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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_lookup.c
  35.  * @brief
  36.  */
  37.  
  38. #include <ipc/ipc.h>
  39. #include <async.h>
  40. #include <errno.h>
  41. #include <string.h>
  42. #include <bool.h>
  43. #include <futex.h>
  44. #include <libadt/list.h>
  45. #include <atomic.h>
  46. #include "vfs.h"
  47.  
  48. #define min(a, b)   ((a) < (b) ? (a) : (b))
  49.  
  50. atomic_t plb_futex = FUTEX_INITIALIZER;
  51. link_t plb_head;    /**< PLB entry ring buffer. */
  52. uint8_t *plb = NULL;
  53.  
  54. /** Perform a path lookup.
  55.  *
  56.  * @param path      Path to be resolved; it needn't be an ASCIIZ string.
  57.  * @param len       Number of path characters pointed by path.
  58.  * @param result    Empty structure where the lookup result will be stored.
  59.  * @param altroot   If non-empty, will be used instead of rootfs as the root
  60.  *          of the whole VFS tree.
  61.  *
  62.  * @return      EOK on success or an error code from errno.h.
  63.  */
  64. int vfs_lookup_internal(char *path, size_t len, vfs_lookup_res_t *result,
  65.     vfs_pair_t *altroot)
  66. {
  67.     vfs_pair_t *root;
  68.  
  69.     if (!len)
  70.         return EINVAL;
  71.  
  72.     if (altroot)
  73.         root = altroot;
  74.     else
  75.         root = (vfs_pair_t *) &rootfs;
  76.  
  77.     if (!root->fs_handle)
  78.         return ENOENT;
  79.    
  80.     futex_down(&plb_futex);
  81.  
  82.     plb_entry_t entry;
  83.     link_initialize(&entry.plb_link);
  84.     entry.len = len;
  85.  
  86.     off_t first;    /* the first free index */
  87.     off_t last; /* the last free index */
  88.  
  89.     if (list_empty(&plb_head)) {
  90.         first = 0;
  91.         last = PLB_SIZE - 1;
  92.     } else {
  93.         plb_entry_t *oldest = list_get_instance(plb_head.next,
  94.             plb_entry_t, plb_link);
  95.         plb_entry_t *newest = list_get_instance(plb_head.prev,
  96.             plb_entry_t, plb_link);
  97.  
  98.         first = (newest->index + newest->len) % PLB_SIZE;
  99.         last = (oldest->index - 1) % PLB_SIZE;
  100.     }
  101.  
  102.     if (first <= last) {
  103.         if ((last - first) + 1 < len) {
  104.             /*
  105.              * The buffer cannot absorb the path.
  106.              */
  107.             futex_up(&plb_futex);
  108.             return ELIMIT;
  109.         }
  110.     } else {
  111.         if (PLB_SIZE - ((first - last) + 1) < len) {
  112.             /*
  113.              * The buffer cannot absorb the path.
  114.              */
  115.             futex_up(&plb_futex);
  116.             return ELIMIT;
  117.         }
  118.     }
  119.  
  120.     /*
  121.      * We know the first free index in PLB and we also know that there is
  122.      * enough space in the buffer to hold our path.
  123.      */
  124.  
  125.     entry.index = first;
  126.     entry.len = len;
  127.  
  128.     /*
  129.      * Claim PLB space by inserting the entry into the PLB entry ring
  130.      * buffer.
  131.      */
  132.     list_append(&entry.plb_link, &plb_head);
  133.    
  134.     futex_up(&plb_futex);
  135.  
  136.     /*
  137.      * Copy the path into PLB.
  138.      */
  139.     size_t cnt1 = min(len, (PLB_SIZE - first) + 1);
  140.     size_t cnt2 = len - cnt1;
  141.    
  142.     memcpy(&plb[first], path, cnt1);
  143.     memcpy(plb, &path[cnt1], cnt2);
  144.  
  145.     ipc_call_t answer;
  146.     int phone = vfs_grab_phone(root->fs_handle);
  147.     aid_t req = async_send_3(phone, VFS_LOOKUP, (ipcarg_t) first,
  148.         (ipcarg_t) (first + len - 1) % PLB_SIZE,
  149.         (ipcarg_t) root->dev_handle, &answer);
  150.     vfs_release_phone(phone);
  151.  
  152.     ipcarg_t rc;
  153.     async_wait_for(req, &rc);
  154.  
  155.     futex_down(&plb_futex);
  156.     list_remove(&entry.plb_link);
  157.     /*
  158.      * Erasing the path from PLB will come handy for debugging purposes.
  159.      */
  160.     memset(&plb[first], 0, cnt1);
  161.     memset(plb, 0, cnt2);
  162.     futex_up(&plb_futex);
  163.  
  164.     if (rc == EOK) {
  165.         result->triplet.fs_handle = (int) IPC_GET_ARG1(answer);
  166.         result->triplet.dev_handle = (int) IPC_GET_ARG2(answer);
  167.         result->triplet.index = (int) IPC_GET_ARG3(answer);
  168.         result->size = (size_t) IPC_GET_ARG4(answer);
  169.     }
  170.  
  171.     return rc;
  172. }
  173.  
  174. /**
  175.  * @}
  176.  */
  177.