Subversion Repositories HelenOS

Rev

Rev 4420 | 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 vfs_ops.c
  35.  * @brief Operations that VFS offers to its clients.
  36.  */
  37.  
  38. #include "vfs.h"
  39. #include <ipc/ipc.h>
  40. #include <async.h>
  41. #include <errno.h>
  42. #include <stdio.h>
  43. #include <stdlib.h>
  44. #include <string.h>
  45. #include <bool.h>
  46. #include <futex.h>
  47. #include <rwlock.h>
  48. #include <libadt/list.h>
  49. #include <unistd.h>
  50. #include <ctype.h>
  51. #include <fcntl.h>
  52. #include <assert.h>
  53. #include <vfs/canonify.h>
  54.  
  55. /* Forward declarations of static functions. */
  56. static int vfs_truncate_internal(fs_handle_t, dev_handle_t, fs_index_t, size_t);
  57.  
  58. /** Pending mount structure. */
  59. typedef struct {
  60.     link_t link;
  61.     char *fs_name;            /**< File system name */
  62.     char *mp;                 /**< Mount point */
  63.     ipc_callid_t callid;      /**< Call ID waiting for the mount */
  64.     ipc_callid_t rid;         /**< Request ID */
  65.     dev_handle_t dev_handle;  /**< Device handle */
  66. } pending_req_t;
  67.  
  68. LIST_INITIALIZE(pending_req);
  69.  
  70. /**
  71.  * This rwlock prevents the race between a triplet-to-VFS-node resolution and a
  72.  * concurrent VFS operation which modifies the file system namespace.
  73.  */
  74. RWLOCK_INITIALIZE(namespace_rwlock);
  75.  
  76. futex_t rootfs_futex = FUTEX_INITIALIZER;
  77. vfs_pair_t rootfs = {
  78.     .fs_handle = 0,
  79.     .dev_handle = 0
  80. };
  81.  
  82. static void vfs_mount_internal(ipc_callid_t rid, dev_handle_t dev_handle,
  83.     fs_handle_t fs_handle, char *mp)
  84. {
  85.     /* Resolve the path to the mountpoint. */
  86.     vfs_lookup_res_t mp_res;
  87.     vfs_node_t *mp_node = NULL;
  88.     int rc;
  89.     int phone;
  90.     futex_down(&rootfs_futex);
  91.     if (rootfs.fs_handle) {
  92.         /* We already have the root FS. */
  93.         rwlock_write_lock(&namespace_rwlock);
  94.         if (str_cmp(mp, "/") == 0) {
  95.             /* Trying to mount root FS over root FS */
  96.             rwlock_write_unlock(&namespace_rwlock);
  97.             futex_up(&rootfs_futex);
  98.             ipc_answer_0(rid, EBUSY);
  99.             return;
  100.         }
  101.        
  102.         rc = vfs_lookup_internal(mp, L_DIRECTORY, &mp_res, NULL);
  103.         if (rc != EOK) {
  104.             /* The lookup failed for some reason. */
  105.             rwlock_write_unlock(&namespace_rwlock);
  106.             futex_up(&rootfs_futex);
  107.             ipc_answer_0(rid, rc);
  108.             return;
  109.         }
  110.        
  111.         mp_node = vfs_node_get(&mp_res);
  112.         if (!mp_node) {
  113.             rwlock_write_unlock(&namespace_rwlock);
  114.             futex_up(&rootfs_futex);
  115.             ipc_answer_0(rid, ENOMEM);
  116.             return;
  117.         }
  118.        
  119.         /*
  120.          * Now we hold a reference to mp_node.
  121.          * It will be dropped upon the corresponding VFS_UNMOUNT.
  122.          * This prevents the mount point from being deleted.
  123.          */
  124.         rwlock_write_unlock(&namespace_rwlock);
  125.     } else {
  126.         /* We still don't have the root file system mounted. */
  127.         if (str_cmp(mp, "/") == 0) {
  128.             vfs_lookup_res_t mr_res;
  129.             vfs_node_t *mr_node;
  130.             ipcarg_t rindex;
  131.             ipcarg_t rsize;
  132.             ipcarg_t rlnkcnt;
  133.            
  134.             /*
  135.              * For this simple, but important case,
  136.              * we are almost done.
  137.              */
  138.            
  139.             /* Tell the mountee that it is being mounted. */
  140.             phone = vfs_grab_phone(fs_handle);
  141.             rc = async_req_1_3(phone, VFS_MOUNTED,
  142.                 (ipcarg_t) dev_handle, &rindex, &rsize, &rlnkcnt);
  143.             vfs_release_phone(phone);
  144.            
