/* Copyright (C) 2009 Red Hat, Inc.
   *
   * See ../COPYING for licensing terms.
   */
  
  #include <linux/mm.h>
  #include <linux/mmu_context.h>

  #include <linux/export.h>

  #include <linux/sched.h>
  
  #include <asm/mmu_context.h>
  
  /*
   * use_mm
   *	Makes the calling kernel thread take on the specified
   *	mm context.
   *	Called by the retry thread execute retries within the
   *	iocb issuer's mm context, so that copy_from/to_user
   *	operations work seamlessly for aio.
   *	(Note: this routine is intended to be called only
   *	from a kernel thread context)
   */
  void use_mm(struct mm_struct *mm)
  {
  	struct mm_struct *active_mm;
  	struct task_struct *tsk = current;
  
  	task_lock(tsk);
  	active_mm = tsk->active_mm;

  	if (active_mm != mm) {
  		atomic_inc(&mm->mm_count);
  		tsk->active_mm = mm;
  	}

  	tsk->mm = mm;

  	switch_mm(active_mm, mm, tsk);
  	task_unlock(tsk);

  	if (active_mm != mm)
  		mmdrop(active_mm);

  }

  EXPORT_SYMBOL_GPL(use_mm);

  
  /*
   * unuse_mm
   *	Reverses the effect of use_mm, i.e. releases the
   *	specified mm context which was earlier taken on
   *	by the calling kernel thread
   *	(Note: this routine is intended to be called only
   *	from a kernel thread context)
   */
  void unuse_mm(struct mm_struct *mm)
  {
  	struct task_struct *tsk = current;
  
  	task_lock(tsk);

  	sync_mm_rss(tsk, mm);

  	tsk->mm = NULL;
  	/* active_mm is still 'mm' */
  	enter_lazy_tlb(mm, tsk);
  	task_unlock(tsk);
  }

  EXPORT_SYMBOL_GPL(unuse_mm);