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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_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. /**
  59.  * This rwlock prevents the race between a triplet-to-VFS-node resolution and a
  60.  * concurrent VFS operation which modifies the file system namespace.
  61.  */
  62. RWLOCK_INITIALIZE(namespace_rwlock);
  63.  
  64. futex_t rootfs_futex = FUTEX_INITIALIZER;
  65. vfs_triplet_t rootfs = {
  66.     .fs_handle = 0,
  67.     .dev_handle = 0,
  68.     .index = 0,
  69. };
  70.  
  71. static int
  72. lookup_root(fs_handle_t fs_handle, dev_handle_t dev_handle,
  73.     vfs_lookup_res_t *result)
  74. {
  75.     vfs_pair_t altroot = {
  76.         .fs_handle = fs_handle,
  77.         .dev_handle = dev_handle,
  78.     };
  79.  
  80.     return vfs_lookup_internal("/", L_DIRECTORY, result, &altroot);
  81. }
  82.  
  83. void vfs_mount(ipc_callid_t rid, ipc_call_t *request)
  84. {
  85.     dev_handle_t dev_handle;
  86.     vfs_node_t *mp_node = NULL;
  87.  
  88.     /*
  89.      * We expect the library to do the device-name to device-handle
  90.      * translation for us, thus the device handle will arrive as ARG1
  91.      * in the request.
  92.      */
  93.     dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);
  94.  
  95.     /*
  96.      * For now, don't make use of ARG2 and ARG3, but they can be used to
  97.      * carry mount options in the future.
  98.      */
  99.  
  100.     ipc_callid_t callid;
  101.     size_t size;
  102.  
  103.     /*
  104.      * Now, we expect the client to send us data with the name of the file
  105.      * system.
  106.      */
  107.     if (!ipc_data_write_receive(&callid, &size)) {
  108.         ipc_answer_0(callid, EINVAL);
  109.         ipc_answer_0(rid, EINVAL);
  110.         return;
  111.     }
  112.  
  113.     /*
  114.      * Don't receive more than is necessary for storing a full file system
  115.      * name.
  116.      */
  117.     if (size < 1 || size > FS_NAME_MAXLEN) {
  118.         ipc_answer_0(callid, EINVAL);
  119.         ipc_answer_0(rid, EINVAL);
  120.         return;
  121.     }
  122.  
  123.     /* Deliver the file system name. */
  124.     char fs_name[FS_NAME_MAXLEN + 1];
  125.     (void) ipc_data_write_finalize(callid, fs_name, size);
  126.     fs_name[size] = '\0';
  127.    
  128.     /*
  129.      * Check if we know a file system with the same name as is in fs_name.
  130.      * This will also give us its file system handle.
  131.      */
  132.     fs_handle_t fs_handle = fs_name_to_handle(fs_name, true);
  133.     if (!fs_handle) {
  134.         ipc_answer_0(rid, ENOENT);
  135.         return;
  136.     }
  137.  
  138.     /* Now, we want the client to send us the mount point. */
  139.     if (!ipc_data_write_receive(&callid, &size)) {
  140.         ipc_answer_0(callid, EINVAL);
  141.         ipc_answer_0(rid, EINVAL);
  142.         return;
  143.     }
  144.  
  145.     /* Check whether size is reasonable wrt. the mount point. */
  146.     if (size < 1 || size > MAX_PATH_LEN) {
  147.         ipc_answer_0(callid, EINVAL);
  148.         ipc_answer_0(rid, EINVAL);
  149.         return;
  150.     }
  151.     /* Allocate buffer for the mount point data being received. */
  152.     uint8_t *buf;
  153.     buf = malloc(size + 1);
  154.     if (!buf) {
  155.         ipc_answer_0(callid, ENOMEM);
  156.         ipc_answer_0(rid, ENOMEM);
  157.         return;
  158.     }
  159.  
  160.     /* Deliver the mount point. */
  161.     (void) ipc_data_write_finalize(callid, buf, size);
  162.     buf[size] = '\0';
  163.  
