[PATCH] NFS: get module in idmap PipeFS notifier callback

[Stanislav Kinsbursky <skinsbursky@parallels.com>]

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>
---
 fs/nfs/idmap.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
index c9c3e1b..f55b80a 100644
--- a/fs/nfs/idmap.c
+++ b/fs/nfs/idmap.c
@@ -557,12 +557,16 @@ 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;
 }