netfs.c

Go to the documentation of this file.

/* FS-Cache netfs (client) registration
 *
 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#define FSCACHE_DEBUG_LEVEL COOKIE
#include <linux/module.h>
#include <linux/slab.h>
#include "internal.h"

static LIST_HEAD(fscache_netfs_list);

/*
 * register a network filesystem for caching
 */
int __fscache_register_netfs(struct fscache_netfs *netfs)
{
    struct fscache_netfs *ptr;
    int ret;

    _enter("{%s}", netfs->name);

    INIT_LIST_HEAD(&netfs->link);

    /* allocate a cookie for the primary index */
    netfs->primary_index =
        kmem_cache_zalloc(fscache_cookie_jar, GFP_KERNEL);

    if (!netfs->primary_index) {
        _leave(" = -ENOMEM");
        return -ENOMEM;
    }

    /* initialise the primary index cookie */
    atomic_set(&netfs->primary_index->usage, 1);
    atomic_set(&netfs->primary_index->n_children, 0);

    netfs->primary_index->def       = &fscache_fsdef_netfs_def;
    netfs->primary_index->parent        = &fscache_fsdef_index;
    netfs->primary_index->netfs_data    = netfs;

    atomic_inc(&netfs->primary_index->parent->usage);
    atomic_inc(&netfs->primary_index->parent->n_children);

    spin_lock_init(&netfs->primary_index->lock);
    INIT_HLIST_HEAD(&netfs->primary_index->backing_objects);

    /* check the netfs type is not already present */
    down_write(&fscache_addremove_sem);

    ret = -EEXIST;
    list_for_each_entry(ptr, &fscache_netfs_list, link) {
        if (strcmp(ptr->name, netfs->name) == 0)
            goto already_registered;
    }

    list_add(&netfs->link, &fscache_netfs_list);
    ret = 0;

    printk(KERN_NOTICE "FS-Cache: Netfs '%s' registered for caching\n",
           netfs->name);

already_registered:
    up_write(&fscache_addremove_sem);

    if (ret < 0) {
        netfs->primary_index->parent = NULL;
        __fscache_cookie_put(netfs->primary_index);
        netfs->primary_index = NULL;
    }

    _leave(" = %d", ret);
    return ret;
}
EXPORT_SYMBOL(__fscache_register_netfs);

/*
 * unregister a network filesystem from the cache
 * - all cookies must have been released first
 */
void __fscache_unregister_netfs(struct fscache_netfs *netfs)
{
    _enter("{%s.%u}", netfs->name, netfs->version);

    down_write(&fscache_addremove_sem);

    list_del(&netfs->link);
    fscache_relinquish_cookie(netfs->primary_index, 0);

    up_write(&fscache_addremove_sem);

    printk(KERN_NOTICE "FS-Cache: Netfs '%s' unregistered from caching\n",
           netfs->name);

    _leave("");
}
EXPORT_SYMBOL(__fscache_unregister_netfs);