  164.     /*
  165.      * Lookup the root node of the filesystem being mounted.
  166.      * In this case, we don't need to take the namespace_futex as the root
  167.      * node cannot be removed. However, we do take a reference to it so
  168.      * that we can track how many times it has been mounted.
  169.      */
  170.     int rc;
  171.     vfs_lookup_res_t mr_res;
  172.     rc = lookup_root(fs_handle, dev_handle, &mr_res);
  173.     if (rc != EOK) {
  174.         free(buf);
  175.         ipc_answer_0(rid, rc);
  176.         return;
  177.     }
  178.     vfs_node_t *mr_node = vfs_node_get(&mr_res);
  179.     if (!mr_node) {
  180.         free(buf);
  181.         ipc_answer_0(rid, ENOMEM);
  182.         return;
  183.     }
  184.  
  185.     /* Finally, we need to resolve the path to the mountpoint. */
  186.     vfs_lookup_res_t mp_res;
  187.     futex_down(&rootfs_futex);
  188.     if (rootfs.fs_handle) {
  189.         /* We already have the root FS. */
  190.         rwlock_write_lock(&namespace_rwlock);
  191.         rc = vfs_lookup_internal(buf, L_DIRECTORY, &mp_res, NULL);
  192.         if (rc != EOK) {
  193.             /* The lookup failed for some reason. */
  194.             rwlock_write_unlock(&namespace_rwlock);
  195.             futex_up(&rootfs_futex);
  196.             vfs_node_put(mr_node);  /* failed -> drop reference */
  197.             free(buf);
  198.             ipc_answer_0(rid, rc);
  199.             return;
  200.         }
  201.         mp_node = vfs_node_get(&mp_res);
  202.         if (!mp_node) {
  203.             rwlock_write_unlock(&namespace_rwlock);
  204.             futex_up(&rootfs_futex);
  205.             vfs_node_put(mr_node);  /* failed -> drop reference */
  206.             free(buf);
  207.             ipc_answer_0(rid, ENOMEM);
  208.             return;
  209.         }
  210.         /*
  211.          * Now we hold a reference to mp_node.
  212.          * It will be dropped upon the corresponding VFS_UNMOUNT.
  213.          * This prevents the mount point from being deleted.
  214.          */
  215.         rwlock_write_unlock(&namespace_rwlock);
  216.     } else {
  217.         /* We still don't have the root file system mounted. */
  218.         if ((size == 1) && (buf[0] == '/')) {
  219.             /* For this simple, but important case, we are done. */
  220.             rootfs = mr_res.triplet;
  221.             futex_up(&rootfs_futex);
  222.             free(buf);
  223.             ipc_answer_0(rid, EOK);
  224.             return;
  225.         } else {
  226.             /*
  227.              * We can't resolve this without the root filesystem
  228.              * being mounted first.
  229.              */
  230.             futex_up(&rootfs_futex);
  231.             free(buf);
  232.             vfs_node_put(mr_node);  /* failed -> drop reference */
  233.             ipc_answer_0(rid, ENOENT);
  234.             return;
  235.         }
  236.     }
  237.     futex_up(&rootfs_futex);
  238.    
  239.     free(buf);  /* The buffer is not needed anymore. */
  240.    
  241.     /*
  242.      * At this point, we have all necessary pieces: file system and device
  243.      * handles, and we know the mount point VFS node and also the root node
  244.      * of the file system being mounted.
  245.      */
  246.  
  247.     int phone = vfs_grab_phone(mp_res.triplet.fs_handle);
  248.     /* Later we can use ARG3 to pass mode/flags. */
  249.     aid_t req1 = async_send_3(phone, VFS_MOUNT,
  250.         (ipcarg_t) mp_res.triplet.dev_handle,
  251.         (ipcarg_t) mp_res.triplet.index, 0, NULL);
  252.     /* The second call uses the same method. */
  253.     aid_t req2 = async_send_3(phone, VFS_MOUNT,
  254.         (ipcarg_t) mr_res.triplet.fs_handle,
  255.         (ipcarg_t) mr_res.triplet.dev_handle,
  256.         (ipcarg_t) mr_res.triplet.index, NULL);
  257.     vfs_release_phone(phone);
  258.  
