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Fix a few nits in vm_pqbatch_process_page().

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- Don't bother masking off non-queue state flags when loading the
  page's atomic state, since it is only required for one of the
  function's assertions.  Update the assertion instead.
- Remove an incorrect comment regarding synchronization with the
  page daemon.  The page daemon only ever checks for PGA_ENQUEUED
  with the page queue lock held.
- When clearing requeue flags, only clear the flags that have been
  acted upon.

Reviewed by:	kib (previous version)
Discussed with:	alc
Tested by:	pho (part of a larger patch)
MFC after:	1 week
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D21368
This commit is contained in:
markj 2019-08-26 20:20:10 +00:00
parent 7c414dcc28
commit 1435952d0e
1 changed files with 13 additions and 9 deletions
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22
sys/vm/vm_page.c
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@ -3081,9 +3081,10 @@ vm_pqbatch_process_page(struct vm_pagequeue *pq, vm_page_t m)
* 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) {
@ -3097,6 +3098,13 @@ vm_pqbatch_process_page(struct vm_pagequeue *pq, vm_page_t m)
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));
@ -3105,12 +3113,8 @@ vm_pqbatch_process_page(struct vm_pagequeue *pq, vm_page_t m)
} 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));
}
}