Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches:

- Add block export infrastructure
- iotests improvements
- Document the throttle block filter
- Misc code cleanups

# gpg: Signature made Fri 02 Oct 2020 15:36:53 BST
# gpg:                using RSA key DC3DEB159A9AF95D3D7456FE7F09B272C88F2FD6
# gpg:                issuer "kwolf@redhat.com"
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>" [full]
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream: (37 commits)
  qcow2: Use L1E_SIZE in qcow2_write_l1_entry()
  qemu-storage-daemon: Fix help line for --export
  iotests: Test block-export-* QMP interface
  iotests: Allow supported and unsupported formats at the same time
  iotests: Introduce qemu_nbd_list_log()
  iotests: Factor out qemu_tool_pipe_and_status()
  nbd: Deprecate nbd-server-add/remove
  nbd: Merge nbd_export_new() and nbd_export_create()
  block/export: Move writable to BlockExportOptions
  block/export: Add query-block-exports
  block/export: Create BlockBackend in blk_exp_add()
  block/export: Move blk to BlockExport
  block/export: Add BLOCK_EXPORT_DELETED event
  block/export: Add block-export-del
  block/export: Move strong user reference to block_exports
  block/export: Add 'id' option to block-export-add
  block/export: Add blk_exp_close_all(_type)
  block/export: Allocate BlockExport in blk_exp_add()
  block/export: Add node-name to BlockExportOptions
  block/export: Move AioContext from NBDExport to BlockExport
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

block.c

@@ -4462,7 +4462,7 @@ static void bdrv_close(BlockDriverState *bs)
 void bdrv_close_all(void)
 {
     assert(job_next(NULL) == NULL);
-    nbd_export_close_all();
+    blk_exp_close_all();
 
     /* Drop references from requests still in flight, such as canceled block
      * jobs whose AIO context has not been polled yet */

