Subversion Repositories HelenOS

Rev

Rev 4306 | Rev 4409 | Go to most recent revision | Blame | Compare with Previous | Last modification | View Log | Download | RSS feed

  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    tmpfs_ops.c
  35.  * @brief   Implementation of VFS operations for the TMPFS file system
  36.  *      server.
  37.  */
  38.  
  39. #include "tmpfs.h"
  40. #include "../../vfs/vfs.h"
  41. #include <ipc/ipc.h>
  42. #include <async.h>
  43. #include <errno.h>
  44. #include <atomic.h>
  45. #include <stdlib.h>
  46. #include <string.h>
  47. #include <stdio.h>
  48. #include <assert.h>
  49. #include <sys/types.h>
  50. #include <libadt/hash_table.h>
  51. #include <as.h>
  52. #include <libfs.h>
  53.  
  54. #define min(a, b)       ((a) < (b) ? (a) : (b))
  55. #define max(a, b)       ((a) > (b) ? (a) : (b))
  56.  
  57. #define DENTRIES_BUCKETS    256
  58.  
  59. #define NAMES_BUCKETS       4
  60.  
  61. /** All root nodes have index 0. */
  62. #define TMPFS_SOME_ROOT     0
  63. /** Global counter for assigning node indices. Shared by all instances. */
  64. fs_index_t tmpfs_next_index = 1;
  65.  
  66. /*
  67.  * Implementation of the libfs interface.
  68.  */
  69.  
  70. /* Forward declarations of static functions. */
  71. static fs_node_t *tmpfs_match(fs_node_t *, const char *);
  72. static fs_node_t *tmpfs_node_get(dev_handle_t, fs_index_t);
  73. static void tmpfs_node_put(fs_node_t *);
  74. static fs_node_t *tmpfs_create_node(dev_handle_t, int);
  75. static int tmpfs_link_node(fs_node_t *, fs_node_t *, const char *);
  76. static int tmpfs_unlink_node(fs_node_t *, fs_node_t *);
  77. static int tmpfs_destroy_node(fs_node_t *);
  78.  
  79. /* Implementation of helper functions. */
  80. static fs_index_t tmpfs_index_get(fs_node_t *fn)
  81. {
  82.     return TMPFS_NODE(fn)->index;
  83. }
  84.  
  85. static size_t tmpfs_size_get(fs_node_t *fn)
  86. {
  87.     return TMPFS_NODE(fn)->size;
  88. }
  89.  
  90. static unsigned tmpfs_lnkcnt_get(fs_node_t *fn)
  91. {
  92.     return TMPFS_NODE(fn)->lnkcnt;
  93. }
  94.  
  95. static bool tmpfs_has_children(fs_node_t *fn)
  96. {
  97.     return TMPFS_NODE(fn)->child != NULL;
  98. }
  99.  
  100. static fs_node_t *tmpfs_root_get(dev_handle_t dev_handle)
  101. {
  102.     return tmpfs_node_get(dev_handle, TMPFS_SOME_ROOT);
  103. }
  104.  
  105. static char tmpfs_plb_get_char(unsigned pos)
  106. {
  107.     return tmpfs_reg.plb_ro[pos % PLB_SIZE];
  108. }
  109.  
  110. static bool tmpfs_is_directory(fs_node_t *fn)
  111. {
  112.     return TMPFS_NODE(fn)->type == TMPFS_DIRECTORY;
  113. }
  114.  
  115. static bool tmpfs_is_file(fs_node_t *fn)
  116. {
  117.     return TMPFS_NODE(fn)->type == TMPFS_FILE;
  118. }
  119.  
  120. /** libfs operations */
  121. libfs_ops_t tmpfs_libfs_ops = {
  122.     .match = tmpfs_match,
  123.     .node_get = tmpfs_node_get,
  124.     .node_put = tmpfs_node_put,
  125.     .create = tmpfs_create_node,
  126.     .destroy = tmpfs_destroy_node,
  127.     .link = tmpfs_link_node,
  128.     .unlink = tmpfs_unlink_node,
  129.     .index_get = tmpfs_index_get,
  130.     .size_get = tmpfs_size_get,
  131.     .lnkcnt_get = tmpfs_lnkcnt_get,
  132.     .has_children = tmpfs_has_children,
  133.     .root_get = tmpfs_root_get,
  134.     .plb_get_char = tmpfs_plb_get_char,
  135.     .is_directory = tmpfs_is_directory,
  136.     .is_file = tmpfs_is_file
  137. };
  138.  
