MFC r196457:

Set priority of vdev_geom threads and zvol threads to PRIBIO.

Index: sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c
===================================================================
--- sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c	(wersja 196879)
+++ sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c	(kopia robocza)
@@ -194,6 +194,10 @@ vdev_geom_worker(void *arg)
 	zio_t *zio;
 	struct bio *bp;
 
+	thread_lock(curthread);
+	sched_prio(curthread, PRIBIO);
+	thread_unlock(curthread);
+
 	ctx = arg;
 	for (;;) {
 		mtx_lock(&ctx->gc_queue_mtx);
Index: sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c
===================================================================
--- sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c	(wersja 196879)
+++ sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c	(kopia robocza)
@@ -402,6 +402,10 @@ zvol_worker(void *arg)
 	zvol_state_t *zv;
 	struct bio *bp;
 
+	thread_lock(curthread);
+	sched_prio(curthread, PRIBIO);
+	thread_unlock(curthread);
+
 	zv = arg;
 	for (;;) {
 		mtx_lock(&zv->zv_queue_mtx);