block/export/export.c

@@ -0,0 +1,325 @@
+/*
+ * Common block export infrastructure
+ *
+ * Copyright (c) 2012, 2020 Red Hat, Inc.
+ *
+ * Authors:
+ * Paolo Bonzini <pbonzini@redhat.com>
+ * Kevin Wolf <kwolf@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * later.  See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+
+#include "block/block.h"
+#include "sysemu/block-backend.h"
+#include "block/export.h"
+#include "block/nbd.h"
+#include "qapi/error.h"
+#include "qapi/qapi-commands-block-export.h"
+#include "qapi/qapi-events-block-export.h"
+#include "qemu/id.h"
+
+static const BlockExportDriver *blk_exp_drivers[] = {
+    &blk_exp_nbd,
+};
+
+/* Only accessed from the main thread */
+static QLIST_HEAD(, BlockExport) block_exports =
+    QLIST_HEAD_INITIALIZER(block_exports);
+
+BlockExport *blk_exp_find(const char *id)
+{
+    BlockExport *exp;
+
+    QLIST_FOREACH(exp, &block_exports, next) {
+        if (strcmp(id, exp->id) == 0) {
+            return exp;
+        }
+    }
+
+    return NULL;
+}
+
+static const BlockExportDriver *blk_exp_find_driver(BlockExportType type)
+{
+    int i;
+
+    for (i = 0; i < ARRAY_SIZE(blk_exp_drivers); i++) {
+        if (blk_exp_drivers[i]->type == type) {
+            return blk_exp_drivers[i];
+        }
+    }
+    return NULL;
+}
+
+BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp)
+{
+    const BlockExportDriver *drv;
+    BlockExport *exp = NULL;
+    BlockDriverState *bs;
+    BlockBackend *blk;
+    AioContext *ctx;
+    uint64_t perm;
+    int ret;
+
+    if (!id_wellformed(export->id)) {
+        error_setg(errp, "Invalid block export id");
+        return NULL;
+    }
+    if (blk_exp_find(export->id)) {
+        error_setg(errp, "Block export id '%s' is already in use", export->id);
+        return NULL;
+    }
+
+    drv = blk_exp_find_driver(export->type);
+    if (!drv) {
+        error_setg(errp, "No driver found for the requested export type");
+        return NULL;
+    }
+
+    bs = bdrv_lookup_bs(NULL, export->node_name, errp);
+    if (!bs) {
+        return NULL;
+    }
+
+    if (!export->has_writable) {
+        export->writable = false;
+    }
+    if (bdrv_is_read_only(bs) && export->writable) {
+        error_setg(errp, "Cannot export read-only node as writable");
+        return NULL;
+    }
+
+    ctx = bdrv_get_aio_context(bs);
+    aio_context_acquire(ctx);
+
+    /*
+     * Block exports are used for non-shared storage migration. Make sure
+     * that BDRV_O_INACTIVE is cleared and the image is ready for write
+     * access since the export could be available before migration handover.
+     * ctx was acquired in the caller.
+     */
+    bdrv_invalidate_cache(bs, NULL);
+
+    perm = BLK_PERM_CONSISTENT_READ;
+    if (export->writable) {
+        perm |= BLK_PERM_WRITE;
+    }
+
+    blk = blk_new(ctx, perm, BLK_PERM_ALL);
+    ret = blk_insert_bs(blk, bs, errp);
+    if (ret < 0) {
+        goto fail;
+    }
+
+    if (!export->has_writethrough) {
+        export->writethrough = false;
+    }
+    blk_set_enable_write_cache(blk, !export->writethrough);
+
+    assert(drv->instance_size >= sizeof(BlockExport));
+    exp = g_malloc0(drv->instance_size);
+    *exp = (BlockExport) {
+        .drv        = drv,
+        .refcount   = 1,
+        .user_owned = true,
+        .id         = g_strdup(export->id),
+        .ctx        = ctx,
+        .blk        = blk,
+    };
+
+    ret = drv->create(exp, export, errp);
+    if (ret < 0) {
+        goto fail;
+    }
+
+    assert(exp->blk != NULL);
+
+    QLIST_INSERT_HEAD(&block_exports, exp, next);
+
+    aio_context_release(ctx);
+    return exp;
+
+fail:
+    blk_unref(blk);
+    aio_context_release(ctx);
+    if (exp) {
+        g_free(exp->id);
+        g_free(exp);
+    }
+    return NULL;
+}
+
+/* Callers must hold exp->ctx lock */
+void blk_exp_ref(BlockExport *exp)
+{
+    assert(exp->refcount > 0);
+    exp->refcount++;
+}
+
+/* Runs in the main thread */
+static void blk_exp_delete_bh(void *opaque)
+{
+    BlockExport *exp = opaque;
+    AioContext *aio_context = exp->ctx;
+
+    aio_context_acquire(aio_context);
+
+    assert(exp->refcount == 0);
+    QLIST_REMOVE(exp, next);
+    exp->drv->delete(exp);
+    blk_unref(exp->blk);
+    qapi_event_send_block_export_deleted(exp->id);
+    g_free(exp->id);
+    g_free(exp);
+
+    aio_context_release(aio_context);
+}
+
+/* Callers must hold exp->ctx lock */
+void blk_exp_unref(BlockExport *exp)
+{
+    assert(exp->refcount > 0);
+    if (--exp->refcount == 0) {
+        /* Touch the block_exports list only in the main thread */
+        aio_bh_schedule_oneshot(qemu_get_aio_context(), blk_exp_delete_bh,
+                                exp);
+    }
+}
+
+/*
+ * Drops the user reference to the export and requests that all client
+ * connections and other internally held references start to shut down. When
+ * the function returns, there may still be active references while the export
+ * is in the process of shutting down.
+ *
+ * Acquires exp->ctx internally. Callers must *not* hold the lock.
+ */
+void blk_exp_request_shutdown(BlockExport *exp)
+{
+    AioContext *aio_context = exp->ctx;
+
+    aio_context_acquire(aio_context);
+
+    /*
+     * If the user doesn't own the export any more, it is already shutting
+     * down. We must not call .request_shutdown and decrease the refcount a
+     * second time.
+     */
+    if (!exp->user_owned) {
+        goto out;
+    }
+
+    exp->drv->request_shutdown(exp);
+
+    assert(exp->user_owned);
+    exp->user_owned = false;
+    blk_exp_unref(exp);
+
+out:
+    aio_context_release(aio_context);
+}
+
+/*
+ * Returns whether a block export of the given type exists.
+ * type == BLOCK_EXPORT_TYPE__MAX checks for an export of any type.
+ */
+static bool blk_exp_has_type(BlockExportType type)
+{
+    BlockExport *exp;
+
+    if (type == BLOCK_EXPORT_TYPE__MAX) {
+        return !QLIST_EMPTY(&block_exports);
+    }
+
+    QLIST_FOREACH(exp, &block_exports, next) {
+        if (exp->drv->type == type) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+/* type == BLOCK_EXPORT_TYPE__MAX for all types */
+void blk_exp_close_all_type(BlockExportType type)
+{
+    BlockExport *exp, *next;
+
+    assert(in_aio_context_home_thread(qemu_get_aio_context()));
+
+    QLIST_FOREACH_SAFE(exp, &block_exports, next, next) {
+        if (type != BLOCK_EXPORT_TYPE__MAX && exp->drv->type != type) {
+            continue;
+        }
+        blk_exp_request_shutdown(exp);
+    }
+
+    AIO_WAIT_WHILE(NULL, blk_exp_has_type(type));
+}
+
+void blk_exp_close_all(void)
+{
+    blk_exp_close_all_type(BLOCK_EXPORT_TYPE__MAX);
+}
+
+void qmp_block_export_add(BlockExportOptions *export, Error **errp)
+{
+    blk_exp_add(export, errp);
+}
+
+void qmp_block_export_del(const char *id,
+                          bool has_mode, BlockExportRemoveMode mode,
+                          Error **errp)
+{
+    ERRP_GUARD();
+    BlockExport *exp;
+
+    exp = blk_exp_find(id);
+    if (exp == NULL) {
+        error_setg(errp, "Export '%s' is not found", id);
+        return;
+    }
+    if (!exp->user_owned) {
+        error_setg(errp, "Export '%s' is already shutting down", id);
+        return;
+    }
+
+    if (!has_mode) {
+        mode = BLOCK_EXPORT_REMOVE_MODE_SAFE;
+    }
+    if (mode == BLOCK_EXPORT_REMOVE_MODE_SAFE && exp->refcount > 1) {
+        error_setg(errp, "export '%s' still in use", exp->id);
+        error_append_hint(errp, "Use mode='hard' to force client "
+                          "disconnect\n");
+        return;
+    }
+
+    blk_exp_request_shutdown(exp);
+}
+
+BlockExportInfoList *qmp_query_block_exports(Error **errp)
+{
+    BlockExportInfoList *head = NULL, **p_next = &head;
+    BlockExport *exp;
+
+    QLIST_FOREACH(exp, &block_exports, next) {
+        BlockExportInfoList *entry = g_new0(BlockExportInfoList, 1);
+        BlockExportInfo *info = g_new(BlockExportInfo, 1);
+        *info = (BlockExportInfo) {
+            .id             = g_strdup(exp->id),
+            .type           = exp->drv->type,
+            .node_name      = g_strdup(bdrv_get_node_name(blk_bs(exp->blk))),
+            .shutting_down  = !exp->user_owned,
+        };
+
+        entry->value = info;
+        *p_next = entry;
+        p_next = &entry->next;
+    }
+
+    return head;
+}

