Archipelago » qemu

/*

 * QEMU Block driver for  NBD

 *

 * Copyright (C) 2008 Bull S.A.S.

 *     Author: Laurent Vivier <Laurent.Vivier@bull.net>

 *

 * Some parts:

 *    Copyright (C) 2007 Anthony Liguori <anthony@codemonkey.ws>

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to deal

 * in the Software without restriction, including without limitation the rights

 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

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

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL

 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 * THE SOFTWARE.

 */

#include "qemu-common.h"

#include "nbd.h"

#include "block_int.h"

#include "module.h"

#include "qemu_socket.h"

#include <sys/types.h>

#include <unistd.h>

#define EN_OPTSTR ":exportname="

/* #define DEBUG_NBD */

#if defined(DEBUG_NBD)

#define logout(fmt, ...) \

                fprintf(stderr, "nbd\t%-24s" fmt, __func__, ##__VA_ARGS__)

#else

#define logout(fmt, ...) ((void)0)

#endif

#define MAX_NBD_REQUESTS        16

#define HANDLE_TO_INDEX(bs, handle) ((handle) ^ ((uint64_t)(intptr_t)bs))

#define INDEX_TO_HANDLE(bs, index)  ((index)  ^ ((uint64_t)(intptr_t)bs))

typedef struct BDRVNBDState {

    int sock;

    uint32_t nbdflags;

    off_t size;

    size_t blocksize;

    char *export_name; /* An NBD server may export several devices */

    CoMutex send_mutex;

    CoMutex free_sema;

    Coroutine *send_coroutine;

    int in_flight;

    Coroutine *recv_coroutine[MAX_NBD_REQUESTS];

    struct nbd_reply reply;

    /* If it begins with  '/', this is a UNIX domain socket. Otherwise,

     * it's a string of the form <hostname|ip4|\[ip6\]>:port

     */

    char *host_spec;

} BDRVNBDState;

static int nbd_config(BDRVNBDState *s, const char *filename, int flags)

{

    char *file;

    char *export_name;

    const char *host_spec;

    const char *unixpath;

    int err = -EINVAL;

    file = g_strdup(filename);

    export_name = strstr(file, EN_OPTSTR);

    if (export_name) {

        if (export_name[strlen(EN_OPTSTR)] == 0) {

            goto out;

        }

        export_name[0] = 0; /* truncate 'file' */

        export_name += strlen(EN_OPTSTR);

        s->export_name = g_strdup(export_name);

    }

    /* extract the host_spec - fail if it's not nbd:... */

    if (!strstart(file, "nbd:", &host_spec)) {

        goto out;

    }

    /* are we a UNIX or TCP socket? */

    if (strstart(host_spec, "unix:", &unixpath)) {

        if (unixpath[0] != '/') { /* We demand  an absolute path*/

            goto out;

        }

        s->host_spec = g_strdup(unixpath);

    } else {

        s->host_spec = g_strdup(host_spec);

    }

    err = 0;

out:

    g_free(file);

    if (err != 0) {

        g_free(s->export_name);

        g_free(s->host_spec);

    }

    return err;

}

static void nbd_coroutine_start(BDRVNBDState *s, struct nbd_request *request)

{

    int i;

    /* Poor man semaphore.  The free_sema is locked when no other request

     * can be accepted, and unlocked after receiving one reply.  */

    if (s->in_flight >= MAX_NBD_REQUESTS - 1) {

        qemu_co_mutex_lock(&s->free_sema);

        assert(s->in_flight < MAX_NBD_REQUESTS);

    }

    s->in_flight++;

    for (i = 0; i < MAX_NBD_REQUESTS; i++) {

        if (s->recv_coroutine[i] == NULL) {

            s->recv_coroutine[i] = qemu_coroutine_self();

            break;

        }

    }

    assert(i < MAX_NBD_REQUESTS);

    request->handle = INDEX_TO_HANDLE(s, i);

}

static int nbd_have_request(void *opaque)

{

    BDRVNBDState *s = opaque;

    return s->in_flight > 0;

}

static void nbd_reply_ready(void *opaque)

{

    BDRVNBDState *s = opaque;

    uint64_t i;

    int ret;

    if (s->reply.handle == 0) {

        /* No reply already in flight.  Fetch a header.  It is possible

         * that another thread has done the same thing in parallel, so

         * the socket is not readable anymore.