  259.     ipcarg_t rc1;
  260.     ipcarg_t rc2;
  261.     async_wait_for(req1, &rc1);
  262.     async_wait_for(req2, &rc2);
  263.  
  264.     if ((rc1 != EOK) || (rc2 != EOK)) {
  265.         /* Mount failed, drop references to mr_node and mp_node. */
  266.         vfs_node_put(mr_node);
  267.         if (mp_node)
  268.             vfs_node_put(mp_node);
  269.     }
  270.    
  271.     if (rc2 == EOK)
  272.         ipc_answer_0(rid, rc1);
  273.     else if (rc1 == EOK)
  274.         ipc_answer_0(rid, rc2);
  275.     else
  276.         ipc_answer_0(rid, rc1);
  277. }
  278.  
  279. void vfs_open(ipc_callid_t rid, ipc_call_t *request)
  280. {
  281.     if (!vfs_files_init()) {
  282.         ipc_answer_0(rid, ENOMEM);
  283.         return;
  284.     }
  285.  
  286.     /*
  287.      * The POSIX interface is open(path, oflag, mode).
  288.      * We can receive oflags and mode along with the VFS_OPEN call; the path
  289.      * will need to arrive in another call.
  290.      *
  291.      * We also receive one private, non-POSIX set of flags called lflag
  292.      * used to pass information to vfs_lookup_internal().
  293.      */
  294.     int lflag = IPC_GET_ARG1(*request);
  295.     int oflag = IPC_GET_ARG2(*request);
  296.     int mode = IPC_GET_ARG3(*request);
  297.     size_t len;
  298.  
  299.     if (oflag & O_CREAT)
  300.         lflag |= L_CREATE;
  301.     if (oflag & O_EXCL)
  302.         lflag |= L_EXCLUSIVE;
  303.  
  304.     ipc_callid_t callid;
  305.  
  306.     if (!ipc_data_write_receive(&callid, &len)) {
  307.         ipc_answer_0(callid, EINVAL);
  308.         ipc_answer_0(rid, EINVAL);
  309.         return;
  310.     }
  311.     char *path = malloc(len + 1);
  312.     if (!path) {
  313.         ipc_answer_0(callid, ENOMEM);
  314.         ipc_answer_0(rid, ENOMEM);
  315.         return;
  316.     }
  317.     int rc;
  318.     if ((rc = ipc_data_write_finalize(callid, path, len))) {
  319.         ipc_answer_0(rid, rc);
  320.         free(path);
  321.         return;
  322.     }
  323.     path[len] = '\0';
  324.    
  325.     /*
  326.      * Avoid the race condition in which the file can be deleted before we
  327.      * find/create-and-lock the VFS node corresponding to the looked-up
  328.      * triplet.
  329.      */
  330.     if (lflag & L_CREATE)
  331.         rwlock_write_lock(&namespace_rwlock);
  332.     else
  333.         rwlock_read_lock(&namespace_rwlock);
  334.  
  335.     /* The path is now populated and we can call vfs_lookup_internal(). */
  336.     vfs_lookup_res_t lr;
  337.     rc = vfs_lookup_internal(path, lflag, &lr, NULL);
  338.     if (rc) {
  339.         if (lflag & L_CREATE)
  340.             rwlock_write_unlock(&namespace_rwlock);
  341.         else
  342.             rwlock_read_unlock(&namespace_rwlock);
  343.         ipc_answer_0(rid, rc);
  344.         free(path);
  345.         return;
  346.     }
  347.  
  348.     /* Path is no longer needed. */
  349.     free(path);
  350.  
  351.     vfs_node_t *node = vfs_node_get(&lr);
  352.     if (lflag & L_CREATE)
  353.         rwlock_write_unlock(&namespace_rwlock);
  354.     else
  355.         rwlock_read_unlock(&namespace_rwlock);
  356.  
