[PATCH v7 0/2] NFSD: memory shrinker for NFSv4 clients

[Dai Ngo <dai.ngo@oracle.com>]

This patch series implements the memory shrinker for NFSv4 clients
to react to system low memory condition.

The first patch adds a counter to keep track of the number of
courtesy clients in the system.

The second patch implements the courtesy_client_reaper used to
expiring the courtesy clients.

By destroying the courtesy clients, all states associated with
these clients are also released.

v2:
. fix kernel test robot errors in nfsd.h when CONFIG_NFSD_V4 not defined.

v3:
. add mod_delayed_work in nfsd_courtesy_client_scan to kick start
  the laundromat.

v4:
. replace the use of xchg() with vanilla '=' in patch 1.

v5:
. rename nfsd_courtesy_client_count to nfsd_courtesy_clients
. add helper nfsd4_update_courtesy_client_count
. move nfsd_register_client_shrinker into nfsd4_init_leases_net
. move nfsd4_leases_net_shutdown from nfsd.h to nfs4state.c
. do away with shrinker 'scan' callback, just return SHRINK_STOP
. remove unused nfsd_client_shrinker_reapcount

v6:
. create courtesy_client_reaper and a separate delayed_work for it
  using the laundromat_wq. 
  I tried merging nfs4_get_courtesy_client_reaplist and
  nfs4_get_client_reaplist but it make the code looks ugly and
  hard to read so I leave them as separate for now.

v7:
. patch1: rename nfsd4_decr_courtesy_client_count to
  nfsd4_dec_courtesy_client_count
. patch 2: get rid of nfsd_client_shrinker_cb_count and do not
  reschedule courtesy_client_reaper
---

Dai Ngo (2):
      NFSD: keep track of the number of courtesy clients in the system
      NFSD: add shrinker to reap courtesy clients on low memory condition

 fs/nfsd/netns.h     |   4 ++
 fs/nfsd/nfs4state.c | 111 +++++++++++++++++++++++++++++++++++++++++++----
 fs/nfsd/nfsctl.c    |   6 ++-
 fs/nfsd/nfsd.h      |   7 ++-
 4 files changed, 115 insertions(+), 13 deletions(-)