Merge tag 'nfsd-6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux

Pull nfsd updates from Chuck Lever:
 "Mike Snitzer has prototyped a mechanism for disabling I/O caching in
  NFSD. This is introduced in v6.18 as an experimental feature. This
  enables scaling NFSD in /both/ directions:

   - NFS service can be supported on systems with small memory
     footprints, such as low-cost cloud instances

   - Large NFS workloads will be less likely to force the eviction of
     server-local activity, helping it avoid thrashing

  Jeff Layton contributed a number of fixes to the new attribute
  delegation implementation (based on a pending Internet RFC) that we
  hope will make attribute delegation reliable enough to enable by
  default, as it is on the Linux NFS client.

  The remaining patches in this pull request are clean-ups and minor
  optimizations. Many thanks to the contributors, reviewers, testers,
  and bug reporters who participated during the v6.18 NFSD development
  cycle"

* tag 'nfsd-6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux: (42 commits)
  nfsd: discard nfserr_dropit
  SUNRPC: Make RPCSEC_GSS_KRB5 select CRYPTO instead of depending on it
  NFSD: Add io_cache_{read,write} controls to debugfs
  NFSD: Do the grace period check in ->proc_layoutget
  nfsd: delete unnecessary NULL check in __fh_verify()
  NFSD: Allow layoutcommit during grace period
  NFSD: Disallow layoutget during grace period
  sunrpc: fix "occurence"->"occurrence"
  nfsd: Don't force CRYPTO_LIB_SHA256 to be built-in
  nfsd: nfserr_jukebox in nlm_fopen should lead to a retry
  NFSD: Reduce DRC bucket size
  NFSD: Delay adding new entries to LRU
  SUNRPC: Move the svc_rpcb_cleanup() call sites
  NFS: Remove rpcbind cleanup for NFSv4.0 callback
  nfsd: unregister with rpcbind when deleting a transport
  NFSD: Drop redundant conversion to bool
  sunrpc: eliminate return pointer in svc_tcp_sendmsg()
  sunrpc: fix pr_notice in svc_tcp_sendto() to show correct length
  nfsd: decouple the xprtsec policy check from check_nfsd_access()
  NFSD: Fix destination buffer size in nfsd4_ssc_setup_dul()
  ...

1 files changed, 14 insertions, 1 deletions

diff --git a/fs/nfsd/lockd.c b/fs/nfsd/lockd.c
index edc9f75dc75c..c774ce9aa296 100644
--- a/fs/nfsd/lockd.c
+++ b/fs/nfsd/lockd.c
@@ -57,7 +57,20 @@ nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f, struct file **filp,
 	switch (nfserr) {
 	case nfs_ok:
 		return 0;
-	case nfserr_dropit:
+	case nfserr_jukebox:
+		/* this error can indicate a presence of a conflicting
+		 * delegation to an NLM lock request. Options are:
+		 * (1) For now, drop this request and make the client
+		 * retry. When delegation is returned, client's lock retry
+		 * will complete.
+		 * (2) NLM4_DENIED as per "spec" signals to the client
+		 * that the lock is unavailable now but client can retry.
+		 * Linux client implementation does not. It treats
+		 * NLM4_DENIED same as NLM4_FAILED and errors the request.
+		 * (3) For the future, treat this as blocked lock and try
+		 * to callback when the delegation is returned but might
+		 * not have a proper lock request to block on.
+		 */
 		return nlm_drop_reply;
 	case nfserr_stale:
 		return nlm_stale_fh;