7938 disable LBA weighting on files and SSDs
Reviewed by: Yuri Pankov <yuripv@gmx.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>

*** 21,30 ****
--- 21,31 ----
  /*
   * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
   * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
   * Copyright 2016 Nexenta Systems, Inc.  All rights reserved.
   * Copyright (c) 2013 Joyent, Inc.  All rights reserved.
+  * Copyright (c) 2017 James S Blachly, MD <james.blachly@gmail.com>
   */
  
  #include <sys/zfs_context.h>
  #include <sys/spa_impl.h>
  #include <sys/refcount.h>
*** 270,279 ****
--- 271,281 ----
          dev_t dev;
          int otyp;
          boolean_t validate_devid = B_FALSE;
          ddi_devid_t devid;
          uint64_t capacity = 0, blksz = 0, pbsize;
+         int device_rotational;
  
          /*
           * We must have a pathname, and it must be absolute.
           */
          if (vd->vdev_path == NULL || vd->vdev_path[0] != '/') {
*** 542,551 ****
--- 544,560 ----
                  (void) ldi_ioctl(dvd->vd_lh, DKIOCSETWCE, (intptr_t)&wce,
                      FKIOCTL, kcred, NULL);
          }
  
          /*
+          * Inform the ZIO pipeline if we are non-rotational
+          */
+         device_rotational = ldi_prop_get_int(dvd->vd_lh, LDI_DEV_T_ANY,
+             "device-rotational", 1);
+         vd->vdev_nonrot = (device_rotational ? B_FALSE : B_TRUE);
+ 
+         /*
           * Clear the nowritecache bit, so that on a vdev_reopen() we will
           * try again.
           */
          vd->vdev_nowritecache = B_FALSE;