zvol: Fix suspend lock leaks

In several functions, we use a flag variable to track whether
zv_suspend_lock is held.  This flag was not getting reset in a
particular case where we need to retry the underlying operation,
resulting in a lock leak.  Make sure to update the flag where necessary.

Signed-off-by: Mark Johnston <markj@FreeBSD.org>

module/os/freebsd/zfs/zvol_os.c

@@ -292,6 +292,7 @@ zvol_geom_open(struct g_provider *pp, int flag, int count)
 			if (!mutex_tryenter(&spa_namespace_lock)) {
 				mutex_exit(&zv->zv_state_lock);
 				rw_exit(&zv->zv_suspend_lock);
+				drop_suspend = B_FALSE;
 				kern_yield(PRI_USER);
 				goto retry;
 			} else {
@@ -983,6 +984,7 @@ zvol_cdev_open(struct cdev *dev, int flags, int fmt, struct thread *td)
 			if (!mutex_tryenter(&spa_namespace_lock)) {
 				mutex_exit(&zv->zv_state_lock);
 				rw_exit(&zv->zv_suspend_lock);
+				drop_suspend = B_FALSE;
 				kern_yield(PRI_USER);
 				goto retry;
 			} else {

module/os/linux/zfs/zvol_os.c

@@ -791,6 +791,7 @@ zvol_open(struct block_device *bdev, fmode_t flag)
 			if (!mutex_tryenter(&spa_namespace_lock)) {
 				mutex_exit(&zv->zv_state_lock);
 				rw_exit(&zv->zv_suspend_lock);
+				drop_suspend = B_FALSE;
 
 #ifdef HAVE_BLKDEV_GET_ERESTARTSYS
 				schedule();