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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 <ipc/ipc.h>
  39. #include <async.h>
  40. #include <errno.h>
  41. #include <stdio.h>
  42. #include <stdlib.h>
  43. #include <string.h>
  44. #include <bool.h>
  45. #include <futex.h>
  46. #include <rwlock.h>
  47. #include <libadt/list.h>
  48. #include <unistd.h>
  49. #include <ctype.h>
  50. #include <fcntl.h>
  51. #include <assert.h>
  52. #include <atomic.h>
  53. #include "vfs.h"
  54.  
  55. /* Forward declarations of static functions. */
  56. static int vfs_truncate_internal(int, int, unsigned long, 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. atomic_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 lookup_root(int fs_handle, int dev_handle, vfs_lookup_res_t *result)
  72. {
  73.     vfs_pair_t altroot = {
  74.         .fs_handle = fs_handle,
  75.         .dev_handle = dev_handle,
  76.     };
  77.  
  78.     return vfs_lookup_internal("/", strlen("/"), L_DIRECTORY, result,
  79.         &altroot);
  80. }
  81.  
  82. void vfs_mount(ipc_callid_t rid, ipc_call_t *request)
  83. {
  84.     int dev_handle;
  85.     vfs_node_t *mp_node = NULL;
  86.  
  87.     /*
  88.      * We expect the library to do the device-name to device-handle
  89.      * translation for us, thus the device handle will arrive as ARG1
  90.      * in the request.
  91.      */
  92.     dev_handle = IPC_GET_ARG1(*request);
  93.  
  94.     /*
  95.      * For now, don't make use of ARG2 and ARG3, but they can be used to
  96.      * carry mount options in the future.
  97.      */
  98.  
  99.     ipc_callid_t callid;
  100.     size_t size;
  101.  
  102.     /*
  103.      * Now, we expect the client to send us data with the name of the file
  104.      * system.
  105.      */
  106.     if (!ipc_data_write_receive(&callid, &size)) {
  107.         ipc_answer_0(callid, EINVAL);
  108.         ipc_answer_0(rid, EINVAL);
  109.         return;
  110.     }
  111.  
  112.     /*
  113.      * Don't receive more than is necessary for storing a full file system
  114.      * name.
  115.      */
  116.     if (size < 1 || size > FS_NAME_MAXLEN) {
  117.         ipc_answer_0(callid, EINVAL);
  118.         ipc_answer_0(rid, EINVAL);
  119.         return;
  120.     }
  121.  
  122.     /* Deliver the file system name. */
  123.     char fs_name[FS_NAME_MAXLEN + 1];
  124.     (void) ipc_data_write_finalize(callid, fs_name, size);
  125.     fs_name[size] = '\0';
  126.    
  127.     /*
  128.      * Check if we know a file system with the same name as is in fs_name.
  129.      * This will also give us its file system handle.
  130.      */
  131.     int fs_handle = fs_name_to_handle(fs_name, true);
  132.     if (!fs_handle) {
  133.         ipc_answer_0(rid, ENOENT);
  134.         return;
  135.     }
  136.  
  137.     /* Now, we want the client to send us the mount point. */
  138.     if (!ipc_data_write_receive(&callid, &size)) {
  139.         ipc_answer_0(callid, EINVAL);
  140.         ipc_answer_0(rid, EINVAL);
  141.         return;
  142.     }
  143.  
  144.     /* Check whether size is reasonable wrt. the mount point. */
  145.     if (size < 1 || size > MAX_PATH_LEN) {
  146.         ipc_answer_0(callid, EINVAL);
  147.         ipc_answer_0(rid, EINVAL);
  148.         return;
  149.     }
  150.     /* Allocate buffer for the mount point data being received. */
  151.     uint8_t *buf;
  152.     buf = malloc(size);
  153.     if (!buf) {
  154.         ipc_answer_0(callid, ENOMEM);
  155.         ipc_answer_0(rid, ENOMEM);
  156.         return;
  157.     }
  158.  
  159.     /* Deliver the mount point. */
  160.     (void) ipc_data_write_finalize(callid, buf, size);
  161.  
  162.     /*
  163.      * Lookup the root node of the filesystem being mounted.
  164.      * In this case, we don't need to take the namespace_futex as the root
  165.      * node cannot be removed. However, we do take a reference to it so
  166.      * that we can track how many times it has been mounted.