  139. /** Hash table of all directory entries. */
  140. hash_table_t dentries;
  141.  
  142. #define DENTRIES_KEY_INDEX  0
  143. #define DENTRIES_KEY_DEV    1
  144.  
  145. /* Implementation of hash table interface for the dentries hash table. */
  146. static hash_index_t dentries_hash(unsigned long key[])
  147. {
  148.     return key[DENTRIES_KEY_INDEX] % DENTRIES_BUCKETS;
  149. }
  150.  
  151. static int dentries_compare(unsigned long key[], hash_count_t keys,
  152.     link_t *item)
  153. {
  154.     tmpfs_dentry_t *dentry = hash_table_get_instance(item, tmpfs_dentry_t,
  155.         dh_link);
  156.     return (dentry->index == key[DENTRIES_KEY_INDEX] &&
  157.         dentry->dev_handle == key[DENTRIES_KEY_DEV]);
  158. }
  159.  
  160. static void dentries_remove_callback(link_t *item)
  161. {
  162. }
  163.  
  164. /** TMPFS dentries hash table operations. */
  165. hash_table_operations_t dentries_ops = {
  166.     .hash = dentries_hash,
  167.     .compare = dentries_compare,
  168.     .remove_callback = dentries_remove_callback
  169. };
  170.  
  171. typedef struct {
  172.     char *name;
  173.     tmpfs_dentry_t *parent;
  174.     link_t link;
  175. } tmpfs_name_t;
  176.  
  177. /* Implementation of hash table interface for the names hash table. */
  178. static hash_index_t names_hash(unsigned long *key)
  179. {
  180.     tmpfs_dentry_t *dentry = (tmpfs_dentry_t *) *key;
  181.     return dentry->index % NAMES_BUCKETS;
  182. }
  183.  
  184. static int names_compare(unsigned long *key, hash_count_t keys, link_t *item)
  185. {
  186.     tmpfs_dentry_t *dentry = (tmpfs_dentry_t *) *key;
  187.     tmpfs_name_t *namep = hash_table_get_instance(item, tmpfs_name_t,
  188.         link);
  189.     return dentry == namep->parent;
  190. }
  191.  
  192. static void names_remove_callback(link_t *item)
  193. {
  194.     tmpfs_name_t *namep = hash_table_get_instance(item, tmpfs_name_t,
  195.         link);
  196.     free(namep->name);
  197.     free(namep);
  198. }
  199.  
  200. /** TMPFS node names hash table operations. */
  201. static hash_table_operations_t names_ops = {
  202.     .hash = names_hash,
  203.     .compare = names_compare,
  204.     .remove_callback = names_remove_callback
  205. };
  206.  
  207. static void tmpfs_name_initialize(tmpfs_name_t *namep)
  208. {
  209.     namep->name = NULL;
  210.     namep->parent = NULL;
  211.     link_initialize(&namep->link);
  212. }
  213.  
  214. static bool tmpfs_dentry_initialize(tmpfs_dentry_t *dentry)
  215. {
  216.     dentry->bp = NULL;
  217.     dentry->index = 0;
  218.     dentry->dev_handle = 0;
  219.     dentry->sibling = NULL;
  220.     dentry->child = NULL;
  221.     dentry->type = TMPFS_NONE;
  222.     dentry->lnkcnt = 0;
  223.     dentry->size = 0;
  224.     dentry->data = NULL;
  225.     link_initialize(&dentry->dh_link);
  226.     return (bool)hash_table_create(&dentry->names, NAMES_BUCKETS, 1,
  227.         &names_ops);
  228. }
  229.  
  230. bool tmpfs_init(void)
  231. {
  232.     if (!hash_table_create(&dentries, DENTRIES_BUCKETS, 2, &dentries_ops))
  233.         return false;
  234.    
  235.     return true;
  236. }
  237.  
  238. static bool tmpfs_instance_init(dev_handle_t dev_handle)
  239. {
  240.     fs_node_t *rfn;
  241.    
  242.     rfn = tmpfs_create_node(dev_handle, L_DIRECTORY);
  243.     if (!rfn)
  244.         return false;
  245.     TMPFS_NODE(rfn)->lnkcnt = 0;    /* FS root is not linked */
  246.     return true;
  247. }
  248.  
  249. /** Compare one component of path to a directory entry.