block/export/meson.build

@@ -0,0 +1 @@
+block_ss.add(files('export.c'))

block/meson.build

@@ -110,6 +110,8 @@ block_ss.add(module_block_h)
 block_ss.add(files('stream.c'))
 
 softmmu_ss.add(files('qapi-sysemu.c'))
+
+subdir('export')
 subdir('monitor')
 
 modules += {'block': block_modules}

block/monitor/block-hmp-cmds.c

@@ -40,6 +40,7 @@
 #include "sysemu/block-backend.h"
 #include "sysemu/blockdev.h"
 #include "qapi/qapi-commands-block.h"
+#include "qapi/qapi-commands-block-export.h"
 #include "qapi/qmp/qdict.h"
 #include "qapi/error.h"
 #include "qapi/qmp/qerror.h"
@@ -397,7 +398,7 @@ void hmp_nbd_server_start(Monitor *mon, const QDict *qdict)
     Error *local_err = NULL;
     BlockInfoList *block_list, *info;
     SocketAddress *addr;
-    BlockExportNbd export;
+    NbdServerAddOptions export;
 
     if (writable && !all) {
         error_setg(&local_err, "-w only valid together with -a");
@@ -410,7 +411,7 @@ void hmp_nbd_server_start(Monitor *mon, const QDict *qdict)
         goto exit;
     }
 
