smb3: Do not send SMB3 SET_INFO if nothing changed

commit fd09b7d3 upstream.

An earlier commit had a typo which prevented the
optimization from working:

commit 18dd8e1a ("Do not send SMB3 SET_INFO request if nothing is changing")

Thank you to Metze for noticing this.  Also clear a
reserved field in the FILE_BASIC_INFO struct we send
that should be zero (all the other fields in that
struct were set or cleared explicitly already in
cifs_set_file_info).
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
CC: Stable <stable@vger.kernel.org> # 4.9.x+
Reported-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/cifs/inode.c

@@ -1063,6 +1063,8 @@ cifs_set_file_info(struct inode *inode, struct iattr *attrs, unsigned int xid,
 	if (!server->ops->set_file_info)
 		return -ENOSYS;
 
+	info_buf.Pad = 0;
+
 	if (attrs->ia_valid & ATTR_ATIME) {
 		set_time = true;
 		info_buf.LastAccessTime =

fs/cifs/smb2inode.c

@@ -267,7 +267,7 @@ smb2_set_file_info(struct inode *inode, const char *full_path,
 	int rc;
 
 	if ((buf->CreationTime == 0) && (buf->LastAccessTime == 0) &&
-	    (buf->LastWriteTime == 0) && (buf->ChangeTime) &&
+	    (buf->LastWriteTime == 0) && (buf->ChangeTime == 0) &&
 	    (buf->Attributes == 0))
 		return 0; /* would be a no op, no sense sending this */