diff --git a/man/man4/zfs.4 b/man/man4/zfs.4
index 6a628e7f3..a98ec519a 100644
--- a/man/man4/zfs.4
+++ b/man/man4/zfs.4
@@ -1355,17 +1355,30 @@ This parameter only applies on Linux.
 This parameter is ignored if
 .Sy zfs_vdev_disk_classic Ns = Ns Sy 1 .
 .
-.It Sy zfs_vdev_disk_classic Ns = Ns Sy 0 Ns | Ns 1 Pq uint
-If set to 1, OpenZFS will submit IO to Linux using the method it used in 2.2
-and earlier.
-This "classic" method has known issues with highly fragmented IO requests and
-is slower on many workloads, but it has been in use for many years and is known
-to be very stable.
-If you set this parameter, please also open a bug report why you did so,
+.It Sy zfs_vdev_disk_classic Ns = Ns 0 Ns | Ns Sy 1 Pq uint
+Controls the method used to submit IO to the Linux block layer
+(default
+.Sy 1 "classic" Ns
+)
+.Pp
+If set to 1, the "classic" method is used.
+This is the method that has been in use since the earliest versions of
+ZFS-on-Linux.
+It has known issues with highly fragmented IO requests and is less efficient on
+many workloads, but it well known and well understood.
+.Pp
+If set to 0, the "new" method is used.
+This method is available since 2.2.4 and should resolve all known issues and be
+far more efficient, but has not had as much testing.
+In the 2.2.x series, this parameter defaults to 1, to use the "classic" method.
+.Pp
+It is not recommended that you change it except on advice from the OpenZFS
+developers.
+If you do change it, please also open a bug report describing why you did so,
 including the workload involved and any error messages.
 .Pp
-This parameter and the classic submission method will be removed once we have
-total confidence in the new method.
+This parameter and the "classic" submission method will be removed in a future
+release of OpenZFS once we have total confidence in the new method.
 .Pp
 This parameter only applies on Linux, and can only be set at module load time.
 .
diff --git a/module/os/linux/zfs/vdev_disk.c b/module/os/linux/zfs/vdev_disk.c
index 36468fc21..e1c19a085 100644
--- a/module/os/linux/zfs/vdev_disk.c
+++ b/module/os/linux/zfs/vdev_disk.c
@@ -969,8 +969,10 @@ vdev_disk_io_rw(zio_t *zio)
 /*
  * This is the classic, battle-tested BIO submission code. Until we're totally
  * sure that the new code is safe and correct in all cases, this will remain
- * available and can be enabled by setting zfs_vdev_disk_classic=1 at module
- * load time.
+ * available.
+ *
+ * It is enabled by setting zfs_vdev_disk_classic=1 at module load time. It is
+ * enabled (=1) by default since 2.2.4, and disabled by default (=0) on master.
  *
  * These functions have been renamed to vdev_classic_* to make it clear what
  * they belong to, but their implementations are unchanged.
@@ -1468,7 +1470,7 @@ vdev_disk_rele(vdev_t *vd)
  * BIO submission method. See comment above about vdev_classic.
  * Set zfs_vdev_disk_classic=0 for new, =1 for classic
  */
-static uint_t zfs_vdev_disk_classic = 0;	/* default new */
+static uint_t zfs_vdev_disk_classic = 1;	/* default classic */
 
 /* Set submission function from module parameter */
 static int