text: /*
   * GPL HEADER START
   *
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 only,
   * as published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License version 2 for more details (a copy is included
   * in the LICENSE file that accompanied this code).
   *
   * You should have received a copy of the GNU General Public License
   * version 2 along with this program; If not, see
   * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
   *
   * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
   * CA 95054 USA or visit www.sun.com if you need additional information or
   * have any questions.
   *
   * GPL HEADER END
   */
  /*
   * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
   * Use is subject to license terms.
   *
   * Copyright (c) 2011, 2012, Intel Corporation.
   */
  /*
   * This file is part of Lustre, http://www.lustre.org/
   * Lustre is a trademark of Sun Microsystems, Inc.
   *
   * lustre/ptlrpc/sec_gc.c
   *
   * Author: Eric Mei <ericm@clusterfs.com>
   */
  
  #define DEBUG_SUBSYSTEM S_SEC
  
  #include "../../include/linux/libcfs/libcfs.h"
  
  #include "../include/obd_support.h"
  #include "../include/obd_class.h"
  #include "../include/lustre_net.h"
  #include "../include/lustre_sec.h"
  
  #include "ptlrpc_internal.h"
  
  #define SEC_GC_INTERVAL (30 * 60)
  
  
  static struct mutex sec_gc_mutex;
  static LIST_HEAD(sec_gc_list);
  static spinlock_t sec_gc_list_lock;
  
  static LIST_HEAD(sec_gc_ctx_list);
  static spinlock_t sec_gc_ctx_list_lock;
  
  static struct ptlrpc_thread sec_gc_thread;
  static atomic_t sec_gc_wait_del = ATOMIC_INIT(0);
  
  
  void sptlrpc_gc_add_sec(struct ptlrpc_sec *sec)
  {
  	LASSERT(sec->ps_policy->sp_cops->gc_ctx);
  	LASSERT(sec->ps_gc_interval > 0);
  	LASSERT(list_empty(&sec->ps_gc_list));
  
  	sec->ps_gc_next = get_seconds() + sec->ps_gc_interval;
  
  	spin_lock(&sec_gc_list_lock);
  	list_add_tail(&sec_gc_list, &sec->ps_gc_list);
  	spin_unlock(&sec_gc_list_lock);
  
  	CDEBUG(D_SEC, "added sec %p(%s)\n", sec, sec->ps_policy->sp_name);
  }
  EXPORT_SYMBOL(sptlrpc_gc_add_sec);
  
  void sptlrpc_gc_del_sec(struct ptlrpc_sec *sec)
  {
  	if (list_empty(&sec->ps_gc_list))
  		return;
  
  	might_sleep();
  
  	/* signal before list_del to make iteration in gc thread safe */
  	atomic_inc(&sec_gc_wait_del);
  
  	spin_lock(&sec_gc_list_lock);
  	list_del_init(&sec->ps_gc_list);
  	spin_unlock(&sec_gc_list_lock);
  
  	/* barrier */
  	mutex_lock(&sec_gc_mutex);
  	mutex_unlock(&sec_gc_mutex);
  
  	atomic_dec(&sec_gc_wait_del);
  
  	CDEBUG(D_SEC, "del sec %p(%s)\n", sec, sec->ps_policy->sp_name);
  }
  EXPORT_SYMBOL(sptlrpc_gc_del_sec);
  
  void sptlrpc_gc_add_ctx(struct ptlrpc_cli_ctx *ctx)
  {
  	LASSERT(list_empty(&ctx->cc_gc_chain));
  
  	CDEBUG(D_SEC, "hand over ctx %p(%u->%s)\n",
  	       ctx, ctx->cc_vcred.vc_uid, sec2target_str(ctx->cc_sec));
  	spin_lock(&sec_gc_ctx_list_lock);
  	list_add(&ctx->cc_gc_chain, &sec_gc_ctx_list);
  	spin_unlock(&sec_gc_ctx_list_lock);
  
  	thread_add_flags(&sec_gc_thread, SVC_SIGNAL);
  	wake_up(&sec_gc_thread.t_ctl_waitq);
  }
  EXPORT_SYMBOL(sptlrpc_gc_add_ctx);
  
  static void sec_process_ctx_list(void)
  {
  	struct ptlrpc_cli_ctx *ctx;
  
  	spin_lock(&sec_gc_ctx_list_lock);
  
  	while (!list_empty(&sec_gc_ctx_list)) {
  		ctx = list_entry(sec_gc_ctx_list.next,
  				     struct ptlrpc_cli_ctx, cc_gc_chain);
  		list_del_init(&ctx->cc_gc_chain);
  		spin_unlock(&sec_gc_ctx_list_lock);
  
