Subversion Repositories HelenOS

/*

 * Copyright (c) 2007 Jakub Jermar

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * - Redistributions of source code must retain the above copyright

 *   notice, this list of conditions and the following disclaimer.

 * - Redistributions in binary form must reproduce the above copyright

 *   notice, this list of conditions and the following disclaimer in the

 *   documentation and/or other materials provided with the distribution.

 * - The name of the author may not be used to endorse or promote products

 *   derived from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES

 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.

 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,

 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT

 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

/** @addtogroup fs

 * @{

 */

/**

 * @file    vfs_mount.c

 * @brief   VFS_MOUNT method.

 */

#include <ipc/ipc.h>

#include <async.h>

#include <errno.h>

#include <stdlib.h>

#include <string.h>

#include <bool.h>

#include <futex.h>

#include <libadt/list.h>

#include "vfs.h"

atomic_t rootfs_futex = FUTEX_INITIALIZER;

vfs_triplet_t rootfs = {

    .fs_handle = 0,

    .dev_handle = 0,

    .index = 0,

};

static int lookup_root(int fs_handle, int dev_handle, vfs_triplet_t *root)

{

    vfs_pair_t altroot = {

        .fs_handle = fs_handle,

        .dev_handle = dev_handle,

    };

    return vfs_lookup_internal("/", strlen("/"), root, &altroot);

}

void vfs_mount(ipc_callid_t rid, ipc_call_t *request)

{

    int dev_handle;

    vfs_node_t *mp_node = NULL;

    /*

     * We expect the library to do the device-name to device-handle

     * translation for us, thus the device handle will arrive as ARG1

     * in the request.

     */

    dev_handle = IPC_GET_ARG1(*request);

    /*

     * For now, don't make use of ARG2 and ARG3, but they can be used to

     * carry mount options in the future.

     */

    ipc_callid_t callid;

    size_t size;

    /*

     * Now, we expect the client to send us data with the name of the file

     * system.

     */

    if (!ipc_data_write_receive(&callid, &size)) {

        ipc_answer_0(callid, EINVAL);

        ipc_answer_0(rid, EINVAL);

        return;

    }

    /*

     * Don't receive more than is necessary for storing a full file system

     * name.

     */

    if (size < 1 || size > FS_NAME_MAXLEN) {

        ipc_answer_0(callid, EINVAL);

        ipc_answer_0(rid, EINVAL);

        return;

    }

    /*

     * Deliver the file system name.

     */

    char fs_name[FS_NAME_MAXLEN + 1];

    (void) ipc_data_write_finalize(callid, fs_name, size);

    fs_name[size] = '\0';

    /*

     * Check if we know a file system with the same name as is in fs_name.

     * This will also give us its file system handle.

     */

    int fs_handle = fs_name_to_handle(fs_name, true);

    if (!fs_handle) {

        ipc_answer_0(rid, ENOENT);

        return;

    }

    /*

     * Now, we want the client to send us the mount point.

     */

    if (!ipc_data_write_receive(&callid, &size)) {

        ipc_answer_0(callid, EINVAL);

        ipc_answer_0(rid, EINVAL);

        return;

    }

    /*

     * Check whether size is reasonable wrt. the mount point.

     */

    if (size < 1 || size > MAX_PATH_LEN) {

        ipc_answer_0(callid, EINVAL);

        ipc_answer_0(rid, EINVAL);

        return;

    }

    /*

     * Allocate buffer for the mount point data being received.

     */

    uint8_t *buf;

    buf = malloc(size);

    if (!buf) {

        ipc_answer_0(callid, ENOMEM);

        ipc_answer_0(rid, ENOMEM);

        return;

    }

    /*

     * Deliver the mount point.

     */

    (void) ipc_data_write_finalize(callid, buf, size);

    /*

     * Lookup the root node of the filesystem being mounted.

     * In this case, we don't need to take the unlink_futex as the root node

     * cannot be removed. However, we do take a reference to it so that

     * we can track how many times it has been mounted.

     */

    int rc;

    vfs_triplet_t mounted_root;

    rc = lookup_root(fs_handle, dev_handle, &mounted_root);

    if (rc != EOK) {

        free(buf);

        ipc_answer_0(rid, rc);

        return;

    }

    vfs_node_t *mr_node = vfs_node_get(&mounted_root);

    if (!mr_node) {

        free(buf);

        ipc_answer_0(rid, ENOMEM);

        return;

    }

    /*

     * Finally, we need to resolve the path to the mountpoint.

     */

    vfs_triplet_t mp;

    futex_down(&rootfs_futex);

    if (rootfs.fs_handle) {

        /*

         * We already have the root FS.

         */

        futex_down(&unlink_futex);

        rc = vfs_lookup_internal(buf, size, &mp, NULL);

        if (rc != EOK) {

            /*

             * The lookup failed for some reason.

             */

            futex_up(&unlink_futex);

            futex_up(&rootfs_futex);

            vfs_node_put(mr_node);  /* failed -> drop reference */

            free(buf);

            ipc_answer_0(rid, rc);

            return;

        }

        mp_node = vfs_node_get(&mp);

        if (!mp_node) {

            futex_up(&unlink_futex);

            futex_up(&rootfs_futex);

            vfs_node_put(mr_node);  /* failed -> drop reference */

            free(buf);

            ipc_answer_0(rid, ENOMEM);

            return;

        }

        /*

         * Now we hold a reference to mp_node.

         * It will be dropped upon the corresponding VFS_UNMOUNT.

         * This prevents the mount point from being deleted.

         */

        futex_up(&unlink_futex);

    } else {

        /*

         * We still don't have the root file system mounted.

         */

        if ((size == 1) && (buf[0] == '/')) {

            /*

             * For this simple, but important case, we are done.

             */

            rootfs = mounted_root;

            futex_up(&rootfs_futex);

            free(buf);

            ipc_answer_0(rid, EOK);

            return;

        } else {

            /*

             * We can't resolve this without the root filesystem

             * being mounted first.

             */

            futex_up(&rootfs_futex);

            free(buf);

            vfs_node_put(mr_node);  /* failed -> drop reference */

            ipc_answer_0(rid, ENOENT);

            return;

        }

    }

    futex_up(&rootfs_futex);

    free(buf);  /* The buffer is not needed anymore. */

    /*

     * At this point, we have all necessary pieces: file system and device

     * handles, and we know the mount point VFS node and also the root node

     * of the file system being mounted.

     */

    int phone = vfs_grab_phone(mp.fs_handle);

    /* Later we can use ARG3 to pass mode/flags. */

    aid_t req1 = async_send_3(phone, VFS_MOUNT, (ipcarg_t) mp.dev_handle,

        (ipcarg_t) mp.index, 0, NULL);

    /* The second call uses the same method. */

    aid_t req2 = async_send_3(phone, VFS_MOUNT,

        (ipcarg_t) mounted_root.fs_handle,

        (ipcarg_t) mounted_root.dev_handle, (ipcarg_t) mounted_root.index,

        NULL);

    vfs_release_phone(phone);

    ipcarg_t rc1;

    ipcarg_t rc2;

    async_wait_for(req1, &rc1);

    async_wait_for(req2, &rc2);

    if ((rc1 != EOK) || (rc2 != EOK)) {

        /* Mount failed, drop references to mr_node and mp_node. */

        vfs_node_put(mr_node);

        if (mp_node)

            vfs_node_put(mp_node);

    }

    if (rc2 == EOK)

        ipc_answer_0(rid, rc1);

    else if (rc1 == EOK)

        ipc_answer_0(rid, rc2);

    else

        ipc_answer_0(rid, rc1);

}

/**

 * @}

 */