itself, it will be clamped.
Setting it to zero will cause the kernel's ideal size to be used.
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,
+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.
+.Pp
+This parameter only applies on Linux, and can only be set at module load time.
.
.It Sy zfs_expire_snapshot Ns = Ns Sy 300 Ns s Pq int
Time before expiring
/* XXX: Implement me as a vnode rele for the device */
}
+/*
+ * 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 */
+
+/* Set submission function from module parameter */
+static int
+vdev_disk_param_set_classic(const char *buf, zfs_kernel_param_t *kp)
+{
+ int err = param_set_uint(buf, kp);
+ if (err < 0)
+ return (SET_ERROR(err));
+
+ vdev_disk_io_rw_fn =
+ zfs_vdev_disk_classic ? vdev_classic_physio : vdev_disk_io_rw;
+
+ printk(KERN_INFO "ZFS: forcing %s BIO submission\n",
+ zfs_vdev_disk_classic ? "classic" : "new");
+
+ return (0);
+}
+
/*
* At first use vdev use, set the submission function from the default value if
* it hasn't been set already.
(void) tsd;
if (vdev_disk_io_rw_fn == NULL)
- /* XXX make configurable */
- vdev_disk_io_rw_fn = 0 ? vdev_classic_physio : vdev_disk_io_rw;
+ vdev_disk_io_rw_fn = zfs_vdev_disk_classic ?
+ vdev_classic_physio : vdev_disk_io_rw;
return (0);
}
ZFS_MODULE_PARAM(zfs_vdev_disk, zfs_vdev_disk_, max_segs, UINT, ZMOD_RW,
"Maximum number of data segments to add to an IO request (min 4)");
+
+ZFS_MODULE_PARAM_CALL(zfs_vdev_disk, zfs_vdev_disk_, classic,
+ vdev_disk_param_set_classic, param_get_uint, ZMOD_RD,
+ "Use classic BIO submission method");