qemu/block/nbd-client.c
Eric Blake a89ef0c357 nbd: don't request FUA on FLUSH
The NBD protocol does not clearly document what will happen
if a client sends NBD_CMD_FLAG_FUA on NBD_CMD_FLUSH.
Historically, both the qemu and upstream NBD servers silently
ignored that flag, but that feels a bit risky.  Meanwhile, the
qemu NBD client unconditionally sends the flag (without even
bothering to check whether the caller cares; at least with
NBD_CMD_WRITE the client only sends FUA if requested by a
higher layer).

There is ongoing discussion on the NBD list to fix the
protocol documentation to require that the server MUST ignore
the flag (unless the kernel folks can better explain what FUA
means for a flush), but until those doc improvements land, the
current nbd.git master was recently changed to reject the flag
with EINVAL (see nbd commit ab22e082), which now makes it
impossible for a qemu client to use FLUSH with an upstream NBD
server.

We should not send FUA with flush unless the upstream protocol
documents what it will do, and even then, it should be something
that the caller can opt into, rather than being unconditional.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1459526902-32561-1-git-send-email-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-04-05 11:46:52 +02:00

437 lines
13 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 "qemu/osdep.h"
#include "nbd-client.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(BlockDriverState *bs)
{
NbdClientSession *client = nbd_get_client_session(bs);
if (!client->ioc) { /* Already closed */
return;
}
/* finish any pending coroutines */
qio_channel_shutdown(client->ioc,
QIO_CHANNEL_SHUTDOWN_BOTH,
NULL);
nbd_recv_coroutines_enter_all(client);
nbd_client_detach_aio_context(bs);
object_unref(OBJECT(client->sioc));
client->sioc = NULL;
object_unref(OBJECT(client->ioc));
client->ioc = NULL;
}
static void nbd_reply_ready(void *opaque)
{
BlockDriverState *bs = opaque;
NbdClientSession *s = nbd_get_client_session(bs);
uint64_t i;
int ret;
if (!s->ioc) { /* Already closed */
return;
}
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->ioc, &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(bs);
}
static void nbd_restart_write(void *opaque)
{
BlockDriverState *bs = opaque;
qemu_coroutine_enter(nbd_get_client_session(bs)->send_coroutine, NULL);
}
static int nbd_co_send_request(BlockDriverState *bs,
struct nbd_request *request,
QEMUIOVector *qiov, int offset)
{
NbdClientSession *s = nbd_get_client_session(bs);
AioContext *aio_context;
int rc, ret, i;
qemu_co_mutex_lock(&s->send_mutex);
for (i = 0; i < MAX_NBD_REQUESTS; i++) {
if (s->recv_coroutine[i] == NULL) {
s->recv_coroutine[i] = qemu_coroutine_self();
break;
}
}
g_assert(qemu_in_coroutine());
assert(i < MAX_NBD_REQUESTS);
request->handle = INDEX_TO_HANDLE(s, i);
if (!s->ioc) {
qemu_co_mutex_unlock(&s->send_mutex);
return -EPIPE;
}
s->send_coroutine = qemu_coroutine_self();
aio_context = bdrv_get_aio_context(bs);
aio_set_fd_handler(aio_context, s->sioc->fd, false,
nbd_reply_ready, nbd_restart_write, bs);
if (qiov) {
qio_channel_set_cork(s->ioc, true);
rc = nbd_send_request(s->ioc, request);
if (rc >= 0) {
ret = nbd_wr_syncv(s->ioc, qiov->iov, qiov->niov,
offset, request->len, 0);
if (ret != request->len) {
rc = -EIO;
}
}
qio_channel_set_cork(s->ioc, false);
} else {
rc = nbd_send_request(s->ioc, request);
}
aio_set_fd_handler(aio_context, s->sioc->fd, false,
nbd_reply_ready, NULL, bs);
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 ||
!s->ioc) {
reply->error = EIO;
} else {
if (qiov && reply->error == 0) {
ret = nbd_wr_syncv(s->ioc, qiov->iov, qiov->niov,
offset, request->len, 1);
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)
{
/* 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++;
/* s->recv_coroutine[i] is set as soon as we get the send_lock. */
}
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(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov,
int offset)
{
NbdClientSession *client = nbd_get_client_session(bs);
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(bs, &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(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov,
int offset, int *flags)
{
NbdClientSession *client = nbd_get_client_session(bs);
struct nbd_request request = { .type = NBD_CMD_WRITE };
struct nbd_reply reply;
ssize_t ret;
if ((*flags & BDRV_REQ_FUA) && (client->nbdflags & NBD_FLAG_SEND_FUA)) {
*flags &= ~BDRV_REQ_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(bs, &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_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);
}
int nbd_client_co_writev(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov, int *flags)
{
int offset = 0;
int ret;
while (nb_sectors > NBD_MAX_SECTORS) {
ret = nbd_co_writev_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset,
flags);
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, flags);
}
int nbd_client_co_flush(BlockDriverState *bs)
{
NbdClientSession *client = nbd_get_client_session(bs);
struct nbd_request request = { .type = NBD_CMD_FLUSH };
struct nbd_reply reply;
ssize_t ret;
if (!(client->nbdflags & NBD_FLAG_SEND_FLUSH)) {
return 0;
}
request.from = 0;
request.len = 0;
nbd_coroutine_start(client, &request);
ret = nbd_co_send_request(bs, &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_co_discard(BlockDriverState *bs, int64_t sector_num,
int nb_sectors)
{
NbdClientSession *client = nbd_get_client_session(bs);
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(bs, &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_detach_aio_context(BlockDriverState *bs)
{
aio_set_fd_handler(bdrv_get_aio_context(bs),
nbd_get_client_session(bs)->sioc->fd,
false, NULL, NULL, NULL);
}
void nbd_client_attach_aio_context(BlockDriverState *bs,
AioContext *new_context)
{
aio_set_fd_handler(new_context, nbd_get_client_session(bs)->sioc->fd,
false, nbd_reply_ready, NULL, bs);
}
void nbd_client_close(BlockDriverState *bs)
{
NbdClientSession *client = nbd_get_client_session(bs);
struct nbd_request request = {
.type = NBD_CMD_DISC,
.from = 0,
.len = 0
};
if (client->ioc == NULL) {
return;
}
nbd_send_request(client->ioc, &request);
nbd_teardown_connection(bs);
}
int nbd_client_init(BlockDriverState *bs,
QIOChannelSocket *sioc,
const char *export,
QCryptoTLSCreds *tlscreds,
const char *hostname,
Error **errp)
{
NbdClientSession *client = nbd_get_client_session(bs);
int ret;
/* NBD handshake */
logout("session init %s\n", export);
qio_channel_set_blocking(QIO_CHANNEL(sioc), true, NULL);
ret = nbd_receive_negotiate(QIO_CHANNEL(sioc), export,
&client->nbdflags,
tlscreds, hostname,
&client->ioc,
&client->size, errp);
if (ret < 0) {
logout("Failed to negotiate with the NBD server\n");
return ret;
}
qemu_co_mutex_init(&client->send_mutex);
qemu_co_mutex_init(&client->free_sema);
client->sioc = sioc;
object_ref(OBJECT(client->sioc));
if (!client->ioc) {
client->ioc = QIO_CHANNEL(sioc);
object_ref(OBJECT(client->ioc));
}
/* Now that we're connected, set the socket to be non-blocking and
* kick the reply mechanism. */
qio_channel_set_blocking(QIO_CHANNEL(sioc), false, NULL);
nbd_client_attach_aio_context(bs, bdrv_get_aio_context(bs));
logout("Established connection with NBD server\n");
return 0;
}