         */

        ret = nbd_receive_reply(s->sock, &s->reply);

        if (ret == -EAGAIN) {

            return;

        }

        if (ret < 0) {

            s->reply.handle = 0;

            goto fail;

        }

    }

    /* There's no need for a mutex on the receive side, because the

     * handler acts as a synchronization point and ensures that only

     * one coroutine is called until the reply finishes.  */

    i = HANDLE_TO_INDEX(s, s->reply.handle);

    if (i >= MAX_NBD_REQUESTS) {

        goto fail;

    }

    if (s->recv_coroutine[i]) {

        qemu_coroutine_enter(s->recv_coroutine[i], NULL);

        return;

    }

fail:

    for (i = 0; i < MAX_NBD_REQUESTS; i++) {

        if (s->recv_coroutine[i]) {

            qemu_coroutine_enter(s->recv_coroutine[i], NULL);

        }

    }

}

static void nbd_restart_write(void *opaque)

{

    BDRVNBDState *s = opaque;

    qemu_coroutine_enter(s->send_coroutine, NULL);

}

static int nbd_co_send_request(BDRVNBDState *s, struct nbd_request *request,

                               struct iovec *iov, int offset)

{

    int rc, ret;

    qemu_co_mutex_lock(&s->send_mutex);

    s->send_coroutine = qemu_coroutine_self();

    qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, nbd_restart_write,

                            nbd_have_request, s);

    rc = nbd_send_request(s->sock, request);

    if (rc >= 0 && iov) {

        ret = qemu_co_sendv(s->sock, iov, request->len, offset);

        if (ret != request->len) {

            return -EIO;

        }

    }

    qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, NULL,

                            nbd_have_request, s);

    s->send_coroutine = NULL;

    qemu_co_mutex_unlock(&s->send_mutex);

    return rc;

}

static void nbd_co_receive_reply(BDRVNBDState *s, struct nbd_request *request,

                                 struct nbd_reply *reply,

                                 struct iovec *iov, int offset)

{

    int ret;

    /* Wait until we're woken up by the read handler.  TODO: perhaps

     * peek at the next reply and avoid yielding if it's ours?  */

    qemu_coroutine_yield();

    *reply = s->reply;

    if (reply->handle != request->handle) {

        reply->error = EIO;

    } else {

        if (iov && reply->error == 0) {

            ret = qemu_co_recvv(s->sock, iov, request->len, offset);

            if (ret != request->len) {

                reply->error = EIO;

            }

        }

        /* Tell the read handler to read another header.  */

        s->reply.handle = 0;

    }

}

static void nbd_coroutine_end(BDRVNBDState *s, struct nbd_request *request)

{

    int i = HANDLE_TO_INDEX(s, request->handle);

    s->recv_coroutine[i] = NULL;

    if (s->in_flight-- == MAX_NBD_REQUESTS) {

        qemu_co_mutex_unlock(&s->free_sema);

    }

}

static int nbd_establish_connection(BlockDriverState *bs)

{

    BDRVNBDState *s = bs->opaque;

    int sock;

    int ret;

    off_t size;

    size_t blocksize;

    if (s->host_spec[0] == '/') {

        sock = unix_socket_outgoing(s->host_spec);

    } else {

        sock = tcp_socket_outgoing_spec(s->host_spec);

    }

    /* Failed to establish connection */

    if (sock < 0) {

        logout("Failed to establish connection to NBD server\n");

        return -errno;

    }

    /* NBD handshake */

    ret = nbd_receive_negotiate(sock, s->export_name, &s->nbdflags, &size,

                                &blocksize);

    if (ret < 0) {

        logout("Failed to negotiate with the NBD server\n");

        closesocket(sock);

        return ret;

    }

    /* Now that we're connected, set the socket to be non-blocking and

     * kick the reply mechanism.  */

    socket_set_nonblock(sock);

    qemu_aio_set_fd_handler(sock, nbd_reply_ready, NULL,

                            nbd_have_request, s);

    s->sock = sock;

    s->size = size;

    s->blocksize = blocksize;

    logout("Established connection with NBD server\n");

    return 0;

}

static void nbd_teardown_connection(BlockDriverState *bs)

{

    BDRVNBDState *s = bs->opaque;

    struct nbd_request request;

    request.type = NBD_CMD_DISC;

    request.from = 0;

    request.len = 0;

    nbd_send_request(s->sock, &request);

    qemu_aio_set_fd_handler(s->sock, NULL, NULL, NULL, NULL);

    closesocket(s->sock);

}

static int nbd_open(BlockDriverState *bs, const char* filename, int flags)

{

    BDRVNBDState *s = bs->opaque;

    int result;

    qemu_co_mutex_init(&s->send_mutex);

    qemu_co_mutex_init(&s->free_sema);

    /* Pop the config into our state object. Exit if invalid. */

    result = nbd_config(s, filename, flags);

    if (result != 0) {

        return result;

    }

    /* establish TCP connection, return error if it fails

     * TODO: Configurable retry-until-timeout behaviour.

     */

    result = nbd_establish_connection(bs);

    return result;

}

static int nbd_co_readv_1(BlockDriverState *bs, int64_t sector_num,

                          int nb_sectors, QEMUIOVector *qiov,

                          int offset)

{

    BDRVNBDState *s = bs->opaque;

    struct nbd_request request;

    struct nbd_reply reply;

    ssize_t ret;

    request.type = NBD_CMD_READ;

    request.from = sector_num * 512;

    request.len = nb_sectors * 512;

    nbd_coroutine_start(s, &request);

    ret = nbd_co_send_request(s, &request, NULL, 0);

    if (ret < 0) {

        reply.error = -ret;

    } else {

        nbd_co_receive_reply(s, &request, &reply, qiov->iov, offset);

