vfs_node.c

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/*
 * Copyright (c) 2008 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "vfs.h"
#include <stdlib.h>
#include <str.h>
#include <fibril_synch.h>
#include <adt/hash_table.h>
#include <assert.h>
#include <async.h>
#include <errno.h>

FIBRIL_MUTEX_INITIALIZE(nodes_mutex);

#define NODES_BUCKETS_LOG       8
#define NODES_BUCKETS           (1 << NODES_BUCKETS_LOG)

hash_table_t nodes;

#define KEY_FS_HANDLE   0
#define KEY_DEV_HANDLE  1
#define KEY_INDEX       2

static hash_index_t nodes_hash(unsigned long []);
static int nodes_compare(unsigned long [], hash_count_t, link_t *);
static void nodes_remove_callback(link_t *);

hash_table_operations_t nodes_ops = {
        .hash = nodes_hash,
        .compare = nodes_compare,
        .remove_callback = nodes_remove_callback
};

bool vfs_nodes_init(void)
{
        return hash_table_create(&nodes, NODES_BUCKETS, 3, &nodes_ops);
}

static inline void _vfs_node_addref(vfs_node_t *node)
{
        node->refcnt++;
}

void vfs_node_addref(vfs_node_t *node)
{
        fibril_mutex_lock(&nodes_mutex);
        _vfs_node_addref(node);
        fibril_mutex_unlock(&nodes_mutex);
}

void vfs_node_delref(vfs_node_t *node)
{
        bool free_vfs_node = false;
        bool free_fs_node = false;

        fibril_mutex_lock(&nodes_mutex);
        if (node->refcnt-- == 1) {
                /*
                 * We are dropping the last reference to this node.
                 * Remove it from the VFS node hash table.
                 */
                unsigned long key[] = {
                        [KEY_FS_HANDLE] = node->fs_handle,
                        [KEY_DEV_HANDLE] = node->devmap_handle,
                        [KEY_INDEX] = node->index
                };
                hash_table_remove(&nodes, key, 3);
                free_vfs_node = true;
                if (!node->lnkcnt)
                        free_fs_node = true;
        }
        fibril_mutex_unlock(&nodes_mutex);

        if (free_fs_node) {
                /* 
                 * The node is not visible in the file system namespace.
                 * Free up its resources.
                 */
                int phone = vfs_grab_phone(node->fs_handle);
                sysarg_t rc;
                rc = async_req_2_0(phone, VFS_OUT_DESTROY,
                    (sysarg_t)node->devmap_handle, (sysarg_t)node->index);
                assert(rc == EOK);
                vfs_release_phone(node->fs_handle, phone);
        }
        if (free_vfs_node)
                free(node);
}

void vfs_node_forget(vfs_node_t *node)
{
        fibril_mutex_lock(&nodes_mutex);
        unsigned long key[] = {
                [KEY_FS_HANDLE] = node->fs_handle,
                [KEY_DEV_HANDLE] = node->devmap_handle,
                [KEY_INDEX] = node->index
        };
        hash_table_remove(&nodes, key, 3);
        fibril_mutex_unlock(&nodes_mutex);
        free(node);
}

vfs_node_t *vfs_node_get(vfs_lookup_res_t *result)
{
        unsigned long key[] = {
                [KEY_FS_HANDLE] = result->triplet.fs_handle,
                [KEY_DEV_HANDLE] = result->triplet.devmap_handle,
                [KEY_INDEX] = result->triplet.index
        };
        link_t *tmp;
        vfs_node_t *node;

        fibril_mutex_lock(&nodes_mutex);
        tmp = hash_table_find(&nodes, key);
        if (!tmp) {
                node = (vfs_node_t *) malloc(sizeof(vfs_node_t));
                if (!node) {
                        fibril_mutex_unlock(&nodes_mutex);
                        return NULL;
                }
                memset(node, 0, sizeof(vfs_node_t));
                node->fs_handle = result->triplet.fs_handle;
                node->devmap_handle = result->triplet.devmap_handle;
                node->index = result->triplet.index;
                node->size = result->size;
                node->lnkcnt = result->lnkcnt;
                node->type = result->type;
                link_initialize(&node->nh_link);
                fibril_rwlock_initialize(&node->contents_rwlock);
                hash_table_insert(&nodes, key, &node->nh_link);
        } else {
                node = hash_table_get_instance(tmp, vfs_node_t, nh_link);
                if (node->type == VFS_NODE_UNKNOWN &&
                    result->type != VFS_NODE_UNKNOWN) {
                        /* Upgrade the node type. */
                        node->type = result->type;
                }
        }

        assert(node->size == result->size || node->type != VFS_NODE_FILE);
        assert(node->lnkcnt == result->lnkcnt);
        assert(node->type == result->type || result->type == VFS_NODE_UNKNOWN);

        _vfs_node_addref(node);
        fibril_mutex_unlock(&nodes_mutex);

        return node;
}

void vfs_node_put(vfs_node_t *node)
{
        vfs_node_delref(node);
}

hash_index_t nodes_hash(unsigned long key[])
{
        hash_index_t a = key[KEY_FS_HANDLE] << (NODES_BUCKETS_LOG / 4);
        hash_index_t b = (a | key[KEY_DEV_HANDLE]) << (NODES_BUCKETS_LOG / 2);
        
        return (b | key[KEY_INDEX]) & (NODES_BUCKETS - 1);
}

int nodes_compare(unsigned long key[], hash_count_t keys, link_t *item)
{
        vfs_node_t *node = hash_table_get_instance(item, vfs_node_t, nh_link);
        return (node->fs_handle == (fs_handle_t) key[KEY_FS_HANDLE]) &&
            (node->devmap_handle == key[KEY_DEV_HANDLE]) &&
            (node->index == key[KEY_INDEX]);
}

void nodes_remove_callback(link_t *item)
{
}

struct refcnt_data {
        unsigned refcnt;
        fs_handle_t fs_handle;
        devmap_handle_t devmap_handle;
};

static void refcnt_visitor(link_t *item, void *arg)
{
        vfs_node_t *node = hash_table_get_instance(item, vfs_node_t, nh_link);
        struct refcnt_data *rd = (void *) arg;

        if ((node->fs_handle == rd->fs_handle) &&
            (node->devmap_handle == rd->devmap_handle))
                rd->refcnt += node->refcnt;
}

unsigned
vfs_nodes_refcount_sum_get(fs_handle_t fs_handle, devmap_handle_t devmap_handle)
{
        struct refcnt_data rd = {
                .refcnt = 0,
                .fs_handle = fs_handle,
                .devmap_handle = devmap_handle
        };

        fibril_mutex_lock(&nodes_mutex);
        hash_table_apply(&nodes, refcnt_visitor, &rd);
        fibril_mutex_unlock(&nodes_mutex);

        return rd.refcnt;
}

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