FreeBSD: avoid memory allocation in arc_prune_async

Reviewed-by: Ryan Moeller <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by:	Alexander Motin <[email protected]>
Closes openzfs#12049

Author: amotin

module/os/freebsd/zfs/arc_os.c

@@ -158,10 +158,9 @@ arc_default_max(uint64_t min, uint64_t allmem)
 static void
 arc_prune_task(void *arg)
 {
-	int64_t nr_scan = *(int64_t *)arg;
+	int64_t nr_scan = (intptr_t)arg;
 
 	arc_reduce_target_size(ptob(nr_scan));
-	free(arg, M_TEMP);
 #if __FreeBSD_version >= 1300139
 	sx_xlock(&arc_vnlru_lock);
 	vnlru_free_vfsops(nr_scan, &zfs_vfsops, arc_vnlru_marker);
@@ -186,13 +185,12 @@ void
 arc_prune_async(int64_t adjust)
 {
 
-	int64_t *adjustptr;
-
-	if ((adjustptr = malloc(sizeof (int64_t), M_TEMP, M_NOWAIT)) == NULL)
-		return;
-
-	*adjustptr = adjust;
-	taskq_dispatch(arc_prune_taskq, arc_prune_task, adjustptr, TQ_SLEEP);
+#ifndef __LP64__
+	if (adjust > INTPTR_MAX)
+		adjust = INTPTR_MAX;
+#endif
+	taskq_dispatch(arc_prune_taskq, arc_prune_task,
+	    (void *)(intptr_t)adjust, TQ_SLEEP);
 	ARCSTAT_BUMP(arcstat_prune);
 }