The NFSv4.1 server code has always only supported a single callback
slot. This has the effect of serializing all the callbacks on the
server, which can cause a bottleneck when there is a lot of callback
activity. This patchset allows the NFS server to use up to 32
backchannel slots when communicating with clients.

Note that so far, we don't have a great way to drive a lot of concurrent
backchannel activity with standard testsuites. I did set up a server
with two clients and had one client open a bunch of files, and a second
client fork off a bunch of processes that statx'ed those files
repeatedly. With that I was able to see the parallelization in action
via CB_GETATTR activity. I'm still thinking about how best to test this
with pynfs.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
Jeff Layton (2):
      nfsd: remove nfsd4_session->se_bchannel
      nfsd: allow for more callback session slots

 fs/nfsd/nfs4callback.c | 107 +++++++++++++++++++++++++++++++++++--------------
 fs/nfsd/nfs4state.c    |   9 +++--
 fs/nfsd/state.h        |  13 +++---
 fs/nfsd/trace.h        |   2 +-
 4 files changed, 89 insertions(+), 42 deletions(-)
---
base-commit: c7b8826b41906db1c930cbb10abb94eb24247f20
change-id: 20241025-bcwide-6bd7e4b63db2

Best regards,
-- 
Jeff Layton <jlayton@kernel.org>