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Permit vm_page_wire() to be called on pages not belonging to an object.

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For such pages ref_count is effectively a consumer-managed field, but
there is no harm in calling vm_page_wire() on them.
vm_page_unwire_noq() handles them as well.  Relax the vm_page_wire()
assertions to permit this case which is triggered by some out-of-tree
code. [1]

Also guard a conditional assertion with INVARIANTS.  Otherwise the
conditions are evaluated even though the result is unused. [2]

Reported by:	bz, cem [1], kib [2]
Reviewed by:	dougm, kib
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D26173
This commit is contained in:
Mark Johnston 2020-08-25 13:45:06 +00:00
parent 0c54932d50
commit 411096d034
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=364768
1 changed files with 6 additions and 5 deletions
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11
sys/vm/vm_page.c
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@ -3854,18 +3854,19 @@ vm_page_free_pages_toq(struct spglist *free, bool update_wire_count)
}
/*
* Mark this page as wired down, preventing reclamation by the page daemon
* or when the containing object is destroyed.
* Mark this page as wired down. For managed pages, this prevents reclamation
* by the page daemon, or when the containing object, if any, is destroyed.
*/
void
vm_page_wire(vm_page_t m)
{
u_int old;
KASSERT(m->object != NULL,
("vm_page_wire: page %p does not belong to an object", m));
if (!vm_page_busied(m) && !vm_object_busied(m->object))
#ifdef INVARIANTS
if (m->object != NULL && !vm_page_busied(m) &&
!vm_object_busied(m->object))
VM_OBJECT_ASSERT_LOCKED(m->object);
#endif
KASSERT((m->flags & PG_FICTITIOUS) == 0 ||
VPRC_WIRE_COUNT(m->ref_count) >= 1,
("vm_page_wire: fictitious page %p has zero wirings", m));