[qemu.git] / block / nbd-client.c

/*
 * QEMU Block driver for  NBD
 *
 * Copyright (C) 2008 Bull S.A.S.
 *     Author: Laurent Vivier <[email protected]>
 *
 * Some parts:
 *    Copyright (C) 2007 Anthony Liguori <[email protected]>
 *
 * 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 "nbd-client.h"
#include "qemu/sockets.h"

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

static void nbd_recv_coroutines_enter_all(NbdClientSession *s)
{
    int i;

    for (i = 0; i < MAX_NBD_REQUESTS; i++) {
        if (s->recv_coroutine[i]) {
            qemu_coroutine_enter(s->recv_coroutine[i], NULL);
        }
    }
}

static void nbd_reply_ready(void *opaque)
{
    NbdClientSession *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:
    nbd_recv_coroutines_enter_all(s);
}

static void nbd_restart_write(void *opaque)
{
    NbdClientSession *s = opaque;

    qemu_coroutine_enter(s->send_coroutine, NULL);
}

static int nbd_co_send_request(NbdClientSession *s,
    struct nbd_request *request,
    QEMUIOVector *qiov, 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, s);
    if (qiov) {
        if (!s->is_unix) {
            socket_set_cork(s->sock, 1);
        }
        rc = nbd_send_request(s->sock, request);
        if (rc >= 0) {
            ret = qemu_co_sendv(s->sock, qiov->iov, qiov->niov,
                                offset, request->len);
            if (ret != request->len) {
                rc = -EIO;
            }
        }
        if (!s->is_unix) {
            socket_set_cork(s->sock, 0);
        }
    } else {
        rc = nbd_send_request(s->sock, request);
    }
    qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, NULL, s);
    s->send_coroutine = NULL;
    qemu_co_mutex_unlock(&s->send_mutex);
    return rc;
}

static void nbd_co_receive_reply(NbdClientSession *s,
    struct nbd_request *request, struct nbd_reply *reply,
    QEMUIOVector *qiov, 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 (qiov && reply->error == 0) {
            ret = qemu_co_recvv(s->sock, qiov->iov, qiov->niov,
                                offset, request->len);
            if (ret != request->len) {
                reply->error = EIO;
            }
        }

        /* Tell the read handler to read another header.  */
        s->reply.handle = 0;
    }
}

static void nbd_coroutine_start(NbdClientSession *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 void nbd_coroutine_end(NbdClientSession *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_co_readv_1(NbdClientSession *client, int64_t sector_num,
                          int nb_sectors, QEMUIOVector *qiov,
                          int offset)
{
    struct nbd_request request = { .type = NBD_CMD_READ };
    struct nbd_reply reply;
    ssize_t ret;

    request.from = sector_num * 512;
    request.len = nb_sectors * 512;

    nbd_coroutine_start(client, &request);
    ret = nbd_co_send_request(client, &request, NULL, 0);
    if (ret < 0) {
        reply.error = -ret;
    } else {
        nbd_co_receive_reply(client, &request, &reply, qiov, offset);
    }
    nbd_coroutine_end(client, &request);
    return -reply.error;

}

static int nbd_co_writev_1(NbdClientSession *client, int64_t sector_num,
                           int nb_sectors, QEMUIOVector *qiov,
                           int offset)
{
    struct nbd_request request = { .type = NBD_CMD_WRITE };
    struct nbd_reply reply;
    ssize_t ret;

    if (!bdrv_enable_write_cache(client->bs) &&
        (client->nbdflags & NBD_FLAG_SEND_FUA)) {
        request.type |= NBD_CMD_FLAG_FUA;
    }

    request.from = sector_num * 512;
    request.len = nb_sectors * 512;

    nbd_coroutine_start(client, &request);
    ret = nbd_co_send_request(client, &request, qiov, offset);
    if (ret < 0) {
        reply.error = -ret;
    } else {
        nbd_co_receive_reply(client, &request, &reply, NULL, 0);
    }
    nbd_coroutine_end(client, &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

int nbd_client_session_co_readv(NbdClientSession *client, 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(client, 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(client, sector_num, nb_sectors, qiov, offset);
}

int nbd_client_session_co_writev(NbdClientSession *client, 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(client, 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(client, sector_num, nb_sectors, qiov, offset);
}

int nbd_client_session_co_flush(NbdClientSession *client)
{
    struct nbd_request request = { .type = NBD_CMD_FLUSH };
    struct nbd_reply reply;
    ssize_t ret;

