[LU-8050] Drop llog_cookie usage from RPC on wire data

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.10.0
• Severity: 3
• Assignee: nasf (Inactive)
• Reporter: nasf (Inactive)

Description

Originally, obdo::o_lcookie is for destroy with unlink cookie from MDS, it is obsolete in 2.8. And then, it is reused by the OSP to save on memory allocations as following comment:

        /*
         * this is a trick: to save on memory allocations we put cookie
         * into the request, but don't set corresponded flag in o_valid
         * so that OST doesn't interpret this cookie. once the request
         * is committed on OST we take cookie from the request and cancel
         */

Currently, we needs more fields in the obdo structure to transfer more information from client to OST. The obdo::o_lcookie is good candidate. So we need adjust OSP logic to NOT use such field for non-onwire RPC data usage.