1 files changed, 52 insertions, 18 deletions

diff --git a/fs/nfsd/localio.c b/fs/nfsd/localio.c
index 238647fa379e..80d9ff6608a7 100644
--- a/fs/nfsd/localio.c
+++ b/fs/nfsd/localio.c
@@ -24,21 +24,6 @@
 #include "filecache.h"
 #include "cache.h"
 
-static const struct nfsd_localio_operations nfsd_localio_ops = {
-	.nfsd_net_try_get  = nfsd_net_try_get,
-	.nfsd_net_put  = nfsd_net_put,
-	.nfsd_open_local_fh = nfsd_open_local_fh,
-	.nfsd_file_put_local = nfsd_file_put_local,
-	.nfsd_file_get = nfsd_file_get,
-	.nfsd_file_put = nfsd_file_put,
-	.nfsd_file_file = nfsd_file_file,
-};
-
-void nfsd_localio_ops_init(void)
-{
-	nfs_to = &nfsd_localio_ops;
-}
-
 /**
  * nfsd_open_local_fh - lookup a local filehandle @nfs_fh and map to nfsd_file
  *
@@ -47,6 +32,7 @@ void nfsd_localio_ops_init(void)
  * @rpc_clnt: rpc_clnt that the client established
  * @cred: cred that the client established
  * @nfs_fh: filehandle to lookup
+ * @nfp: place to find the nfsd_file, or store it if it was non-NULL
  * @fmode: fmode_t to use for open
  *
  * This function maps a local fh to a path on a local filesystem.
@@ -57,10 +43,11 @@ void nfsd_localio_ops_init(void)
  * set. Caller (NFS client) is responsible for calling nfsd_net_put and
  * nfsd_file_put (via nfs_to_nfsd_file_put_local).
  */
-struct nfsd_file *
+static struct nfsd_file *
 nfsd_open_local_fh(struct net *net, struct auth_domain *dom,
 		   struct rpc_clnt *rpc_clnt, const struct cred *cred,
-		   const struct nfs_fh *nfs_fh, const fmode_t fmode)
+		   const struct nfs_fh *nfs_fh, struct nfsd_file __rcu **pnf,
+		   const fmode_t fmode)
 {
 	int mayflags = NFSD_MAY_LOCALIO;
 	struct svc_cred rq_cred;
@@ -71,6 +58,15 @@ nfsd_open_local_fh(struct net *net, struct auth_domain *dom,
 	if (nfs_fh->size > NFS4_FHSIZE)
 		return ERR_PTR(-EINVAL);
 
+	if (!nfsd_net_try_get(net))
+		return ERR_PTR(-ENXIO);
+
+	rcu_read_lock();
+	localio = nfsd_file_get(rcu_dereference(*pnf));
+	rcu_read_unlock();
+	if (localio)
+		return localio;
+
 	/* nfs_fh -> svc_fh */
 	fh_init(&fh, NFS4_FHSIZE);
 	fh.fh_handle.fh_size = nfs_fh->size;
@@ -92,9 +88,47 @@ nfsd_open_local_fh(struct net *net, struct auth_domain *dom,
 	if (rq_cred.cr_group_info)
 		put_group_info(rq_cred.cr_group_info);
 
+	if (!IS_ERR(localio)) {
+		struct nfsd_file *new;
+		if (!nfsd_net_try_get(net)) {
+			nfsd_file_put(localio);
+			nfsd_net_put(net);
+			return ERR_PTR(-ENXIO);
+		}
+		nfsd_file_get(localio);
+	again:
+		new = unrcu_pointer(cmpxchg(pnf, NULL, RCU_INITIALIZER(localio)));
+		if (new) {
+			/* Some other thread installed an nfsd_file */
+			if (nfsd_file_get(new) == NULL)
+				goto again;
+			/*
+			 * Drop the ref we were going to install and the
+			 * one we were going to return.
+			 */
+			nfsd_file_put(localio);
+			nfsd_file_put(localio);
+			localio = new;
+		}
+	} else
+		nfsd_net_put(net);
+
 	return localio;
 }
-EXPORT_SYMBOL_GPL(nfsd_open_local_fh);
+
+static const struct nfsd_localio_operations nfsd_localio_ops = {
+	.nfsd_net_try_get  = nfsd_net_try_get,
+	.nfsd_net_put  = nfsd_net_put,
+	.nfsd_open_local_fh = nfsd_open_local_fh,
+	.nfsd_file_put_local = nfsd_file_put_local,
+	.nfsd_file_get_local = nfsd_file_get_local,
+	.nfsd_file_file = nfsd_file_file,
+};
+
+void nfsd_localio_ops_init(void)
+{
+	nfs_to = &nfsd_localio_ops;
+}
 
 /*
  * UUID_IS_LOCAL XDR functions