[PATCH v3 0/4] protect access to bc_serv

[Olga Kornievskaia <okorniev@redhat.com>]

This patch series tries to address the problem that can arise when
the client is shutting down but gets a backchannel request. As it
stands now, In nfs4_shutdown_client() we call nfs4_destroy_callback()
which would destroy/free the bc_serv structure stored in an xprt
structure. But the xprt structure is still around for a bit until
it's destroyed. If we get backchannel request after svc_destroy()
is called, then in xprt_complete_bc_request() we are accessing freed
memory.

I propose to use bc_pa_lock lock to protect access to the bc_serv
structure and make sure we free/nullify bc_serv under the lock
and then access it under a lock in  xs_complete_bs_request() and
rpcrdma_bc_receive_call().

-- v3 Addressing Anna'a comments. (1) created function for shared
code between tcp/rdma backchannel and (2) created
xprt_svc_destroy_nullify_bc() for both on/off CONFIG_SUNRPC_BACKCHANNEL
values.

-- v2 fixing kernel test bot reported compile error in usage of
xprt_svc_destroy_nullify_bc (CONFIG_SUNRPC_BACKCHANNEL toggle related)

Olga Kornievskaia (4):
  NFSv4.1: pass transport for callback shutdown
  SUNRPC: cleanup common code in backchannel request
  SUNRPC: new helper function for stopping backchannel server
  NFSv4.1: protect destroying and nullifying bc_serv structure

 fs/nfs/callback.c                 |  7 +++++--
 fs/nfs/callback.h                 |  3 ++-
 fs/nfs/nfs4client.c               |  9 ++++++--
 include/linux/sunrpc/bc_xprt.h    |  6 ++++++
 net/sunrpc/backchannel_rqst.c     | 35 ++++++++++++++++++++++++++++---
 net/sunrpc/xprtrdma/backchannel.c |  8 ++-----
 6 files changed, 54 insertions(+), 14 deletions(-)

-- 
2.47.1