  145.             if (rc != EOK) {
  146.                 futex_up(&rootfs_futex);
  147.                 ipc_answer_0(rid, rc);
  148.                 return;
  149.             }
  150.            
  151.             mr_res.triplet.fs_handle = fs_handle;
  152.             mr_res.triplet.dev_handle = dev_handle;
  153.             mr_res.triplet.index = (fs_index_t) rindex;
  154.             mr_res.size = (size_t) rsize;
  155.             mr_res.lnkcnt = (unsigned) rlnkcnt;
  156.             mr_res.type = VFS_NODE_DIRECTORY;
  157.            
  158.             rootfs.fs_handle = fs_handle;
  159.             rootfs.dev_handle = dev_handle;
  160.             futex_up(&rootfs_futex);
  161.            
  162.             /* Add reference to the mounted root. */
  163.             mr_node = vfs_node_get(&mr_res);
  164.             assert(mr_node);
  165.            
  166.             ipc_answer_0(rid, rc);
  167.             return;
  168.         } else {
  169.             /*
  170.              * We can't resolve this without the root filesystem
  171.              * being mounted first.
  172.              */
  173.             futex_up(&rootfs_futex);
  174.             ipc_answer_0(rid, ENOENT);
  175.             return;
  176.         }
  177.     }
  178.     futex_up(&rootfs_futex);
  179.    
  180.     /*
  181.      * At this point, we have all necessary pieces: file system and device
  182.      * handles, and we know the mount point VFS node.
  183.      */
  184.    
  185.     phone = vfs_grab_phone(mp_res.triplet.fs_handle);
  186.     rc = async_req_4_0(phone, VFS_MOUNT,
  187.         (ipcarg_t) mp_res.triplet.dev_handle,
  188.         (ipcarg_t) mp_res.triplet.index,
  189.         (ipcarg_t) fs_handle,
  190.         (ipcarg_t) dev_handle);
  191.     vfs_release_phone(phone);
  192.    
  193.     if (rc != EOK) {
  194.         /* Mount failed, drop reference to mp_node. */
  195.         if (mp_node)
  196.             vfs_node_put(mp_node);
  197.     }
  198.    
  199.     ipc_answer_0(rid, rc);
  200. }
  201.  
  202. /** Process pending mount requests */
  203. void vfs_process_pending_mount()
  204. {
  205.     link_t *cur;
  206.    
  207. loop:
  208.     for (cur = pending_req.next; cur != &pending_req; cur = cur->next) {
  209.         pending_req_t *pr = list_get_instance(cur, pending_req_t, link);
  210.        
  211.         fs_handle_t fs_handle = fs_name_to_handle(pr->fs_name, true);
  212.         if (!fs_handle)
  213.             continue;
  214.        
  215.         /* Acknowledge that we know fs_name. */
  216.         ipc_answer_0(pr->callid, EOK);
  217.        
  218.         /* Do the mount */
  219.         vfs_mount_internal(pr->rid, pr->dev_handle, fs_handle, pr->mp);
  220.        
  221.         free(pr->fs_name);
  222.         free(pr->mp);
  223.         list_remove(cur);
  224.         free(pr);
  225.         goto loop;
  226.     }
  227. }
  228.  
  229. void vfs_mount(ipc_callid_t rid, ipc_call_t *request)
  230. {
  231.     /*
  232.      * We expect the library to do the device-name to device-handle
  233.      * translation for us, thus the device handle will arrive as ARG1
  234.      * in the request.
  235.      */
  236.     dev_handle_t dev_handle = (dev_handle_t) IPC_GET_ARG1(*request);
  237.    
  238.     /*
  239.      * Mount flags are passed as ARG2.
  240.      */
  241.     unsigned int flags = (unsigned int) IPC_GET_ARG2(*request);
  242.    
  243.     /*
  244.      * For now, don't make use of ARG3, but it can be used to
  245.      * carry mount options in the future.
  246.      */
  247.    
  248.     /* We want the client to send us the mount point. */
  249.     ipc_callid_t callid;
  250.     size_t size;
  251.     if (!ipc_data_write_receive(&callid, &size)) {
  252.         ipc_answer_0(callid, EINVAL);
  253.         ipc_answer_0(rid, EINVAL);
  254.         return;
  255.     }
  256.    
  257.     /* Check whether size is reasonable wrt. the mount point. */
  258.     if ((size < 1) || (size > MAX_PATH_LEN)) {
  259.         ipc_answer_0(callid, EINVAL);
  260.         ipc_answer_0(rid, EINVAL);
  261.         return;
  262.     }
  263.    
