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2590 jermar 1
/*
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 * Copyright (c) 2008 Jakub Jermar
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 *
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 * - Redistributions of source code must retain the above copyright
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 *   notice, this list of conditions and the following disclaimer.
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 * - Redistributions in binary form must reproduce the above copyright
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 *   notice, this list of conditions and the following disclaimer in the
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 *   documentation and/or other materials provided with the distribution.
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 * - The name of the author may not be used to endorse or promote products
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 *   derived from this software without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */
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/** @addtogroup fs
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 * @{
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 */
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/**
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 * @file    vfs_node.c
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 * @brief   Various operations on VFS nodes have their home in this file.
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 */
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#include "vfs.h"
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#include <stdlib.h>
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#include <string.h>
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#include <futex.h>
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#include <rwlock.h>
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#include <libadt/hash_table.h>
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#include <assert.h>
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#include <async.h>
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#include <errno.h>
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/** Futex protecting the VFS node hash table. */
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futex_t nodes_futex = FUTEX_INITIALIZER;
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#define NODES_BUCKETS_LOG   8
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#define NODES_BUCKETS       (1 << NODES_BUCKETS_LOG)
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/** VFS node hash table containing all active, in-memory VFS nodes. */
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hash_table_t nodes;
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#define KEY_FS_HANDLE   0
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#define KEY_DEV_HANDLE  1
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#define KEY_INDEX   2
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static hash_index_t nodes_hash(unsigned long []);
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static int nodes_compare(unsigned long [], hash_count_t, link_t *);
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static void nodes_remove_callback(link_t *);
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/** VFS node hash table operations. */
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hash_table_operations_t nodes_ops = {
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    .hash = nodes_hash,
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    .compare = nodes_compare,
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    .remove_callback = nodes_remove_callback
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};
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/** Initialize the VFS node hash table.
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 *
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 * @return      Return true on success, false on failure.
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 */
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bool vfs_nodes_init(void)
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{
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    return hash_table_create(&nodes, NODES_BUCKETS, 3, &nodes_ops);
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}
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static inline void _vfs_node_addref(vfs_node_t *node)
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{
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    node->refcnt++;
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}
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/** Increment reference count of a VFS node.
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 *
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 * @param node      VFS node that will have its refcnt incremented.
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 */
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void vfs_node_addref(vfs_node_t *node)
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{
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    futex_down(&nodes_futex);
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    _vfs_node_addref(node);
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    futex_up(&nodes_futex);
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}
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/** Decrement reference count of a VFS node.
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 *
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 * This function handles the case when the reference count drops to zero.
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 *
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 * @param node      VFS node that will have its refcnt decremented.
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 */
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void vfs_node_delref(vfs_node_t *node)
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{
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    bool free_vfs_node = false;
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    bool free_fs_node = false;
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    futex_down(&nodes_futex);
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    if (node->refcnt-- == 1) {
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        /*
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         * We are dropping the last reference to this node.
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         * Remove it from the VFS node hash table.
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         */
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        unsigned long key[] = {
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            [KEY_FS_HANDLE] = node->fs_handle,
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            [KEY_DEV_HANDLE] = node->dev_handle,
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            [KEY_INDEX] = node->index
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        };
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        hash_table_remove(&nodes, key, 3);
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        free_vfs_node = true;
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        if (!node->lnkcnt)
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            free_fs_node = true;
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    }
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    futex_up(&nodes_futex);
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    if (free_fs_node) {
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        /*
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         * The node is not visible in the file system namespace.
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         * Free up its resources.
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         */
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        int phone = vfs_grab_phone(node->fs_handle);
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        ipcarg_t rc;
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        rc = async_req_2_0(phone, VFS_DESTROY,
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            (ipcarg_t)node->dev_handle, (ipcarg_t)node->index);
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        assert(rc == EOK);
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        vfs_release_phone(phone);
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    }
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    if (free_vfs_node)
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        free(node);
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}
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/** Find VFS node.
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 *
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 * This function will try to lookup the given triplet in the VFS node hash
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 * table. In case the triplet is not found there, a new VFS node is created.
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 * In any case, the VFS node will have its reference count incremented. Every
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 * node returned by this call should be eventually put back by calling
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 * vfs_node_put() on it.
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 *
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 * @param result    Populated lookup result structure.
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 *
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 * @return      VFS node corresponding to the given triplet.
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 */
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vfs_node_t *vfs_node_get(vfs_lookup_res_t *result)
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{
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    unsigned long key[] = {
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        [KEY_FS_HANDLE] = result->triplet.fs_handle,
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        [KEY_DEV_HANDLE] = result->triplet.dev_handle,
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        [KEY_INDEX] = result->triplet.index
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    };
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    link_t *tmp;
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    vfs_node_t *node;
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    futex_down(&nodes_futex);
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    tmp = hash_table_find(&nodes, key);
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    if (!tmp) {
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        node = (vfs_node_t *) malloc(sizeof(vfs_node_t));
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        if (!node) {
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            futex_up(&nodes_futex);
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            return NULL;
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        }
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        memset(node, 0, sizeof(vfs_node_t));
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        node->fs_handle = result->triplet.fs_handle;
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        node->dev_handle = result->triplet.dev_handle;
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        node->index = result->triplet.index;
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        node->size = result->size;
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        node->lnkcnt = result->lnkcnt;
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        node->type = result->type;
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        link_initialize(&node->nh_link);
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        rwlock_initialize(&node->contents_rwlock);
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        hash_table_insert(&nodes, key, &node->nh_link);
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    } else {
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        node = hash_table_get_instance(tmp, vfs_node_t, nh_link);  
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        if (node->type == VFS_NODE_UNKNOWN &&
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            result->type != VFS_NODE_UNKNOWN) {
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            /* Upgrade the node type. */
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            node->type = result->type;
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        }
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    }
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    assert(node->size == result->size);
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    assert(node->lnkcnt == result->lnkcnt);
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    assert(node->type == result->type || result->type == VFS_NODE_UNKNOWN);
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    _vfs_node_addref(node);
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    futex_up(&nodes_futex);
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    return node;
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}
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/** Return VFS node when no longer needed by the caller.
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 *
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 * This function will remove the reference on the VFS node created by
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 * vfs_node_get(). This function can only be called as a closing bracket to the
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 * preceding vfs_node_get() call.
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 *
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 * @param node      VFS node being released.
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 */
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void vfs_node_put(vfs_node_t *node)
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{
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    vfs_node_delref(node);
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}
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hash_index_t nodes_hash(unsigned long key[])
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{
216
    hash_index_t a = key[KEY_FS_HANDLE] << (NODES_BUCKETS_LOG / 4);
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    hash_index_t b = (a | key[KEY_DEV_HANDLE]) << (NODES_BUCKETS_LOG / 2);
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    return (b | key[KEY_INDEX]) & (NODES_BUCKETS - 1);
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}
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222
int nodes_compare(unsigned long key[], hash_count_t keys, link_t *item)
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{
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    vfs_node_t *node = hash_table_get_instance(item, vfs_node_t, nh_link);
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    return (node->fs_handle == key[KEY_FS_HANDLE]) &&
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        (node->dev_handle == key[KEY_DEV_HANDLE]) &&
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        (node->index == key[KEY_INDEX]);
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}
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void nodes_remove_callback(link_t *item)
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{
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}
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/**
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 * @}
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 */