    if (!(client->nbdflags & NBD_FLAG_SEND_FLUSH)) {
        return 0;
    }

    if (client->nbdflags & NBD_FLAG_SEND_FUA) {
        request.type |= NBD_CMD_FLAG_FUA;
    }

    request.from = 0;
    request.len = 0;

    nbd_coroutine_start(client, &request);
    ret = nbd_co_send_request(client, &request, NULL, 0);
    if (ret < 0) {
        reply.error = -ret;
    } else {
        nbd_co_receive_reply(client, &request, &reply, NULL, 0);
    }
    nbd_coroutine_end(client, &request);
    return -reply.error;
}

int nbd_client_session_co_discard(NbdClientSession *client, int64_t sector_num,
    int nb_sectors)
{
    struct nbd_request request = { .type = NBD_CMD_TRIM };
    struct nbd_reply reply;
    ssize_t ret;

    if (!(client->nbdflags & NBD_FLAG_SEND_TRIM)) {
        return 0;
    }
    request.from = sector_num * 512;
    request.len = nb_sectors * 512;

    nbd_coroutine_start(client, &request);
    ret = nbd_co_send_request(client, &request, NULL, 0);
    if (ret < 0) {
        reply.error = -ret;
    } else {
        nbd_co_receive_reply(client, &request, &reply, NULL, 0);
    }
    nbd_coroutine_end(client, &request);
    return -reply.error;

}

static void nbd_teardown_connection(NbdClientSession *client)
{
    struct nbd_request request = {
        .type = NBD_CMD_DISC,
        .from = 0,
        .len = 0
    };

    nbd_send_request(client->sock, &request);

    /* finish any pending coroutines */
    shutdown(client->sock, 2);
    nbd_recv_coroutines_enter_all(client);

    qemu_aio_set_fd_handler(client->sock, NULL, NULL, NULL);
    closesocket(client->sock);
    client->sock = -1;
}

void nbd_client_session_close(NbdClientSession *client)
{
    if (!client->bs) {
        return;
    }

    nbd_teardown_connection(client);
    client->bs = NULL;
}

int nbd_client_session_init(NbdClientSession *client, BlockDriverState *bs,
    int sock, const char *export)
{
    int ret;

    /* NBD handshake */
    logout("session init %s\n", export);
    qemu_set_block(sock);
    ret = nbd_receive_negotiate(sock, export,
                                &client->nbdflags, &client->size,
                                &client->blocksize);
    if (ret < 0) {
        logout("Failed to negotiate with the NBD server\n");
        closesocket(sock);
        return ret;
    }

    qemu_co_mutex_init(&client->send_mutex);
    qemu_co_mutex_init(&client->free_sema);
    client->bs = bs;
    client->sock = sock;

    /* Now that we're connected, set the socket to be non-blocking and
     * kick the reply mechanism.  */
    qemu_set_nonblock(sock);
    qemu_aio_set_fd_handler(sock, nbd_reply_ready, NULL, client);

