nfs: cache all open LOCALIO nfsd_file(s) in client

This commit switches from leaning heavily on NFSD's filecache (in
terms of GC'd nfsd_files) back to caching nfsd_files in the
client. A later commit will add the callback mechanism needed to
allow NFSD to force the NFS client to cleanup all cached nfsd_files.

Add nfs_fh_localio_init() and 'struct nfs_fh_localio' to cache opened
nfsd_file(s) (both a RO and RW nfsd_file is able to be opened and
cached for a given nfs_fh).

Update nfs_local_open_fh() to cache the nfsd_file once it is opened
using __nfs_local_open_fh().

Introduce nfs_close_local_fh() to clear the cached open nfsd_files and
call nfs_to_nfsd_file_put_local().

Refcounting is such that:
- nfs_local_open_fh() is paired with nfs_close_local_fh().
- __nfs_local_open_fh() is paired with nfs_to_nfsd_file_put_local().
- nfs_local_file_get() is paired with nfs_local_file_put().

Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

2 files changed, 29 insertions, 9 deletions

diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 039898d70954..67ae2c3f41d2 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -77,6 +77,23 @@ struct nfs_lock_context {
 	struct rcu_head	rcu_head;
 };
 
+struct nfs_file_localio {
+	struct nfsd_file __rcu *ro_file;
+	struct nfsd_file __rcu *rw_file;
+	struct list_head list;
+	void __rcu *nfs_uuid; /* opaque pointer to 'nfs_uuid_t' */
+};
+
+static inline void nfs_localio_file_init(struct nfs_file_localio *nfl)
+{
+#if IS_ENABLED(CONFIG_NFS_LOCALIO)
+	nfl->ro_file = NULL;
+	nfl->rw_file = NULL;
+	INIT_LIST_HEAD(&nfl->list);
+	nfl->nfs_uuid = NULL;
+#endif
+}
+
 struct nfs4_state;
 struct nfs_open_context {
 	struct nfs_lock_context lock_context;
@@ -87,15 +104,16 @@ struct nfs_open_context {
 	struct nfs4_state *state;
 	fmode_t mode;
 
+	int error;
 	unsigned long flags;
 #define NFS_CONTEXT_BAD			(2)
 #define NFS_CONTEXT_UNLOCK	(3)
 #define NFS_CONTEXT_FILE_OPEN		(4)
-	int error;
 
-	struct list_head list;
 	struct nfs4_threshold	*mdsthreshold;
+	struct list_head list;
 	struct rcu_head	rcu_head;
+	struct nfs_file_localio nfl;
 };
 
 struct nfs_open_dir_context {
diff --git a/include/linux/nfslocalio.h b/include/linux/nfslocalio.h
index 4d5583873f41..7cfc6720ed26 100644
--- a/include/linux/nfslocalio.h
+++ b/include/linux/nfslocalio.h
@@ -6,10 +6,6 @@
 #ifndef __LINUX_NFSLOCALIO_H
 #define __LINUX_NFSLOCALIO_H
 
-
-/* nfsd_file structure is purposely kept opaque to NFS client */
-struct nfsd_file;
-
 #if IS_ENABLED(CONFIG_NFS_LOCALIO)
 
 #include <linux/module.h>
@@ -21,6 +17,7 @@ struct nfsd_file;
 #include <net/net_namespace.h>
 
 struct nfs_client;
+struct nfs_file_localio;
 
 /*
  * Useful to allow a client to negotiate if localio
@@ -52,6 +49,7 @@ extern struct nfsd_file *
 nfsd_open_local_fh(struct net *, struct auth_domain *, struct rpc_clnt *,
 		   const struct cred *, const struct nfs_fh *,
 		   const fmode_t) __must_hold(rcu);
+void nfs_close_local_fh(struct nfs_file_localio *);
 
 struct nfsd_localio_operations {
 	bool (*nfsd_serv_try_get)(struct net *);
@@ -73,7 +71,8 @@ extern const struct nfsd_localio_operations *nfs_to;
 
 struct nfsd_file *nfs_open_local_fh(nfs_uuid_t *,
 		   struct rpc_clnt *, const struct cred *,
-		   const struct nfs_fh *, const fmode_t);
+		   const struct nfs_fh *, struct nfs_file_localio *,
+		   const fmode_t);
 
 static inline void nfs_to_nfsd_net_put(struct net *net)
 {
@@ -100,12 +99,15 @@ static inline void nfs_to_nfsd_file_put_local(struct nfsd_file *localio)
 }
 
 #else   /* CONFIG_NFS_LOCALIO */
-static inline void nfsd_localio_ops_init(void)
+
+struct nfs_file_localio;
+static inline void nfs_close_local_fh(struct nfs_file_localio *nfl)
 {
 }
-static inline void nfs_to_nfsd_file_put_local(struct nfsd_file *localio)
+static inline void nfsd_localio_ops_init(void)
 {
 }
+
 #endif  /* CONFIG_NFS_LOCALIO */
 
 #endif  /* __LINUX_NFSLOCALIO_H */