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vm_reserv: Fix list locking in vm_reserv_reclaim_contig()

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The per-domain partpop queue is locked by the combination of the
per-domain lock and individual reservation mutexes.
vm_reserv_reclaim_contig() scans the queue looking for partially
populated reservations that can be reclaimed in order to satisfy the
caller's allocation.

During the scan, we drop the per-domain lock.  At this point, the rvn
pointer may be invalidated.  Take care to load rvn after re-acquiring
the per-domain lock.

While here, simplify the condition used to check whether a reservation
was dequeued while the per-domain lock was dropped.

Reviewed by:	alc, kib
Reported by:	gallatin
MFC after:	3 days
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D29203
This commit is contained in:
Mark Johnston 2021-03-11 10:34:28 -05:00 committed by Mark Johnston
parent 1645a4ae64
commit 968079f253
1 changed files with 4 additions and 3 deletions
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7
sys/vm/vm_reserv.c
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@ -1344,8 +1344,8 @@ vm_reserv_reclaim_contig(int domain, u_long npages, vm_paddr_t low,
TAILQ_INSERT_AFTER(queue, rv, marker, partpopq);
vm_reserv_domain_unlock(domain);
vm_reserv_lock(rv);
if (!rv->inpartpopq ||
TAILQ_NEXT(rv, partpopq) != marker) {
if (TAILQ_PREV(marker, vm_reserv_queue, partpopq) !=
rv) {
vm_reserv_unlock(rv);
vm_reserv_domain_lock(domain);
rvn = TAILQ_NEXT(marker, partpopq);
@ -1363,8 +1363,9 @@ vm_reserv_reclaim_contig(int domain, u_long npages, vm_paddr_t low,
vm_reserv_unlock(rv);
return (true);
}
vm_reserv_unlock(rv);
vm_reserv_domain_lock(domain);
rvn = TAILQ_NEXT(rv, partpopq);
vm_reserv_unlock(rv);
}
vm_reserv_domain_unlock(domain);
vm_reserv_domain_scan_unlock(domain);