RPC: fragment too large with transition to 3.4

[Jamie Heilman <jamie@audible.transient.net>]

Jamie Heilman wrote:
> It's looking like my issues with "RPC: fragment too large" may be
> something else entirely at this point, I've noticed other weird
> network behavior that I'm gonna have to try to isolate before I keep
> blaming nfs changes.  Though for some reason my
> /proc/fs/nfsd/max_block_size ends up only 128KiB w/3.4 where it was
> 512KiB w/3.3.

OK, I get it now.  32-bit PAE system w/4G of RAM (minus a chunk for
the IGP video etc.) for my NFS server, and the max_block_size
calculation changed significantly in commit
508f92275624fc755104b17945bdc822936f1918 to account for rpc buffers
only being in low memory.  That means whereas in 3.3 the math came out
to having a target size of roughly 843241 my new target size in 3.4 is
only 219959-ish, so choosing 128KiB is understandable.  The problem
was that all my clients had negotiated their nfs mounts against the
v3.3 value of 512KiB, and when I rebooted into 3.4... they hit the
wall attempting larger transfers and become uselessly stuck at that
point.  If I remount everything before doing any large transfers, then
it negotiates a lower wsize and things work fine.  So everything is
working as planned I suppose... the transition between 3.3 and 3.4 is
just a bit rough.

-- 
Jamie Heilman                     http://audible.transient.net/~jamie/