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5fcbeb0681
With the experimental x-nbd-server-add-bitmap command, there was a window of time where an NBD client could see the export but not the associated dirty bitmap, which can cause a client that planned on using the dirty bitmap to be forced to treat the entire image as dirty as a safety fallback. Furthermore, if the QMP client successfully exports a disk but then fails to add the bitmap, it has to take on the burden of removing the export. Since we don't allow changing the exposed dirty bitmap (whether to a different bitmap, or removing advertisement of the bitmap), it is nicer to make the bitmap tied to the export at the time the export is created, with automatic failure to export if the bitmap is not available. The experimental command included an optional 'bitmap-export-name' field for remapping the name exposed over NBD to be different from the bitmap name stored on disk. However, my libvirt demo code for implementing differential backups on top of persistent bitmaps did not need to take advantage of that feature (it is instead possible to create a new temporary bitmap with the desired name, use block-dirty-bitmap-merge to merge one or more persistent bitmaps into the temporary, then associate the temporary with the NBD export, if control is needed over the exported bitmap name). Hence, I'm not copying that part of the experiment over to the stable addition. For more details on the libvirt demo, see https://www.redhat.com/archives/libvir-list/2018-October/msg01254.html, https://kvmforum2018.sched.com/event/FzuB/facilitating-incremental-backup-eric-blake-red-hat This patch focuses on the user interface, and reduces (but does not completely eliminate) the window where an NBD client can see the export but not the dirty bitmap, with less work to clean up after errors. Later patches will add further cleanups now that this interface is declared stable via a single QMP command, including removing the race window. Update test 223 to use the new interface. Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-Id: <20190111194720.15671-6-eblake@redhat.com>
259 lines
6.4 KiB
C
259 lines
6.4 KiB
C
/*
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* Serving QEMU block devices via NBD
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*
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* Copyright (c) 2012 Red Hat, Inc.
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*
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* Author: Paolo Bonzini <pbonzini@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or
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* later. See the COPYING file in the top-level directory.
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*/
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#include "qemu/osdep.h"
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#include "sysemu/blockdev.h"
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#include "sysemu/block-backend.h"
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#include "hw/block/block.h"
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#include "qapi/error.h"
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#include "qapi/qapi-commands-block.h"
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#include "sysemu/sysemu.h"
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#include "block/nbd.h"
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#include "io/channel-socket.h"
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#include "io/net-listener.h"
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typedef struct NBDServerData {
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QIONetListener *listener;
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QCryptoTLSCreds *tlscreds;
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} NBDServerData;
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static NBDServerData *nbd_server;
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static void nbd_blockdev_client_closed(NBDClient *client, bool ignored)
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{
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nbd_client_put(client);
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}
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static void nbd_accept(QIONetListener *listener, QIOChannelSocket *cioc,
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gpointer opaque)
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{
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qio_channel_set_name(QIO_CHANNEL(cioc), "nbd-server");
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nbd_client_new(cioc, nbd_server->tlscreds, NULL,
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nbd_blockdev_client_closed);
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}
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static void nbd_server_free(NBDServerData *server)
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{
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if (!server) {
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return;
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}
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qio_net_listener_disconnect(server->listener);
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object_unref(OBJECT(server->listener));
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if (server->tlscreds) {
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object_unref(OBJECT(server->tlscreds));
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}
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g_free(server);
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}
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static QCryptoTLSCreds *nbd_get_tls_creds(const char *id, Error **errp)
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{
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Object *obj;
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QCryptoTLSCreds *creds;
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obj = object_resolve_path_component(
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object_get_objects_root(), id);
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if (!obj) {
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error_setg(errp, "No TLS credentials with id '%s'",
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id);
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return NULL;
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}
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creds = (QCryptoTLSCreds *)
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object_dynamic_cast(obj, TYPE_QCRYPTO_TLS_CREDS);
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if (!creds) {
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error_setg(errp, "Object with id '%s' is not TLS credentials",
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id);
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return NULL;
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}
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if (creds->endpoint != QCRYPTO_TLS_CREDS_ENDPOINT_SERVER) {
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error_setg(errp,
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"Expecting TLS credentials with a server endpoint");
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return NULL;
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}
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object_ref(obj);
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return creds;
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}
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void nbd_server_start(SocketAddress *addr, const char *tls_creds,
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Error **errp)
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{
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if (nbd_server) {
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error_setg(errp, "NBD server already running");
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return;
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}
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nbd_server = g_new0(NBDServerData, 1);
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nbd_server->listener = qio_net_listener_new();
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qio_net_listener_set_name(nbd_server->listener,
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"nbd-listener");
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if (qio_net_listener_open_sync(nbd_server->listener, addr, errp) < 0) {
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goto error;
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}
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if (tls_creds) {
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nbd_server->tlscreds = nbd_get_tls_creds(tls_creds, errp);
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if (!nbd_server->tlscreds) {
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goto error;
