nfsd: count NFSv4 callback operations per netns

The NFS server tracks per-operation call counts for the forward channel
(proc4ops) but keeps no statistics for the NFSv4 backchannel (callback)
operations it sends to clients.

Add a per-netns array of percpu counters for callback operations, indexed
by RFC 8881 callback opcode (OP_CB_GETATTR..OP_CB_OFFLOAD), and bump the
relevant counter in nfsd4_run_cb(), which is hit exactly once per callback
that is actually queued.

CB_GETATTR is sent when a GETATTR conflicts with an outstanding write
delegation, which is roughly what the dedicated wdeleg_getattr counter
tracked. The two are not identical: the old counter incremented on every
such conflict, whereas the CB_GETATTR counter only counts callbacks that
are actually queued, so concurrent conflicts that coalesce onto an
already in-flight CB_GETATTR are now counted once rather than once per
conflict. Report the procfs "wdeleg_getattr" line from the CB_GETATTR
counter and drop the now-redundant NFSD_STATS_WDELEG_GETATTR counter, its
helper, and its increment site.

Assisted-by: LLM
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260717-exportd-netlink-v7-5-b7ce17b83b60@kernel.org
Signed-off-by: Chuck Lever <cel@kernel.org>

0 files changed, 0 insertions, 0 deletions