  357.     /* Truncate the file if requested and if necessary. */
  358.     if (oflag & O_TRUNC) {
  359.         rwlock_write_lock(&node->contents_rwlock);
  360.         if (node->size) {
  361.             rc = vfs_truncate_internal(node->fs_handle,
  362.                 node->dev_handle, node->index, 0);
  363.             if (rc) {
  364.                 rwlock_write_unlock(&node->contents_rwlock);
  365.                 vfs_node_put(node);
  366.                 ipc_answer_0(rid, rc);
  367.                 return;
  368.             }
  369.             node->size = 0;
  370.         }
  371.         rwlock_write_unlock(&node->contents_rwlock);
  372.     }
  373.  
  374.     /*
  375.      * Get ourselves a file descriptor and the corresponding vfs_file_t
  376.      * structure.
  377.      */
  378.     int fd = vfs_fd_alloc();
  379.     if (fd < 0) {
  380.         vfs_node_put(node);
  381.         ipc_answer_0(rid, fd);
  382.         return;
  383.     }
  384.     vfs_file_t *file = vfs_file_get(fd);
  385.     file->node = node;
  386.     if (oflag & O_APPEND)
  387.         file->append = true;
  388.  
  389.     /*
  390.      * The following increase in reference count is for the fact that the
  391.      * file is being opened and that a file structure is pointing to it.
  392.      * It is necessary so that the file will not disappear when
  393.      * vfs_node_put() is called. The reference will be dropped by the
  394.      * respective VFS_CLOSE.
  395.      */
  396.     vfs_node_addref(node);
  397.     vfs_node_put(node);
  398.  
  399.     /* Success! Return the new file descriptor to the client. */
  400.     ipc_answer_1(rid, EOK, fd);
  401. }
  402.  
  403. void vfs_close(ipc_callid_t rid, ipc_call_t *request)
  404. {
  405.     int fd = IPC_GET_ARG1(*request);
  406.     if (fd >= MAX_OPEN_FILES) {
  407.         ipc_answer_0(rid, EBADF);
  408.         return;
  409.     }
  410.     vfs_fd_free(fd);
  411.     ipc_answer_0(rid, EOK);
  412. }
  413.  
  414. static void vfs_rdwr(ipc_callid_t rid, ipc_call_t *request, bool read)
  415. {
  416.  
  417.     /*
  418.      * The following code strongly depends on the fact that the files data
  419.      * structure can be only accessed by a single fibril and all file
  420.      * operations are serialized (i.e. the reads and writes cannot
  421.      * interleave and a file cannot be closed while it is being read).
  422.      *
  423.      * Additional synchronization needs to be added once the table of
  424.      * open files supports parallel access!
  425.      */
  426.  
  427.     int fd = IPC_GET_ARG1(*request);
  428.  
  429.     /* Lookup the file structure corresponding to the file descriptor. */
  430.     vfs_file_t *file = vfs_file_get(fd);
  431.     if (!file) {
  432.         ipc_answer_0(rid, ENOENT);
  433.         return;
  434.     }
  435.  
  436.     /*
  437.      * Now we need to receive a call with client's
  438.      * IPC_M_DATA_READ/IPC_M_DATA_WRITE request.
  439.      */
  440.     ipc_callid_t callid;
  441.     int res;
  442.     if (read)
  443.         res = ipc_data_read_receive(&callid, NULL);
  444.     else
  445.         res = ipc_data_write_receive(&callid, NULL);
  446.     if (!res) {
  447.         ipc_answer_0(callid, EINVAL);
  448.         ipc_answer_0(rid, EINVAL);
  449.         return;
  450.     }
  451.  
  452.     /*
  453.      * Lock the open file structure so that no other thread can manipulate
  454.      * the same open file at a time.
  455.      */
  456.     futex_down(&file->lock);
  457.  
  458.     /*
  459.      * Lock the file's node so that no other client can read/write to it at
  460.      * the same time.
  461.      */
  462.     if (read)
  463.         rwlock_read_lock(&file->node->contents_rwlock);
  464.     else
  465.         rwlock_write_lock(&file->node->contents_rwlock);
  466.  