  167.      */
  168.     int rc;
  169.     vfs_lookup_res_t mr_res;
  170.     rc = lookup_root(fs_handle, dev_handle, &mr_res);
  171.     if (rc != EOK) {
  172.         free(buf);
  173.         ipc_answer_0(rid, rc);
  174.         return;
  175.     }
  176.     vfs_node_t *mr_node = vfs_node_get(&mr_res);
  177.     if (!mr_node) {
  178.         free(buf);
  179.         ipc_answer_0(rid, ENOMEM);
  180.         return;
  181.     }
  182.  
  183.     /* Finally, we need to resolve the path to the mountpoint. */
  184.     vfs_lookup_res_t mp_res;
  185.     futex_down(&rootfs_futex);
  186.     if (rootfs.fs_handle) {
  187.         /* We already have the root FS. */
  188.         rwlock_write_lock(&namespace_rwlock);
  189.         rc = vfs_lookup_internal(buf, size, L_DIRECTORY, &mp_res,
  190.             NULL);
  191.         if (rc != EOK) {
  192.             /* The lookup failed for some reason. */
  193.             rwlock_write_unlock(&namespace_rwlock);
  194.             futex_up(&rootfs_futex);
  195.             vfs_node_put(mr_node);  /* failed -> drop reference */
  196.             free(buf);
  197.             ipc_answer_0(rid, rc);
  198.             return;
  199.         }
  200.         mp_node = vfs_node_get(&mp_res);
  201.         if (!mp_node) {
  202.             rwlock_write_unlock(&namespace_rwlock);
  203.             futex_up(&rootfs_futex);
  204.             vfs_node_put(mr_node);  /* failed -> drop reference */
  205.             free(buf);
  206.             ipc_answer_0(rid, ENOMEM);
  207.             return;
  208.         }
  209.         /*
  210.          * Now we hold a reference to mp_node.
  211.          * It will be dropped upon the corresponding VFS_UNMOUNT.
  212.          * This prevents the mount point from being deleted.
  213.          */
  214.         rwlock_write_unlock(&namespace_rwlock);
  215.     } else {
  216.         /* We still don't have the root file system mounted. */
  217.         if ((size == 1) && (buf[0] == '/')) {
  218.             /* For this simple, but important case, we are done. */
  219.             rootfs = mr_res.triplet;
  220.             futex_up(&rootfs_futex);
  221.             free(buf);
  222.             ipc_answer_0(rid, EOK);
  223.             return;
  224.         } else {
  225.             /*
  226.              * We can't resolve this without the root filesystem
  227.              * being mounted first.
  228.              */
  229.             futex_up(&rootfs_futex);
  230.             free(buf);
  231.             vfs_node_put(mr_node);  /* failed -> drop reference */
  232.             ipc_answer_0(rid, ENOENT);
  233.             return;
  234.         }
  235.     }
  236.     futex_up(&rootfs_futex);
  237.    
  238.     free(buf);  /* The buffer is not needed anymore. */
  239.    
  240.     /*
  241.      * At this point, we have all necessary pieces: file system and device
  242.      * handles, and we know the mount point VFS node and also the root node
  243.      * of the file system being mounted.
  244.      */
  245.  
  246.     int phone = vfs_grab_phone(mp_res.triplet.fs_handle);
  247.     /* Later we can use ARG3 to pass mode/flags. */
  248.     aid_t req1 = async_send_3(phone, VFS_MOUNT,
  249.         (ipcarg_t) mp_res.triplet.dev_handle,
  250.         (ipcarg_t) mp_res.triplet.index, 0, NULL);
  251.     /* The second call uses the same method. */
  252.     aid_t req2 = async_send_3(phone, VFS_MOUNT,
  253.         (ipcarg_t) mr_res.triplet.fs_handle,
  254.         (ipcarg_t) mr_res.triplet.dev_handle,
  255.         (ipcarg_t) mr_res.triplet.index, NULL);
  256.     vfs_release_phone(phone);
  257.  
  258.     ipcarg_t rc1;
  259.     ipcarg_t rc2;
  260.     async_wait_for(req1, &rc1);
  261.     async_wait_for(req2, &rc2);
  262.  
  263.     if ((rc1 != EOK) || (rc2 != EOK)) {
  264.         /* Mount failed, drop references to mr_node and mp_node. */
  265.         vfs_node_put(mr_node);
  266.         if (mp_node)
  267.             vfs_node_put(mp_node);
  268.     }
  269.    
