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  1. /*
  2.  * Copyright (c) 2007 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_rdwr.c
  35.  * @brief
  36.  */
  37.  
  38. #include "vfs.h"
  39. #include <ipc/ipc.h>
  40. #include <async.h>
  41. #include <errno.h>
  42. #include <rwlock.h>
  43.  
  44. static void vfs_rdwr(ipc_callid_t rid, ipc_call_t *request, bool read)
  45. {
  46.  
  47.     /*
  48.      * The following code strongly depends on the fact that the files data
  49.      * structure can be only accessed by a single fibril and all file
  50.      * operations are serialized (i.e. the reads and writes cannot
  51.      * interleave and a file cannot be closed while it is being read).
  52.      *
  53.      * Additional synchronization needs to be added once the table of
  54.      * open files supports parallel access!
  55.      */
  56.  
  57.     int fd = IPC_GET_ARG1(*request);
  58.  
  59.     /*
  60.      * Lookup the file structure corresponding to the file descriptor.
  61.      */
  62.     vfs_file_t *file = vfs_file_get(fd);
  63.     if (!file) {
  64.         ipc_answer_0(rid, ENOENT);
  65.         return;
  66.     }
  67.  
  68.     /*
  69.      * Now we need to receive a call with client's
  70.      * IPC_M_DATA_READ/IPC_M_DATA_WRITE request.
  71.      */
  72.     ipc_callid_t callid;
  73.     int res;
  74.     if (read)
  75.         res = ipc_data_read_receive(&callid, NULL);
  76.     else
  77.         res = ipc_data_write_receive(&callid, NULL);
  78.     if (!res) {
  79.         ipc_answer_0(callid, EINVAL);
  80.         ipc_answer_0(rid, EINVAL);
  81.         return;
  82.     }
  83.  
  84.     /*
  85.      * Lock the open file structure so that no other thread can manipulate
  86.      * the same open file at a time.
  87.      */
  88.     futex_down(&file->lock);
  89.  
  90.     /*
  91.      * Lock the file's node so that no other client can read/write to it at
  92.      * the same time.
  93.      */
  94.     if (read)
  95.         rwlock_reader_lock(&file->node->contents_rwlock);
  96.     else
  97.         rwlock_writer_lock(&file->node->contents_rwlock);
  98.  
  99.     int fs_phone = vfs_grab_phone(file->node->fs_handle);  
  100.    
  101.     /*
  102.      * Make a VFS_READ/VFS_WRITE request at the destination FS server.
  103.      */
  104.     aid_t msg;
  105.     ipc_call_t answer;
  106.     msg = async_send_3(fs_phone, IPC_GET_METHOD(*request),
  107.         file->node->dev_handle, file->node->index, file->pos, &answer);
  108.    
  109.     /*
  110.      * Forward the IPC_M_DATA_READ/IPC_M_DATA_WRITE request to the
  111.      * destination FS server. The call will be routed as if sent by
  112.      * ourselves. Note that call arguments are immutable in this case so we
  113.      * don't have to bother.
  114.      */
  115.     ipc_forward_fast(callid, fs_phone, 0, 0, 0, IPC_FF_ROUTE_FROM_ME);
  116.  
  117.     vfs_release_phone(fs_phone);
  118.  
  119.     /*
  120.      * Wait for reply from the FS server.
  121.      */
  122.     ipcarg_t rc;
  123.     async_wait_for(msg, &rc);
  124.     size_t bytes = IPC_GET_ARG1(answer);
  125.  
  126.     /*
  127.      * Unlock the VFS node.
  128.      */
  129.     if (read)
  130.         rwlock_reader_unlock(&file->node->contents_rwlock);
  131.     else
  132.         rwlock_writer_unlock(&file->node->contents_rwlock);
  133.  
  134.     /*
  135.      * Update the position pointer and unlock the open file.
  136.      */
  137.     file->pos += bytes;
  138.     futex_up(&file->lock);
  139.  
  140.     /*
  141.      * FS server's reply is the final result of the whole operation we
  142.      * return to the client.
  143.      */
  144.     ipc_answer_1(rid, rc, bytes);
  145. }
  146.  
  147.  
  148. void vfs_read(ipc_callid_t rid, ipc_call_t *request)
  149. {
  150.     vfs_rdwr(rid, request, true);
  151. }
  152.  
  153. void vfs_write(ipc_callid_t rid, ipc_call_t *request)
  154. {
  155.     vfs_rdwr(rid, request, false);
  156. }
  157.  
  158. /**
  159.  * @}
  160.  */
  161.