  467.     int fs_phone = vfs_grab_phone(file->node->fs_handle);  
  468.    
  469.     /* Make a VFS_READ/VFS_WRITE request at the destination FS server. */
  470.     aid_t msg;
  471.     ipc_call_t answer;
  472.     if (!read && file->append)
  473.         file->pos = file->node->size;
  474.     msg = async_send_3(fs_phone, IPC_GET_METHOD(*request),
  475.         file->node->dev_handle, file->node->index, file->pos, &answer);
  476.    
  477.     /*
  478.      * Forward the IPC_M_DATA_READ/IPC_M_DATA_WRITE request to the
  479.      * destination FS server. The call will be routed as if sent by
  480.      * ourselves. Note that call arguments are immutable in this case so we
  481.      * don't have to bother.
  482.      */
  483.     ipc_forward_fast(callid, fs_phone, 0, 0, 0, IPC_FF_ROUTE_FROM_ME);
  484.  
  485.     vfs_release_phone(fs_phone);
  486.  
  487.     /* Wait for reply from the FS server. */
  488.     ipcarg_t rc;
  489.     async_wait_for(msg, &rc);
  490.     size_t bytes = IPC_GET_ARG1(answer);
  491.  
  492.     /* Unlock the VFS node. */
  493.     if (read)
  494.         rwlock_read_unlock(&file->node->contents_rwlock);
  495.     else {
  496.         /* Update the cached version of node's size. */
  497.         if (rc == EOK)
  498.             file->node->size = IPC_GET_ARG2(answer);
  499.         rwlock_write_unlock(&file->node->contents_rwlock);
  500.     }
  501.  
  502.     /* Update the position pointer and unlock the open file. */
  503.     if (rc == EOK)
  504.         file->pos += bytes;
  505.     futex_up(&file->lock);
  506.  
  507.     /*
  508.      * FS server's reply is the final result of the whole operation we
  509.      * return to the client.
  510.      */
  511.     ipc_answer_1(rid, rc, bytes);
  512. }
  513.  
  514. void vfs_read(ipc_callid_t rid, ipc_call_t *request)
  515. {
  516.     vfs_rdwr(rid, request, true);
  517. }
  518.  
  519. void vfs_write(ipc_callid_t rid, ipc_call_t *request)
  520. {
  521.     vfs_rdwr(rid, request, false);
  522. }
  523.  
  524. void vfs_seek(ipc_callid_t rid, ipc_call_t *request)
  525. {
  526.     int fd = (int) IPC_GET_ARG1(*request);
  527.     off_t off = (off_t) IPC_GET_ARG2(*request);
  528.     int whence = (int) IPC_GET_ARG3(*request);
  529.  
  530.  
  531.     /* Lookup the file structure corresponding to the file descriptor. */
  532.     vfs_file_t *file = vfs_file_get(fd);
  533.     if (!file) {
  534.         ipc_answer_0(rid, ENOENT);
  535.         return;
  536.     }
  537.  
  538.     off_t newpos;
  539.     futex_down(&file->lock);
  540.     if (whence == SEEK_SET) {
  541.         file->pos = off;
  542.         futex_up(&file->lock);
  543.         ipc_answer_1(rid, EOK, off);
  544.         return;
  545.     }
  546.     if (whence == SEEK_CUR) {
  547.         if (file->pos + off < file->pos) {
  548.             futex_up(&file->lock);
  549.             ipc_answer_0(rid, EOVERFLOW);
  550.             return;
  551.         }
  552.         file->pos += off;
  553.         newpos = file->pos;
  554.         futex_up(&file->lock);
  555.         ipc_answer_1(rid, EOK, newpos);
  556.         return;
  557.     }
  558.     if (whence == SEEK_END) {
  559.         rwlock_read_lock(&file->node->contents_rwlock);
  560.         size_t size = file->node->size;
  561.         rwlock_read_unlock(&file->node->contents_rwlock);
  562.         if (size + off < size) {
  563.             futex_up(&file->lock);
  564.             ipc_answer_0(rid, EOVERFLOW);
  565.             return;
  566.         }
  567.         newpos = size + off;
  568.         futex_up(&file->lock);
  569.         ipc_answer_1(rid, EOK, newpos);
  570.         return;
  571.     }
  572.     futex_up(&file->lock);
  573.     ipc_answer_0(rid, EINVAL);
  574. }
  575.  