  		LASSERT(ctx->cc_sec);
  		LASSERT(atomic_read(&ctx->cc_refcount) == 1);
  		CDEBUG(D_SEC, "gc pick up ctx %p(%u->%s)\n",
  		       ctx, ctx->cc_vcred.vc_uid, sec2target_str(ctx->cc_sec));
  		sptlrpc_cli_ctx_put(ctx, 1);
  
  		spin_lock(&sec_gc_ctx_list_lock);
  	}
  
  	spin_unlock(&sec_gc_ctx_list_lock);
  }
  
  static void sec_do_gc(struct ptlrpc_sec *sec)
  {
  	LASSERT(sec->ps_policy->sp_cops->gc_ctx);
  
  	if (unlikely(sec->ps_gc_next == 0)) {
  		CDEBUG(D_SEC, "sec %p(%s) has 0 gc time\n",
  		      sec, sec->ps_policy->sp_name);
  		return;
  	}
  
  	CDEBUG(D_SEC, "check on sec %p(%s)\n", sec, sec->ps_policy->sp_name);
  
  	if (cfs_time_after(sec->ps_gc_next, get_seconds()))
  		return;
  
  	sec->ps_policy->sp_cops->gc_ctx(sec);
  	sec->ps_gc_next = get_seconds() + sec->ps_gc_interval;
  }
  
  static int sec_gc_main(void *arg)
  {
  	struct ptlrpc_thread *thread = (struct ptlrpc_thread *) arg;
  	struct l_wait_info lwi;
  
  	unshare_fs_struct();
  
  	/* Record that the thread is running */
  	thread_set_flags(thread, SVC_RUNNING);
  	wake_up(&thread->t_ctl_waitq);
  
  	while (1) {
  		struct ptlrpc_sec *sec;
  
  		thread_clear_flags(thread, SVC_SIGNAL);
  		sec_process_ctx_list();
  again:
  		/* go through sec list do gc.
  		 * FIXME here we iterate through the whole list each time which
  		 * is not optimal. we perhaps want to use balanced binary tree
  		 * to trace each sec as order of expiry time.
  		 * another issue here is we wakeup as fixed interval instead of
  		 * according to each sec's expiry time */
  		mutex_lock(&sec_gc_mutex);
  		list_for_each_entry(sec, &sec_gc_list, ps_gc_list) {
  			/* if someone is waiting to be deleted, let it
  			 * proceed as soon as possible. */
  			if (atomic_read(&sec_gc_wait_del)) {
  				CDEBUG(D_SEC, "deletion pending, start over\n");
  				mutex_unlock(&sec_gc_mutex);
  				goto again;
  			}
  
  			sec_do_gc(sec);
  		}
  		mutex_unlock(&sec_gc_mutex);
  
  		/* check ctx list again before sleep */
  		sec_process_ctx_list();
  
  		lwi = LWI_TIMEOUT(SEC_GC_INTERVAL * HZ, NULL, NULL);
  		l_wait_event(thread->t_ctl_waitq,
  			     thread_is_stopping(thread) ||
  			     thread_is_signal(thread),
  			     &lwi);
  
  		if (thread_test_and_clear_flags(thread, SVC_STOPPING))
  			break;
  	}
  
  	thread_set_flags(thread, SVC_STOPPED);
  	wake_up(&thread->t_ctl_waitq);
  	return 0;
  }
  
  int sptlrpc_gc_init(void)
  {
  	struct l_wait_info lwi = { 0 };
  	struct task_struct *task;
  
  	mutex_init(&sec_gc_mutex);
  	spin_lock_init(&sec_gc_list_lock);
  	spin_lock_init(&sec_gc_ctx_list_lock);
  
  	/* initialize thread control */
  	memset(&sec_gc_thread, 0, sizeof(sec_gc_thread));
  	init_waitqueue_head(&sec_gc_thread.t_ctl_waitq);
  
  	task = kthread_run(sec_gc_main, &sec_gc_thread, "sptlrpc_gc");
  	if (IS_ERR(task)) {
  		CERROR("can't start gc thread: %ld\n", PTR_ERR(task));
  		return PTR_ERR(task);
  	}
  
  	l_wait_event(sec_gc_thread.t_ctl_waitq,
  		     thread_is_running(&sec_gc_thread), &lwi);
  	return 0;
  }
  
  void sptlrpc_gc_fini(void)
  {
  	struct l_wait_info lwi = { 0 };
  
  	thread_set_flags(&sec_gc_thread, SVC_STOPPING);
  	wake_up(&sec_gc_thread.t_ctl_waitq);
  
  	l_wait_event(sec_gc_thread.t_ctl_waitq,
  		     thread_is_stopped(&sec_gc_thread), &lwi);
  }
  