source: mainline/uspace/srv/fs/tmpfs/tmpfs.c@ b8b23c8

/*
 * Copyright (c) 2006 Martin Decky
 * Copyright (c) 2008 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        tmpfs.c
 * @brief       File system driver for in-memory file system.
 *
 * Every instance of tmpfs exists purely in memory and has neither a disk layout
 * nor any permanent storage (e.g. disk blocks). With each system reboot, data
 * stored in a tmpfs file system is lost.
 */

#include "tmpfs.h"
#include <ipc/ipc.h>
#include <ipc/services.h>
#include <async.h>
#include <errno.h>
#include <unistd.h>
#include <stdio.h>
#include <libfs.h>
#include "../../vfs/vfs.h"


vfs_info_t tmpfs_vfs_info = {
        .name = "tmpfs",
        .ops = {
                [IPC_METHOD_TO_VFS_OP(VFS_LOOKUP)] = VFS_OP_DEFINED,
                [IPC_METHOD_TO_VFS_OP(VFS_OPEN)] = VFS_OP_DEFINED,
                [IPC_METHOD_TO_VFS_OP(VFS_CLOSE)] = VFS_OP_DEFINED,
                [IPC_METHOD_TO_VFS_OP(VFS_READ)] = VFS_OP_DEFINED,
                [IPC_METHOD_TO_VFS_OP(VFS_WRITE)] = VFS_OP_DEFINED,
                [IPC_METHOD_TO_VFS_OP(VFS_TRUNCATE)] = VFS_OP_NULL,
                [IPC_METHOD_TO_VFS_OP(VFS_RENAME)] = VFS_OP_NULL,
                [IPC_METHOD_TO_VFS_OP(VFS_OPENDIR)] = VFS_OP_NULL,
                [IPC_METHOD_TO_VFS_OP(VFS_READDIR)] = VFS_OP_NULL,
                [IPC_METHOD_TO_VFS_OP(VFS_CLOSEDIR)] = VFS_OP_NULL,
                [IPC_METHOD_TO_VFS_OP(VFS_UNLINK)] = VFS_OP_NULL,
                [IPC_METHOD_TO_VFS_OP(VFS_MOUNT)] = VFS_OP_NULL,
                [IPC_METHOD_TO_VFS_OP(VFS_UNMOUNT)] = VFS_OP_NULL,
        }
};

fs_reg_t tmpfs_reg;

/**
 * This connection fibril processes VFS requests from VFS.
 *
 * In order to support simultaneous VFS requests, our design is as follows.
 * The connection fibril accepts VFS requests from VFS. If there is only one
 * instance of the fibril, VFS will need to serialize all VFS requests it sends
 * to FAT. To overcome this bottleneck, VFS can send TMPFS the
 * IPC_M_CONNECT_ME_TO call. In that case, a new connection fibril will be
 * created, which in turn will accept the call. Thus, a new phone will be
 * opened for VFS.
 *
 * There are few issues with this arrangement. First, VFS can run out of
 * available phones. In that case, VFS can close some other phones or use one
 * phone for more serialized requests. Similarily, TMPFS can refuse to duplicate
 * the connection. VFS should then just make use of already existing phones and
 * route its requests through them. To avoid paying the fibril creation price 
 * upon each request, TMPFS might want to keep the connections open after the
 * request has been completed.
 */
static void tmpfs_connection(ipc_callid_t iid, ipc_call_t *icall)
{
        if (iid) {
                /*
                 * This only happens for connections opened by
                 * IPC_M_CONNECT_ME_TO calls as opposed to callback connections
                 * created by IPC_M_CONNECT_TO_ME.
                 */
                ipc_answer_0(iid, EOK);
        }
        
        dprintf("VFS-TMPFS connection established.\n");
        while (1) {
                ipc_callid_t callid;
                ipc_call_t call;
        
                callid = async_get_call(&call);
                switch  (IPC_GET_METHOD(call)) {
                case VFS_LOOKUP:
                        tmpfs_lookup(callid, &call);
                        break;
                case VFS_READ:
                        tmpfs_read(callid, &call);
                        break;
                default:
                        ipc_answer_0(callid, ENOTSUP);
                        break;
                }
        }
}

int main(int argc, char **argv)
{
        int vfs_phone;

        printf("TMPFS: HelenOS TMPFS file system server.\n");

        vfs_phone = ipc_connect_me_to(PHONE_NS, SERVICE_VFS, 0, 0);
        while (vfs_phone < EOK) {
                usleep(10000);
                vfs_phone = ipc_connect_me_to(PHONE_NS, SERVICE_VFS, 0, 0);
        }
        
        int rc;
        rc = fs_register(vfs_phone, &tmpfs_reg, &tmpfs_vfs_info,
            tmpfs_connection);
        if (rc != EOK) {
                printf("Failed to register the TMPFS file system (%d)\n", rc);
                return rc;
        }
        
        dprintf("TMPFS filesystem registered, fs_handle=%d.\n",
            tmpfs_reg.fs_handle);

        async_manager();
        /* not reached */
        return 0;
}

/**
 * @}
 */