svn commit: r316460 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs

[Steven Hartland]

Author: smh
Date: Mon Apr  3 13:11:28 2017
New Revision: 316460
URL: https://svnweb.freebsd.org/changeset/base/316460

Log:
  Fix expandsz 16.0E vals and vdev_min_asize of RAIDZ children
  
  When a member of a RAIDZ has been replaced with a device smaller than the
  original, then the top level vdev can report its expand size as 16.0E.
  
  The reduced child asize causes the RAIDZ to have a vdev_asize lower than its
  vdev_max_asize which then results in an underflow during the calculation of
  the parents expand size.
  
  Fix this by updating the vdev_asize if it shrinks, which is already
  protected by a check against vdev_min_asize so should always be safe.
  
  Also for RAIDZ vdevs, ensure that the sum of their child vdev_min_asize is
  always greater than the parents vdev_min_size.
  
  Fixes: https://www.illumos.org/issues/7885
  
  MFC after:	2 weeks
  Sponsored by:	Multiplay

Modified:
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev.c

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev.c	Mon Apr  3 13:06:28 2017	(r316459)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev.c	Mon Apr  3 13:11:28 2017	(r316460)
@@ -229,7 +229,8 @@ vdev_get_min_asize(vdev_t *vd)
 	 * so each child must provide at least 1/Nth of its asize.
 	 */
 	if (pvd->vdev_ops == &vdev_raidz_ops)
-		return (pvd->vdev_min_asize / pvd->vdev_children);
+		return ((pvd->vdev_min_asize + pvd->vdev_children - 1) /
+		    pvd->vdev_children);
 
 	return (pvd->vdev_min_asize);
 }
@@ -1377,7 +1378,7 @@ vdev_open(vdev_t *vd)
 	vd->vdev_psize = psize;
 
 	/*
-	 * Make sure the allocatable size hasn't shrunk.
+	 * Make sure the allocatable size hasn't shrunk too much.
 	 */
 	if (asize < vd->vdev_min_asize) {
 		vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
@@ -1417,12 +1418,21 @@ vdev_open(vdev_t *vd)
 	}
 
 	/*
-	 * If all children are healthy and the asize has increased,
-	 * then we've experienced dynamic LUN growth.  If automatic
-	 * expansion is enabled then use the additional space.
-	 */
-	if (vd->vdev_state == VDEV_STATE_HEALTHY && asize > vd->vdev_asize &&
-	    (vd->vdev_expanding || spa->spa_autoexpand))
+	 * If all children are healthy we update asize if either:
+	 * The asize has increased, due to a device expansion caused by dynamic
+	 * LUN growth or vdev replacement, and automatic expansion is enabled;
+	 * making the additional space available.
+	 *
+	 * The asize has decreased, due to a device shrink usually caused by a
+	 * vdev replace with a smaller device. This ensures that calculations
+	 * based of max_asize and asize e.g. esize are always valid. It's safe
+	 * to do this as we've already validated that asize is greater than
+	 * vdev_min_asize.
+	 */
+	if (vd->vdev_state == VDEV_STATE_HEALTHY &&
+	    ((asize > vd->vdev_asize &&
+	    (vd->vdev_expanding || spa->spa_autoexpand)) ||
+	    (asize < vd->vdev_asize)))
 		vd->vdev_asize = asize;
 
 	vdev_set_min_asize(vd);