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  1. /*
  2.  * Copyright (c) 2008 Jakub Jermar
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /** @addtogroup fs
  30.  * @{
  31.  */
  32.  
  33. /**
  34.  * @file    vfs_node.c
  35.  * @brief   Various operations on VFS nodes have their home in this file.
  36.  */
  37.  
  38. #include "vfs.h"
  39. #include <stdlib.h>
  40. #include <string.h>
  41. #include <atomic.h>
  42. #include <futex.h>
  43. #include <rwlock.h>
  44. #include <libadt/hash_table.h>
  45. #include <assert.h>
  46. #include <async.h>
  47. #include <errno.h>
  48.  
  49. /** Futex protecting the VFS node hash table. */
  50. atomic_t nodes_futex = FUTEX_INITIALIZER;
  51.  
  52. #define NODES_BUCKETS_LOG   8
  53. #define NODES_BUCKETS       (1 << NODES_BUCKETS_LOG)
  54.  
  55. /** VFS node hash table containing all active, in-memory VFS nodes. */
  56. hash_table_t nodes;
  57.  
  58. #define KEY_FS_HANDLE   0
  59. #define KEY_DEV_HANDLE  1
  60. #define KEY_INDEX   2
  61.  
  62. static hash_index_t nodes_hash(unsigned long []);
  63. static int nodes_compare(unsigned long [], hash_count_t, link_t *);
  64. static void nodes_remove_callback(link_t *);
  65.  
  66. /** VFS node hash table operations. */
  67. hash_table_operations_t nodes_ops = {
  68.     .hash = nodes_hash,
  69.     .compare = nodes_compare,
  70.     .remove_callback = nodes_remove_callback
  71. };
  72.  
  73. /** Initialize the VFS node hash table.
  74.  *
  75.  * @return      Return true on success, false on failure.
  76.  */
  77. bool vfs_nodes_init(void)
  78. {
  79.     return hash_table_create(&nodes, NODES_BUCKETS, 3, &nodes_ops);
  80. }
  81.  
  82. static inline void _vfs_node_addref(vfs_node_t *node)
  83. {
  84.     node->refcnt++;
  85. }
  86.  
  87. /** Increment reference count of a VFS node.
  88.  *
  89.  * @param node      VFS node that will have its refcnt incremented.
  90.  */
  91. void vfs_node_addref(vfs_node_t *node)
  92. {
  93.     futex_down(&nodes_futex);
  94.     _vfs_node_addref(node);
  95.     futex_up(&nodes_futex);
  96. }
  97.  
  98. /** Decrement reference count of a VFS node.
  99.  *
  100.  * This function handles the case when the reference count drops to zero.
  101.  *
  102.  * @param node      VFS node that will have its refcnt decremented.
  103.  */
  104. void vfs_node_delref(vfs_node_t *node)
  105. {
  106.     bool free_vfs_node = false;
  107.     bool free_fs_node = false;
  108.  
  109.     futex_down(&nodes_futex);
  110.     if (node->refcnt-- == 1) {
  111.         /*
  112.          * We are dropping the last reference to this node.
  113.          * Remove it from the VFS node hash table.
  114.          */
  115.         unsigned long key[] = {
  116.             [KEY_FS_HANDLE] = node->fs_handle,
  117.             [KEY_DEV_HANDLE] = node->dev_handle,
  118.             [KEY_INDEX] = node->index
  119.         };
  120.         hash_table_remove(&nodes, key, 3);
  121.         free_vfs_node = true;
  122.         if (!node->lnkcnt)
  123.             free_fs_node = true;
  124.     }
  125.     futex_up(&nodes_futex);
  126.  
  127.     if (free_fs_node) {
  128.         /*
  129.          * The node is not visible in the file system namespace.
  130.          * Free up its resources.
