svn commit: r339335 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs

[Alexander Motin]

Author: mav
Date: Fri Oct 12 16:55:28 2018
New Revision: 339335
URL: https://svnweb.freebsd.org/changeset/base/339335

Log:
  Avoid zero-sized kmem_alloc() in vdev_compact_children().
  
  The device evacuation code adds a dependency that
  vdev_compact_children() be able to properly empty the vdev_child
  array by setting it to NULL and zeroing vdev_children.  Under Linux,
  kmem_alloc() and related functions return a sentinel pointer rather
  than NULL for zero-sized allocations.
  
  This is a part of ZoL port of device removal patch:
  
  commit a1d477c24c7badc89c60955995fd84d311938486
  Author: Matthew Ahrens <mahrens at delphix.com>
  Ported-by: Tim Chase <tim at chase2k.com>
  
  Approved by:	re (kib)
  MFC after:	1 week

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	Fri Oct 12 16:24:49 2018	(r339334)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev.c	Fri Oct 12 16:55:28 2018	(r339335)
@@ -505,17 +505,24 @@ vdev_compact_children(vdev_t *pvd)
 
 	ASSERT(spa_config_held(pvd->vdev_spa, SCL_ALL, RW_WRITER) == SCL_ALL);
 
+	if (oldc == 0)
+		return;
+
 	for (int c = newc = 0; c < oldc; c++)
 		if (pvd->vdev_child[c])
 			newc++;
 
-	newchild = kmem_alloc(newc * sizeof (vdev_t *), KM_SLEEP);
+	if (newc > 0) {
+		newchild = kmem_alloc(newc * sizeof (vdev_t *), KM_SLEEP);
 
-	for (int c = newc = 0; c < oldc; c++) {
-		if ((cvd = pvd->vdev_child[c]) != NULL) {
-			newchild[newc] = cvd;
-			cvd->vdev_id = newc++;
+		for (int c = newc = 0; c < oldc; c++) {
+			if ((cvd = pvd->vdev_child[c]) != NULL) {
+				newchild[newc] = cvd;
+				cvd->vdev_id = newc++;
+			}
 		}
+	} else {
+		newchild = NULL;
 	}
 
 	kmem_free(pvd->vdev_child, oldc * sizeof (vdev_t *));