  270.     if (rc2 == EOK)
  271.         ipc_answer_0(rid, rc1);
  272.     else if (rc1 == EOK)
  273.         ipc_answer_0(rid, rc2);
  274.     else
  275.         ipc_answer_0(rid, rc1);
  276. }
  277.  
  278. void vfs_open(ipc_callid_t rid, ipc_call_t *request)
  279. {
  280.     if (!vfs_files_init()) {
  281.         ipc_answer_0(rid, ENOMEM);
  282.         return;
  283.     }
  284.  
  285.     /*
  286.      * The POSIX interface is open(path, oflag, mode).
  287.      * We can receive oflags and mode along with the VFS_OPEN call; the path
  288.      * will need to arrive in another call.
  289.      *
  290.      * We also receive one private, non-POSIX set of flags called lflag
  291.      * used to pass information to vfs_lookup_internal().
  292.      */
  293.     int lflag = IPC_GET_ARG1(*request);
  294.     int oflag = IPC_GET_ARG2(*request);
  295.     int mode = IPC_GET_ARG3(*request);
  296.     size_t len;
  297.  
  298.     if (oflag & O_CREAT)
  299.         lflag |= L_CREATE;
  300.     if (oflag & O_EXCL)
  301.         lflag |= L_EXCLUSIVE;
  302.  
  303.     ipc_callid_t callid;
  304.  
  305.     if (!ipc_data_write_receive(&callid, &len)) {
  306.         ipc_answer_0(callid, EINVAL);
  307.         ipc_answer_0(rid, EINVAL);
  308.         return;
  309.     }
  310.  
  311.     /*
  312.      * Now we are on the verge of accepting the path.
  313.      *
  314.      * There is one optimization we could do in the future: copy the path
  315.      * directly into the PLB using some kind of a callback.
  316.      */
  317.     char *path = malloc(len);
  318.    
  319.     if (!path) {
  320.         ipc_answer_0(callid, ENOMEM);
  321.         ipc_answer_0(rid, ENOMEM);
  322.         return;
  323.     }
  324.  
  325.     int rc;
  326.     if ((rc = ipc_data_write_finalize(callid, path, len))) {
  327.         ipc_answer_0(rid, rc);
  328.         free(path);
  329.         return;
  330.     }
  331.    
  332.     /*
  333.      * Avoid the race condition in which the file can be deleted before we
  334.      * find/create-and-lock the VFS node corresponding to the looked-up
  335.      * triplet.
  336.      */
  337.     if (lflag & L_CREATE)
  338.         rwlock_write_lock(&namespace_rwlock);
  339.     else
  340.         rwlock_read_lock(&namespace_rwlock);
  341.  
  342.     /* The path is now populated and we can call vfs_lookup_internal(). */
  343.     vfs_lookup_res_t lr;
  344.     rc = vfs_lookup_internal(path, len, lflag, &lr, NULL);
  345.     if (rc) {
  346.         if (lflag & L_CREATE)
  347.             rwlock_write_unlock(&namespace_rwlock);
  348.         else
  349.             rwlock_read_unlock(&namespace_rwlock);
  350.         ipc_answer_0(rid, rc);
  351.         free(path);
  352.         return;
  353.     }
  354.  
  355.     /* Path is no longer needed. */
  356.     free(path);
  357.  
  358.     vfs_node_t *node = vfs_node_get(&lr);
  359.     if (lflag & L_CREATE)
  360.         rwlock_write_unlock(&namespace_rwlock);
  361.     else
  362.         rwlock_read_unlock(&namespace_rwlock);
  363.  
  364.     /* Truncate the file if requested and if necessary. */
  365.     if (oflag & O_TRUNC) {
  366.         rwlock_write_lock(&node->contents_rwlock);
  367.         if (node->size) {
  368.             rc = vfs_truncate_internal(node->fs_handle,
  369.                 node->dev_handle, node->index, 0);
  370.             if (rc) {
  371.                 rwlock_write_unlock(&node->contents_rwlock);
  372.                 vfs_node_put(node);
  373.                 ipc_answer_0(rid, rc);
  374.                 return;
  375.             }
  376.             node->size = 0;
  377.         }
  378.         rwlock_write_unlock(&node->contents_rwlock);
  379.     }
  380.  
  381.     /*
  382.      * Get ourselves a file descriptor and the corresponding vfs_file_t
  383.      * structure.