    logout("Established connection with NBD server\n");
    return 0;
}
Commit	Line	Data
2302c1ca MAL	1	/*
	2	* QEMU Block driver for NBD
	3	*
	4	* Copyright (C) 2008 Bull S.A.S.
	5	* Author: Laurent Vivier <[email protected]>
	6	*
	7	* Some parts:
	8	* Copyright (C) 2007 Anthony Liguori <[email protected]>
	9	*
	10	* Permission is hereby granted, free of charge, to any person obtaining a copy
	11	* of this software and associated documentation files (the "Software"), to deal
	12	* in the Software without restriction, including without limitation the rights
	13	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	14	* copies of the Software, and to permit persons to whom the Software is
	15	* furnished to do so, subject to the following conditions:
	16	*
	17	* The above copyright notice and this permission notice shall be included in
	18	* all copies or substantial portions of the Software.
	19	*
	20	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	21	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	22	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	23	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	24	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	25	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	26	* THE SOFTWARE.
	27	*/
	28
	29	#include "nbd-client.h"
	30	#include "qemu/sockets.h"
	31
	32	#define HANDLE_TO_INDEX(bs, handle) ((handle) ^ ((uint64_t)(intptr_t)bs))
	33	#define INDEX_TO_HANDLE(bs, index) ((index) ^ ((uint64_t)(intptr_t)bs))
	34
69152c09 MAL	35	static void nbd_recv_coroutines_enter_all(NbdClientSession *s)
	36	{
	37	int i;
	38
	39	for (i = 0; i < MAX_NBD_REQUESTS; i++) {
	40	if (s->recv_coroutine[i]) {
	41	qemu_coroutine_enter(s->recv_coroutine[i], NULL);
	42	}
	43	}
	44	}
	45
2302c1ca MAL	46	static void nbd_reply_ready(void *opaque)
	47	{
	48	NbdClientSession *s = opaque;
	49	uint64_t i;
	50	int ret;
	51
	52	if (s->reply.handle == 0) {
	53	/* No reply already in flight. Fetch a header. It is possible
	54	* that another thread has done the same thing in parallel, so
	55	* the socket is not readable anymore.
	56	*/
	57	ret = nbd_receive_reply(s->sock, &s->reply);
	58	if (ret == -EAGAIN) {
	59	return;
	60	}
	61	if (ret < 0) {
	62	s->reply.handle = 0;
	63	goto fail;
	64	}
	65	}
	66
	67	/* There's no need for a mutex on the receive side, because the
	68	* handler acts as a synchronization point and ensures that only
	69	* one coroutine is called until the reply finishes. */
	70	i = HANDLE_TO_INDEX(s, s->reply.handle);
	71	if (i >= MAX_NBD_REQUESTS) {
	72	goto fail;
	73	}
	74
	75	if (s->recv_coroutine[i]) {
	76	qemu_coroutine_enter(s->recv_coroutine[i], NULL);
	77	return;
	78	}
	79
	80	fail:
69152c09	81	nbd_recv_coroutines_enter_all(s);
2302c1ca MAL	82	}
	83
	84	static void nbd_restart_write(void *opaque)
	85	{
	86	NbdClientSession *s = opaque;
	87
	88	qemu_coroutine_enter(s->send_coroutine, NULL);
	89	}
	90
	91	static int nbd_co_send_request(NbdClientSession *s,
	92	struct nbd_request *request,
	93	QEMUIOVector *qiov, int offset)
	94	{
	95	int rc, ret;
	96
	97	qemu_co_mutex_lock(&s->send_mutex);
	98	s->send_coroutine = qemu_coroutine_self();
	99	qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, nbd_restart_write, s);
	100	if (qiov) {
	101	if (!s->is_unix) {
	102	socket_set_cork(s->sock, 1);
	103	}
	104	rc = nbd_send_request(s->sock, request);
	105	if (rc >= 0) {
	106	ret = qemu_co_sendv(s->sock, qiov->iov, qiov->niov,
	107	offset, request->len);
	108	if (ret != request->len) {
	109	rc = -EIO;
	110	}
	111	}
	112	if (!s->is_unix) {
	113	socket_set_cork(s->sock, 0);
	114	}
	115	} else {
	116	rc = nbd_send_request(s->sock, request);
	117	}
	118	qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, NULL, s);
	119	s->send_coroutine = NULL;
	120	qemu_co_mutex_unlock(&s->send_mutex);
	121	return rc;
	122	}
	123