  250.  *
  251.  * @param parentp   Pointer to node from which we descended.
  252.  * @param childp    Pointer to node to compare the path component with.
  253.  * @param component Array of characters holding component name.
  254.  *
  255.  * @return      True on match, false otherwise.
  256.  */
  257. static bool
  258. tmpfs_match_one(tmpfs_dentry_t *parentp, tmpfs_dentry_t *childp,
  259.     const char *component)
  260. {
  261.     unsigned long key = (unsigned long) parentp;
  262.     link_t *hlp = hash_table_find(&childp->names, &key);
  263.     assert(hlp);
  264.     tmpfs_name_t *namep = hash_table_get_instance(hlp, tmpfs_name_t, link);
  265.     return !str_cmp(namep->name, component);
  266. }
  267.  
  268. fs_node_t *tmpfs_match(fs_node_t *pfn, const char *component)
  269. {
  270.     tmpfs_dentry_t *parentp = TMPFS_NODE(pfn);
  271.     tmpfs_dentry_t *childp = parentp->child;
  272.  
  273.     while (childp && !tmpfs_match_one(parentp, childp, component))
  274.         childp = childp->sibling;
  275.  
  276.     return FS_NODE(childp);
  277. }
  278.  
  279. fs_node_t *tmpfs_node_get(dev_handle_t dev_handle, fs_index_t index)
  280. {
  281.     unsigned long key[] = {
  282.         [DENTRIES_KEY_INDEX] = index,
  283.         [DENTRIES_KEY_DEV] = dev_handle
  284.     };
  285.     link_t *lnk = hash_table_find(&dentries, key);
  286.     if (!lnk)
  287.         return NULL;
  288.     return FS_NODE(hash_table_get_instance(lnk, tmpfs_dentry_t, dh_link));
  289. }
  290.  
  291. void tmpfs_node_put(fs_node_t *fn)
  292. {
  293.     /* nothing to do */
  294. }
  295.  
  296. fs_node_t *tmpfs_create_node(dev_handle_t dev_handle, int lflag)
  297. {
  298.     assert((lflag & L_FILE) ^ (lflag & L_DIRECTORY));
  299.  
  300.     fs_node_t *fn = malloc(sizeof(fs_node_t));
  301.     if (!fn)
  302.         return NULL;
  303.    
  304.     tmpfs_dentry_t *node = malloc(sizeof(tmpfs_dentry_t));
  305.     if (!node) {
  306.         free(fn);
  307.         return NULL;
  308.     }
  309.     if (!tmpfs_dentry_initialize(node)) {
  310.         free(fn);
  311.         free(node);
  312.         return NULL;
  313.     }
  314.     fn->data = node;
  315.     node->bp = fn;  /* establish the back pointer */
  316.     if (!tmpfs_root_get(dev_handle))
  317.         node->index = TMPFS_SOME_ROOT;
  318.     else
  319.         node->index = tmpfs_next_index++;
  320.     node->dev_handle = dev_handle;
  321.     if (lflag & L_DIRECTORY)
  322.         node->type = TMPFS_DIRECTORY;
  323.     else
  324.         node->type = TMPFS_FILE;
  325.  
  326.     /* Insert the new node into the dentry hash table. */
  327.     unsigned long key[] = {
  328.         [DENTRIES_KEY_INDEX] = node->index,
  329.         [DENTRIES_KEY_DEV] = node->dev_handle
  330.     };
  331.     hash_table_insert(&dentries, key, &node->dh_link);
  332.     return fn;
  333. }
  334.  
  335. int tmpfs_link_node(fs_node_t *pfn, fs_node_t *cfn, const char *nm)
  336. {
  337.     tmpfs_dentry_t *parentp = TMPFS_NODE(pfn);
  338.     tmpfs_dentry_t *childp = TMPFS_NODE(cfn);
  339.  
  340.     assert(parentp->type == TMPFS_DIRECTORY);
  341.  
  342.     tmpfs_name_t *namep = malloc(sizeof(tmpfs_name_t));
  343.     if (!namep)
  344.         return ENOMEM;
  345.     tmpfs_name_initialize(namep);
  346.     size_t size = str_size(nm);
  347.     namep->name = malloc(size + 1);
  348.     if (!namep->name) {
  349.         free(namep);
  350.         return ENOMEM;
  351.     }
  352.     str_cpy(namep->name, size + 1, nm);
  353.     namep->parent = parentp;
  354.    
