zpool reopen should detect expanded devices

Update bdev_capacity to have wholedisk vdevs query the
size of the underlying block device (correcting for the size
of the efi parition and partition alignment) and therefore detect
expanded space.

Correct vdev_get_stats_ex so that the expandsize is aligned
to metaslab size and new space is only reported if it is large
enough for a new metaslab.

Reviewed by: Don Brady <don.brady@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: John Wren Kennedy <jwk404@gmail.com>
Signed-off-by: sara hartse <sara.hartse@delphix.com>
External-issue: LX-165
Closes #7546
Issue #7582

lib/libzfs/libzfs_pool.c

@@ -22,7 +22,7 @@
 /*
  * Copyright 2015 Nexenta Systems, Inc.  All rights reserved.
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2011, 2014 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2018 by Delphix. All rights reserved.
  * Copyright 2016 Igor Kozhukhov <ikozhukhov@gmail.com>
  * Copyright (c) 2017 Datto Inc.
  */
@@ -42,6 +42,7 @@
 #include <sys/efi_partition.h>
 #include <sys/vtoc.h>
 #include <sys/zfs_ioctl.h>
+#include <sys/vdev_disk.h>
 #include <dlfcn.h>
 
 #include "zfs_namecheck.h"
@@ -912,17 +913,6 @@ zpool_prop_get_feature(zpool_handle_t *zhp, const char *propname, char *buf,
 	return (0);
 }
 
-/*
- * Don't start the slice at the default block of 34; many storage
- * devices will use a stripe width of 128k, other vendors prefer a 1m
- * alignment.  It is best to play it safe and ensure a 1m alignment
- * given 512B blocks.  When the block size is larger by a power of 2
- * we will still be 1m aligned.  Some devices are sensitive to the
- * partition ending alignment as well.
- */
-#define	NEW_START_BLOCK		2048
-#define	PARTITION_END_ALIGNMENT	2048
-
 /*
  * Validate the given pool name, optionally putting an extended error message in
  * 'buf'.