  576. int
  577. vfs_truncate_internal(fs_handle_t fs_handle, dev_handle_t dev_handle,
  578.     fs_index_t index, size_t size)
  579. {
  580.     ipcarg_t rc;
  581.     int fs_phone;
  582.    
  583.     fs_phone = vfs_grab_phone(fs_handle);
  584.     rc = async_req_3_0(fs_phone, VFS_TRUNCATE, (ipcarg_t)dev_handle,
  585.         (ipcarg_t)index, (ipcarg_t)size);
  586.     vfs_release_phone(fs_phone);
  587.     return (int)rc;
  588. }
  589.  
  590. void vfs_truncate(ipc_callid_t rid, ipc_call_t *request)
  591. {
  592.     int fd = IPC_GET_ARG1(*request);
  593.     size_t size = IPC_GET_ARG2(*request);
  594.     int rc;
  595.  
  596.     vfs_file_t *file = vfs_file_get(fd);
  597.     if (!file) {
  598.         ipc_answer_0(rid, ENOENT);
  599.         return;
  600.     }
  601.     futex_down(&file->lock);
  602.  
  603.     rwlock_write_lock(&file->node->contents_rwlock);
  604.     rc = vfs_truncate_internal(file->node->fs_handle,
  605.         file->node->dev_handle, file->node->index, size);
  606.     if (rc == EOK)
  607.         file->node->size = size;
  608.     rwlock_write_unlock(&file->node->contents_rwlock);
  609.  
  610.     futex_up(&file->lock);
  611.     ipc_answer_0(rid, (ipcarg_t)rc);
  612. }
  613.  
  614. void vfs_mkdir(ipc_callid_t rid, ipc_call_t *request)
  615. {
  616.     int mode = IPC_GET_ARG1(*request);
  617.  
  618.     size_t len;
  619.     ipc_callid_t callid;
  620.  
  621.     if (!ipc_data_write_receive(&callid, &len)) {
  622.         ipc_answer_0(callid, EINVAL);
  623.         ipc_answer_0(rid, EINVAL);
  624.         return;
  625.     }
  626.     char *path = malloc(len + 1);
  627.     if (!path) {
  628.         ipc_answer_0(callid, ENOMEM);
  629.         ipc_answer_0(rid, ENOMEM);
  630.         return;
  631.     }
  632.     int rc;
  633.     if ((rc = ipc_data_write_finalize(callid, path, len))) {
  634.         ipc_answer_0(rid, rc);
  635.         free(path);
  636.         return;
  637.     }
  638.     path[len] = '\0';
  639.    
  640.     rwlock_write_lock(&namespace_rwlock);
  641.     int lflag = L_DIRECTORY | L_CREATE | L_EXCLUSIVE;
  642.     rc = vfs_lookup_internal(path, lflag, NULL, NULL);
  643.     rwlock_write_unlock(&namespace_rwlock);
  644.     free(path);
  645.     ipc_answer_0(rid, rc);
  646. }
  647.  
  648. void vfs_unlink(ipc_callid_t rid, ipc_call_t *request)
  649. {
  650.     int lflag = IPC_GET_ARG1(*request);
  651.  
  652.     size_t len;
  653.     ipc_callid_t callid;
  654.  
  655.     if (!ipc_data_write_receive(&callid, &len)) {
  656.         ipc_answer_0(callid, EINVAL);
  657.         ipc_answer_0(rid, EINVAL);
  658.         return;
  659.     }
  660.     char *path = malloc(len + 1);
  661.     if (!path) {
  662.         ipc_answer_0(callid, ENOMEM);
  663.         ipc_answer_0(rid, ENOMEM);
  664.         return;
  665.     }
  666.     int rc;
  667.     if ((rc = ipc_data_write_finalize(callid, path, len))) {
  668.         ipc_answer_0(rid, rc);
  669.         free(path);
  670.         return;
  671.     }
  672.     path[len] = '\0';
  673.    
