qemu/block/nbd-client.c
Stefan Hajnoczi 4a41a2d68a nbd: close socket if connection breaks
nbd_receive_reply() is called by the event loop whenever data is
available or the socket has been closed by the remote side.

This patch closes the socket when an error occurs to prevent the
nbd_receive_reply() handler from being called indefinitely after the
connection has failed.

Note that we were already correctly returning EIO for pending requests
but leaving the nbd_receive_reply() handler registered resulted in high
CPU consumption and a flood of error messages.

Reuse nbd_teardown_connection() to close the socket.

Reported-by: Zhifeng Cai <bluewindow@h3c.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-03-14 16:28:28 +01:00

389 lines
11 KiB
C

/*
* 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 "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_teardown_connection(NbdClientSession *client)
{
/* 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;
}
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_teardown_connection(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;
}
void nbd_client_session_close(NbdClientSession *client)
{
struct nbd_request request = {
.type = NBD_CMD_DISC,
.from = 0,
.len = 0
};
if (!client->bs) {
return;
}
if (client->sock == -1) {
return;
}
nbd_send_request(client->sock, &request);
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;
}