-    nbd_server_start(addr, NULL, NULL, &local_err);
+    nbd_server_start(addr, NULL, NULL, 0, &local_err);
     qapi_free_SocketAddress(addr);
     if (local_err != NULL) {
         goto exit;
@@ -430,7 +431,7 @@ void hmp_nbd_server_start(Monitor *mon, const QDict *qdict)
             continue;
         }
 
-        export = (BlockExportNbd) {
+        export = (NbdServerAddOptions) {
             .device         = info->value->device,
             .has_writable   = true,
             .writable       = writable,
@@ -457,7 +458,7 @@ void hmp_nbd_server_add(Monitor *mon, const QDict *qdict)
     bool writable = qdict_get_try_bool(qdict, "writable", false);
     Error *local_err = NULL;
 
-    BlockExportNbd export = {
+    NbdServerAddOptions export = {
         .device         = (char *) device,
         .has_name       = !!name,
         .name           = (char *) name,
@@ -475,8 +476,8 @@ void hmp_nbd_server_remove(Monitor *mon, const QDict *qdict)
     bool force = qdict_get_try_bool(qdict, "force", false);
     Error *err = NULL;
 
-    /* Rely on NBD_SERVER_REMOVE_MODE_SAFE being the default */
-    qmp_nbd_server_remove(name, force, NBD_SERVER_REMOVE_MODE_HARD, &err);
+    /* Rely on BLOCK_EXPORT_REMOVE_MODE_SAFE being the default */
+    qmp_nbd_server_remove(name, force, BLOCK_EXPORT_REMOVE_MODE_HARD, &err);
     hmp_handle_error(mon, err);
 }
 

block/qcow2-cluster.c

@@ -240,14 +240,14 @@ int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index)
     }
 
     ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L1,
-            s->l1_table_offset + 8 * l1_start_index, bufsize, false);
+            s->l1_table_offset + L1E_SIZE * l1_start_index, bufsize, false);
     if (ret < 0) {
         return ret;
     }
 
     BLKDBG_EVENT(bs->file, BLKDBG_L1_UPDATE);
     ret = bdrv_pwrite_sync(bs->file,
-                           s->l1_table_offset + 8 * l1_start_index,
+                           s->l1_table_offset + L1E_SIZE * l1_start_index,
                            buf, bufsize);
     if (ret < 0) {
         return ret;

block/sheepdog.c

@@ -740,7 +740,7 @@ static coroutine_fn void reconnect_to_sdog(void *opaque)
         if (s->fd < 0) {
             trace_sheepdog_reconnect_to_sdog();
             error_report_err(local_err);
-            qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, 1000000000ULL);
+            qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, NANOSECONDS_PER_SECOND);
         }
     };
 

blockdev-nbd.c

@@ -14,7 +14,7 @@
 #include "sysemu/block-backend.h"
 #include "hw/block/block.h"
 #include "qapi/error.h"
-#include "qapi/qapi-commands-block.h"
+#include "qapi/qapi-commands-block-export.h"
 #include "block/nbd.h"
 #include "io/channel-socket.h"
 #include "io/net-listener.h"
@@ -23,23 +23,52 @@ typedef struct NBDServerData {
     QIONetListener *listener;
     QCryptoTLSCreds *tlscreds;
     char *tlsauthz;
+    uint32_t max_connections;
+    uint32_t connections;
 } NBDServerData;
 
 static NBDServerData *nbd_server;
+static bool is_qemu_nbd;
+
+static void nbd_update_server_watch(NBDServerData *s);
+
+void nbd_server_is_qemu_nbd(bool value)
+{
+    is_qemu_nbd = value;
+}
+
+bool nbd_server_is_running(void)
+{
+    return nbd_server || is_qemu_nbd;
+}
 
 static void nbd_blockdev_client_closed(NBDClient *client, bool ignored)
 {
     nbd_client_put(client);
+    assert(nbd_server->connections > 0);
+    nbd_server->connections--;
+    nbd_update_server_watch(nbd_server);
 }
 
 static void nbd_accept(QIONetListener *listener, QIOChannelSocket *cioc,
                        gpointer opaque)
 {
+    nbd_server->connections++;
+    nbd_update_server_watch(nbd_server);
+
     qio_channel_set_name(QIO_CHANNEL(cioc), "nbd-server");
     nbd_client_new(cioc, nbd_server->tlscreds, nbd_server->tlsauthz,
                    nbd_blockdev_client_closed);
 }
 