  674.     rwlock_write_lock(&namespace_rwlock);
  675.     lflag &= L_DIRECTORY;   /* sanitize lflag */
  676.     vfs_lookup_res_t lr;
  677.     rc = vfs_lookup_internal(path, lflag | L_UNLINK, &lr, NULL);
  678.     free(path);
  679.     if (rc != EOK) {
  680.         rwlock_write_unlock(&namespace_rwlock);
  681.         ipc_answer_0(rid, rc);
  682.         return;
  683.     }
  684.  
  685.     /*
  686.      * The name has already been unlinked by vfs_lookup_internal().
  687.      * We have to get and put the VFS node to ensure that it is
  688.      * VFS_DESTROY'ed after the last reference to it is dropped.
  689.      */
  690.     vfs_node_t *node = vfs_node_get(&lr);
  691.     futex_down(&nodes_futex);
  692.     node->lnkcnt--;
  693.     futex_up(&nodes_futex);
  694.     rwlock_write_unlock(&namespace_rwlock);
  695.     vfs_node_put(node);
  696.     ipc_answer_0(rid, EOK);
  697. }
  698.  
  699. void vfs_rename(ipc_callid_t rid, ipc_call_t *request)
  700. {
  701.     size_t len;
  702.     ipc_callid_t callid;
  703.     int rc;
  704.  
  705.     /* Retrieve the old path. */
  706.     if (!ipc_data_write_receive(&callid, &len)) {
  707.         ipc_answer_0(callid, EINVAL);
  708.         ipc_answer_0(rid, EINVAL);
  709.         return;
  710.     }
  711.     char *old = malloc(len + 1);
  712.     if (!old) {
  713.         ipc_answer_0(callid, ENOMEM);
  714.         ipc_answer_0(rid, ENOMEM);
  715.         return;
  716.     }
  717.     if ((rc = ipc_data_write_finalize(callid, old, len))) {
  718.         ipc_answer_0(rid, rc);
  719.         free(old);
  720.         return;
  721.     }
  722.     old[len] = '\0';
  723.    
  724.     /* Retrieve the new path. */
  725.     if (!ipc_data_write_receive(&callid, &len)) {
  726.         ipc_answer_0(callid, EINVAL);
  727.         ipc_answer_0(rid, EINVAL);
  728.         free(old);
  729.         return;
  730.     }
  731.     char *new = malloc(len + 1);
  732.     if (!new) {
  733.         ipc_answer_0(callid, ENOMEM);
  734.         ipc_answer_0(rid, ENOMEM);
  735.         free(old);
  736.         return;
  737.     }
  738.     if ((rc = ipc_data_write_finalize(callid, new, len))) {
  739.         ipc_answer_0(rid, rc);
  740.         free(old);
  741.         free(new);
  742.         return;
  743.     }
  744.     new[len] = '\0';
  745.  
  746.     char *oldc = canonify(old, &len);
  747.     char *newc = canonify(new, NULL);
  748.     if (!oldc || !newc) {
  749.         ipc_answer_0(rid, EINVAL);
  750.         free(old);
  751.         free(new);
  752.         return;
  753.     }
  754.     if (!strncmp(newc, oldc, len)) {
  755.         /* oldc is a prefix of newc */
  756.         ipc_answer_0(rid, EINVAL);
  757.         free(old);
  758.         free(new);
  759.         return;
  760.     }
  761.    