  384.      */
  385.     int fd = vfs_fd_alloc();
  386.     if (fd < 0) {
  387.         vfs_node_put(node);
  388.         ipc_answer_0(rid, fd);
  389.         return;
  390.     }
  391.     vfs_file_t *file = vfs_file_get(fd);
  392.     file->node = node;
  393.     if (oflag & O_APPEND)
  394.         file->append = true;
  395.  
  396.     /*
  397.      * The following increase in reference count is for the fact that the
  398.      * file is being opened and that a file structure is pointing to it.
  399.      * It is necessary so that the file will not disappear when
  400.      * vfs_node_put() is called. The reference will be dropped by the
  401.      * respective VFS_CLOSE.
  402.      */
  403.     vfs_node_addref(node);
  404.     vfs_node_put(node);
  405.  
  406.     /* Success! Return the new file descriptor to the client. */
  407.     ipc_answer_1(rid, EOK, fd);
  408. }
  409.  
  410. void vfs_close(ipc_callid_t rid, ipc_call_t *request)
  411. {
  412.     int fd = IPC_GET_ARG1(*request);
  413.     if (fd >= MAX_OPEN_FILES) {
  414.         ipc_answer_0(rid, EBADF);
  415.         return;
  416.     }
  417.     vfs_fd_free(fd);
  418.     ipc_answer_0(rid, EOK);
  419. }
  420.  
  421. static void vfs_rdwr(ipc_callid_t rid, ipc_call_t *request, bool read)
  422. {
  423.  
  424.     /*
  425.      * The following code strongly depends on the fact that the files data
  426.      * structure can be only accessed by a single fibril and all file
  427.      * operations are serialized (i.e. the reads and writes cannot
  428.      * interleave and a file cannot be closed while it is being read).
  429.      *
  430.      * Additional synchronization needs to be added once the table of
  431.      * open files supports parallel access!
  432.      */
  433.  
  434.     int fd = IPC_GET_ARG1(*request);
  435.  
  436.     /* Lookup the file structure corresponding to the file descriptor. */
  437.     vfs_file_t *file = vfs_file_get(fd);
  438.     if (!file) {
  439.         ipc_answer_0(rid, ENOENT);
  440.         return;
  441.     }
  442.  
  443.     /*
  444.      * Now we need to receive a call with client's
  445.      * IPC_M_DATA_READ/IPC_M_DATA_WRITE request.
  446.      */
  447.     ipc_callid_t callid;
  448.     int res;
  449.     if (read)
  450.         res = ipc_data_read_receive(&callid, NULL);
  451.     else
  452.         res = ipc_data_write_receive(&callid, NULL);
  453.     if (!res) {
  454.         ipc_answer_0(callid, EINVAL);
  455.         ipc_answer_0(rid, EINVAL);
  456.         return;
  457.     }
  458.  
  459.     /*
  460.      * Lock the open file structure so that no other thread can manipulate
  461.      * the same open file at a time.
  462.      */
  463.     futex_down(&file->lock);
  464.  
  465.     /*
  466.      * Lock the file's node so that no other client can read/write to it at
  467.      * the same time.
  468.      */
  469.     if (read)
  470.         rwlock_read_lock(&file->node->contents_rwlock);
  471.     else
  472.         rwlock_write_lock(&file->node->contents_rwlock);
  473.  
  474.     int fs_phone = vfs_grab_phone(file->node->fs_handle);  
  475.    
  476.     /* Make a VFS_READ/VFS_WRITE request at the destination FS server. */
  477.     aid_t msg;
  478.     ipc_call_t answer;
  479.     if (!read && file->append)
  480.         file->pos = file->node->size;
  481.     msg = async_send_3(fs_phone, IPC_GET_METHOD(*request),
  482.         file->node->dev_handle, file->node->index, file->pos, &answer);
  483.    
  484.     /*
  485.      * Forward the IPC_M_DATA_READ/IPC_M_DATA_WRITE request to the
  486.      * destination FS server. The call will be routed as if sent by
  487.      * ourselves. Note that call arguments are immutable in this case so we
  488.      * don't have to bother.
  489.      */
  490.     ipc_forward_fast(callid, fs_phone, 0, 0, 0, IPC_FF_ROUTE_FROM_ME);
  491.  
  492.     vfs_release_phone(fs_phone);
  493.  
