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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_mount.c
  35.  * @brief   VFS_MOUNT method.
  36.  */
  37.  
  38. #include <ipc/ipc.h>
  39. #include <async.h>
  40. #include <errno.h>
  41. #include <stdlib.h>
  42. #include <string.h>
  43. #include <bool.h>
  44. #include <futex.h>
  45. #include <libadt/list.h>
  46. #include "vfs.h"
  47.  
  48. atomic_t rootfs_futex = FUTEX_INITIALIZER;
  49. vfs_triplet_t rootfs = {
  50.     .fs_handle = 0,
  51.     .dev_handle = 0,
  52.     .index = 0,
  53. };
  54.  
  55. static int lookup_root(int fs_handle, int dev_handle, vfs_triplet_t *root)
  56. {
  57.     vfs_pair_t altroot = {
  58.         .fs_handle = fs_handle,
  59.         .dev_handle = dev_handle,
  60.     };
  61.  
  62.     return vfs_lookup_internal("/", strlen("/"), root, &altroot);
  63. }
  64.  
  65. void vfs_mount(ipc_callid_t rid, ipc_call_t *request)
  66. {
  67.     int dev_handle;
  68.     vfs_node_t *mp_node = NULL;
  69.  
  70.     /*
  71.      * We expect the library to do the device-name to device-handle
  72.      * translation for us, thus the device handle will arrive as ARG1
  73.      * in the request.
  74.      */
  75.     dev_handle = IPC_GET_ARG1(*request);
  76.  
  77.     /*
  78.      * For now, don't make use of ARG2 and ARG3, but they can be used to
  79.      * carry mount options in the future.
  80.      */
  81.  
  82.     ipc_callid_t callid;
  83.     size_t size;
  84.  
  85.     /*
  86.      * Now, we expect the client to send us data with the name of the file
  87.      * system.
  88.      */
  89.     if (!ipc_data_write_receive(&callid, &size)) {
  90.         ipc_answer_0(callid, EINVAL);
  91.         ipc_answer_0(rid, EINVAL);
  92.         return;
  93.     }
  94.  
  95.     /*
  96.      * Don't receive more than is necessary for storing a full file system
  97.      * name.
  98.      */
  99.     if (size < 1 || size > FS_NAME_MAXLEN) {
  100.         ipc_answer_0(callid, EINVAL);
  101.         ipc_answer_0(rid, EINVAL);
  102.         return;
  103.     }
  104.  
  105.     /*
  106.      * Deliver the file system name.
  107.      */
  108.     char fs_name[FS_NAME_MAXLEN + 1];
  109.     (void) ipc_data_write_finalize(callid, fs_name, size);
  110.     fs_name[size] = '\0';
  111.    
  112.     /*
  113.      * Check if we know a file system with the same name as is in fs_name.
  114.      * This will also give us its file system handle.
  115.      */
  116.     int fs_handle = fs_name_to_handle(fs_name, true);
  117.     if (!fs_handle) {
  118.         ipc_answer_0(rid, ENOENT);
  119.         return;
  120.     }
  121.  
  122.     /*
  123.      * Now, we want the client to send us the mount point.
  124.      */
  125.     if (!ipc_data_write_receive(&callid, &size)) {
  126.         ipc_answer_0(callid, EINVAL);
  127.         ipc_answer_0(rid, EINVAL);
  128.         return;
  129.     }
  130.  
  131.     /*
  132.      * Check whether size is reasonable wrt. the mount point.
  133.      */
  134.     if (size < 1 || size > MAX_PATH_LEN) {
  135.         ipc_answer_0(callid, EINVAL);
  136.         ipc_answer_0(rid, EINVAL);
  137.         return;
  138.     }
  139.     /*
  140.      * Allocate buffer for the mount point data being received.
  141.      */
  142.     uint8_t *buf;
  143.     buf = malloc(size);
  144.     if (!buf) {
  145.         ipc_answer_0(callid, ENOMEM);
  146.         ipc_answer_0(rid, ENOMEM);
  147.         return;
  148.     }
  149.  
  150.     /*
  151.      * Deliver the mount point.
  152.      */
  153.     (void) ipc_data_write_finalize(callid, buf, size);
  154.  