  264.     /* Allocate buffer for the mount point data being received. */
  265.     char *mp = malloc(size + 1);
  266.     if (!mp) {
  267.         ipc_answer_0(callid, ENOMEM);
  268.         ipc_answer_0(rid, ENOMEM);
  269.         return;
  270.     }
  271.    
  272.     /* Deliver the mount point. */
  273.     ipcarg_t retval = ipc_data_write_finalize(callid, mp, size);
  274.     if (retval != EOK) {
  275.         ipc_answer_0(rid, EREFUSED);
  276.         free(mp);
  277.         return;
  278.     }
  279.     mp[size] = '\0';
  280.    
  281.     /*
  282.      * Now, we expect the client to send us data with the name of the file
  283.      * system.
  284.      */
  285.     if (!ipc_data_write_receive(&callid, &size)) {
  286.         ipc_answer_0(callid, EINVAL);
  287.         ipc_answer_0(rid, EINVAL);
  288.         free(mp);
  289.         return;
  290.     }
  291.    
  292.     /*
  293.      * Don't receive more than is necessary for storing a full file system
  294.      * name.
  295.      */
  296.     if ((size < 1) || (size > FS_NAME_MAXLEN)) {
  297.         ipc_answer_0(callid, EINVAL);
  298.         ipc_answer_0(rid, EINVAL);
  299.         free(mp);
  300.         return;
  301.     }
  302.    
  303.     /*
  304.      * Allocate buffer for file system name.
  305.      */
  306.     char *fs_name = (char *) malloc(size + 1);
  307.     if (fs_name == NULL) {
  308.         ipc_answer_0(callid, ENOMEM);
  309.         ipc_answer_0(rid, EREFUSED);
  310.         free(mp);
  311.         return;
  312.     }
  313.    
  314.     /* Deliver the file system name. */
  315.     retval = ipc_data_write_finalize(callid, fs_name, size);
  316.     if (retval != EOK) {
  317.         ipc_answer_0(rid, EREFUSED);
  318.         free(mp);
  319.         free(fs_name);
  320.         return;
  321.     }
  322.     fs_name[size] = '\0';
  323.    
  324.     /*
  325.      * Check if we know a file system with the same name as is in fs_name.
  326.      * This will also give us its file system handle.
  327.      */
  328.     fs_handle_t fs_handle = fs_name_to_handle(fs_name, true);
  329.     if (!fs_handle) {
  330.         if (flags & IPC_FLAG_BLOCKING) {
  331.             /* Blocking mount, add to pending list */
  332.             pending_req_t *pr = (pending_req_t *) malloc(sizeof(pending_req_t));
  333.             if (!pr) {
  334.                 ipc_answer_0(callid, ENOMEM);
  335.                 ipc_answer_0(rid, ENOMEM);
  336.                 free(mp);
  337.                 free(fs_name);
  338.                 return;
  339.             }
  340.            
  341.             pr->fs_name = fs_name;
  342.             pr->mp = mp;
  343.             pr->callid = callid;
  344.             pr->rid = rid;
  345.             pr->dev_handle = dev_handle;
  346.             link_initialize(&pr->link);
  347.             list_append(&pr->link, &pending_req);
  348.             return;
  349.         }
  350.        
  351.         ipc_answer_0(callid, ENOENT);
  352.         ipc_answer_0(rid, ENOENT);
  353.         free(mp);
  354.         free(fs_name);
  355.         return;
  356.     }
  357.    
  358.     /* Acknowledge that we know fs_name. */
  359.     ipc_answer_0(callid, EOK);
  360.    
  361.     /* Do the mount */
  362.     vfs_mount_internal(rid, dev_handle, fs_handle, mp);
  363.     free(mp);
  364.     free(fs_name);
  365. }
  366.  
  367. void vfs_open(ipc_callid_t rid, ipc_call_t *request)
  368. {
  369.     if (!vfs_files_init()) {
  370.         ipc_answer_0(rid, ENOMEM);
  371.         return;
  372.     }
  373.  
  374.     /*
  375.      * The POSIX interface is open(path, oflag, mode).
  376.      * We can receive oflags and mode along with the VFS_OPEN call; the path
  377.      * will need to arrive in another call.
  378.      *
  379.      * We also receive one private, non-POSIX set of flags called lflag
  380.      * used to pass information to vfs_lookup_internal().
  381.      */
  382.     int lflag = IPC_GET_ARG1(*request);
  383.     int oflag = IPC_GET_ARG2(*request);
  384.     int mode = IPC_GET_ARG3(*request);
  385.     size_t len;
  386.  
  387.     /*
  388.      * Make sure that we are called with exactly one of L_FILE and
  389.      * L_DIRECTORY.