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}
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/* TODO SOCKET_ADDRESS_TYPE_FD where fd has AF_INET or AF_INET6 */
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if (addr->type != SOCKET_ADDRESS_TYPE_INET) {
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error_setg(errp, "TLS is only supported with IPv4/IPv6");
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goto error;
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}
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}
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qio_net_listener_set_client_func(nbd_server->listener,
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nbd_accept,
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NULL,
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NULL);
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return;
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error:
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nbd_server_free(nbd_server);
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nbd_server = NULL;
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}
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void qmp_nbd_server_start(SocketAddressLegacy *addr,
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bool has_tls_creds, const char *tls_creds,
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Error **errp)
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{
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SocketAddress *addr_flat = socket_address_flatten(addr);
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nbd_server_start(addr_flat, tls_creds, errp);
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qapi_free_SocketAddress(addr_flat);
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}
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void qmp_nbd_server_add(const char *device, bool has_name, const char *name,
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bool has_writable, bool writable,
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bool has_bitmap, const char *bitmap, Error **errp)
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{
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BlockDriverState *bs = NULL;
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BlockBackend *on_eject_blk;
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NBDExport *exp;
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if (!nbd_server) {
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error_setg(errp, "NBD server not running");
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return;
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}
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if (!has_name) {
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name = device;
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}
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if (nbd_export_find(name)) {
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error_setg(errp, "NBD server already has export named '%s'", name);
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return;
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}
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on_eject_blk = blk_by_name(device);
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bs = bdrv_lookup_bs(device, device, errp);
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if (!bs) {
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return;
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}
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if (!has_writable) {
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writable = false;
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}
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if (bdrv_is_read_only(bs)) {
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writable = false;
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}
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exp = nbd_export_new(bs, 0, -1, name, NULL,
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writable ? 0 : NBD_FLAG_READ_ONLY,
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NULL, false, on_eject_blk, errp);
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if (!exp) {
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return;
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}
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/* The list of named exports has a strong reference to this export now and
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* our only way of accessing it is through nbd_export_find(), so we can drop
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* the strong reference that is @exp. */
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nbd_export_put(exp);
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if (has_bitmap) {
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Error *err = NULL;
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nbd_export_bitmap(exp, bitmap, bitmap, &err);
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if (err) {
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error_propagate(errp, err);
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nbd_export_remove(exp, NBD_SERVER_REMOVE_MODE_HARD, NULL);
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}
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}
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}
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void qmp_nbd_server_remove(const char *name,
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bool has_mode, NbdServerRemoveMode mode,
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Error **errp)
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{
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NBDExport *exp;
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if (!nbd_server) {
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error_setg(errp, "NBD server not running");
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return;
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}
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exp = nbd_export_find(name);
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if (exp == NULL) {
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error_setg(errp, "Export '%s' is not found", name);
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return;
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}
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if (!has_mode) {
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mode = NBD_SERVER_REMOVE_MODE_SAFE;
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}
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nbd_export_remove(exp, mode, errp);
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}
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void qmp_nbd_server_stop(Error **errp)
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{
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if (!nbd_server) {
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error_setg(errp, "NBD server not running");
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return;
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}
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nbd_export_close_all();
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nbd_server_free(nbd_server);
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nbd_server = NULL;
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}
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void qmp_x_nbd_server_add_bitmap(const char *name, const char *bitmap,
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bool has_bitmap_export_name,
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const char *bitmap_export_name,
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Error **errp)
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{
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NBDExport *exp;
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if (!nbd_server) {
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error_setg(errp, "NBD server not running");
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return;
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}
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exp = nbd_export_find(name);
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if (exp == NULL) {
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error_setg(errp, "Export '%s' is not found", name);
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return;
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}
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nbd_export_bitmap(exp, bitmap,
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has_bitmap_export_name ? bitmap_export_name : bitmap,
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errp);
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}
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