/*
   * Cache operations for Coda.
   * For Linux 2.1: (C) 1997 Carnegie Mellon University
   * For Linux 2.3: (C) 2000 Carnegie Mellon University
   *
   * Carnegie Mellon encourages users of this code to contribute improvements
   * to the Coda project http://www.coda.cs.cmu.edu/ <coda@cs.cmu.edu>.
   */
  
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/time.h>
  #include <linux/fs.h>
  #include <linux/stat.h>
  #include <linux/errno.h>
  #include <asm/uaccess.h>
  #include <linux/string.h>
  #include <linux/list.h>

  #include <linux/sched.h>

  #include <linux/spinlock.h>

  
  #include <linux/coda.h>

  #include <linux/coda_psdev.h>

  #include "coda_linux.h"
  #include "coda_cache.h"

  
  static atomic_t permission_epoch = ATOMIC_INIT(0);
  
  /* replace or extend an acl cache hit */
  void coda_cache_enter(struct inode *inode, int mask)
  {
  	struct coda_inode_info *cii = ITOC(inode);

  	spin_lock(&cii->c_lock);

  	cii->c_cached_epoch = atomic_read(&permission_epoch);

  	if (cii->c_uid != current_fsuid()) {
  		cii->c_uid = current_fsuid();

                  cii->c_cached_perm = mask;
          } else
                  cii->c_cached_perm |= mask;

  	spin_unlock(&cii->c_lock);

  }
  
  /* remove cached acl from an inode */
  void coda_cache_clear_inode(struct inode *inode)
  {
  	struct coda_inode_info *cii = ITOC(inode);

  	spin_lock(&cii->c_lock);

  	cii->c_cached_epoch = atomic_read(&permission_epoch) - 1;

  	spin_unlock(&cii->c_lock);

  }
  
  /* remove all acl caches */
  void coda_cache_clear_all(struct super_block *sb)
  {

  	atomic_inc(&permission_epoch);
  }
  
  
  /* check if the mask has been matched against the acl already */
  int coda_cache_check(struct inode *inode, int mask)
  {
  	struct coda_inode_info *cii = ITOC(inode);

  	int hit;

  	spin_lock(&cii->c_lock);
  	hit = (mask & cii->c_cached_perm) == mask &&
  	    cii->c_uid == current_fsuid() &&
  	    cii->c_cached_epoch == atomic_read(&permission_epoch);
  	spin_unlock(&cii->c_lock);

  	return hit;

  }
  
  
  /* Purging dentries and children */
  /* The following routines drop dentries which are not
     in use and flag dentries which are in use to be 
     zapped later.
  
     The flags are detected by:
     - coda_dentry_revalidate (for lookups) if the flag is C_PURGE
     - coda_dentry_delete: to remove dentry from the cache when d_count
       falls to zero
     - an inode method coda_revalidate (for attributes) if the 
       flag is C_VATTR
  */
  
  /* this won't do any harm: just flag all children */
  static void coda_flag_children(struct dentry *parent, int flag)
  {
  	struct list_head *child;
  	struct dentry *de;

  	spin_lock(&parent->d_lock);

  	list_for_each(child, &parent->d_subdirs)
  	{

  		de = list_entry(child, struct dentry, d_u.d_child);

  		/* don't know what to do with negative dentries */
  		if ( ! de->d_inode ) 
  			continue;
  		coda_flag_inode(de->d_inode, flag);
  	}

  	spin_unlock(&parent->d_lock);

  	return; 
  }
  
  void coda_flag_inode_children(struct inode *inode, int flag)
  {
  	struct dentry *alias_de;
  
  	if ( !inode || !S_ISDIR(inode->i_mode)) 
  		return; 
  
  	alias_de = d_find_alias(inode);
  	if (!alias_de)
  		return;
  	coda_flag_children(alias_de, flag);
  	shrink_dcache_parent(alias_de);
  	dput(alias_de);
  }