  494.     /* Wait for reply from the FS server. */
  495.     ipcarg_t rc;
  496.     async_wait_for(msg, &rc);
  497.     size_t bytes = IPC_GET_ARG1(answer);
  498.  
  499.     /* Unlock the VFS node. */
  500.     if (read)
  501.         rwlock_read_unlock(&file->node->contents_rwlock);
  502.     else {
  503.         /* Update the cached version of node's size. */
  504.         if (rc == EOK)
  505.             file->node->size = IPC_GET_ARG2(answer);
  506.         rwlock_write_unlock(&file->node->contents_rwlock);
  507.     }
  508.  
  509.     /* Update the position pointer and unlock the open file. */
  510.     if (rc == EOK)
  511.         file->pos += bytes;
  512.     futex_up(&file->lock);
  513.  
  514.     /*
  515.      * FS server's reply is the final result of the whole operation we
  516.      * return to the client.
  517.      */
  518.     ipc_answer_1(rid, rc, bytes);
  519. }
  520.  
  521. void vfs_read(ipc_callid_t rid, ipc_call_t *request)
  522. {
  523.     vfs_rdwr(rid, request, true);
  524. }
  525.  
  526. void vfs_write(ipc_callid_t rid, ipc_call_t *request)
  527. {
  528.     vfs_rdwr(rid, request, false);
  529. }
  530.  
  531. void vfs_seek(ipc_callid_t rid, ipc_call_t *request)
  532. {
  533.     int fd = (int) IPC_GET_ARG1(*request);
  534.     off_t off = (off_t) IPC_GET_ARG2(*request);
  535.     int whence = (int) IPC_GET_ARG3(*request);
  536.  
  537.  
  538.     /* Lookup the file structure corresponding to the file descriptor. */
  539.     vfs_file_t *file = vfs_file_get(fd);
  540.     if (!file) {
  541.         ipc_answer_0(rid, ENOENT);
  542.         return;
  543.     }
  544.  
  545.     off_t newpos;
  546.     futex_down(&file->lock);
  547.     if (whence == SEEK_SET) {
  548.         file->pos = off;
  549.         futex_up(&file->lock);
  550.         ipc_answer_1(rid, EOK, off);
  551.         return;
  552.     }
  553.     if (whence == SEEK_CUR) {
  554.         if (file->pos + off < file->pos) {
  555.             futex_up(&file->lock);
  556.             ipc_answer_0(rid, EOVERFLOW);
  557.             return;
  558.         }
  559.         file->pos += off;
  560.         newpos = file->pos;
  561.         futex_up(&file->lock);
  562.         ipc_answer_1(rid, EOK, newpos);
  563.         return;
  564.     }
  565.     if (whence == SEEK_END) {
  566.         rwlock_read_lock(&file->node->contents_rwlock);
  567.         size_t size = file->node->size;
  568.         rwlock_read_unlock(&file->node->contents_rwlock);
  569.         if (size + off < size) {
  570.             futex_up(&file->lock);
  571.             ipc_answer_0(rid, EOVERFLOW);
  572.             return;
  573.         }
  574.         newpos = size + off;
  575.         futex_up(&file->lock);
  576.         ipc_answer_1(rid, EOK, newpos);
  577.         return;
  578.     }
  579.     futex_up(&file->lock);
  580.     ipc_answer_0(rid, EINVAL);
  581. }
  582.  
  583. int vfs_truncate_internal(int fs_handle, int dev_handle, unsigned long index,
  584.     size_t size)
  585. {
  586.     ipcarg_t rc;
  587.     int fs_phone;
  588.    
  589.     fs_phone = vfs_grab_phone(fs_handle);
  590.     rc = async_req_3_0(fs_phone, VFS_TRUNCATE, (ipcarg_t)dev_handle,
  591.         (ipcarg_t)index, (ipcarg_t)size);
  592.     vfs_release_phone(fs_phone);
  593.     return (int)rc;
  594. }
  595.  
  596. void vfs_truncate(ipc_callid_t rid, ipc_call_t *request)
  597. {
  598.     int fd = IPC_GET_ARG1(*request);
  599.     size_t size = IPC_GET_ARG2(*request);
  600.     int rc;
  601.  
  602.     vfs_file_t *file = vfs_file_get(fd);
  603.     if (!file) {
  604.         ipc_answer_0(rid, ENOENT);
  605.         return;
  606.     }
  607.     futex_down(&file->lock);
  608.  
