source: mainline/uspace/srv/fs/tmpfs/tmpfs.c@ 79ae36dd

/*
 * 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/services.h>
#include <ns.h>
#include <async.h>
#include <errno.h>
#include <unistd.h>
#include <stdio.h>
#include <task.h>
#include <libfs.h>
#include "../../vfs/vfs.h"

#define NAME "tmpfs"


vfs_info_t tmpfs_vfs_info = {
        .name = NAME,
        .concurrent_read_write = false,
        .write_retains_size = false,
};

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.
                 */
                async_answer_0(iid, EOK);
        }
        
        dprintf(NAME ": connection opened\n");
        
        while (true) {
                ipc_call_t call;
                ipc_callid_t callid = async_get_call(&call);
                
                if (!IPC_GET_IMETHOD(call))
                        return;
                
                switch (IPC_GET_IMETHOD(call)) {
                case VFS_OUT_MOUNTED:
                        tmpfs_mounted(callid, &call);
                        break;
                case VFS_OUT_MOUNT:
                        tmpfs_mount(callid, &call);
                        break;
                case VFS_OUT_UNMOUNTED:
                        tmpfs_unmounted(callid, &call);
                        break;
                case VFS_OUT_UNMOUNT:
                        tmpfs_unmount(callid, &call);
                        break;
                case VFS_OUT_LOOKUP:
                        tmpfs_lookup(callid, &call);
                        break;
                case VFS_OUT_READ:
                        tmpfs_read(callid, &call);
                        break;
                case VFS_OUT_WRITE:
                        tmpfs_write(callid, &call);
                        break;
                case VFS_OUT_TRUNCATE:
                        tmpfs_truncate(callid, &call);
                        break;
                case VFS_OUT_CLOSE:
                        tmpfs_close(callid, &call);
                        break;
                case VFS_OUT_DESTROY:
                        tmpfs_destroy(callid, &call);
                        break;
                case VFS_OUT_OPEN_NODE:
                        tmpfs_open_node(callid, &call);
                        break;
                case VFS_OUT_STAT:
                        tmpfs_stat(callid, &call);
                        break;
                case VFS_OUT_SYNC:
                        tmpfs_sync(callid, &call);
                        break;
                default:
                        async_answer_0(callid, ENOTSUP);
                        break;
                }
        }
}

int main(int argc, char **argv)
{
        printf(NAME ": HelenOS TMPFS file system server\n");
        
        if (!tmpfs_init()) {
                printf(NAME ": failed to initialize TMPFS\n");
                return -1;
        }
        
        async_sess_t *vfs_sess = service_connect_blocking(EXCHANGE_SERIALIZE,
            SERVICE_VFS, 0, 0);
        if (!vfs_sess) {
                printf(NAME ": Unable to connect to VFS\n");
                return -1;
        }
        
        int rc = fs_register(vfs_sess, &tmpfs_reg, &tmpfs_vfs_info,
            tmpfs_connection);
        if (rc != EOK) {
                printf(NAME ": Failed to register file system (%d)\n", rc);
                return rc;
        }
        
        printf(NAME ": Accepting connections\n");
        task_retval(0);
        async_manager();
        
        /* Not reached */
        return 0;
}

/**
 * @}
 */