  390.      */
  391.     if ((lflag & (L_FILE | L_DIRECTORY)) == 0 ||
  392.         (lflag & (L_FILE | L_DIRECTORY)) == (L_FILE | L_DIRECTORY)) {
  393.         ipc_answer_0(rid, EINVAL);
  394.         return;
  395.     }
  396.  
  397.     if (oflag & O_CREAT)
  398.         lflag |= L_CREATE;
  399.     if (oflag & O_EXCL)
  400.         lflag |= L_EXCLUSIVE;
  401.  
  402.     ipc_callid_t callid;
  403.  
  404.     if (!ipc_data_write_receive(&callid, &len)) {
  405.         ipc_answer_0(callid, EINVAL);
  406.         ipc_answer_0(rid, EINVAL);
  407.         return;
  408.     }
  409.     char *path = malloc(len + 1);
  410.     if (!path) {
  411.         ipc_answer_0(callid, ENOMEM);
  412.         ipc_answer_0(rid, ENOMEM);
  413.         return;
  414.     }
  415.     int rc;
  416.     if ((rc = ipc_data_write_finalize(callid, path, len))) {
  417.         ipc_answer_0(rid, rc);
  418.         free(path);
  419.         return;
  420.     }
  421.     path[len] = '\0';
  422.    
  423.     /*
  424.      * Avoid the race condition in which the file can be deleted before we
  425.      * find/create-and-lock the VFS node corresponding to the looked-up
  426.      * triplet.
  427.      */
  428.     if (lflag & L_CREATE)
  429.         rwlock_write_lock(&namespace_rwlock);
  430.     else
  431.         rwlock_read_lock(&namespace_rwlock);
  432.  
  433.     /* The path is now populated and we can call vfs_lookup_internal(). */
  434.     vfs_lookup_res_t lr;
  435.     rc = vfs_lookup_internal(path, lflag, &lr, NULL);
  436.     if (rc) {
  437.         if (lflag & L_CREATE)
  438.             rwlock_write_unlock(&namespace_rwlock);
  439.         else
  440.             rwlock_read_unlock(&namespace_rwlock);
  441.         ipc_answer_0(rid, rc);
  442.         free(path);
  443.         return;
  444.     }
  445.  
  446.     /* Path is no longer needed. */
  447.     free(path);
  448.  
  449.     vfs_node_t *node = vfs_node_get(&lr);
  450.     if (lflag & L_CREATE)
  451.         rwlock_write_unlock(&namespace_rwlock);
  452.     else
  453.         rwlock_read_unlock(&namespace_rwlock);
  454.  
  455.     /* Truncate the file if requested and if necessary. */
  456.     if (oflag & O_TRUNC) {
  457.         rwlock_write_lock(&node->contents_rwlock);
  458.         if (node->size) {
  459.             rc = vfs_truncate_internal(node->fs_handle,
  460.                 node->dev_handle, node->index, 0);
  461.             if (rc) {
  462.                 rwlock_write_unlock(&node->contents_rwlock);
  463.                 vfs_node_put(node);
  464.                 ipc_answer_0(rid, rc);
  465.                 return;
  466.             }
  467.             node->size = 0;
  468.         }
  469.         rwlock_write_unlock(&node->contents_rwlock);
  470.     }
  471.  
  472.     /*
  473.      * Get ourselves a file descriptor and the corresponding vfs_file_t
  474.      * structure.
  475.      */
  476.     int fd = vfs_fd_alloc();
  477.     if (fd < 0) {
  478.         vfs_node_put(node);
  479.         ipc_answer_0(rid, fd);
  480.         return;
  481.     }
  482.     vfs_file_t *file = vfs_file_get(fd);
  483.     file->node = node;
  484.     if (oflag & O_APPEND)
  485.         file->append = true;
  486.  
  487.     /*
  488.      * The following increase in reference count is for the fact that the
  489.      * file is being opened and that a file structure is pointing to it.
  490.      * It is necessary so that the file will not disappear when
  491.      * vfs_node_put() is called. The reference will be dropped by the
  492.      * respective VFS_CLOSE.
  493.      */
  494.     vfs_node_addref(node);
  495.     vfs_node_put(node);
  496.  
  497.     /* Success! Return the new file descriptor to the client. */
  498.     ipc_answer_1(rid, EOK, fd);
  499. }
  500.  
  501. void vfs_close(ipc_callid_t rid, ipc_call_t *request)
  502. {
  503.     int fd = IPC_GET_ARG1(*request);
  504.     int rc = vfs_fd_free(fd);
  505.     ipc_answer_0(rid, rc);
  506. }
  507.  
