NFS: Slow down state manager after an unhandled error

If the state manager thread is not actually able to fully recover from
some situation, it wakes up waiters, who kick off a new state manager
thread.  Quite often the fresh invocation of the state manager is just
as successful.

This results in a livelock as the client dumps thousands of NFS
requests a second on the network in a vain attempt to recover.  Not
very friendly.

To mitigate this situation, add a delay in the state manager after
an unhandled error, so that the client sends just a few requests
every second in this case.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index bd8ed01cb0ea..38eeefd95375 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -2015,6 +2015,7 @@ out_error:
         pr_warn_ratelimited("NFS: state manager%s%s failed on NFSv4 server %s"
                         " with error %d\n", section_sep, section,
                         clp->cl_hostname, -status);
+        ssleep(1);
         nfs4_end_drain_session(clp);
         nfs4_clear_state_manager_bit(clp);
 }