+static void nbd_update_server_watch(NBDServerData *s)
+{
+    if (!s->max_connections || s->connections < s->max_connections) {
+        qio_net_listener_set_client_func(s->listener, nbd_accept, NULL, NULL);
+    } else {
+        qio_net_listener_set_client_func(s->listener, NULL, NULL, NULL);
+    }
+}
 
 static void nbd_server_free(NBDServerData *server)
 {
@@ -88,7 +117,8 @@ static QCryptoTLSCreds *nbd_get_tls_creds(const char *id, Error **errp)
 
 
 void nbd_server_start(SocketAddress *addr, const char *tls_creds,
-                      const char *tls_authz, Error **errp)
+                      const char *tls_authz, uint32_t max_connections,
+                      Error **errp)
 {
     if (nbd_server) {
         error_setg(errp, "NBD server already running");
@@ -96,6 +126,7 @@ void nbd_server_start(SocketAddress *addr, const char *tls_creds,
     }
 
     nbd_server = g_new0(NBDServerData, 1);
+    nbd_server->max_connections = max_connections;
     nbd_server->listener = qio_net_listener_new();
 
     qio_net_listener_set_name(nbd_server->listener,
@@ -120,10 +151,7 @@ void nbd_server_start(SocketAddress *addr, const char *tls_creds,
 
     nbd_server->tlsauthz = g_strdup(tls_authz);
 
-    qio_net_listener_set_client_func(nbd_server->listener,
-                                     nbd_accept,
-                                     NULL,
-                                     NULL);
+    nbd_update_server_watch(nbd_server);
 
     return;
 
@@ -134,117 +162,100 @@ void nbd_server_start(SocketAddress *addr, const char *tls_creds,
 
 void nbd_server_start_options(NbdServerOptions *arg, Error **errp)
 {
-    nbd_server_start(arg->addr, arg->tls_creds, arg->tls_authz, errp);
+    nbd_server_start(arg->addr, arg->tls_creds, arg->tls_authz,
+                     arg->max_connections, errp);
 }
 
 void qmp_nbd_server_start(SocketAddressLegacy *addr,
                           bool has_tls_creds, const char *tls_creds,
                           bool has_tls_authz, const char *tls_authz,
+                          bool has_max_connections, uint32_t max_connections,
                           Error **errp)
 {
     SocketAddress *addr_flat = socket_address_flatten(addr);
 
-    nbd_server_start(addr_flat, tls_creds, tls_authz, errp);
+    nbd_server_start(addr_flat, tls_creds, tls_authz, max_connections, errp);
     qapi_free_SocketAddress(addr_flat);
 }
 
-void qmp_nbd_server_add(BlockExportNbd *arg, Error **errp)
+void qmp_nbd_server_add(NbdServerAddOptions *arg, Error **errp)
 {
-    BlockDriverState *bs = NULL;
+    BlockExport *export;
+    BlockDriverState *bs;
     BlockBackend *on_eject_blk;
-    NBDExport *exp;
-    int64_t len;
-    AioContext *aio_context;
-
-    if (!nbd_server) {
-        error_setg(errp, "NBD server not running");
-        return;
-    }
-
-    if (!arg->has_name) {
-        arg->name = arg->device;
-    }
-
-    if (strlen(arg->name) > NBD_MAX_STRING_SIZE) {
-        error_setg(errp, "export name '%s' too long", arg->name);
-        return;
-    }
-
-    if (arg->description && strlen(arg->description) > NBD_MAX_STRING_SIZE) {
-        error_setg(errp, "description '%s' too long", arg->description);
-        return;
-    }
-
-    if (nbd_export_find(arg->name)) {
-        error_setg(errp, "NBD server already has export named '%s'", arg->name);
-        return;
-    }
-
-    on_eject_blk = blk_by_name(arg->device);
+    BlockExportOptions *export_opts;
 
     bs = bdrv_lookup_bs(arg->device, arg->device, errp);
     if (!bs) {
         return;
     }
 
