nfs_common: prepare for the NFS client to use nfsd_file for LOCALIO

The next commit will introduce nfsd_open_local_fh() which returns an
nfsd_file structure.  This commit exposes LOCALIO's required NFSD
symbols to the NFS client:

- Make nfsd_open_local_fh() symbol and other required NFSD symbols
  available to NFS in a global 'nfs_to' nfsd_localio_operations
  struct (global access suggested by Trond, nfsd_localio_operations
  suggested by NeilBrown).  The next commit will also introduce
  nfsd_localio_ops_init() that init_nfsd() will call to initialize
  'nfs_to'.

- Introduce nfsd_file_file() that provides access to nfsd_file's
  backing file.  Keeps nfsd_file structure opaque to NFS client (as
  suggested by Jeff Layton).

- Introduce nfsd_file_put_local() that will put the reference to the
  nfsd_file's associated nn->nfsd_serv and then put the reference to
  the nfsd_file (as suggested by NeilBrown).

Suggested-by: Trond Myklebust <trond.myklebust@hammerspace.com> # nfs_to
Suggested-by: NeilBrown <neilb@suse.de> # nfsd_localio_operations
Suggested-by: Jeff Layton <jlayton@kernel.org> # nfsd_file_file
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Reviewed-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

diff --git a/fs/nfs_common/nfslocalio.c b/fs/nfs_common/nfslocalio.c
index f0bff023bb5e75962c6654bf9a7bc3c80c850464..f61761ad19b17071a520bb6f919fe3537093b11d 100644 (file)
--- a/fs/nfs_common/nfslocalio.c
+++ b/fs/nfs_common/nfslocalio.c
@@ -72,7 +72,7 @@ void nfs_uuid_is_local(const uuid_t *uuid, struct list_head *list,
                 * invalidated.
                 */
                list_move(&nfs_uuid->list, list);
-               nfs_uuid->net = net;
+               rcu_assign_pointer(nfs_uuid->net, net);
 
                __module_get(mod);
                nfsd_mod = mod;
@@ -114,3 +114,26 @@ void nfs_uuid_invalidate_one_client(nfs_uuid_t *nfs_uuid)
        }
 }
 EXPORT_SYMBOL_GPL(nfs_uuid_invalidate_one_client);
+
+/*
+ * The NFS LOCALIO code needs to call into NFSD using various symbols,
+ * but cannot be statically linked, because that will make the NFS
+ * module always depend on the NFSD module.
+ *
+ * 'nfs_to' provides NFS access to NFSD functions needed for LOCALIO,
+ * its lifetime is tightly coupled to the NFSD module and will always
+ * be available to NFS LOCALIO because any successful client<->server
+ * LOCALIO handshake results in a reference on the NFSD module (above),
+ * so NFS implicitly holds a reference to the NFSD module and its
+ * functions in the 'nfs_to' nfsd_localio_operations cannot disappear.
+ *
+ * If the last NFS client using LOCALIO disconnects (and its reference
+ * on NFSD dropped) then NFSD could be unloaded, resulting in 'nfs_to'
+ * functions being invalid pointers. But if NFSD isn't loaded then NFS
+ * will not be able to handshake with NFSD and will have no cause to
+ * try to call 'nfs_to' function pointers. If/when NFSD is reloaded it
+ * will reinitialize the 'nfs_to' function pointers and make LOCALIO
+ * possible.
+ */
+const struct nfsd_localio_operations *nfs_to;
+EXPORT_SYMBOL_GPL(nfs_to);

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index caeffc43ca4b1907d4713be37ae01298e1845cbc..414b5bf738df9dc106124689225adacccf25f124 100644 (file)
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -390,6 +390,34 @@ nfsd_file_put(struct nfsd_file *nf)
                nfsd_file_free(nf);
 }
 
