OpenZFS 6093 - zfsctl_shares_lookup

6093 zfsctl_shares_lookup should only VN_RELE() on zfs_zget() success

Reviewed by: Gordon Ross <[email protected]>
Reviewed by: Matthew Ahrens <[email protected]>
Reviewed by: George Wilson <[email protected]>
Approved by: Robert Mustacchi <[email protected]>
Ported-by: Brian Behlendorf <[email protected]>

OpenZFS-issue: https://www.illumos.org/issues/6093
OpenZFS-commit: openzfs/openzfs@0f92170
Closes #4630

This function was always implemented slightly differently under Linux
and therefore never suffered from this issue.  The patch has been
updated and applied as cleanup in order to minimize differences with
the upstream OpenZFS code.

Author: Dan McDonald

module/zfs/zfs_ctldir.c

@@ -28,6 +28,7 @@
  *   Rohan Puri <[email protected]>
  *   Brian Behlendorf <[email protected]>
  * Copyright (c) 2013 by Delphix. All rights reserved.
+ * Copyright 2015, OmniTI Computer Consulting, Inc. All rights reserved.
  */
 
 /*
@@ -1245,21 +1246,16 @@ zfsctl_shares_lookup(struct inode *dip, char *name, struct inode **ipp,
 		return (SET_ERROR(ENOTSUP));
 	}
 
-	error = zfs_zget(zsb, zsb->z_shares_dir, &dzp);
-	if (error) {
-		ZFS_EXIT(zsb);
-		return (error);
+	if ((error = zfs_zget(zsb, zsb->z_shares_dir, &dzp)) == 0) {
+		error = zfs_lookup(ZTOI(dzp), name, &ip, 0, cr, NULL, NULL);
+		iput(ZTOI(dzp));
 	}
 
-	error = zfs_lookup(ZTOI(dzp), name, &ip, 0, cr, NULL, NULL);
-
-	iput(ZTOI(dzp));
 	ZFS_EXIT(zsb);
 
 	return (error);
 }
 
-
 /*
  * Initialize the various pieces we'll need to create and manipulate .zfs
  * directories.  Currently this is unused but available.