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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 <futex.h>
  42. #include <rwlock.h>
  43. #include <libadt/hash_table.h>
  44. #include <assert.h>
  45. #include <async.h>
  46. #include <errno.h>
  47.  
  48. /** Futex protecting the VFS node hash table. */
  49. futex_t nodes_futex = FUTEX_INITIALIZER;
  50.  
  51. #define NODES_BUCKETS_LOG   8
  52. #define NODES_BUCKETS       (1 << NODES_BUCKETS_LOG)
  53.  
  54. /** VFS node hash table containing all active, in-memory VFS nodes. */
  55. hash_table_t nodes;
  56.  
  57. #define KEY_FS_HANDLE   0
  58. #define KEY_DEV_HANDLE  1
  59. #define KEY_INDEX   2
  60.  
  61. static hash_index_t nodes_hash(unsigned long []);
  62. static int nodes_compare(unsigned long [], hash_count_t, link_t *);
  63. static void nodes_remove_callback(link_t *);
  64.  
  65. /** VFS node hash table operations. */
  66. hash_table_operations_t nodes_ops = {
  67.     .hash = nodes_hash,
  68.     .compare = nodes_compare,
  69.     .remove_callback = nodes_remove_callback
  70. };
  71.  
  72. /** Initialize the VFS node hash table.
  73.  *
  74.  * @return      Return true on success, false on failure.
  75.  */
  76. bool vfs_nodes_init(void)
  77. {
  78.     return hash_table_create(&nodes, NODES_BUCKETS, 3, &nodes_ops);
  79. }
  80.  
  81. static inline void _vfs_node_addref(vfs_node_t *node)
  82. {
  83.     node->refcnt++;
  84. }
  85.  
  86. /** Increment reference count of a VFS node.
  87.  *
  88.  * @param node      VFS node that will have its refcnt incremented.
  89.  */
  90. void vfs_node_addref(vfs_node_t *node)
  91. {
  92.     futex_down(&nodes_futex);
  93.     _vfs_node_addref(node);
  94.     futex_up(&nodes_futex);
  95. }
  96.  
  97. /** Decrement reference count of a VFS node.
  98.  *
  99.  * This function handles the case when the reference count drops to zero.
  100.  *
  101.  * @param node      VFS node that will have its refcnt decremented.
  102.  */
  103. void vfs_node_delref(vfs_node_t *node)
  104. {
  105.     bool free_vfs_node = false;
  106.     bool free_fs_node = false;
  107.  
  108.     futex_down(&nodes_futex);
  109.     if (node->refcnt-- == 1) {
  110.         /*
  111.          * We are dropping the last reference to this node.
  112.          * Remove it from the VFS node hash table.
  113.          */
  114.         unsigned long key[] = {
  115.             [KEY_FS_HANDLE] = node->fs_handle,
  116.             [KEY_DEV_HANDLE] = node->dev_handle,
  117.             [KEY_INDEX] = node->index
  118.         };
  119.         hash_table_remove(&nodes, key, 3);
  120.         free_vfs_node = true;
  121.         if (!node->lnkcnt)
  122.             free_fs_node = true;
  123.     }
  124.     futex_up(&nodes_futex);
  125.  
  126.     if (free_fs_node) {
  127.         /*
  128.          * The node is not visible in the file system namespace.
  129.          * Free up its resources.
  130.          */
  131.         int phone = vfs_grab_phone(node->fs_handle);
  132.         ipcarg_t rc;
  133.         rc = async_req_2_0(phone, VFS_DESTROY,
  134.             (ipcarg_t)node->dev_handle, (ipcarg_t)node->index);
  135.         assert(rc == EOK);
  136.         vfs_release_phone(phone);
  137.     }
  138.     if (free_vfs_node)
  139.         free(node);
  140. }
  141.  
  142. /** Find VFS node.
  143.  *
  144.  * This function will try to lookup the given triplet in the VFS node hash
  145.  * table. In case the triplet is not found there, a new VFS node is created.
  146.  * In any case, the VFS node will have its reference count incremented. Every
  147.  * node returned by this call should be eventually put back by calling
  148.  * vfs_node_put() on it.
  149.  *
  150.  * @param result    Populated lookup result structure.
  151.  *
  152.  * @return      VFS node corresponding to the given triplet.
  153.  */
  154. vfs_node_t *vfs_node_get(vfs_lookup_res_t *result)
  155. {
  156.     unsigned long key[] = {
  157.         [KEY_FS_HANDLE] = result->triplet.fs_handle,
  158.         [KEY_DEV_HANDLE] = result->triplet.dev_handle,
  159.         [KEY_INDEX] = result->triplet.index
  160.     };
  161.     link_t *tmp;
  162.     vfs_node_t *node;
  163.  
  164.     futex_down(&nodes_futex);
  165.     tmp = hash_table_find(&nodes, key);
  166.     if (!tmp) {
  167.         node = (vfs_node_t *) malloc(sizeof(vfs_node_t));
  168.         if (!node) {
  169.             futex_up(&nodes_futex);
  170.             return NULL;
  171.         }
  172.         memset(node, 0, sizeof(vfs_node_t));
  173.         node->fs_handle = result->triplet.fs_handle;
  174.         node->dev_handle = result->triplet.dev_handle;
  175.         node->index = result->triplet.index;
  176.         node->size = result->size;
  177.         node->lnkcnt = result->lnkcnt;
  178.         link_initialize(&node->nh_link);
  179.         rwlock_initialize(&node->contents_rwlock);
  180.         hash_table_insert(&nodes, key, &node->nh_link);
  181.     } else {
  182.         node = hash_table_get_instance(tmp, vfs_node_t, nh_link);  
  183.     }
  184.  
  185.     assert(node->size == result->size);
  186.     assert(node->lnkcnt == result->lnkcnt);
  187.  
  188.     _vfs_node_addref(node);
  189.     futex_up(&nodes_futex);
  190.  
  191.     return node;
  192. }
  193.  
  194. /** Return VFS node when no longer needed by the caller.
  195.  *
  196.  * This function will remove the reference on the VFS node created by
  197.  * vfs_node_get(). This function can only be called as a closing bracket to the
  198.  * preceding vfs_node_get() call.
  199.  *
  200.  * @param node      VFS node being released.
  201.  */
  202. void vfs_node_put(vfs_node_t *node)
  203. {
  204.     vfs_node_delref(node);
  205. }
  206.  
  207. hash_index_t nodes_hash(unsigned long key[])
  208. {
  209.     hash_index_t a = key[KEY_FS_HANDLE] << (NODES_BUCKETS_LOG / 4);
  210.     hash_index_t b = (a | key[KEY_DEV_HANDLE]) << (NODES_BUCKETS_LOG / 2);
  211.    
  212.     return (b | key[KEY_INDEX]) & (NODES_BUCKETS - 1);
  213. }
  214.  
  215. int nodes_compare(unsigned long key[], hash_count_t keys, link_t *item)
  216. {
  217.     vfs_node_t *node = hash_table_get_instance(item, vfs_node_t, nh_link);
  218.     return (node->fs_handle == key[KEY_FS_HANDLE]) &&
  219.         (node->dev_handle == key[KEY_DEV_HANDLE]) &&
  220.         (node->index == key[KEY_INDEX]);
  221. }
  222.  
  223. void nodes_remove_callback(link_t *item)
  224. {
  225. }
  226.  
  227. /**
  228.  * @}
  229.  */
  230.