OpenZFS 9318 - vol_volsize_to_reservation does not account for raidz skip blocks

When a volume is created in a pool with raidz vdevs and
volblocksize != 128k, the volume can reference more space than is
reserved with the automatically calculated refreservation.  There
are two deficiencies in vol_volsize_to_reservation that contribute
to this:

  1) Skip blocks may be added to keep each allocation a multiple
     of parity + 1. This is the dominating factor when volblocksize
     is close to 2^ashift.

  2) raidz deflation for 128 KB blocks is different for most other
     block sizes.

See "The theory of raidz space accounting" comment in
libzfs_dataset.c for a full explanation.

Authored by: Mike Gerdts <[email protected]>
Reviewed by: Richard Elling <[email protected]>
Reviewed by: Sanjay Nadkarni <[email protected]>
Reviewed by: Jerry Jelinek <[email protected]>
Reviewed by: Matt Ahrens <[email protected]>
Reviewed by: Kody Kantor <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Approved by: Dan McDonald <[email protected]>
Ported-by: Mike Gerdts <[email protected]>

Porting Notes:
* ZTS: wait for zvols to exist before writing
* ZTS: use log_must_busy with {zpool|zfs} destroy

OpenZFS-issue: https://www.illumos.org/issues/9318
OpenZFS-commit: https://github.com/illumos/illumos-gate/commit/b73ccab0
Closes #8973

1 files changed, 3 insertions, 2 deletions

diff --git a/include/libzfs.h b/include/libzfs.h
index 8b348746a..79e7692cd 100644
--- a/include/libzfs.h
+++ b/include/libzfs.h
@@ -22,7 +22,7 @@
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2011, 2018 by Delphix. All rights reserved.
- * Copyright (c) 2012, Joyent, Inc. All rights reserved.
+ * Copyright Joyent, Inc.
  * Copyright (c) 2013 Steven Hartland. All rights reserved.
  * Copyright (c) 2016, Intel Corporation.
  * Copyright 2016 Nexenta Systems, Inc.
@@ -688,7 +688,8 @@ extern int zfs_hold(zfs_handle_t *, const char *, const char *,
 extern int zfs_hold_nvl(zfs_handle_t *, int, nvlist_t *);
 extern int zfs_release(zfs_handle_t *, const char *, const char *, boolean_t);
 extern int zfs_get_holds(zfs_handle_t *, nvlist_t **);
-extern uint64_t zvol_volsize_to_reservation(uint64_t, nvlist_t *);
+extern uint64_t zvol_volsize_to_reservation(zpool_handle_t *, uint64_t,
+    nvlist_t *);
 
 typedef int (*zfs_userspace_cb_t)(void *arg, const char *domain,
     uid_t rid, uint64_t space);