[pnfs] Request for an additional recommended attribute

[Glasgow_Jason at emc.com]

In describing how the pNFS block client will implement fencing, it became necessary to define the maximum time that an I/O can be outstanding.  The client needs to communicate its value to the pNFS server.  The most appropriate means of doing so seems to be to provide a per server R/W recommended attribute, which clients can write.

I propose updating section 5.6 "Recommended Attributes - Definitions" with the following

maximum_io_time  74 uint32    R/W   The default maximum time that a client
                                    I/O to a data server can be active.
                                    Clients may update this value.



This parameter is defined in the next version of the pNFS block layout spec as follows:

--
"maximum_io_time" is the maximum time it can take for a client I/O to the storage system to either complete or fail; this value is often 30 seconds or 60 seconds, but may be longer in some environments. .  If the maximum client I/O time cannot be bounded, this timed lease mechanism MUST NOT be used.  The client can use GETATTR to query the server's default setting of "maximum_io_time".  The server must respond with the maximum I/O time in seconds.  If the client's maximum I/O time is greater than the server's default, then the client MUST use SETATTR to inform the server of its maximum_I/O time.
--

Are there comments on introducing this new attribute into the NFSv4 minor version 1 spec?  Is this a valid means of communicating a client specific value to the server?

-Jason Glasgow