Similar to D32635, I believe there could be a race between the NFS
client VOP_LOOKUP() and file Writing that could result in stale file
attributes being loaded into the NFS vnode by VOP_LOOKUP().
I have not been able to reproduce a failure due to this race, but
I believe that there are two possibilities:
- The Lookup RPC happens while VOP_WRITE() is being executed and loads stale file attributes after VOP_WRITE() returns when it has already completed the Write/Commit RPC(s). --> For this case, setting the local modify timestamp at the end of VOP_WRITE() should ensure that stale file attributes are not loaded.
- The Lookup RPC occurs after VOP_WRITE() has returned, while asynchronous Write/Commit RPCs are in progress and then is blocked by the vnode held by VOP_OPEN/VOP_CLOSE/VOP_FSYNC which will flush writes via ncl_flush() or ncl_vinvalbuf(), clearing the NMODIFIED flag (which indicates Writes-in-progress). The VOP_LOOKUP() then acquires the NFS vnode lock and fills in stale file attributes. --> Setting the local modify timestamp in ncl_flsuh() and ncl_vinvalbuf() when they clear NMODIFIED should ensure that stale file attributes are not loaded.
This patch does the above.