7938 Port ZOL #3712 disable LBA weighting on files and SSDs

*** 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>
*** 269,278 ****
--- 270,281 ----
          dev_t dev;
          int otyp;
          boolean_t validate_devid = B_FALSE;
          ddi_devid_t devid;
          uint64_t capacity = 0, blksz = 0, pbsize;
+         int device_solid_state;
+         char *vendorp;  /* will point to inquiry-vendor-id */
  
          /*
           * We must have a pathname, and it must be absolute.
           */
          if (vd->vdev_path == NULL || vd->vdev_path[0] != '/') {
*** 541,550 ****
--- 544,575 ----
                  (void) ldi_ioctl(dvd->vd_lh, DKIOCSETWCE, (intptr_t)&wce,
                      FKIOCTL, kcred, NULL);
          }
  
          /*
+          * Inform the ZIO pipeline if we are non-rotational:
+          * 1. Check if device is SSD
+          * 2. If not SSD, check if device is Virtio
+          */
+         device_solid_state = ldi_prop_get_int(dvd->vd_lh, LDI_DEV_T_ANY,
+             "device-solid-state", 0);
+         vd->vdev_nonrot = (device_solid_state ? B_TRUE : B_FALSE);
+ 
+         if (device_solid_state == 0 &&
+             ldi_prop_exists(dvd->vd_lh, LDI_DEV_T_ANY, "inquiry-vendor-id")) {
+                 ldi_prop_lookup_string(dvd->vd_lh, LDI_DEV_T_ANY,
+                     "inquiry-vendor-id", &vendorp);
+                 if (strncmp(vendorp, "Virtio", 6) == 0)
+                     vd->vdev_nonrot = B_TRUE;
+                 ddi_prop_free(vendorp);
+         }
+ 
+         cmn_err(CE_NOTE, "[vdev_disk_open] %s :: device-solid-state "
+             "== %d :: vd->vdev_nonrot == %d\n", vd->vdev_path,
+             device_solid_state, (int) vd->vdev_nonrot);
+ 
+         /*
           * Clear the nowritecache bit, so that on a vdev_reopen() we will
           * try again.
           */
          vd->vdev_nowritecache = B_FALSE;