  508. static void vfs_rdwr(ipc_callid_t rid, ipc_call_t *request, bool read)
  509. {
  510.  
  511.     /*
  512.      * The following code strongly depends on the fact that the files data
  513.      * structure can be only accessed by a single fibril and all file
  514.      * operations are serialized (i.e. the reads and writes cannot
  515.      * interleave and a file cannot be closed while it is being read).
  516.      *
  517.      * Additional synchronization needs to be added once the table of
  518.      * open files supports parallel access!
  519.      */
  520.  
  521.     int fd = IPC_GET_ARG1(*request);
  522.    
  523.     /* Lookup the file structure corresponding to the file descriptor. */
  524.     vfs_file_t *file = vfs_file_get(fd);
  525.     if (!file) {
  526.         ipc_answer_0(rid, ENOENT);
  527.         return;
  528.     }
  529.    
  530.     /*
  531.      * Now we need to receive a call with client's
  532.      * IPC_M_DATA_READ/IPC_M_DATA_WRITE request.
  533.      */
  534.     ipc_callid_t callid;
  535.     int res;
  536.     if (read)
  537.         res = ipc_data_read_receive(&callid, NULL);
  538.     else
  539.         res = ipc_data_write_receive(&callid, NULL);
  540.     if (!res) {
  541.         ipc_answer_0(callid, EINVAL);
  542.         ipc_answer_0(rid, EINVAL);
  543.         return;
  544.     }
  545.    
  546.     /*
  547.      * Lock the open file structure so that no other thread can manipulate
  548.      * the same open file at a time.
  549.      */
  550.     futex_down(&file->lock);
  551.  
  552.     /*
  553.      * Lock the file's node so that no other client can read/write to it at
  554.      * the same time.
  555.      */
  556.     if (read)
  557.         rwlock_read_lock(&file->node->contents_rwlock);
  558.     else
  559.         rwlock_write_lock(&file->node->contents_rwlock);
  560.  
  561.     if (file->node->type == VFS_NODE_DIRECTORY) {
  562.         /*
  563.          * Make sure that no one is modifying the namespace
  564.          * while we are in readdir().
  565.          */
  566.         assert(read);
  567.         rwlock_read_lock(&namespace_rwlock);
  568.     }
  569.    
  570.     int fs_phone = vfs_grab_phone(file->node->fs_handle);  
  571.    
  572.     /* Make a VFS_READ/VFS_WRITE request at the destination FS server. */
  573.     aid_t msg;
  574.     ipc_call_t answer;
  575.     if (!read && file->append)
  576.         file->pos = file->node->size;
  577.     msg = async_send_3(fs_phone, IPC_GET_METHOD(*request),
  578.         file->node->dev_handle, file->node->index, file->pos, &answer);
  579.    
  580.     /*
  581.      * Forward the IPC_M_DATA_READ/IPC_M_DATA_WRITE request to the
  582.      * destination FS server. The call will be routed as if sent by
  583.      * ourselves. Note that call arguments are immutable in this case so we
  584.      * don't have to bother.
  585.      */
  586.     ipc_forward_fast(callid, fs_phone, 0, 0, 0, IPC_FF_ROUTE_FROM_ME);
  587.    
  588.     vfs_release_phone(fs_phone);
  589.    
  590.     /* Wait for reply from the FS server. */
  591.     ipcarg_t rc;
  592.     async_wait_for(msg, &rc);
  593.     size_t bytes = IPC_GET_ARG1(answer);
  594.  
  595.     if (file->node->type == VFS_NODE_DIRECTORY)
  596.         rwlock_read_unlock(&namespace_rwlock);
  597.    
  598.     /* Unlock the VFS node. */
  599.     if (read)
  600.         rwlock_read_unlock(&file->node->contents_rwlock);
  601.     else {
  602.         /* Update the cached version of node's size. */
  603.         if (rc == EOK)
  604.             file->node->size = IPC_GET_ARG2(answer);
  605.         rwlock_write_unlock(&file->node->contents_rwlock);
  606.     }
  607.    
  608.     /* Update the position pointer and unlock the open file. */
  609.     if (rc == EOK)
  610.         file->pos += bytes;
  611.     futex_up(&file->lock);
  612.    
  613.     /*
  614.      * FS server's reply is the final result of the whole operation we
  615.      * return to the client.
  616.      */
  617.     ipc_answer_1(rid, rc, bytes);
  618. }
  619.  
  620. void vfs_read(ipc_callid_t rid, ipc_call_t *request)
  621. {
  622.     vfs_rdwr(rid, request, true);
  623. }
  624.  
