K 10
svn:author
V 5
markj
K 8
svn:date
V 27
2018-05-04T17:17:30.838643Z
K 7
svn:log
V 594
Fix some races introduced in r332974.

With r332974, when performing a synchronized access of a page's "queue"
field, one must first check whether the page is logically dequeued. If
so, then the page lock does not prevent the page from being removed
from its page queue. Intoduce vm_page_queue(), which returns the page's
logical queue index. In some cases, direct access to the "queue" field
is still required, but such accesses should be confined to sys/vm.

Reported and tested by:	pho
Reviewed by:	kib
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D15280

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