Currently we return only layout lock for any open. With patches from LU-10948 we'll also return a lookup lock.

But I suspect on a successful create we should return a full set of bits except perhaps open lock - this would allow the name to be hashed and cache the attributes too.

In workloads like mdtest it's kind of important because after initial create the subsequent stat would be a 100% local operation as opposed to going to the server for a lookup or inode attrs revalidate.

There are basically no downsides. If we do create and then a lot of clients do conflicting things to the file - that's a single lock cancel to matter what anyway.