  625. void vfs_write(ipc_callid_t rid, ipc_call_t *request)
  626. {
  627.     vfs_rdwr(rid, request, false);
  628. }
  629.  
  630. void vfs_seek(ipc_callid_t rid, ipc_call_t *request)
  631. {
  632.     int fd = (int) IPC_GET_ARG1(*request);
  633.     off_t off = (off_t) IPC_GET_ARG2(*request);
  634.     int whence = (int) IPC_GET_ARG3(*request);
  635.  
  636.  
  637.     /* Lookup the file structure corresponding to the file descriptor. */
  638.     vfs_file_t *file = vfs_file_get(fd);
  639.     if (!file) {
  640.         ipc_answer_0(rid, ENOENT);
  641.         return;
  642.     }
  643.  
  644.     off_t newpos;
  645.     futex_down(&file->lock);
  646.     if (whence == SEEK_SET) {
  647.         file->pos = off;
  648.         futex_up(&file->lock);
  649.         ipc_answer_1(rid, EOK, off);
  650.         return;
  651.     }
  652.     if (whence == SEEK_CUR) {
  653.         if (file->pos + off < file->pos) {
  654.             futex_up(&file->lock);
  655.             ipc_answer_0(rid, EOVERFLOW);
  656.             return;
  657.         }
  658.         file->pos += off;
  659.         newpos = file->pos;
  660.         futex_up(&file->lock);
  661.         ipc_answer_1(rid, EOK, newpos);
  662.         return;
  663.     }
  664.     if (whence == SEEK_END) {
  665.         rwlock_read_lock(&file->node->contents_rwlock);
  666.         size_t size = file->node->size;
  667.         rwlock_read_unlock(&file->node->contents_rwlock);
  668.         if (size + off < size) {
  669.             futex_up(&file->lock);
  670.             ipc_answer_0(rid, EOVERFLOW);
  671.             return;
  672.         }
  673.         newpos = size + off;
  674.         futex_up(&file->lock);
  675.         ipc_answer_1(rid, EOK, newpos);
  676.         return;
  677.     }
  678.     futex_up(&file->lock);
  679.     ipc_answer_0(rid, EINVAL);
  680. }
  681.  
  682. int
  683. vfs_truncate_internal(fs_handle_t fs_handle, dev_handle_t dev_handle,
  684.     fs_index_t index, size_t size)
  685. {
  686.     ipcarg_t rc;
  687.     int fs_phone;
  688.    
  689.     fs_phone = vfs_grab_phone(fs_handle);
  690.     rc = async_req_3_0(fs_phone, VFS_TRUNCATE, (ipcarg_t)dev_handle,
  691.         (ipcarg_t)index, (ipcarg_t)size);
  692.     vfs_release_phone(fs_phone);
  693.     return (int)rc;
  694. }
  695.  
  696. void vfs_truncate(ipc_callid_t rid, ipc_call_t *request)
  697. {
  698.     int fd = IPC_GET_ARG1(*request);
  699.     size_t size = IPC_GET_ARG2(*request);
  700.     int rc;
  701.  
  702.     vfs_file_t *file = vfs_file_get(fd);
  703.     if (!file) {
  704.         ipc_answer_0(rid, ENOENT);
  705.         return;
  706.     }
  707.     futex_down(&file->lock);
  708.  
  709.     rwlock_write_lock(&file->node->contents_rwlock);
  710.     rc = vfs_truncate_internal(file->node->fs_handle,
  711.         file->node->dev_handle, file->node->index, size);
  712.     if (rc == EOK)
  713.         file->node->size = size;
  714.     rwlock_write_unlock(&file->node->contents_rwlock);
  715.  
  716.     futex_up(&file->lock);
  717.     ipc_answer_0(rid, (ipcarg_t)rc);
  718. }
  719.  
  720. void vfs_mkdir(ipc_callid_t rid, ipc_call_t *request)
  721. {
  722.     int mode = IPC_GET_ARG1(*request);
  723.  
  724.     size_t len;
  725.     ipc_callid_t callid;
  726.  
  727.     if (!ipc_data_write_receive(&callid, &len)) {
  728.         ipc_answer_0(callid, EINVAL);
  729.         ipc_answer_0(rid, EINVAL);
  730.         return;
  731.     }
  732.     char *path = malloc(len + 1);
  733.     if (!path) {
  734.         ipc_answer_0(callid, ENOMEM);
  735.         ipc_answer_0(rid, ENOMEM);
  736.         return;
  737.     }
  738.     int rc;
  739.     if ((rc = ipc_data_write_finalize(callid, path, len))) {
  740.         ipc_answer_0(rid, rc);
  741.         free(path);
  742.         return;
  743.     }
  744.     path[len] = '\0';
  745.    
