[PATCH v5 0/5] sunrpc: hardcode pool_mode to pernode, remove other modes

[Jeff Layton <jlayton@kernel.org>]

This has a few small fixes and comment cleanups and also implements
Neil's suggestion to remove serv.sv_nrpools:

Patches #1 and #3 address what is a shortcoming of the existing code --
namely that the server can be configured to schedule RPCs to pools with
no threads in them.

The first patch addresses this problem: if the chosen pool has no
threads, then choose another that does.

The third patch tries to prevent this situation in the
auto-thread-placement case by ensuring that each populated node has at
least one thread.

The last two patches implement Neil's suggestion to eliminate
serv.sv_nrpools. This has the side effect of getting the modulus out of
the svc_pool_for_cpu() hotpath as well.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
Changes in v5:
- Expand patch to eliminate modulus to also eliminate serv.sv_nrpools field
- Revised comments in svc_pool_for_cpu()
- Link to v4: https://lore.kernel.org/r/20260701-sunrpc-pool-mode-v4-0-b3d867e4c8f9@kernel.org

Changes in v4:
- Drop 5/4 RCU patch
- Only let pooled services consult the map
- Comment and commit log fixes
- Link to v3: https://lore.kernel.org/r/20260629-sunrpc-pool-mode-v3-0-d92676606dfd@kernel.org

Changes in v3:
- Add patch to ensure that we don't route requests to empty pools
- When auto-distributing threads, always create at least one thread per populated pool
- Use sysfs_match_string for the module parameter
- Reword deprecation printk to be more vague about removal
- Explicitly set m_count == 0 in svc_pool_map_get()
- Optimize svc_pool_for_cpu() by eliminating modulus ops
- Link to v2: https://lore.kernel.org/r/20260625-sunrpc-pool-mode-v2-1-4f512b6e1ee8@kernel.org

Changes in v2:
- Accept any previously-accepted setting for pool_mode
- Link to v1: https://lore.kernel.org/r/20260423-sunrpc-pool-mode-v1-1-b7f20e35749b@kernel.org

---
Jeff Layton (5):
      sunrpc: route to a populated pool in svc_pool_for_cpu()
      sunrpc: hardcode pool_mode to pernode, remove other modes
      sunrpc: guarantee a thread per pool when auto-distributing
      sunrpc: tear down pool counters before dropping the pool map reference
      sunrpc: derive the pool count instead of caching it in sv_nrpools

 Documentation/admin-guide/kernel-parameters.txt |  20 +-
 fs/nfsd/nfsctl.c                                |   2 +-
 fs/nfsd/nfssvc.c                                |  10 +-
 include/linux/sunrpc/svc.h                      |   2 +-
 net/sunrpc/svc.c                                | 355 +++++++++---------------
 net/sunrpc/svc_xprt.c                           |   6 +-
 6 files changed, 152 insertions(+), 243 deletions(-)
---
base-commit: ee6ae4a6bf3565b880dfb420017337475dfbc9ea
change-id: 20260423-sunrpc-pool-mode-3e6b56320dc4

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