[PATCH v2 1/1] NFSv4: Allow FREE_STATEID to clean up delegations

[Benjamin Coddington <bcodding@redhat.com>]

The NFS client's list of delegations can grow quite large (well beyond the
delegation watermark) if the server is revoking or there are repeated
events that expire state.  Once this happens, the revoked delegations can
cause a performance problem for subsequent walks of the
servers->delegations list when the client tries to test and free state.

If we can determine that the FREE_STATEID operation has completed without
error, we can prune the delegation from the list.

Since the NFS client combines TEST_STATEID with FREE_STATEID in its minor
version operations, there isn't an easy way to communicate success of
FREE_STATEID.  Rather than re-arrange quite a number of calling paths to
break out the separate procedures, let's signal the success of FREE_STATEID
by setting the stateid's type.

Set NFS4_FREED_STATEID_TYPE for stateids that have been successfully
discarded from the server, and use that type to signal that the delegation
can be cleaned up.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
---
 fs/nfs/delegation.c  | 25 ++++++++++++++++++-------
 fs/nfs/nfs4_fs.h     |  3 +--
 fs/nfs/nfs4proc.c    | 12 ++++++------
 include/linux/nfs4.h |  1 +
 4 files changed, 26 insertions(+), 15 deletions(-)

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index 4db912f56230..b746793cf730 100644
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -1006,13 +1006,6 @@ static void nfs_revoke_delegation(struct inode *inode,
 		nfs_inode_find_state_and_recover(inode, stateid);
 }
 
-void nfs_remove_bad_delegation(struct inode *inode,
-		const nfs4_stateid *stateid)
-{
-	nfs_revoke_delegation(inode, stateid);
-}
-EXPORT_SYMBOL_GPL(nfs_remove_bad_delegation);
-
 void nfs_delegation_mark_returned(struct inode *inode,
 		const nfs4_stateid *stateid)
 {
@@ -1054,6 +1047,24 @@ void nfs_delegation_mark_returned(struct inode *inode,
 	nfs_inode_find_state_and_recover(inode, stateid);
 }
 
+/**
+ * nfs_remove_bad_delegation - handle delegations that are unusable
+ * @inode: inode to process
+ * @stateid: the delegation's stateid
+ *
+ * If the server ACK-ed our FREE_STATEID then clean
+ * up the delegation, else mark and keep the revoked state.
+ */
+void nfs_remove_bad_delegation(struct inode *inode,
+		const nfs4_stateid *stateid)
+{
+	if (stateid && stateid->type == NFS4_FREED_STATEID_TYPE)
+		nfs_delegation_mark_returned(inode, stateid);
+	else
+		nfs_revoke_delegation(inode, stateid);
+}
+EXPORT_SYMBOL_GPL(nfs_remove_bad_delegation);
+
 /**
  * nfs_expire_unused_delegation_types
  * @clp: client to process
diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index 7d383d29a995..d3ca91f60fc1 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -67,8 +67,7 @@ struct nfs4_minor_version_ops {
 	void	(*free_lock_state)(struct nfs_server *,
 			struct nfs4_lock_state *);
 	int	(*test_and_free_expired)(struct nfs_server *,
-					 const nfs4_stateid *,
-					 const struct cred *);
+					 nfs4_stateid *, const struct cred *);
 	struct nfs_seqid *
 		(*alloc_seqid)(struct nfs_seqid_counter *, gfp_t);
 	void	(*session_trunk)(struct rpc_clnt *clnt,
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 6e95db6c17e9..c969e6b0dd84 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -105,7 +105,7 @@ static struct rpc_task *_nfs41_proc_sequence(struct nfs_client *clp,
 		bool is_privileged);
 static int nfs41_test_stateid(struct nfs_server *, const nfs4_stateid *,
 			      const struct cred *);
-static int nfs41_free_stateid(struct nfs_server *, const nfs4_stateid *,
+static int nfs41_free_stateid(struct nfs_server *, nfs4_stateid *,
 			      const struct cred *, bool);
 #endif
 
@@ -2886,16 +2886,14 @@ static int nfs40_open_expired(struct nfs4_state_owner *sp, struct nfs4_state *st
 }
 
 static int nfs40_test_and_free_expired_stateid(struct nfs_server *server,
-					       const nfs4_stateid *stateid,
-					       const struct cred *cred)
+					       nfs4_stateid *stateid, const struct cred *cred)
 {
 	return -NFS4ERR_BAD_STATEID;
 }
 
 #if defined(CONFIG_NFS_V4_1)
 static int nfs41_test_and_free_expired_stateid(struct nfs_server *server,
-					       const nfs4_stateid *stateid,
-					       const struct cred *cred)
+					       nfs4_stateid *stateid, const struct cred *cred)
 {
 	int status;
 
@@ -2904,6 +2902,7 @@ static int nfs41_test_and_free_expired_stateid(struct nfs_server *server,
 		break;
 	case NFS4_INVALID_STATEID_TYPE:
 	case NFS4_SPECIAL_STATEID_TYPE:
+	case NFS4_FREED_STATEID_TYPE:
 		return -NFS4ERR_BAD_STATEID;
 	case NFS4_REVOKED_STATEID_TYPE:
 		goto out_free;
@@ -10570,7 +10569,7 @@ static const struct rpc_call_ops nfs41_free_stateid_ops = {
  * Note: this function is always asynchronous.
  */
 static int nfs41_free_stateid(struct nfs_server *server,
-		const nfs4_stateid *stateid,
+		nfs4_stateid *stateid,
 		const struct cred *cred,
 		bool privileged)
 {
@@ -10610,6 +10609,7 @@ static int nfs41_free_stateid(struct nfs_server *server,
 	if (IS_ERR(task))
 		return PTR_ERR(task);
 	rpc_put_task(task);
+	stateid->type = NFS4_FREED_STATEID_TYPE;
 	return 0;
 }
 
diff --git a/include/linux/nfs4.h b/include/linux/nfs4.h
index 9ac83ca88326..8ec5766cb22f 100644
--- a/include/linux/nfs4.h
+++ b/include/linux/nfs4.h
@@ -72,6 +72,7 @@ struct nfs4_stateid_struct {
 		NFS4_LAYOUT_STATEID_TYPE,
 		NFS4_PNFS_DS_STATEID_TYPE,
 		NFS4_REVOKED_STATEID_TYPE,
+		NFS4_FREED_STATEID_TYPE,
 	} type;
 };
 
-- 
2.47.0