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qemu/block/nbd.c

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/*
* 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(s->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);
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