    }

    nbd_coroutine_end(s, &request);

    return -reply.error;

}

static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num,

                           int nb_sectors, QEMUIOVector *qiov,

                           int offset)

{

    BDRVNBDState *s = bs->opaque;

    struct nbd_request request;

    struct nbd_reply reply;

    ssize_t ret;

    request.type = NBD_CMD_WRITE;

    if (!bdrv_enable_write_cache(bs) && (s->nbdflags & NBD_FLAG_SEND_FUA)) {

        request.type |= NBD_CMD_FLAG_FUA;

    }

    request.from = sector_num * 512;

    request.len = nb_sectors * 512;

    nbd_coroutine_start(s, &request);

    ret = nbd_co_send_request(s, &request, qiov->iov, offset);

    if (ret < 0) {

        reply.error = -ret;

    } else {

        nbd_co_receive_reply(s, &request, &reply, NULL, 0);

    }

    nbd_coroutine_end(s, &request);

    return -reply.error;

}

/* qemu-nbd has a limit of slightly less than 1M per request.  Try to

 * remain aligned to 4K. */

#define NBD_MAX_SECTORS 2040

static int nbd_co_readv(BlockDriverState *bs, int64_t sector_num,

                        int nb_sectors, QEMUIOVector *qiov)

{

    int offset = 0;

    int ret;

    while (nb_sectors > NBD_MAX_SECTORS) {

        ret = nbd_co_readv_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset);

        if (ret < 0) {

            return ret;

        }

        offset += NBD_MAX_SECTORS * 512;

        sector_num += NBD_MAX_SECTORS;

        nb_sectors -= NBD_MAX_SECTORS;

    }

    return nbd_co_readv_1(bs, sector_num, nb_sectors, qiov, offset);

}

static int nbd_co_writev(BlockDriverState *bs, int64_t sector_num,

                         int nb_sectors, QEMUIOVector *qiov)

{

    int offset = 0;

    int ret;

    while (nb_sectors > NBD_MAX_SECTORS) {

        ret = nbd_co_writev_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset);

        if (ret < 0) {

            return ret;

        }

        offset += NBD_MAX_SECTORS * 512;

        sector_num += NBD_MAX_SECTORS;

        nb_sectors -= NBD_MAX_SECTORS;

    }

    return nbd_co_writev_1(bs, sector_num, nb_sectors, qiov, offset);

}

static int nbd_co_flush(BlockDriverState *bs)

{

    BDRVNBDState *s = bs->opaque;

    struct nbd_request request;

    struct nbd_reply reply;

    ssize_t ret;

    if (!(s->nbdflags & NBD_FLAG_SEND_FLUSH)) {

        return 0;

    }

    request.type = NBD_CMD_FLUSH;

    if (s->nbdflags & NBD_FLAG_SEND_FUA) {

        request.type |= NBD_CMD_FLAG_FUA;

    }

    request.from = 0;

    request.len = 0;

    nbd_coroutine_start(s, &request);

    ret = nbd_co_send_request(s, &request, NULL, 0);

    if (ret < 0) {

        reply.error = -ret;

    } else {

        nbd_co_receive_reply(s, &request, &reply, NULL, 0);

    }

    nbd_coroutine_end(s, &request);

    return -reply.error;

}

static int nbd_co_discard(BlockDriverState *bs, int64_t sector_num,

                          int nb_sectors)

{

    BDRVNBDState *s = bs->opaque;

    struct nbd_request request;

    struct nbd_reply reply;

    ssize_t ret;

    if (!(s->nbdflags & NBD_FLAG_SEND_TRIM)) {

        return 0;

    }

    request.type = NBD_CMD_TRIM;

    request.from = sector_num * 512;;

    request.len = nb_sectors * 512;

    nbd_coroutine_start(s, &request);

    ret = nbd_co_send_request(s, &request, NULL, 0);

    if (ret < 0) {

        reply.error = -ret;

    } else {

        nbd_co_receive_reply(s, &request, &reply, NULL, 0);

    }

    nbd_coroutine_end(s, &request);

    return -reply.error;

}

static void nbd_close(BlockDriverState *bs)

{

    BDRVNBDState *s = bs->opaque;

    g_free(s->export_name);

    g_free(s->host_spec);

    nbd_teardown_connection(bs);

}

static int64_t nbd_getlength(BlockDriverState *bs)

{

    BDRVNBDState *s = bs->opaque;

    return s->size;

}

static BlockDriver bdrv_nbd = {

    .format_name         = "nbd",

    .instance_size       = sizeof(BDRVNBDState),

    .bdrv_file_open      = nbd_open,

    .bdrv_co_readv       = nbd_co_readv,

    .bdrv_co_writev      = nbd_co_writev,

    .bdrv_close          = nbd_close,

    .bdrv_co_flush_to_os = nbd_co_flush,

    .bdrv_co_discard     = nbd_co_discard,

    .bdrv_getlength      = nbd_getlength,

    .protocol_name       = "nbd",

};

static void bdrv_nbd_init(void)

{

    bdrv_register(&bdrv_nbd);

}

block_init(bdrv_nbd_init);