NFS: Clean up nfs_sb_active/nfs_sb_deactive

Instead of causing umount requests to block on server->active_wq while the
asynchronous sillyrename deletes are executing, we can use the sb->s_active
counter to obtain a reference to the super_block, and then release that
reference in nfs_async_unlink_release().
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/client.c

@@ -850,7 +850,6 @@ static struct nfs_server *nfs_alloc_server(void)
 	INIT_LIST_HEAD(&server->client_link);
 	INIT_LIST_HEAD(&server->master_link);
 
-	init_waitqueue_head(&server->active_wq);
 	atomic_set(&server->active, 0);
 
 	server->io_stats = nfs_alloc_iostats();

fs/nfs/internal.h

@@ -163,8 +163,8 @@ extern struct rpc_stat nfs_rpcstat;
 
 extern int __init register_nfs_fs(void);
 extern void __exit unregister_nfs_fs(void);
-extern void nfs_sb_active(struct nfs_server *server);
-extern void nfs_sb_deactive(struct nfs_server *server);
+extern void nfs_sb_active(struct super_block *sb);
+extern void nfs_sb_deactive(struct super_block *sb);
 
 /* namespace.c */
 extern char *nfs_path(const char *base,

fs/nfs/super.c

@@ -209,7 +209,6 @@ 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 int nfs_remount(struct super_block *sb, int *flags, char *raw_data);
 
 static struct file_system_type nfs_fs_type = {
@@ -232,7 +231,6 @@ 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,
@@ -337,26 +335,20 @@ void __exit unregister_nfs_fs(void)
 	unregister_filesystem(&nfs_fs_type);
 }
 
-void nfs_sb_active(struct nfs_server *server)
+void nfs_sb_active(struct super_block *sb)
 {
-	atomic_inc(&server->active);
-}
+	struct nfs_server *server = NFS_SB(sb);
 
-void nfs_sb_deactive(struct nfs_server *server)
-{
-	if (atomic_dec_and_test(&server->active))
-		wake_up(&server->active_wq);
+	if (atomic_inc_return(&server->active) == 1)
+		atomic_inc(&sb->s_active);
 }
 
-static void nfs_put_super(struct super_block *sb)
+void nfs_sb_deactive(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);
+
+	if (atomic_dec_and_test(&server->active))
+		deactivate_super(sb);
 }
 
 /*

fs/nfs/unlink.c

@@ -99,7 +99,7 @@ static void nfs_async_unlink_release(void *calldata)
 
 	nfs_dec_sillycount(data->dir);
 	nfs_free_unlinkdata(data);
-	nfs_sb_deactive(NFS_SB(sb));
+	nfs_sb_deactive(sb);
 }
 
 static const struct rpc_call_ops nfs_unlink_ops = {
@@ -118,6 +118,7 @@ static int nfs_do_call_unlink(struct dentry *parent, struct inode *dir, struct n
 		.rpc_message = &msg,
 		.callback_ops = &nfs_unlink_ops,
 		.callback_data = data,
+		.workqueue = nfsiod_workqueue,
 		.flags = RPC_TASK_ASYNC,
 	};
 	struct rpc_task *task;
@@ -149,7 +150,7 @@ static int nfs_do_call_unlink(struct dentry *parent, struct inode *dir, struct n
 		nfs_dec_sillycount(dir);
 		return 0;
 	}
-	nfs_sb_active(NFS_SERVER(dir));
+	nfs_sb_active(dir->i_sb);
 	data->args.fh = NFS_FH(dir);
 	nfs_fattr_init(&data->res.dir_attr);
 

include/linux/nfs_fs_sb.h

@@ -119,7 +119,6 @@ struct nfs_server {
 	void (*destroy)(struct nfs_server *);
 
 	atomic_t active; /* Keep trace of any activity to this server */
-	wait_queue_head_t active_wq;  /* Wait for any activity to stop  */
 
 	/* mountd-related mount options */
 	struct sockaddr_storage	mountd_address;