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diff --git a/sys/vm/vm_reserv.h b/sys/vm/vm_reserv.h
--- a/sys/vm/vm_reserv.h
+++ b/sys/vm/vm_reserv.h
@@ -51,6 +51,9 @@
vm_paddr_t boundary);
vm_page_t vm_reserv_alloc_page(vm_object_t object, vm_pindex_t pindex,
int domain, int req, vm_page_t mpred);
+int vm_reserv_alloc_npages(vm_object_t object, vm_pindex_t pindex,
+ int domain, vm_page_t mpred, int req, u_long npages,
+ vm_page_t *ma);
void vm_reserv_break_all(vm_object_t object);
boolean_t vm_reserv_free_page(vm_page_t m);
void vm_reserv_init(void);
diff --git a/sys/vm/vm_reserv.c b/sys/vm/vm_reserv.c
--- a/sys/vm/vm_reserv.c
+++ b/sys/vm/vm_reserv.c
@@ -848,6 +848,133 @@
return (m_ret);
}
+/*
+ * Attempts to allocate a contiguous run of "npages" physical pages from an
+ * existing or newly created reservation, starting from the offset "pindex".
+ * Stores the beginning of the newly allocated run to 'ma' and returns the
+ * number of allocated pages.
+ *
+ * The page "mpred" must immediately precede the offset "pindex" within the
+ * specified object.
+ *
+ * The object must be locked.
+ */
+int
+vm_reserv_alloc_npages(vm_object_t object, vm_pindex_t pindex, int domain,
+ vm_page_t mpred, int req, u_long npages, vm_page_t *ma)
+{
+ struct vm_domain *vmd;
+ vm_page_t m, msucc;
+ vm_pindex_t first, leftcap, rightcap;
+ vm_reserv_t rv;
+ int index, got;
+ int end;
+
+ VM_OBJECT_ASSERT_WLOCKED(object);
+ MPASS(npages > 0);
+ vmd = VM_DOMAIN(domain);
+
+ /*
+ * Is a reservation fundamentally impossible?
+ */
+ if (pindex < VM_RESERV_INDEX(object, pindex) || pindex >= object->size)
+ return (0);
+ /*
+ * Look for an existing reservation.
+ */
+ npages = min(VM_LEVEL_0_NPAGES, npages);
+ rv = vm_reserv_from_object(object, pindex, mpred, &msucc);
+ if (rv == NULL) {
+ /*
+ * Could a reservation fit between the first index to the left
+ * that can be used and the first index to the right that cannot
+ * be used?
+ *
+ * We must synchronize with the reserv object lock to protect
+ * the pindex/object of the resulting reservations against
+ * rename while we are inspecting.
+ */
+ first = pindex - VM_RESERV_INDEX(object, pindex);
+ vm_reserv_object_lock(object);
+ if (mpred != NULL) {
+ if ((rv = vm_reserv_from_page(mpred))->object != object)
+ leftcap = mpred->pindex + 1;
+ else
+ leftcap = rv->pindex + VM_LEVEL_0_NPAGES;
+ if (leftcap > first) {
+ vm_reserv_object_unlock(object);
+ return (0);
+ }
+ }
+ if (msucc != NULL) {
+ if ((rv = vm_reserv_from_page(msucc))->object != object)
+ rightcap = msucc->pindex;
+ else
+ rightcap = rv->pindex;
+ if (first + VM_LEVEL_0_NPAGES > rightcap) {
+ vm_reserv_object_unlock(object);
+ return (0);
+ }
+ }
+ vm_reserv_object_unlock(object);
+
+ /*
+ * Would the last new reservation extend past the end of the
+ * object?
+ *
+ * If the object is unlikely to grow don't allocate a
+ * reservation for the tail.
+ */
+ if ((object->flags & OBJ_ANON) == 0 &&
+ first + VM_LEVEL_0_NPAGES > object->size)
+ return (0);
+
+ /*
+ * Allocate and populate the new reservation.
+ */
+ m = NULL;
+ if (vm_domain_allocate(vmd, req, npages)) {
+ vm_domain_free_lock(vmd);
+ m = vm_phys_alloc_pages(domain, VM_FREEPOOL_DEFAULT,
+ VM_LEVEL_0_ORDER);
+ vm_domain_free_unlock(vmd);
+ if (m == NULL) {
+ vm_domain_freecnt_inc(vmd, npages);
+ return (0);
+ }
+ } else
+ return (0);
+
+ rv = vm_reserv_from_page(m);
+ vm_reserv_lock(rv);
+ KASSERT(rv->pages == m,
+ ("vm_reserv_alloc_page: reserv %p's pages is corrupted",
+ rv));
+ vm_reserv_insert(rv, object, first);
+ } else {
+ if (!vm_domain_allocate(vmd, req, npages))
+ return (0);
+ vm_reserv_lock(rv);
+ }
+
+ KASSERT(object != kernel_object || rv->domain == domain,
+ ("vm_reserv_alloc_page: domain mismatch"));
+
+ index = VM_RESERV_INDEX(object, pindex);
+ bit_ffs_at(rv->popmap, index, VM_LEVEL_0_NPAGES, &end);
+ if (end == -1)
+ end = VM_LEVEL_0_NPAGES;
+ end = min(index + npages, end);
+ vm_reserv_populate_range(rv, index, end);
+ vm_reserv_unlock(rv);
+ got = end - index;
+ if (got < npages)
+ vm_domain_freecnt_inc(vmd, npages - got);
+ *ma = &rv->pages[index];
+
+ return (got);
+}
+
/*
* Allocate a physical page from an existing or newly created reservation.
*

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