  355.     childp->lnkcnt++;
  356.  
  357.     unsigned long key = (unsigned long) parentp;
  358.     hash_table_insert(&childp->names, &key, &namep->link);
  359.  
  360.     /* Insert the new node into the namespace. */
  361.     if (parentp->child) {
  362.         tmpfs_dentry_t *tmp = parentp->child;
  363.         while (tmp->sibling)
  364.             tmp = tmp->sibling;
  365.         tmp->sibling = childp;
  366.     } else {
  367.         parentp->child = childp;
  368.     }
  369.  
  370.     return EOK;
  371. }
  372.  
  373. int tmpfs_unlink_node(fs_node_t *pfn, fs_node_t *cfn)
  374. {
  375.     tmpfs_dentry_t *parentp = TMPFS_NODE(pfn);
  376.     tmpfs_dentry_t *childp = TMPFS_NODE(cfn);
  377.  
  378.     if (!parentp)
  379.         return EBUSY;
  380.  
  381.     if (childp->child)
  382.         return ENOTEMPTY;
  383.  
  384.     if (parentp->child == childp) {
  385.         parentp->child = childp->sibling;
  386.     } else {
  387.         /* TODO: consider doubly linked list for organizing siblings. */
  388.         tmpfs_dentry_t *tmp = parentp->child;
  389.         while (tmp->sibling != childp)
  390.             tmp = tmp->sibling;
  391.         tmp->sibling = childp->sibling;
  392.     }
  393.     childp->sibling = NULL;
  394.  
  395.     unsigned long key = (unsigned long) parentp;
  396.     hash_table_remove(&childp->names, &key, 1);
  397.  
  398.     childp->lnkcnt--;
  399.  
  400.     return EOK;
  401. }
  402.  
  403. int tmpfs_destroy_node(fs_node_t *fn)
  404. {
  405.     tmpfs_dentry_t *dentry = TMPFS_NODE(fn);
  406.    
  407.     assert(!dentry->lnkcnt);
  408.     assert(!dentry->child);
  409.     assert(!dentry->sibling);
  410.  
  411.     unsigned long key[] = {
  412.         [DENTRIES_KEY_INDEX] = dentry->index,
  413.         [DENTRIES_KEY_DEV] = dentry->dev_handle
  414.     };
  415.     hash_table_remove(&dentries, key, 2);
  416.  
  417.     hash_table_destroy(&dentry->names);
  418.  
  419.     if (dentry->type == TMPFS_FILE)
  420.         free(dentry->data);
  421.     free(dentry->bp);
  422.     free(dentry);
  423.     return EOK;
  424. }
  425.  
  426. void tmpfs_mounted(ipc_callid_t rid, ipc_call_t *request)
  427. {
  428.     dev_handle_t dev_handle = (dev_handle_t) IPC_GET_ARG1(*request);
  429.  
  430.     /* accept the mount options */
  431.     ipc_callid_t callid;
  432.     size_t size;
  433.     if (!ipc_data_write_receive(&callid, &size)) {
  434.         ipc_answer_0(callid, EINVAL);
  435.         ipc_answer_0(rid, EINVAL);
  436.         return;
  437.     }
  438.     char *opts = malloc(size + 1);
  439.     if (!opts) {
  440.         ipc_answer_0(callid, ENOMEM);
  441.         ipc_answer_0(rid, ENOMEM);
  442.         return;
  443.     }
  444.     ipcarg_t retval = ipc_data_write_finalize(callid, opts, size);
  445.     if (retval != EOK) {
  446.         ipc_answer_0(rid, retval);
  447.         free(opts);
  448.         return;
  449.     }
  450.     opts[size] = '\0';
  451.  
  452.     /* Initialize TMPFS instance. */
  453.     if (!tmpfs_instance_init(dev_handle)) {
  454.         ipc_answer_0(rid, ENOMEM);
  455.         return;
  456.     }
  457.  
  458.     tmpfs_dentry_t *root = TMPFS_NODE(tmpfs_root_get(dev_handle));
  459.     if (str_cmp(opts, "restore") == 0) {
  460.         if (tmpfs_restore(dev_handle))
  461.             ipc_answer_3(rid, EOK, root->index, root->size,
  462.                 root->lnkcnt);
  463.         else
  464.             ipc_answer_0(rid, ELIMIT);
  465.     } else {
  466.         ipc_answer_3(rid, EOK, root->index, root->size, root->lnkcnt);
  467.     }
  468. }
  469.  