  746.     rwlock_write_lock(&namespace_rwlock);
  747.     int lflag = L_DIRECTORY | L_CREATE | L_EXCLUSIVE;
  748.     rc = vfs_lookup_internal(path, lflag, NULL, NULL);
  749.     rwlock_write_unlock(&namespace_rwlock);
  750.     free(path);
  751.     ipc_answer_0(rid, rc);
  752. }
  753.  
  754. void vfs_unlink(ipc_callid_t rid, ipc_call_t *request)
  755. {
  756.     int lflag = IPC_GET_ARG1(*request);
  757.  
  758.     size_t len;
  759.     ipc_callid_t callid;
  760.  
  761.     if (!ipc_data_write_receive(&callid, &len)) {
  762.         ipc_answer_0(callid, EINVAL);
  763.         ipc_answer_0(rid, EINVAL);
  764.         return;
  765.     }
  766.     char *path = malloc(len + 1);
  767.     if (!path) {
  768.         ipc_answer_0(callid, ENOMEM);
  769.         ipc_answer_0(rid, ENOMEM);
  770.         return;
  771.     }
  772.     int rc;
  773.     if ((rc = ipc_data_write_finalize(callid, path, len))) {
  774.         ipc_answer_0(rid, rc);
  775.         free(path);
  776.         return;
  777.     }
  778.     path[len] = '\0';
  779.    
  780.     rwlock_write_lock(&namespace_rwlock);
  781.     lflag &= L_DIRECTORY;   /* sanitize lflag */
  782.     vfs_lookup_res_t lr;
  783.     rc = vfs_lookup_internal(path, lflag | L_UNLINK, &lr, NULL);
  784.     free(path);
  785.     if (rc != EOK) {
  786.         rwlock_write_unlock(&namespace_rwlock);
  787.         ipc_answer_0(rid, rc);
  788.         return;
  789.     }
  790.  
  791.     /*
  792.      * The name has already been unlinked by vfs_lookup_internal().
  793.      * We have to get and put the VFS node to ensure that it is
  794.      * VFS_DESTROY'ed after the last reference to it is dropped.
  795.      */
  796.     vfs_node_t *node = vfs_node_get(&lr);
  797.     futex_down(&nodes_futex);
  798.     node->lnkcnt--;
  799.     futex_up(&nodes_futex);
  800.     rwlock_write_unlock(&namespace_rwlock);
  801.     vfs_node_put(node);
  802.     ipc_answer_0(rid, EOK);
  803. }
  804.  
  805. void vfs_rename(ipc_callid_t rid, ipc_call_t *request)
  806. {
  807.     size_t olen, nlen;
  808.     ipc_callid_t callid;
  809.     int rc;
  810.  
  811.     /* Retrieve the old path. */
  812.     if (!ipc_data_write_receive(&callid, &olen)) {
  813.         ipc_answer_0(callid, EINVAL);
  814.         ipc_answer_0(rid, EINVAL);
  815.         return;
  816.     }
  817.     char *old = malloc(olen + 1);
  818.     if (!old) {
  819.         ipc_answer_0(callid, ENOMEM);
  820.         ipc_answer_0(rid, ENOMEM);
  821.         return;
  822.     }
  823.     if ((rc = ipc_data_write_finalize(callid, old, olen))) {
  824.         ipc_answer_0(rid, rc);
  825.         free(old);
  826.         return;
  827.     }
  828.     old[olen] = '\0';
  829.    
  830.     /* Retrieve the new path. */
  831.     if (!ipc_data_write_receive(&callid, &nlen)) {
  832.         ipc_answer_0(callid, EINVAL);
  833.         ipc_answer_0(rid, EINVAL);
  834.         free(old);
  835.         return;
  836.     }
  837.     char *new = malloc(nlen + 1);
  838.     if (!new) {
  839.         ipc_answer_0(callid, ENOMEM);
  840.         ipc_answer_0(rid, ENOMEM);
  841.         free(old);
  842.         return;
  843.     }
  844.     if ((rc = ipc_data_write_finalize(callid, new, nlen))) {
  845.         ipc_answer_0(rid, rc);
  846.         free(old);
  847.         free(new);
  848.         return;
  849.     }
  850.     new[nlen] = '\0';
  851.  
  852.     char *oldc = canonify(old, &olen);
  853.     char *newc = canonify(new, &nlen);
  854.     if (!oldc || !newc) {
  855.         ipc_answer_0(rid, EINVAL);
  856.         free(old);
  857.         free(new);
  858.         return;
  859.     }
  860.     oldc[olen] = '\0';
  861.     newc[nlen] = '\0';
  862.     if (!str_lcmp(newc, oldc, str_length(oldc))) {
  863.         /* oldc is a prefix of newc */
  864.         ipc_answer_0(rid, EINVAL);
  865.         free(old);
  866.         free(new);
  867.         return;
  868.     }
  869.    
