MFC r318819: MFV r316908: 7541 zpool import/tryimport ioctl returns ENOMEM because provided buffer is too small for config

illumos/illumos-gate@8b65a70b763232c90a91f31eb2010314c02ed338
https://github.com/illumos/illumos-gate/commit/8b65a70b763232c90a91f31eb2010314c02ed338

https://www.illumos.org/issues/7541
  When calling zpool import, zpool does a few ioctls to ZFS.
  zpool allocates a buffer in userland and passes it to the kernel so that ZFS
  can copy info into it. ZFS will use it to put the nvlist that describes the
  pool configuration.
  If the allocated buffer is too small, ZFS will return ENOMEM and the call will
  have to be redone. This wastes CPU time and slows down the import process. This
  happens very often for the ZFS_IOC_POOL_TRYIMPORT call.

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>
Author: Pavel Zakharov <pavel.zakharov@delphix.com>

2 files changed, 7 insertions, 4 deletions

diff --git a/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_impl.h b/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_impl.h
index bd051ae..ded3d88 100644
--- a/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_impl.h
+++ b/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_impl.h
@@ -132,6 +132,8 @@ typedef enum {
 	SHARED_SMB = 0x4
 } zfs_share_type_t;
 
+#define	CONFIG_BUF_MINSIZE	65536
+
 int zfs_error(libzfs_handle_t *, int, const char *);
 int zfs_error_fmt(libzfs_handle_t *, int, const char *, ...);
 void zfs_error_aux(libzfs_handle_t *, const char *, ...);
diff --git a/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_import.c b/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_import.c
index 091b85b..3f6e643 100644
--- a/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_import.c
+++ b/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_import.c
@@ -21,7 +21,7 @@
 
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2016 by Delphix. All rights reserved.
  * Copyright 2015 RackTop Systems.
  * Copyright 2016 Nexenta Systems, Inc.
  */
@@ -379,13 +379,14 @@ refresh_config(libzfs_handle_t *hdl, nvlist_t *config)
 {
 	nvlist_t *nvl;
 	zfs_cmd_t zc = { 0 };
-	int err;
+	int err, dstbuf_size;
 
 	if (zcmd_write_conf_nvlist(hdl, &zc, config) != 0)
 		return (NULL);
 
-	if (zcmd_alloc_dst_nvlist(hdl, &zc,
-	    zc.zc_nvlist_conf_size * 2) != 0) {
+	dstbuf_size = MAX(CONFIG_BUF_MINSIZE, zc.zc_nvlist_conf_size * 4);
+
+	if (zcmd_alloc_dst_nvlist(hdl, &zc, dstbuf_size) != 0) {
 		zcmd_free_nvlists(&zc);
 		return (NULL);
 	}