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Line 34... Line 34...
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 * @file    vfs_node.c
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 * @file    vfs_node.c
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 * @brief   Various operations on VFS nodes have their home in this file.
 35 
 * @brief   Various operations on VFS nodes have their home in this file.
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 */
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 */
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 37 
 
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#include "vfs.h"
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#include "vfs.h"
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 39 
#include <stdlib.h>
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 40 
#include <string.h>
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#include <atomic.h>
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#include <futex.h>
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#include <libadt/hash_table.h>
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/** Futex protecting the VFS node hash table. */
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atomic_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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/** Increment reference count of a VFS node.
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 *
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 *
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 * @param node      VFS node that will have its refcnt incremented.
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 * @param node      VFS node that will have its refcnt incremented.
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 */
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 */
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void vfs_node_addref(vfs_node_t *node)
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void vfs_node_addref(vfs_node_t *node)
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{
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{
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    futex_down(&nodes_futex);
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    _vfs_node_addref(node);
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    /* TODO */
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    futex_up(&nodes_futex);
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}
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}
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/** Decrement reference count of a VFS node.
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/** Decrement reference count of a VFS node.
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 *
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 *
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 * This function handles the case when the reference count drops to zero.
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 * This function handles the case when the reference count drops to zero.
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 *
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 *
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 * @param node      VFS node that will have its refcnt decremented.
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 * @param node      VFS node that will have its refcnt decremented.
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 */
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 */
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void vfs_node_delref(vfs_node_t *node)
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void vfs_node_delref(vfs_node_t *node)
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{
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{
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    futex_down(&nodes_futex);
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    if (node->refcnt-- == 1) {
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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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    /* TODO */
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        };
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        hash_table_remove(&nodes, key, 3);
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    }
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    futex_up(&nodes_futex);
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}
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}
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/** Find VFS node.
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/** Find VFS node.
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 *
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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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 * This function will try to lookup the given triplet in the VFS node hash
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 *
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 *
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 * @return      VFS node corresponding to the given triplet.
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 * @return      VFS node corresponding to the given triplet.
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 */
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 */
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vfs_node_t *vfs_node_get(vfs_triplet_t *triplet)
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vfs_node_t *vfs_node_get(vfs_triplet_t *triplet)
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{
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{
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    unsigned long key[] = {
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        [KEY_FS_HANDLE] = triplet->fs_handle,
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        [KEY_DEV_HANDLE] = triplet->dev_handle,
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        [KEY_INDEX] = 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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    /* TODO */
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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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            return NULL;
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        }
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        memset(node, 0, sizeof(vfs_node_t));
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        node->fs_handle = triplet->fs_handle;
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        node->dev_handle = triplet->fs_handle;
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        node->index = triplet->index;
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        link_initialize(&node->nh_link);
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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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    }
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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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}
 157 
}
77 
 
 158 
 
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/** Return VFS node when no longer needed by the caller.
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/** Return VFS node when no longer needed by the caller.
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 *
 160 
 *
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 * This function will remove the reference on the VFS node created by
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 * This function will remove the reference on the VFS node created by
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void vfs_node_put(vfs_node_t *node)
 167 
void vfs_node_put(vfs_node_t *node)
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{
 168 
{
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    vfs_node_delref(node);
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    vfs_node_delref(node);
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}
 170 
}
90 
 
 171 
 
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 172 
hash_index_t nodes_hash(unsigned long key[])
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 173 
{
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 174 
    hash_index_t a = key[KEY_FS_HANDLE] << (NODES_BUCKETS_LOG / 4);
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 175 
    hash_index_t b = (a | key[KEY_DEV_HANDLE]) << (NODES_BUCKETS_LOG / 2);
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 176 
   
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 177 
    return (b | key[KEY_INDEX]) & ~(NODES_BUCKETS - 1);
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 178 
}
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 179 
 
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 180 
int nodes_compare(unsigned long key[], hash_count_t keys, link_t *item)
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 181 
{
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 182 
    vfs_node_t *node = hash_table_get_instance(item, vfs_node_t, nh_link);
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 183 
    return (node->fs_handle == key[KEY_FS_HANDLE]) &&
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        (node->dev_handle == key[KEY_DEV_HANDLE]) &&
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 185 
        (node->index == key[KEY_INDEX]);
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 186 
}
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 187 
 
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 188 
void nodes_remove_callback(link_t *item)
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 189 
{
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 190 
    vfs_node_t *node = hash_table_get_instance(item, vfs_node_t, nh_link);
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 191 
    free(node);
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 192 
}
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/**
 194 
/**
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 * @}
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 * @}
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 */
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 */