cache.c

linux 内核源代码

/*
 * 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/ <[e-mail]>.
 */

#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/coda.h>
#include <linux/coda_linux.h>
#include <linux/coda_psdev.h>
#include <linux/coda_fs_i.h>
#include <linux/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);

	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;
}

/* remove cached acl from an inode */
void coda_cache_clear_inode(struct inode *inode)
{
	struct coda_inode_info *cii = ITOC(inode);
	cii->c_cached_epoch = atomic_read(&permission_epoch) - 1;
}

/* 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;
	
        hit = (mask & cii->c_cached_perm) == mask &&
		cii->c_uid == current->fsuid &&
		cii->c_cached_epoch == atomic_read(&permission_epoch);

        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(&dcache_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(&dcache_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);
}