-    aio_context = bdrv_get_aio_context(bs);
-    aio_context_acquire(aio_context);
-    len = bdrv_getlength(bs);
-    if (len < 0) {
-        error_setg_errno(errp, -len,
-                         "Failed to determine the NBD export's length");
-        goto out;
+    /*
+     * block-export-add would default to the node-name, but we may have to use
+     * the device name as a default here for compatibility.
+     */
+    if (!arg->has_name) {
+        arg->name = arg->device;
     }
 
-    if (!arg->has_writable) {
-        arg->writable = false;
-    }
+    export_opts = g_new(BlockExportOptions, 1);
+    *export_opts = (BlockExportOptions) {
+        .type                   = BLOCK_EXPORT_TYPE_NBD,
+        .id                     = g_strdup(arg->name),
+        .node_name              = g_strdup(bdrv_get_node_name(bs)),
+        .has_writable           = arg->has_writable,
+        .writable               = arg->writable,
+        .u.nbd = {
+            .has_name           = true,
+            .name               = g_strdup(arg->name),
+            .has_description    = arg->has_description,
+            .description        = g_strdup(arg->description),
+            .has_bitmap         = arg->has_bitmap,
+            .bitmap             = g_strdup(arg->bitmap),
+        },
+    };
+
+    /*
+     * nbd-server-add doesn't complain when a read-only device should be
+     * exported as writable, but simply downgrades it. This is an error with
+     * block-export-add.
+     */
     if (bdrv_is_read_only(bs)) {
-        arg->writable = false;
+        export_opts->has_writable = true;
+        export_opts->writable = false;
     }
 
-    exp = nbd_export_new(bs, 0, len, arg->name, arg->description, arg->bitmap,
-                         !arg->writable, !arg->writable,
-                         NULL, false, on_eject_blk, errp);
-    if (!exp) {
-        goto out;
+    export = blk_exp_add(export_opts, errp);
+    if (!export) {
+        goto fail;
     }
 
-    /* The list of named exports has a strong reference to this export now and
-     * our only way of accessing it is through nbd_export_find(), so we can drop
-     * the strong reference that is @exp. */
-    nbd_export_put(exp);
+    /*
+     * nbd-server-add removes the export when the named BlockBackend used for
+     * @device goes away.
+     */
+    on_eject_blk = blk_by_name(arg->device);
+    if (on_eject_blk) {
+        nbd_export_set_on_eject_blk(export, on_eject_blk);
+    }
 
- out:
-    aio_context_release(aio_context);
+fail:
+    qapi_free_BlockExportOptions(export_opts);
 }
 
 void qmp_nbd_server_remove(const char *name,
-                           bool has_mode, NbdServerRemoveMode mode,
+                           bool has_mode, BlockExportRemoveMode mode,
                            Error **errp)
 {
-    NBDExport *exp;
-    AioContext *aio_context;
+    BlockExport *exp;
 
-    if (!nbd_server) {
-        error_setg(errp, "NBD server not running");
+    exp = blk_exp_find(name);
+    if (exp && exp->drv->type != BLOCK_EXPORT_TYPE_NBD) {
+        error_setg(errp, "Block export '%s' is not an NBD export", name);
         return;
     }
 
-    exp = nbd_export_find(name);
-    if (exp == NULL) {
-        error_setg(errp, "Export '%s' is not found", name);
-        return;
-    }
-
-    if (!has_mode) {
-        mode = NBD_SERVER_REMOVE_MODE_SAFE;
-    }
-
-    aio_context = nbd_export_aio_context(exp);
-    aio_context_acquire(aio_context);
-    nbd_export_remove(exp, mode, errp);
-    aio_context_release(aio_context);
+    qmp_block_export_del(name, has_mode, mode, errp);
 }
 
 void qmp_nbd_server_stop(Error **errp)
@@ -254,7 +265,7 @@ void qmp_nbd_server_stop(Error **errp)
         return;
     }
 
