[CIFS] work around bug in Samba server handling for posix open

Samba server (version 3.3.1 and earlier, and 3.2.8 and earlier) incorrectly
required the O_CREAT flag on posix open (even when a file was not being
created).  This disables posix open (create is still ok) after the first
attempt returns EINVAL (and logs an error, once, recommending that they
update their server).

Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 44ff94d..9fbf4df 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -299,6 +299,7 @@
 	bool unix_ext:1;  /* if false disable Linux extensions to CIFS protocol
 				for this mount even if server would support */
 	bool local_lease:1; /* check leases (only) on local system not remote */
+	bool broken_posix_open; /* e.g. Samba server versions < 3.3.2, 3.2.9 */
 	bool need_reconnect:1; /* connection reset, tid now invalid */
 	/* BB add field for back pointer to sb struct(s)? */
 };