Implemented zpool sync command

This addition will enable us to sync an open TXG to the main pool
on demand. The functionality is similar to 'sync(2)' but 'zpool sync'
will return when data has hit the main storage instead of potentially
just the ZIL as is the case with the 'sync(2)' cmd.

Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed by: Matthew Ahrens <[email protected]>
Signed-off-by: Alek Pinchuk <[email protected]>
Closes #6122 

1 files changed, 23 insertions, 11 deletions

diff --git a/lib/libzfs_core/libzfs_core.c b/lib/libzfs_core/libzfs_core.c
index 17f9931a0..8e36d8459 100644
--- a/lib/libzfs_core/libzfs_core.c
+++ b/lib/libzfs_core/libzfs_core.c
@@ -22,6 +22,7 @@
 /*
  * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
  * Copyright (c) 2013 Steven Hartland. All rights reserved.
+ * Copyright (c) 2017 Datto Inc.
  */
 
 /*
@@ -126,17 +127,20 @@ lzc_ioctl(zfs_ioc_t ioc, const char *name,
 {
 	zfs_cmd_t zc = {"\0"};
 	int error = 0;
-	char *packed;
-	size_t size;
+	char *packed = NULL;
+	size_t size = 0;
 
 	ASSERT3S(g_refcount, >, 0);
 	VERIFY3S(g_fd, !=, -1);
 
-	(void) strlcpy(zc.zc_name, name, sizeof (zc.zc_name));
+	if (name != NULL)
+		(void) strlcpy(zc.zc_name, name, sizeof (zc.zc_name));
 
-	packed = fnvlist_pack(source, &size);
-	zc.zc_nvlist_src = (uint64_t)(uintptr_t)packed;
-	zc.zc_nvlist_src_size = size;
+	if (source != NULL) {
+		packed = fnvlist_pack(source, &size);
+		zc.zc_nvlist_src = (uint64_t)(uintptr_t)packed;
+		zc.zc_nvlist_src_size = size;
+	}
 
 	if (resultp != NULL) {
 		*resultp = NULL;
@@ -341,6 +345,18 @@ lzc_exists(const char *dataset)
 }
 
 /*
+ * outnvl is unused.
+ * It was added to preserve the function signature in case it is
+ * needed in the future.
+ */
+/*ARGSUSED*/
+int
+lzc_sync(const char *pool_name, nvlist_t *innvl, nvlist_t **outnvl)
+{
+	return (lzc_ioctl(ZFS_IOC_POOL_SYNC, pool_name, innvl, NULL));
+}
+
+/*
  * Create "user holds" on snapshots.  If there is a hold on a snapshot,
  * the snapshot can not be destroyed.  (However, it can be marked for deletion
  * by lzc_destroy_snaps(defer=B_TRUE).)
@@ -440,11 +456,7 @@ lzc_release(nvlist_t *holds, nvlist_t **errlist)
 int
 lzc_get_holds(const char *snapname, nvlist_t **holdsp)
 {
-	int error;
-	nvlist_t *innvl = fnvlist_alloc();
-	error = lzc_ioctl(ZFS_IOC_GET_HOLDS, snapname, innvl, holdsp);
-	fnvlist_free(innvl);
-	return (error);
+	return (lzc_ioctl(ZFS_IOC_GET_HOLDS, snapname, NULL, holdsp));
 }
 
 /*