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>

1 files changed, 20 insertions, 2 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 {