  762.     vfs_lookup_res_t old_lr;
  763.     vfs_lookup_res_t new_lr;
  764.     vfs_lookup_res_t new_par_lr;
  765.     rwlock_write_lock(&namespace_rwlock);
  766.     /* Lookup the node belonging to the old file name. */
  767.     rc = vfs_lookup_internal(oldc, L_NONE, &old_lr, NULL);
  768.     if (rc != EOK) {
  769.         rwlock_write_unlock(&namespace_rwlock);
  770.         ipc_answer_0(rid, rc);
  771.         free(old);
  772.         free(new);
  773.         return;
  774.     }
  775.     vfs_node_t *old_node = vfs_node_get(&old_lr);
  776.     if (!old_node) {
  777.         rwlock_write_unlock(&namespace_rwlock);
  778.         ipc_answer_0(rid, ENOMEM);
  779.         free(old);
  780.         free(new);
  781.         return;
  782.     }
  783.     /* Lookup parent of the new file name. */
  784.     rc = vfs_lookup_internal(newc, L_PARENT, &new_par_lr, NULL);
  785.     if (rc != EOK) {
  786.         rwlock_write_unlock(&namespace_rwlock);
  787.         ipc_answer_0(rid, rc);
  788.         free(old);
  789.         free(new);
  790.         return;
  791.     }
  792.     /* Check whether linking to the same file system instance. */
  793.     if ((old_node->fs_handle != new_par_lr.triplet.fs_handle) ||
  794.         (old_node->dev_handle != new_par_lr.triplet.dev_handle)) {
  795.         rwlock_write_unlock(&namespace_rwlock);
  796.         ipc_answer_0(rid, EXDEV);   /* different file systems */
  797.         free(old);
  798.         free(new);
  799.         return;
  800.     }
  801.     /* Destroy the old link for the new name. */
  802.     vfs_node_t *new_node = NULL;
  803.     rc = vfs_lookup_internal(newc, L_UNLINK, &new_lr, NULL);
  804.     switch (rc) {
  805.     case ENOENT:
  806.         /* simply not in our way */
  807.         break;
  808.     case EOK:
  809.         new_node = vfs_node_get(&new_lr);
  810.         if (!new_node) {
  811.             rwlock_write_unlock(&namespace_rwlock);
  812.             ipc_answer_0(rid, ENOMEM);
  813.             free(old);
  814.             free(new);
  815.             return;
  816.         }
  817.         futex_down(&nodes_futex);
  818.         new_node->lnkcnt--;
  819.         futex_up(&nodes_futex);
  820.         break;
  821.     default:
  822.         rwlock_write_unlock(&namespace_rwlock);
  823.         ipc_answer_0(rid, ENOTEMPTY);
  824.         free(old);
  825.         free(new);
  826.         return;
  827.     }
  828.     /* Create the new link for the new name. */
  829.     rc = vfs_lookup_internal(newc, L_LINK, NULL, NULL, old_node->index);
  830.     if (rc != EOK) {
  831.         rwlock_write_unlock(&namespace_rwlock);
  832.         if (new_node)
  833.             vfs_node_put(new_node);
  834.         ipc_answer_0(rid, rc);
  835.         free(old);
  836.         free(new);
  837.         return;
  838.     }
  839.     futex_down(&nodes_futex);
  840.     old_node->lnkcnt++;
  841.     futex_up(&nodes_futex);
  842.     /* Destroy the link for the old name. */
  843.     rc = vfs_lookup_internal(oldc, L_UNLINK, NULL, NULL);
  844.     if (rc != EOK) {
  845.         rwlock_write_unlock(&namespace_rwlock);
  846.         vfs_node_put(old_node);
  847.         if (new_node)
  848.             vfs_node_put(new_node);
  849.         ipc_answer_0(rid, rc);
  850.         free(old);
  851.         free(new);
  852.         return;
  853.     }
  854.     futex_down(&nodes_futex);
  855.     old_node->lnkcnt--;
  856.     futex_up(&nodes_futex);
  857.     rwlock_write_unlock(&namespace_rwlock);
  858.     vfs_node_put(old_node);
  859.     if (new_node)
  860.         vfs_node_put(new_node);
  861.     free(old);
  862.     free(new);
  863.     ipc_answer_0(rid, EOK);
  864. }
  865.  
  866. /**
  867.  * @}
  868.  */
  869.