NFS: Stop sillyname renames and unmounts from racing

Added an active/deactive mechanism to the nfs_server structure
allowing async operations to hold off umount until the
operations are done.

Signed-off-by: Steve Dickson <steved@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 0b0c72a072ff..fda1635dd133 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -202,6 +202,7 @@ static int nfs_get_sb(struct file_system_type *, int, const char *, void *, stru
 static int nfs_xdev_get_sb(struct file_system_type *fs_type,
                 int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt);
 static void nfs_kill_super(struct super_block *);
+static void nfs_put_super(struct super_block *);
 
 static struct file_system_type nfs_fs_type = {
         .owner          = THIS_MODULE,
@@ -223,6 +224,7 @@ static const struct super_operations nfs_sops = {
         .alloc_inode    = nfs_alloc_inode,
         .destroy_inode  = nfs_destroy_inode,
         .write_inode    = nfs_write_inode,
+        .put_super      = nfs_put_super,
         .statfs         = nfs_statfs,
         .clear_inode    = nfs_clear_inode,
         .umount_begin   = nfs_umount_begin,
@@ -325,6 +327,28 @@ void __exit unregister_nfs_fs(void)
         unregister_filesystem(&nfs_fs_type);
 }
 
+void nfs_sb_active(struct nfs_server *server)
+{
+        atomic_inc(&server->active);
+}
+
+void nfs_sb_deactive(struct nfs_server *server)
+{
+        if (atomic_dec_and_test(&server->active))
+                wake_up(&server->active_wq);
+}
+
+static void nfs_put_super(struct super_block *sb)
+{
+        struct nfs_server *server = NFS_SB(sb);
+        /*
+         * Make sure there are no outstanding ops to this server.
+         * If so, wait for them to finish before allowing the
+         * unmount to continue.
+         */
+        wait_event(server->active_wq, atomic_read(&server->active) == 0);
+}
+
 /*
  * Deliver file system statistics to userspace
  */