  155.     /*
  156.      * Lookup the root node of the filesystem being mounted.
  157.      * In this case, we don't need to take the unlink_futex as the root node
  158.      * cannot be removed. However, we do take a reference to it so that
  159.      * we can track how many times it has been mounted.
  160.      */
  161.     int rc;
  162.     vfs_triplet_t mounted_root;
  163.     rc = lookup_root(fs_handle, dev_handle, &mounted_root);
  164.     if (rc != EOK) {
  165.         free(buf);
  166.         ipc_answer_0(rid, rc);
  167.         return;
  168.     }
  169.     vfs_node_t *mr_node = vfs_node_get(&mounted_root);
  170.     if (!mr_node) {
  171.         free(buf);
  172.         ipc_answer_0(rid, ENOMEM);
  173.         return;
  174.     }
  175.  
  176.     /*
  177.      * Finally, we need to resolve the path to the mountpoint.
  178.      */
  179.     vfs_triplet_t mp;
  180.     futex_down(&rootfs_futex);
  181.     if (rootfs.fs_handle) {
  182.         /*
  183.          * We already have the root FS.
  184.          */
  185.         futex_down(&unlink_futex);
  186.         rc = vfs_lookup_internal(buf, size, &mp, NULL);
  187.         if (rc != EOK) {
  188.             /*
  189.              * The lookup failed for some reason.
  190.              */
  191.             futex_up(&unlink_futex);
  192.             futex_up(&rootfs_futex);
  193.             vfs_node_put(mr_node);  /* failed -> drop reference */
  194.             free(buf);
  195.             ipc_answer_0(rid, rc);
  196.             return;
  197.         }
  198.         mp_node = vfs_node_get(&mp);
  199.         if (!mp_node) {
  200.             futex_up(&unlink_futex);
  201.             futex_up(&rootfs_futex);
  202.             vfs_node_put(mr_node);  /* failed -> drop reference */
  203.             free(buf);
  204.             ipc_answer_0(rid, ENOMEM);
  205.             return;
  206.         }
  207.         /*
  208.          * Now we hold a reference to mp_node.
  209.          * It will be dropped upon the corresponding VFS_UNMOUNT.
  210.          * This prevents the mount point from being deleted.
  211.          */
  212.         futex_up(&unlink_futex);
  213.     } else {
  214.         /*
  215.          * We still don't have the root file system mounted.
  216.          */
  217.         if ((size == 1) && (buf[0] == '/')) {
  218.             /*
  219.              * For this simple, but important case, we are done.
  220.              */
  221.             rootfs = mounted_root;
  222.             futex_up(&rootfs_futex);
  223.             free(buf);
  224.             ipc_answer_0(rid, EOK);
  225.             return;
  226.         } else {
  227.             /*
  228.              * We can't resolve this without the root filesystem
  229.              * being mounted first.
  230.              */
  231.             futex_up(&rootfs_futex);
  232.             free(buf);
  233.             vfs_node_put(mr_node);  /* failed -> drop reference */
  234.             ipc_answer_0(rid, ENOENT);
  235.             return;
  236.         }
  237.     }
  238.     futex_up(&rootfs_futex);
  239.    
  240.     free(buf);  /* The buffer is not needed anymore. */
  241.    
  242.     /*
  243.      * At this point, we have all necessary pieces: file system and device
  244.      * handles, and we know the mount point VFS node and also the root node
  245.      * of the file system being mounted.
  246.      */
  247.  
  248.     int phone = vfs_grab_phone(mp.fs_handle);
  249.     /* Later we can use ARG3 to pass mode/flags. */
  250.     aid_t req1 = async_send_3(phone, VFS_MOUNT, (ipcarg_t) mp.dev_handle,
  251.         (ipcarg_t) mp.index, 0, NULL);
  252.     /* The second call uses the same method. */
  253.     aid_t req2 = async_send_3(phone, VFS_MOUNT,
  254.         (ipcarg_t) mounted_root.fs_handle,
  255.         (ipcarg_t) mounted_root.dev_handle, (ipcarg_t) mounted_root.index,
  256.         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. /**
  280.  * @}
  281.  */
  282.