Say I have a file for which a VOP_READ will take five minutes to complete
(I have to restore some of its contents from tape).

Say this file lives in an nfs-exported fs.

How badly would this break an nfs server? The first nfsd to read the file
would sleep for five minutes. What would happen then? Would the client
retry, and possibly send another process to sleep (possibly getting all of
them)?

Would having the nfs server execute all its reads & writes with IO_NDELAY
(and teaching my stuff to return EWOULDBLOCK) make sense?

Take care,

Bill