	124	static void nbd_co_receive_reply(NbdClientSession *s,
	125	struct nbd_request request, struct nbd_reply reply,
	126	QEMUIOVector *qiov, int offset)
	127	{
	128	int ret;
	129
	130	/* Wait until we're woken up by the read handler. TODO: perhaps
	131	* peek at the next reply and avoid yielding if it's ours? */
	132	qemu_coroutine_yield();
	133	*reply = s->reply;
	134	if (reply->handle != request->handle) {
	135	reply->error = EIO;
	136	} else {
	137	if (qiov && reply->error == 0) {
	138	ret = qemu_co_recvv(s->sock, qiov->iov, qiov->niov,
	139	offset, request->len);
	140	if (ret != request->len) {
	141	reply->error = EIO;
	142	}
	143	}
	144
	145	/* Tell the read handler to read another header. */
146	s->reply.handle = 0;
147	}
148	}
149
150	static void nbd_coroutine_start(NbdClientSession *s,
151	struct nbd_request *request)
152	{
153	int i;
154
155	/* Poor man semaphore. The free_sema is locked when no other request
156	* can be accepted, and unlocked after receiving one reply. */
157	if (s->in_flight >= MAX_NBD_REQUESTS - 1) {
158	qemu_co_mutex_lock(&s->free_sema);
159	assert(s->in_flight < MAX_NBD_REQUESTS);
160	}
161	s->in_flight++;
162
163	for (i = 0; i < MAX_NBD_REQUESTS; i++) {
164	if (s->recv_coroutine[i] == NULL) {
165	s->recv_coroutine[i] = qemu_coroutine_self();
166	break;
167	}
168	}
169
170	assert(i < MAX_NBD_REQUESTS);
171	request->handle = INDEX_TO_HANDLE(s, i);
172	}
173
174	static void nbd_coroutine_end(NbdClientSession *s,
175	struct nbd_request *request)
176	{
177	int i = HANDLE_TO_INDEX(s, request->handle);
178	s->recv_coroutine[i] = NULL;
179	if (s->in_flight-- == MAX_NBD_REQUESTS) {
180	qemu_co_mutex_unlock(&s->free_sema);
181	}
182	}
183
184	static int nbd_co_readv_1(NbdClientSession *client, int64_t sector_num,
185	int nb_sectors, QEMUIOVector *qiov,
186	int offset)
187	{
b1b27b64	188	struct nbd_request request = { .type = NBD_CMD_READ };
2302c1ca MAL	189	struct nbd_reply reply;
	190	ssize_t ret;
	191
2302c1ca MAL	192	request.from = sector_num * 512;
	193	request.len = nb_sectors * 512;
	194
	195	nbd_coroutine_start(client, &request);
	196	ret = nbd_co_send_request(client, &request, NULL, 0);
	197	if (ret < 0) {
	198	reply.error = -ret;
	199	} else {
	200	nbd_co_receive_reply(client, &request, &reply, qiov, offset);
	201	}
	202	nbd_coroutine_end(client, &request);
	203	return -reply.error;
	204
	205	}
	206
	207	static int nbd_co_writev_1(NbdClientSession *client, int64_t sector_num,
	208	int nb_sectors, QEMUIOVector *qiov,
	209	int offset)
	210	{
b1b27b64	211	struct nbd_request request = { .type = NBD_CMD_WRITE };
2302c1ca MAL	212	struct nbd_reply reply;
	213	ssize_t ret;
	214
2302c1ca MAL	215	if (!bdrv_enable_write_cache(client->bs) &&
	216	(client->nbdflags & NBD_FLAG_SEND_FUA)) {
	217	request.type \|= NBD_CMD_FLAG_FUA;
	218	}
	219
	220	request.from = sector_num * 512;
	221	request.len = nb_sectors * 512;
	222
	223	nbd_coroutine_start(client, &request);
	224	ret = nbd_co_send_request(client, &request, qiov, offset);
	225	if (ret < 0) {
	226	reply.error = -ret;
	227	} else {
	228	nbd_co_receive_reply(client, &request, &reply, NULL, 0);
	229	}
	230	nbd_coroutine_end(client, &request);
	231	return -reply.error;
	232	}
	233
	234	/* qemu-nbd has a limit of slightly less than 1M per request. Try to
	235	* remain aligned to 4K. */
	236	#define NBD_MAX_SECTORS 2040
	237
	238	int nbd_client_session_co_readv(NbdClientSession *client, int64_t sector_num,
	239	int nb_sectors, QEMUIOVector *qiov)
	240	{
	241	int offset = 0;
	242	int ret;
	243	while (nb_sectors > NBD_MAX_SECTORS) {
	244	ret = nbd_co_readv_1(client, sector_num,
	245	NBD_MAX_SECTORS, qiov, offset);
	246	if (ret < 0) {
	247	return ret;
	248	}
	249	offset += NBD_MAX_SECTORS * 512;
	250	sector_num += NBD_MAX_SECTORS;
	251	nb_sectors -= NBD_MAX_SECTORS;
	252	}
	253	return nbd_co_readv_1(client, sector_num, nb_sectors, qiov, offset);