  609.     rwlock_write_lock(&file->node->contents_rwlock);
  610.     rc = vfs_truncate_internal(file->node->fs_handle,
  611.         file->node->dev_handle, file->node->index, size);
  612.     if (rc == EOK)
  613.         file->node->size = size;
  614.     rwlock_write_unlock(&file->node->contents_rwlock);
  615.  
  616.     futex_up(&file->lock);
  617.     ipc_answer_0(rid, (ipcarg_t)rc);
  618. }
  619.  
  620. void vfs_mkdir(ipc_callid_t rid, ipc_call_t *request)
  621. {
  622.     int mode = IPC_GET_ARG1(*request);
  623.  
  624.     size_t len;
  625.     ipc_callid_t callid;
  626.  
  627.     if (!ipc_data_write_receive(&callid, &len)) {
  628.         ipc_answer_0(callid, EINVAL);
  629.         ipc_answer_0(rid, EINVAL);
  630.         return;
  631.     }
  632.  
  633.     /*
  634.      * Now we are on the verge of accepting the path.
  635.      *
  636.      * There is one optimization we could do in the future: copy the path
  637.      * directly into the PLB using some kind of a callback.
  638.      */
  639.     char *path = malloc(len);
  640.    
  641.     if (!path) {
  642.         ipc_answer_0(callid, ENOMEM);
  643.         ipc_answer_0(rid, ENOMEM);
  644.         return;
  645.     }
  646.  
  647.     int rc;
  648.     if ((rc = ipc_data_write_finalize(callid, path, len))) {
  649.         ipc_answer_0(rid, rc);
  650.         free(path);
  651.         return;
  652.     }
  653.    
  654.     rwlock_write_lock(&namespace_rwlock);
  655.     int lflag = L_DIRECTORY | L_CREATE | L_EXCLUSIVE;
  656.     rc = vfs_lookup_internal(path, len, lflag, NULL, NULL);
  657.     rwlock_write_unlock(&namespace_rwlock);
  658.     free(path);
  659.     ipc_answer_0(rid, rc);
  660. }
  661.  
  662. void vfs_unlink(ipc_callid_t rid, ipc_call_t *request)
  663. {
  664.     int lflag = IPC_GET_ARG1(*request);
  665.  
  666.     size_t len;
  667.     ipc_callid_t callid;
  668.  
  669.     if (!ipc_data_write_receive(&callid, &len)) {
  670.         ipc_answer_0(callid, EINVAL);
  671.         ipc_answer_0(rid, EINVAL);
  672.         return;
  673.     }
  674.  
  675.     /*
  676.      * Now we are on the verge of accepting the path.
  677.      *
  678.      * There is one optimization we could do in the future: copy the path
  679.      * directly into the PLB using some kind of a callback.
  680.      */
  681.     char *path = malloc(len);
  682.    
  683.     if (!path) {
  684.         ipc_answer_0(callid, ENOMEM);
  685.         ipc_answer_0(rid, ENOMEM);
  686.         return;
  687.     }
  688.  
  689.     int rc;
  690.     if ((rc = ipc_data_write_finalize(callid, path, len))) {
  691.         ipc_answer_0(rid, rc);
  692.         free(path);
  693.         return;
  694.     }
  695.    
  696.     rwlock_write_lock(&namespace_rwlock);
  697.     lflag &= L_DIRECTORY;   /* sanitize lflag */
  698.     vfs_lookup_res_t lr;
  699.     rc = vfs_lookup_internal(path, len, lflag | L_DESTROY, &lr, NULL);
  700.     free(path);
  701.     if (rc != EOK) {
  702.         rwlock_write_unlock(&namespace_rwlock);
  703.         ipc_answer_0(rid, rc);
  704.         return;
  705.     }
  706.  
  707.     /*
  708.      * The name has already been unlinked by vfs_lookup_internal().
  709.      * We have to get and put the VFS node to ensure that it is
  710.      * VFS_DESTROY'ed after the last reference to it is dropped.
  711.      */
  712.     vfs_node_t *node = vfs_node_get(&lr);
  713.     node->lnkcnt--;
  714.     rwlock_write_unlock(&namespace_rwlock);
  715.     vfs_node_put(node);
  716.     ipc_answer_0(rid, EOK);
  717. }
  718.  
  719. /**
  720.  * @}
  721.  */
  722.