  870.     vfs_lookup_res_t old_lr;
  871.     vfs_lookup_res_t new_lr;
  872.     vfs_lookup_res_t new_par_lr;
  873.     rwlock_write_lock(&namespace_rwlock);
  874.     /* Lookup the node belonging to the old file name. */
  875.     rc = vfs_lookup_internal(oldc, L_NONE, &old_lr, NULL);
  876.     if (rc != EOK) {
  877.         rwlock_write_unlock(&namespace_rwlock);
  878.         ipc_answer_0(rid, rc);
  879.         free(old);
  880.         free(new);
  881.         return;
  882.     }
  883.     vfs_node_t *old_node = vfs_node_get(&old_lr);
  884.     if (!old_node) {
  885.         rwlock_write_unlock(&namespace_rwlock);
  886.         ipc_answer_0(rid, ENOMEM);
  887.         free(old);
  888.         free(new);
  889.         return;
  890.     }
  891.     /* Lookup parent of the new file name. */
  892.     rc = vfs_lookup_internal(newc, L_PARENT, &new_par_lr, NULL);
  893.     if (rc != EOK) {
  894.         rwlock_write_unlock(&namespace_rwlock);
  895.         ipc_answer_0(rid, rc);
  896.         free(old);
  897.         free(new);
  898.         return;
  899.     }
  900.     /* Check whether linking to the same file system instance. */
  901.     if ((old_node->fs_handle != new_par_lr.triplet.fs_handle) ||
  902.         (old_node->dev_handle != new_par_lr.triplet.dev_handle)) {
  903.         rwlock_write_unlock(&namespace_rwlock);
  904.         ipc_answer_0(rid, EXDEV);   /* different file systems */
  905.         free(old);
  906.         free(new);
  907.         return;
  908.     }
  909.     /* Destroy the old link for the new name. */
  910.     vfs_node_t *new_node = NULL;
  911.     rc = vfs_lookup_internal(newc, L_UNLINK, &new_lr, NULL);
  912.     switch (rc) {
  913.     case ENOENT:
  914.         /* simply not in our way */
  915.         break;
  916.     case EOK:
  917.         new_node = vfs_node_get(&new_lr);
  918.         if (!new_node) {
  919.             rwlock_write_unlock(&namespace_rwlock);
  920.             ipc_answer_0(rid, ENOMEM);
  921.             free(old);
  922.             free(new);
  923.             return;
  924.         }
  925.         futex_down(&nodes_futex);
  926.         new_node->lnkcnt--;
  927.         futex_up(&nodes_futex);
  928.         break;
  929.     default:
  930.         rwlock_write_unlock(&namespace_rwlock);
  931.         ipc_answer_0(rid, ENOTEMPTY);
  932.         free(old);
  933.         free(new);
  934.         return;
  935.     }
  936.     /* Create the new link for the new name. */
  937.     rc = vfs_lookup_internal(newc, L_LINK, NULL, NULL, old_node->index);
  938.     if (rc != EOK) {
  939.         rwlock_write_unlock(&namespace_rwlock);
  940.         if (new_node)
  941.             vfs_node_put(new_node);
  942.         ipc_answer_0(rid, rc);
  943.         free(old);
  944.         free(new);
  945.         return;
  946.     }
  947.     futex_down(&nodes_futex);
  948.     old_node->lnkcnt++;
  949.     futex_up(&nodes_futex);
  950.     /* Destroy the link for the old name. */
  951.     rc = vfs_lookup_internal(oldc, L_UNLINK, NULL, NULL);
  952.     if (rc != EOK) {
  953.         rwlock_write_unlock(&namespace_rwlock);
  954.         vfs_node_put(old_node);
  955.         if (new_node)
  956.             vfs_node_put(new_node);
  957.         ipc_answer_0(rid, rc);
  958.         free(old);
  959.         free(new);
  960.         return;
  961.     }
  962.     futex_down(&nodes_futex);
  963.     old_node->lnkcnt--;
  964.     futex_up(&nodes_futex);
  965.     rwlock_write_unlock(&namespace_rwlock);
  966.     vfs_node_put(old_node);
  967.     if (new_node)
  968.         vfs_node_put(new_node);
  969.     free(old);
  970.     free(new);
  971.     ipc_answer_0(rid, EOK);
  972. }
  973.  
  974. /**
  975.  * @}
  976.  */
  977.