  470. void tmpfs_mount(ipc_callid_t rid, ipc_call_t *request)
  471. {
  472.     dev_handle_t mp_dev_handle = (dev_handle_t) IPC_GET_ARG1(*request);
  473.     fs_index_t mp_index = (fs_index_t) IPC_GET_ARG2(*request);
  474.     fs_handle_t mr_fs_handle = (fs_handle_t) IPC_GET_ARG3(*request);
  475.     dev_handle_t mr_dev_handle = (dev_handle_t) IPC_GET_ARG4(*request);
  476.    
  477.     ipc_answer_0(rid, ENOTSUP);
  478. }
  479.  
  480. void tmpfs_lookup(ipc_callid_t rid, ipc_call_t *request)
  481. {
  482.     libfs_lookup(&tmpfs_libfs_ops, tmpfs_reg.fs_handle, rid, request);
  483. }
  484.  
  485. void tmpfs_read(ipc_callid_t rid, ipc_call_t *request)
  486. {
  487.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  488.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  489.     off_t pos = (off_t)IPC_GET_ARG3(*request);
  490.  
  491.     /*
  492.      * Lookup the respective dentry.
  493.      */
  494.     link_t *hlp;
  495.     unsigned long key[] = {
  496.         [DENTRIES_KEY_INDEX] = index,
  497.         [DENTRIES_KEY_DEV] = dev_handle,
  498.     };
  499.     hlp = hash_table_find(&dentries, key);
  500.     if (!hlp) {
  501.         ipc_answer_0(rid, ENOENT);
  502.         return;
  503.     }
  504.     tmpfs_dentry_t *dentry = hash_table_get_instance(hlp, tmpfs_dentry_t,
  505.         dh_link);
  506.  
  507.     /*
  508.      * Receive the read request.
  509.      */
  510.     ipc_callid_t callid;
  511.     size_t size;
  512.     if (!ipc_data_read_receive(&callid, &size)) {
  513.         ipc_answer_0(callid, EINVAL);  
  514.         ipc_answer_0(rid, EINVAL);
  515.         return;
  516.     }
  517.  
  518.     size_t bytes;
  519.     if (dentry->type == TMPFS_FILE) {
  520.         bytes = max(0, min(dentry->size - pos, size));
  521.         (void) ipc_data_read_finalize(callid, dentry->data + pos,
  522.             bytes);
  523.     } else {
  524.         int i;
  525.         tmpfs_dentry_t *cur;
  526.        
  527.         assert(dentry->type == TMPFS_DIRECTORY);
  528.        
  529.         /*
  530.          * Yes, we really use O(n) algorithm here.
  531.          * If it bothers someone, it could be fixed by introducing a
  532.          * hash table.
  533.          */
  534.         for (i = 0, cur = dentry->child; i < pos && cur; i++,
  535.             cur = cur->sibling)
  536.             ;
  537.  
  538.         if (!cur) {
  539.             ipc_answer_0(callid, ENOENT);
  540.             ipc_answer_1(rid, ENOENT, 0);
  541.             return;
  542.         }
  543.  
  544.         unsigned long key = (unsigned long) dentry;
  545.         link_t *hlp = hash_table_find(&cur->names, &key);
  546.         assert(hlp);
  547.         tmpfs_name_t *namep = hash_table_get_instance(hlp, tmpfs_name_t,
  548.             link);
  549.  
  550.         (void) ipc_data_read_finalize(callid, namep->name,
  551.             str_size(namep->name) + 1);
  552.         bytes = 1;
  553.     }
  554.  
  555.     /*
  556.      * Answer the VFS_READ call.
  557.      */
  558.     ipc_answer_1(rid, EOK, bytes);
  559. }
  560.  
  561. void tmpfs_write(ipc_callid_t rid, ipc_call_t *request)
  562. {
  563.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  564.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  565.     off_t pos = (off_t)IPC_GET_ARG3(*request);
  566.  
  567.     /*
  568.      * Lookup the respective dentry.
  569.      */
  570.     link_t *hlp;
  571.     unsigned long key[] = {
  572.         [DENTRIES_KEY_INDEX] = index,
  573.         [DENTRIES_KEY_DEV] = dev_handle
  574.     };
  575.     hlp = hash_table_find(&dentries, key);
  576.     if (!hlp) {
  577.         ipc_answer_0(rid, ENOENT);
  578.         return;
  579.     }
  580.     tmpfs_dentry_t *dentry = hash_table_get_instance(hlp, tmpfs_dentry_t,
  581.         dh_link);
  582.  
