NFS: Force the legacy idmapper to be single threaded

It was initially coded under the assumption that there would only be one
request at a time, so use a lock to enforce this requirement..

Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
CC: stable@vger.kernel.org [3.4+]
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 8 insertions, 5 deletions

diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
index b5b86a05059c..864c51e4b400 100644
--- a/fs/nfs/idmap.c
+++ b/fs/nfs/idmap.c
@@ -57,6 +57,11 @@ unsigned int nfs_idmap_cache_timeout = 600;
 static const struct cred *id_resolver_cache;
 static struct key_type key_type_id_resolver_legacy;
 
+struct idmap {
+        struct rpc_pipe         *idmap_pipe;
+        struct key_construction *idmap_key_cons;
+        struct mutex            idmap_mutex;
+};
 
 /**
  * nfs_fattr_init_names - initialise the nfs_fattr owner_name/group_name fields
@@ -310,9 +315,11 @@ static ssize_t nfs_idmap_get_key(const char *name, size_t namelen,
                                             name, namelen, type, data,
                                             data_size, NULL);
         if (ret < 0) {
+                mutex_lock(&idmap->idmap_mutex);
                 ret = nfs_idmap_request_key(&key_type_id_resolver_legacy,
                                             name, namelen, type, data,
                                             data_size, idmap);
+                mutex_unlock(&idmap->idmap_mutex);
         }
         return ret;
 }
@@ -354,11 +361,6 @@ static int nfs_idmap_lookup_id(const char *name, size_t namelen, const char *typ
 /* idmap classic begins here */
 module_param(nfs_idmap_cache_timeout, int, 0644);
 
-struct idmap {
-        struct rpc_pipe         *idmap_pipe;
-        struct key_construction *idmap_key_cons;
-};
-
 enum {
         Opt_find_uid, Opt_find_gid, Opt_find_user, Opt_find_group, Opt_find_err
 };
@@ -469,6 +471,7 @@ nfs_idmap_new(struct nfs_client *clp)
                 return error;
         }
         idmap->idmap_pipe = pipe;
+        mutex_init(&idmap->idmap_mutex);
 
         clp->cl_idmap = idmap;
         return 0;