	254	}
	255
	256	int nbd_client_session_co_writev(NbdClientSession *client, int64_t sector_num,
	257	int nb_sectors, QEMUIOVector *qiov)
	258	{
	259	int offset = 0;
	260	int ret;
	261	while (nb_sectors > NBD_MAX_SECTORS) {
	262	ret = nbd_co_writev_1(client, sector_num,
	263	NBD_MAX_SECTORS, qiov, offset);
	264	if (ret < 0) {
	265	return ret;
	266	}
	267	offset += NBD_MAX_SECTORS * 512;
	268	sector_num += NBD_MAX_SECTORS;
	269	nb_sectors -= NBD_MAX_SECTORS;
	270	}
	271	return nbd_co_writev_1(client, sector_num, nb_sectors, qiov, offset);
	272	}
	273
	274	int nbd_client_session_co_flush(NbdClientSession *client)
	275	{
b1b27b64	276	struct nbd_request request = { .type = NBD_CMD_FLUSH };
2302c1ca MAL	277	struct nbd_reply reply;
	278	ssize_t ret;
	279
	280	if (!(client->nbdflags & NBD_FLAG_SEND_FLUSH)) {
	281	return 0;
	282	}
	283
2302c1ca MAL	284	if (client->nbdflags & NBD_FLAG_SEND_FUA) {
	285	request.type \|= NBD_CMD_FLAG_FUA;
	286	}
	287
	288	request.from = 0;
	289	request.len = 0;
	290
	291	nbd_coroutine_start(client, &request);
	292	ret = nbd_co_send_request(client, &request, NULL, 0);
	293	if (ret < 0) {
	294	reply.error = -ret;
	295	} else {
	296	nbd_co_receive_reply(client, &request, &reply, NULL, 0);
	297	}
	298	nbd_coroutine_end(client, &request);
	299	return -reply.error;
	300	}
	301
	302	int nbd_client_session_co_discard(NbdClientSession *client, int64_t sector_num,
	303	int nb_sectors)
	304	{
b1b27b64	305	struct nbd_request request = { .type = NBD_CMD_TRIM };
2302c1ca MAL	306	struct nbd_reply reply;
	307	ssize_t ret;
	308
	309	if (!(client->nbdflags & NBD_FLAG_SEND_TRIM)) {
	310	return 0;
	311	}
2302c1ca MAL	312	request.from = sector_num * 512;
	313	request.len = nb_sectors * 512;
	314
	315	nbd_coroutine_start(client, &request);
	316	ret = nbd_co_send_request(client, &request, NULL, 0);
	317	if (ret < 0) {
	318	reply.error = -ret;
	319	} else {
	320	nbd_co_receive_reply(client, &request, &reply, NULL, 0);
	321	}
	322	nbd_coroutine_end(client, &request);
	323	return -reply.error;
	324
	325	}
	326
	327	static void nbd_teardown_connection(NbdClientSession *client)
	328	{
b1b27b64 MAL	329	struct nbd_request request = {
	330	.type = NBD_CMD_DISC,
	331	.from = 0,
	332	.len = 0
	333	};
2302c1ca	334
2302c1ca MAL	335	nbd_send_request(client->sock, &request);
2302c1ca MAL	336
69152c09 MAL	337	/* finish any pending coroutines */
	338	shutdown(client->sock, 2);
	339	nbd_recv_coroutines_enter_all(client);
	340
2302c1ca MAL	341	qemu_aio_set_fd_handler(client->sock, NULL, NULL, NULL);
	342	closesocket(client->sock);
	343	client->sock = -1;
	344	}
	345
	346	void nbd_client_session_close(NbdClientSession *client)
	347	{
5ad283eb MAL	348	if (!client->bs) {
	349	return;
	350	}
	351
2302c1ca	352	nbd_teardown_connection(client);
5ad283eb	353	client->bs = NULL;
2302c1ca MAL	354	}
2302c1ca MAL	355
e2bc625f MAL	356	int nbd_client_session_init(NbdClientSession client, BlockDriverState bs,
e2bc625f MAL	357	int sock, const char *export)
2302c1ca MAL	358	{
	359	int ret;
	360
	361	/* NBD handshake */
e2bc625f	362	logout("session init %s\n", export);
e53a18e4	363	qemu_set_block(sock);
e2bc625f	364	ret = nbd_receive_negotiate(sock, export,
2302c1ca MAL	365	&client->nbdflags, &client->size,
	366	&client->blocksize);
	367	if (ret < 0) {
	368	logout("Failed to negotiate with the NBD server\n");
	369	closesocket(sock);
	370	return ret;
	371	}
	372
	373	qemu_co_mutex_init(&client->send_mutex);
	374	qemu_co_mutex_init(&client->free_sema);
	375	client->bs = bs;
	376	client->sock = sock;
	377
	378	/* Now that we're connected, set the socket to be non-blocking and
	379	* kick the reply mechanism. */
	380	qemu_set_nonblock(sock);
	381	qemu_aio_set_fd_handler(sock, nbd_reply_ready, NULL, client);
	382
	383	logout("Established connection with NBD server\n");
	384	return 0;
	385	}