  583.     /*
  584.      * Receive the write request.
  585.      */
  586.     ipc_callid_t callid;
  587.     size_t size;
  588.     if (!ipc_data_write_receive(&callid, &size)) {
  589.         ipc_answer_0(callid, EINVAL);  
  590.         ipc_answer_0(rid, EINVAL);
  591.         return;
  592.     }
  593.  
  594.     /*
  595.      * Check whether the file needs to grow.
  596.      */
  597.     if (pos + size <= dentry->size) {
  598.         /* The file size is not changing. */
  599.         (void) ipc_data_write_finalize(callid, dentry->data + pos, size);
  600.         ipc_answer_2(rid, EOK, size, dentry->size);
  601.         return;
  602.     }
  603.     size_t delta = (pos + size) - dentry->size;
  604.     /*
  605.      * At this point, we are deliberately extremely straightforward and
  606.      * simply realloc the contents of the file on every write that grows the
  607.      * file. In the end, the situation might not be as bad as it may look:
  608.      * our heap allocator can save us and just grow the block whenever
  609.      * possible.
  610.      */
  611.     void *newdata = realloc(dentry->data, dentry->size + delta);
  612.     if (!newdata) {
  613.         ipc_answer_0(callid, ENOMEM);
  614.         ipc_answer_2(rid, EOK, 0, dentry->size);
  615.         return;
  616.     }
  617.     /* Clear any newly allocated memory in order to emulate gaps. */
  618.     memset(newdata + dentry->size, 0, delta);
  619.     dentry->size += delta;
  620.     dentry->data = newdata;
  621.     (void) ipc_data_write_finalize(callid, dentry->data + pos, size);
  622.     ipc_answer_2(rid, EOK, size, dentry->size);
  623. }
  624.  
  625. void tmpfs_truncate(ipc_callid_t rid, ipc_call_t *request)
  626. {
  627.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  628.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  629.     size_t size = (off_t)IPC_GET_ARG3(*request);
  630.  
  631.     /*
  632.      * Lookup the respective dentry.
  633.      */
  634.     link_t *hlp;
  635.     unsigned long key[] = {
  636.         [DENTRIES_KEY_INDEX] = index,
  637.         [DENTRIES_KEY_DEV] = dev_handle
  638.     };
  639.     hlp = hash_table_find(&dentries, key);
  640.     if (!hlp) {
  641.         ipc_answer_0(rid, ENOENT);
  642.         return;
  643.     }
  644.     tmpfs_dentry_t *dentry = hash_table_get_instance(hlp, tmpfs_dentry_t,
  645.         dh_link);
  646.  
  647.     if (size == dentry->size) {
  648.         ipc_answer_0(rid, EOK);
  649.         return;
  650.     }
  651.  
  652.     void *newdata = realloc(dentry->data, size);
  653.     if (!newdata) {
  654.         ipc_answer_0(rid, ENOMEM);
  655.         return;
  656.     }
  657.     if (size > dentry->size) {
  658.         size_t delta = size - dentry->size;
  659.         memset(newdata + dentry->size, 0, delta);
  660.     }
  661.     dentry->size = size;
  662.     dentry->data = newdata;
  663.     ipc_answer_0(rid, EOK);
  664. }
  665.  
  666. void tmpfs_destroy(ipc_callid_t rid, ipc_call_t *request)
  667. {
  668.     dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  669.     fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
  670.     int rc;
  671.  
  672.     link_t *hlp;
  673.     unsigned long key[] = {
  674.         [DENTRIES_KEY_INDEX] = index,
  675.         [DENTRIES_KEY_DEV] = dev_handle
  676.     };
  677.     hlp = hash_table_find(&dentries, key);
  678.     if (!hlp) {
  679.         ipc_answer_0(rid, ENOENT);
  680.         return;
  681.     }
  682.     tmpfs_dentry_t *dentry = hash_table_get_instance(hlp, tmpfs_dentry_t,
  683.         dh_link);
  684.     rc = tmpfs_destroy_node(FS_NODE(dentry));
  685.     ipc_answer_0(rid, rc);
  686. }
  687.  
  688. /**
  689.  * @}
  690.  */
  691.