  131.          */
  132.         int phone = vfs_grab_phone(node->fs_handle);
  133.         ipcarg_t rc;
  134.         rc = async_req_2_0(phone, VFS_DESTROY,
  135.             (ipcarg_t)node->dev_handle, (ipcarg_t)node->index);
  136.         assert(rc == EOK);
  137.         vfs_release_phone(phone);
  138.     }
  139.     if (free_vfs_node)
  140.         free(node);
  141. }
  142.  
  143. /** Find VFS node.
  144.  *
  145.  * This function will try to lookup the given triplet in the VFS node hash
  146.  * table. In case the triplet is not found there, a new VFS node is created.
  147.  * In any case, the VFS node will have its reference count incremented. Every
  148.  * node returned by this call should be eventually put back by calling
  149.  * vfs_node_put() on it.
  150.  *
  151.  * @param result    Populated lookup result structure.
  152.  *
  153.  * @return      VFS node corresponding to the given triplet.
  154.  */
  155. vfs_node_t *vfs_node_get(vfs_lookup_res_t *result)
  156. {
  157.     unsigned long key[] = {
  158.         [KEY_FS_HANDLE] = result->triplet.fs_handle,
  159.         [KEY_DEV_HANDLE] = result->triplet.dev_handle,
  160.         [KEY_INDEX] = result->triplet.index
  161.     };
  162.     link_t *tmp;
  163.     vfs_node_t *node;
  164.  
  165.     futex_down(&nodes_futex);
  166.     tmp = hash_table_find(&nodes, key);
  167.     if (!tmp) {
  168.         node = (vfs_node_t *) malloc(sizeof(vfs_node_t));
  169.         if (!node) {
  170.             futex_up(&nodes_futex);
  171.             return NULL;
  172.         }
  173.         memset(node, 0, sizeof(vfs_node_t));
  174.         node->fs_handle = result->triplet.fs_handle;
  175.         node->dev_handle = result->triplet.dev_handle;
  176.         node->index = result->triplet.index;
  177.         node->size = result->size;
  178.         node->lnkcnt = result->lnkcnt;
  179.         link_initialize(&node->nh_link);
  180.         rwlock_initialize(&node->contents_rwlock);
  181.         hash_table_insert(&nodes, key, &node->nh_link);
  182.     } else {
  183.         node = hash_table_get_instance(tmp, vfs_node_t, nh_link);  
  184.     }
  185.  
  186.     assert(node->size == result->size);
  187.     assert(node->lnkcnt == result->lnkcnt);
  188.  
  189.     _vfs_node_addref(node);
  190.     futex_up(&nodes_futex);
  191.  
  192.     return node;
  193. }
  194.  
  195. /** Return VFS node when no longer needed by the caller.
  196.  *
  197.  * This function will remove the reference on the VFS node created by
  198.  * vfs_node_get(). This function can only be called as a closing bracket to the
  199.  * preceding vfs_node_get() call.
  200.  *
  201.  * @param node      VFS node being released.
  202.  */
  203. void vfs_node_put(vfs_node_t *node)
  204. {
  205.     vfs_node_delref(node);
  206. }
  207.  
  208. hash_index_t nodes_hash(unsigned long key[])
  209. {
  210.     hash_index_t a = key[KEY_FS_HANDLE] << (NODES_BUCKETS_LOG / 4);
  211.     hash_index_t b = (a | key[KEY_DEV_HANDLE]) << (NODES_BUCKETS_LOG / 2);
  212.    
  213.     return (b | key[KEY_INDEX]) & (NODES_BUCKETS - 1);
  214. }
  215.  
  216. int nodes_compare(unsigned long key[], hash_count_t keys, link_t *item)
  217. {
  218.     vfs_node_t *node = hash_table_get_instance(item, vfs_node_t, nh_link);
  219.     return (node->fs_handle == key[KEY_FS_HANDLE]) &&
  220.         (node->dev_handle == key[KEY_DEV_HANDLE]) &&
  221.         (node->index == key[KEY_INDEX]);
  222. }
  223.  
  224. void nodes_remove_callback(link_t *item)
  225. {
  226. }
  227.  
  228. /**
  229.  * @}
  230.  */
  231.