/*
   * JFFS2 -- Journalling Flash File System, Version 2.
   *

   * Copyright © 2001-2007 Red Hat, Inc.

   * Copyright © 2004-2010 David Woodhouse <dwmw2@infradead.org>

   *
   * Created by David Woodhouse <dwmw2@infradead.org>
   *
   * For licensing information, see the file 'LICENCE' in this directory.
   *

   */
  
  #include <linux/kernel.h>
  #include <linux/jffs2.h>
  #include <linux/mtd/mtd.h>
  #include <linux/completion.h>

  #include <linux/sched.h>

  #include <linux/freezer.h>

  #include <linux/kthread.h>

  #include "nodelist.h"
  
  
  static int jffs2_garbage_collect_thread(void *);
  
  void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c)
  {

  	assert_spin_locked(&c->erase_completion_lock);

  	if (c->gc_task && jffs2_thread_should_wake(c))
  		send_sig(SIGHUP, c->gc_task, 1);

  }
  
  /* This must only ever be called when no GC thread is currently running */
  int jffs2_start_garbage_collect_thread(struct jffs2_sb_info *c)
  {

  	struct task_struct *tsk;

  	int ret = 0;

  	BUG_ON(c->gc_task);

  	init_completion(&c->gc_thread_start);

  	init_completion(&c->gc_thread_exit);

  	tsk = kthread_run(jffs2_garbage_collect_thread, c, "jffs2_gcd_mtd%d", c->mtd->index);
  	if (IS_ERR(tsk)) {
  		printk(KERN_WARNING "fork failed for JFFS2 garbage collect thread: %ld
  ", -PTR_ERR(tsk));

  		complete(&c->gc_thread_exit);

  		ret = PTR_ERR(tsk);

  	} else {
  		/* Wait for it... */

  		D1(printk(KERN_DEBUG "JFFS2: Garbage collect thread is pid %d
  ", tsk->pid));

  		wait_for_completion(&c->gc_thread_start);

  		ret = tsk->pid;

  	}

  	return ret;
  }
  
  void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c)
  {

  	int wait = 0;

  	spin_lock(&c->erase_completion_lock);
  	if (c->gc_task) {
  		D1(printk(KERN_DEBUG "jffs2: Killing GC task %d
  ", c->gc_task->pid));
  		send_sig(SIGKILL, c->gc_task, 1);

  		wait = 1;

  	}
  	spin_unlock(&c->erase_completion_lock);

  	if (wait)
  		wait_for_completion(&c->gc_thread_exit);

  }
  
  static int jffs2_garbage_collect_thread(void *_c)
  {
  	struct jffs2_sb_info *c = _c;

  	allow_signal(SIGKILL);
  	allow_signal(SIGSTOP);
  	allow_signal(SIGCONT);
  
  	c->gc_task = current;

  	complete(&c->gc_thread_start);

  
  	set_user_nice(current, 10);

  	set_freezable();

  	for (;;) {
  		allow_signal(SIGHUP);

  	again:

  		spin_lock(&c->erase_completion_lock);

  		if (!jffs2_thread_should_wake(c)) {
  			set_current_state (TASK_INTERRUPTIBLE);

  			spin_unlock(&c->erase_completion_lock);

  			D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread sleeping...
  "));

  			schedule();

  		} else
  			spin_unlock(&c->erase_completion_lock);
  			

  		/* Problem - immediately after bootup, the GCD spends a lot
  		 * of time in places like jffs2_kill_fragtree(); so much so
  		 * that userspace processes (like gdm and X) are starved
  		 * despite plenty of cond_resched()s and renicing.  Yield()
  		 * doesn't help, either (presumably because userspace and GCD
  		 * are generally competing for a higher latency resource -
  		 * disk).
  		 * This forces the GCD to slow the hell down.   Pulling an
  		 * inode in with read_inode() is much preferable to having
  		 * the GC thread get there first. */
  		schedule_timeout_interruptible(msecs_to_jiffies(50));

  		if (kthread_should_stop()) {
  			D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread():  kthread_stop() called.
  "));
  			goto die;
  		}

  		/* Put_super will send a SIGKILL and then wait on the sem.

  		 */

  		while (signal_pending(current) || freezing(current)) {

  			siginfo_t info;
  			unsigned long signr;

  			if (try_to_freeze())
  				goto again;

  			signr = dequeue_signal_lock(current, &current->blocked, &info);
  
  			switch(signr) {
  			case SIGSTOP:
  				D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGSTOP received.
  "));
  				set_current_state(TASK_STOPPED);
  				schedule();
  				break;
  
  			case SIGKILL:
  				D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGKILL received.
  "));
  				goto die;
  
  			case SIGHUP:
  				D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGHUP received.
  "));
  				break;
  			default:
  				D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): signal %ld received
  ", signr));
  			}
  		}
  		/* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
  		disallow_signal(SIGHUP);
  
  		D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): pass
  "));
  		if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
  			printk(KERN_NOTICE "No space for garbage collection. Aborting GC thread
  ");
  			goto die;
  		}
  	}
   die:
  	spin_lock(&c->erase_completion_lock);
  	c->gc_task = NULL;
  	spin_unlock(&c->erase_completion_lock);
  	complete_and_exit(&c->gc_thread_exit, 0);
  }