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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.     /*
  83.      * Now, we expect the client to send us data with the name of the file
  84.      * system and the path of the mountpoint.
  85.      */
  86.     ipc_callid_t callid;
  87.     size_t size;
  88.     if (!ipc_data_receive(&callid, NULL, &size)) {
  89.         ipc_answer_0(callid, EINVAL);
  90.         ipc_answer_0(rid, EINVAL);
  91.         return;
  92.     }
  93.  
  94.     /*
  95.      * There is no sense in receiving data that can't hold a single
  96.      * character of path. We won't accept data that exceed certain limits
  97.      * either.
  98.      */
  99.     if ((size < FS_NAME_MAXLEN + 1) ||
  100.         (size > FS_NAME_MAXLEN + MAX_PATH_LEN)) {
  101.         ipc_answer_0(callid, EINVAL);
  102.         ipc_answer_0(rid, EINVAL);
  103.         return;
  104.     }
  105.  
  106.     /*
  107.      * Allocate buffer for the data being received.
  108.      */
  109.     uint8_t *buf;
  110.     buf = malloc(size);
  111.     if (!buf) {
  112.         ipc_answer_0(callid, ENOMEM);
  113.         ipc_answer_0(rid, ENOMEM);
  114.         return;
  115.     }
  116.  
  117.     /*
  118.      * Deliver the data.
  119.      */
  120.     (void) ipc_data_deliver(callid, buf, size);
  121.  
  122.     char fs_name[FS_NAME_MAXLEN + 1];
  123.     memcpy(fs_name, buf, FS_NAME_MAXLEN);
  124.     fs_name[FS_NAME_MAXLEN] = '\0';
  125.  
  126.     /*
  127.      * Check if we know a file system with the same name as is in fs_name.
  128.      * This will also give us its file system handle.
  129.      */
  130.     int fs_handle = fs_name_to_handle(fs_name, true);
  131.     if (!fs_handle) {
  132.         free(buf);
  133.         ipc_answer_0(rid, ENOENT);
  134.         return;
  135.     }
  136.  
  137.     /*
  138.      * Lookup the root node of the filesystem being mounted.
  139.      * In this case, we don't need to take the unlink_futex as the root node
  140.      * cannot be removed. However, we do take a reference to it so that
  141.      * we can track how many times it has been mounted.
  142.      */
  143.     int rc;
  144.     vfs_triplet_t mounted_root;
  145.     rc = lookup_root(fs_handle, dev_handle, &mounted_root);
  146.     if (rc != EOK) {
  147.         free(buf);
  148.         ipc_answer_0(rid, rc);
  149.         return;
  150.     }
  151.     vfs_node_t *mr_node = vfs_node_get(&mounted_root);
  152.     if (!mr_node) {
  153.         free(buf);
  154.         ipc_answer_0(rid, ENOMEM);
  155.         return;
  156.     }
  157.  
  158.     /*
  159.      * Finally, we need to resolve the path to the mountpoint.
  160.      */
  161.     vfs_triplet_t mp;
  162.     futex_down(&rootfs_futex);
  163.     if (rootfs.fs_handle) {
  164.         /*
  165.          * We already have the root FS.
  166.          */
  167.         futex_down(&unlink_futex);
  168.         rc = vfs_lookup_internal((char *) (buf + FS_NAME_MAXLEN),
  169.             size - FS_NAME_MAXLEN, &mp, NULL);
  170.         if (rc != EOK) {
  171.             /*
  172.              * The lookup failed for some reason.
  173.              */
  174.             futex_up(&unlink_futex);
  175.             futex_up(&rootfs_futex);
  176.             vfs_node_put(mr_node);  /* failed -> drop reference */
  177.             free(buf);
  178.             ipc_answer_0(rid, rc);
  179.             return;
  180.         }
  181.         mp_node = vfs_node_get(&mp);
  182.         if (!mp_node) {
  183.             futex_up(&unlink_futex);
  184.             futex_up(&rootfs_futex);
  185.             vfs_node_put(mr_node);  /* failed -> drop reference */
  186.             free(buf);
  187.             ipc_answer_0(rid, ENOMEM);
  188.             return;
  189.         }
  190.         /*
  191.          * Now we hold a reference to mp_node.
  192.          * It will be dropped upon the corresponding VFS_UNMOUNT.
  193.          * This prevents the mount point from being deleted.
  194.          */
  195.         futex_up(&unlink_futex);
  196.     } else {
  197.         /*
  198.          * We still don't have the root file system mounted.
  199.          */
  200.         if ((size - FS_NAME_MAXLEN == strlen("/")) &&
  201.             (buf[FS_NAME_MAXLEN] == '/')) {
  202.             /*
  203.              * For this simple, but important case, we are done.
  204.              */
  205.             rootfs = mounted_root;
  206.             futex_up(&rootfs_futex);
  207.             free(buf);
  208.             ipc_answer_0(rid, EOK);
  209.             return;
  210.         } else {
  211.             /*
  212.              * We can't resolve this without the root filesystem
  213.              * being mounted first.
  214.              */
  215.             futex_up(&rootfs_futex);
  216.             free(buf);
  217.             vfs_node_put(mr_node);  /* failed -> drop reference */
  218.             ipc_answer_0(rid, ENOENT);
  219.             return;
  220.         }
  221.     }
  222.     futex_up(&rootfs_futex);
  223.    
  224.     free(buf);  /* The buffer is not needed anymore. */
  225.    
  226.     /*
  227.      * At this point, we have all necessary pieces: file system and device
  228.      * handles, and we know the mount point VFS node and also the root node
  229.      * of the file system being mounted.
  230.      */
  231.  
  232.     int phone = vfs_grab_phone(mp.fs_handle);
  233.     /* Later we can use ARG3 to pass mode/flags. */
  234.     aid_t req1 = async_send_3(phone, VFS_MOUNT, (ipcarg_t) mp.dev_handle,
  235.         (ipcarg_t) mp.index, 0, NULL);
  236.     /* The second call uses the same method. */
  237.     aid_t req2 = async_send_3(phone, VFS_MOUNT,
  238.         (ipcarg_t) mounted_root.fs_handle,
  239.         (ipcarg_t) mounted_root.dev_handle, (ipcarg_t) mounted_root.index,
  240.         NULL);
  241.  
  242.     ipcarg_t rc1;
  243.     ipcarg_t rc2;
  244.     async_wait_for(req1, &rc1);
  245.     async_wait_for(req2, &rc2);
  246.     vfs_release_phone(phone);
  247.  
  248.     if ((rc1 != EOK) || (rc2 != EOK)) {
  249.         /* Mount failed, drop references to mr_node and mp_node. */
  250.         vfs_node_put(mr_node);
  251.         if (mp_node)
  252.             vfs_node_put(mp_node);
  253.     }
  254.    
  255.     if (rc2 == EOK)
  256.         ipc_answer_0(rid, rc1);
  257.     else if (rc1 == EOK)
  258.         ipc_answer_0(rid, rc2);
  259.     else
  260.         ipc_answer_0(rid, rc1);
  261. }
  262.  
  263. /**
  264.  * @}
  265.  */
  266.