+/**
+ * nfsd_file_put_local - put the reference to nfsd_file and local nfsd_serv
+ * @nf: nfsd_file of which to put the references
+ *
+ * First put the reference of the nfsd_file and then put the
+ * reference to the associated nn->nfsd_serv.
+ */
+void
+nfsd_file_put_local(struct nfsd_file *nf)
+{
+       struct net *net = nf->nf_net;
+
+       nfsd_file_put(nf);
+       nfsd_serv_put(net);
+}
+
+/**
+ * nfsd_file_file - get the backing file of an nfsd_file
+ * @nf: nfsd_file of which to access the backing file.
+ *
+ * Return backing file for @nf.
+ */
+struct file *
+nfsd_file_file(struct nfsd_file *nf)
+{
+       return nf->nf_file;
+}
+
 static void
 nfsd_file_dispose_list(struct list_head *dispose)
 {

diff --git a/fs/nfsd/filecache.h b/fs/nfsd/filecache.h
index 26ada78b8c1e48d73ae5272d4a7962f157e27aa7..cadf3c2689c44c3696cf7e8d6f0f438dd1a1d04b 100644 (file)
--- a/fs/nfsd/filecache.h
+++ b/fs/nfsd/filecache.h
@@ -55,7 +55,9 @@ void nfsd_file_cache_shutdown(void);
 int nfsd_file_cache_start_net(struct net *net);
 void nfsd_file_cache_shutdown_net(struct net *net);
 void nfsd_file_put(struct nfsd_file *nf);
+void nfsd_file_put_local(struct nfsd_file *nf);
 struct nfsd_file *nfsd_file_get(struct nfsd_file *nf);
+struct file *nfsd_file_file(struct nfsd_file *nf);
 void nfsd_file_close_inode_sync(struct inode *inode);
 void nfsd_file_net_dispose(struct nfsd_net *nn);
 bool nfsd_file_is_cached(struct inode *inode);

diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index fa34de5e59bd92854402878b4461aa3f2d7cd87e..f9a6d888ac9d9cb9af0e2687214dfe3ec807ef20 100644 (file)
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -19,6 +19,7 @@
 #include <linux/sunrpc/svc_xprt.h>
 #include <linux/lockd/bind.h>
 #include <linux/nfsacl.h>
+#include <linux/nfslocalio.h>
 #include <linux/seq_file.h>
 #include <linux/inetdevice.h>
 #include <net/addrconf.h>

diff --git a/include/linux/nfslocalio.h b/include/linux/nfslocalio.h
index 4165ff8390c19cf211abadb7f1f8d07c7e96a479..1a39d7d727bd483a903354b205f6e12de4e5f9b0 100644 (file)
--- a/include/linux/nfslocalio.h
+++ b/include/linux/nfslocalio.h
@@ -9,6 +9,7 @@
 #include <linux/module.h>
 #include <linux/list.h>
 #include <linux/uuid.h>
+#include <linux/sunrpc/clnt.h>
 #include <linux/sunrpc/svcauth.h>
 #include <linux/nfs.h>
 #include <net/net_namespace.h>
@@ -22,7 +23,7 @@
 typedef struct {
        uuid_t uuid;
        struct list_head list;
-       struct net *net; /* nfsd's network namespace */
+       struct net __rcu *net; /* nfsd's network namespace */
        struct auth_domain *dom; /* auth_domain for localio */
 } nfs_uuid_t;
 
@@ -33,4 +34,28 @@ void nfs_uuid_is_local(const uuid_t *, struct list_head *,
 void nfs_uuid_invalidate_clients(struct list_head *list);
 void nfs_uuid_invalidate_one_client(nfs_uuid_t *nfs_uuid);
 
+struct nfsd_file;
+
+/* localio needs to map filehandle -> struct nfsd_file */
+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);
+
+struct nfsd_localio_operations {
+       bool (*nfsd_serv_try_get)(struct net *);
+       void (*nfsd_serv_put)(struct net *);
+       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);
+       void (*nfsd_file_put_local)(struct nfsd_file *);
+       struct file *(*nfsd_file_file)(struct nfsd_file *);
+} ____cacheline_aligned;
+
+extern void nfsd_localio_ops_init(void);
+extern const struct nfsd_localio_operations *nfs_to;
+
 #endif  /* __LINUX_NFSLOCALIO_H */