Jeff Roberson 3cf3b4e641 Make page busy state deterministic on free. Pages must be xbusy when ... removed from objects including calls to free. Pages must not be xbusy when freed and not on an object. Strengthen assertions to match these expectations. In practice very little code had to change busy handling to meet these rules but we can now make stronger guarantees to busy holders and avoid conditionally dropping busy in free. Refine vm_page_remove() and vm_page_replace() semantics now that we have stronger guarantees about busy state. This removes redundant and potentially problematic code that has proliferated. Discussed with: markj Reviewed by: kib Differential Revision: https://reviews.freebsd.org/D22822		2019-12-22 06:56:44 +00:00
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gntdev.c	Make page busy state deterministic on free. Pages must be xbusy when	2019-12-22 06:56:44 +00:00