NFS: get module in idmap PipeFS notifier callback

This is bug fix.
Notifier callback is called from SUNRPC module. So before dereferencing NFS
module we have to make sure, that it's alive.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
index b7f348bb618b..ba3019f5934c 100644
--- a/fs/nfs/idmap.c
+++ b/fs/nfs/idmap.c
@@ -554,12 +554,16 @@ static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
         struct nfs_client *clp;
         int error = 0;
 
+        if (!try_module_get(THIS_MODULE))
+                return 0;
+
         while ((clp = nfs_get_client_for_event(sb->s_fs_info, event))) {
                 error = __rpc_pipefs_event(clp, event, sb);
                 nfs_put_client(clp);
                 if (error)
                         break;
         }
+        module_put(THIS_MODULE);
         return error;
 }