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Avoid zero-sized kmem_alloc() in vdev_compact_children().

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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 a1d477c24c
Author: Matthew Ahrens <mahrens@delphix.com>
Ported-by: Tim Chase <tim@chase2k.com>

Approved by:	re (kib)
MFC after:	1 week
This commit is contained in:
Alexander Motin 2018-10-12 16:55:28 +00:00
parent 0f31e1e6a8
commit 178777f516
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=339335
1 changed files with 12 additions and 5 deletions
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17
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev.c
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@ -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 *));