
{
struct vm_pagequeue *pq;
+ vm_page_t next;
+ bool queued;
KASSERT(oldq < PQ_COUNT && newq < PQ_COUNT && oldq != newq,
("vm_page_swapqueue: invalid queues (%d, %d)", oldq, newq));
- KASSERT((m->oflags & VPO_UNMANAGED) == 0,
- ("vm_page_swapqueue: page %p is unmanaged", m));
vm_page_assert_locked(m);
- /*
- * Atomically update the queue field and set PGA_REQUEUE while
- * ensuring that PGA_DEQUEUE has not been set.
- */
pq = &vm_pagequeue_domain(m)->vmd_pagequeues[oldq];
vm_pagequeue_lock(pq);
- if (!vm_page_pqstate_cmpset(m, oldq, newq, PGA_DEQUEUE, PGA_REQUEUE)) {
+
+ /*
+ * The physical queue state might change at any point before the page
+ * queue lock is acquired, so we must verify that we hold the correct
+ * lock before proceeding.
+ */
+ if (__predict_false(m->queue != oldq)) {
vm_pagequeue_unlock(pq);
return;
}
- if ((m->aflags & PGA_ENQUEUED) != 0) {
- vm_pagequeue_remove(pq, m);
+
+ /*
+ * Once the queue index of the page changes, there is nothing
+ * synchronizing with further updates to the physical queue state.
+ * Therefore we must remove the page from the queue now in anticipation
+ * of a successful commit, and be prepared to roll back.
+ */
+ if (__predict_true((m->aflags & PGA_ENQUEUED) != 0)) {
+ next = TAILQ_NEXT(m, plinks.q);
+ TAILQ_REMOVE(&pq->pq_pl, m, plinks.q);
vm_page_aflag_clear(m, PGA_ENQUEUED);
+ queued = true;
+ } else {
+ queued = false;
}
+
+ /*
+ * Atomically update the queue field and set PGA_REQUEUE while
+ * ensuring that PGA_DEQUEUE has not been set.
+ */
+ if (__predict_false(!vm_page_pqstate_cmpset(m, oldq, newq, PGA_DEQUEUE,
+ PGA_REQUEUE))) {
+ if (queued) {
+ vm_page_aflag_set(m, PGA_ENQUEUED);
+ if (next != NULL)
+ TAILQ_INSERT_BEFORE(next, m, plinks.q);
+ else
+ TAILQ_INSERT_TAIL(&pq->pq_pl, m, plinks.q);
+ }
+ vm_pagequeue_unlock(pq);
+ return;
+ }
+ vm_pagequeue_cnt_dec(pq);
vm_pagequeue_unlock(pq);
vm_page_pqbatch_submit(m, newq);
}

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