-    nbd_export_close_all();
+    blk_exp_close_all_type(BLOCK_EXPORT_TYPE_NBD);
 
     nbd_server_free(nbd_server);
     nbd_server = NULL;

docs/system/deprecated.rst

@@ -264,6 +264,12 @@ chardev client socket with ``wait`` option (since 4.0)
 Character devices creating sockets in client mode should not specify
 the 'wait' field, which is only applicable to sockets in server mode
 
+``nbd-server-add`` and ``nbd-server-remove`` (since 5.2)
+''''''''''''''''''''''''''''''''''''''''''''''''''''''''
+
+Use the more generic commands ``block-export-add`` and ``block-export-del``
+instead.
+
 Human Monitor Protocol (HMP) commands
 -------------------------------------
 

docs/throttle.txt

@@ -1,6 +1,6 @@
 The QEMU throttling infrastructure
 ==================================
-Copyright (C) 2016 Igalia, S.L.
+Copyright (C) 2016,2020 Igalia, S.L.
 Author: Alberto Garcia <berto@igalia.com>
 
 This work is licensed under the terms of the GNU GPL, version 2 or
@@ -253,3 +253,109 @@ up. After those 60 seconds the bucket will have leaked 60 x 100 =
 
 Also, due to the way the algorithm works, longer burst can be done at
 a lower I/O rate, e.g. 1000 IOPS during 120 seconds.
+
+
+The 'throttle' block filter
+---------------------------
+Since QEMU 2.11 it is possible to configure the I/O limits using a
+'throttle' block filter. This filter uses the exact same throttling
+infrastructure described above but can be used anywhere in the node
+graph, allowing for more flexibility.
+
+The user can create an arbitrary number of filters and each one of
+them must be assigned to a group that contains the actual I/O limits.
+Different filters can use the same group so the limits are shared as
+described earlier in "Applying I/O limits to groups of disks".
+
+A group can be created using the object-add QMP function:
+
+   { "execute": "object-add",
+     "arguments": {
+       "qom-type": "throttle-group",
+       "id": "group0",
+       "props": {
+         "limits" : {
+           "iops-total": 1000
+           "bps-write": 2097152
+         }
+       }
+     }
+   }
+
+throttle-group has a 'limits' property (of type ThrottleLimits as
+defined in qapi/block-core.json) which can be set on creation or later
+with 'qom-set'.
+
+A throttle-group can also be created with the -object command line
+option but at the moment there is no way to pass a 'limits' parameter
+that contains a ThrottleLimits structure. The solution is to set the
+individual values directly, like in this example:
+
+   -object throttle-group,id=group0,x-iops-total=1000,x-bps-write=2097152
+
+Note however that this is not a stable API (hence the 'x-' prefixes) and
+will disappear when -object gains support for structured options and
+enables use of 'limits'.
+
+Once we have a throttle-group we can use the throttle block filter,
+where the 'file' property must be set to the block device that we want
+to filter:
+
+   { "execute": "blockdev-add",
+     "arguments": {
+        "options":  {
+           "driver": "qcow2",
+           "node-name": "disk0",
+           "file": {
+              "driver": "file",
+              "filename": "/path/to/disk.qcow2"
+           }
+        }
+     }
+   }
+
+   { "execute": "blockdev-add",
+     "arguments": {
+        "driver": "throttle",
+        "node-name": "throttle0",
+        "throttle-group": "group0",
+        "file": "disk0"
+     }
+   }
+
+A similar setup can also be done with the command line, for example:
+
+   -drive driver=throttle,throttle-group=group0,
+          file.driver=qcow2,file.file.filename=/path/to/disk.qcow2
+
+The scenario described so far is very simple but the throttle block
+filter allows for more complex configurations. For example, let's say
+that we have three different drives and we want to set I/O limits for
+each one of them and an additional set of limits for the combined I/O
+of all three drives.
+
+First we would define all throttle groups, one for each one of the
+drives and one that would apply to all of them:
+
+   -object throttle-group,id=limits0,x-iops-total=2000
+   -object throttle-group,id=limits1,x-iops-total=2500
+   -object throttle-group,id=limits2,x-iops-total=3000
+   -object throttle-group,id=limits012,x-iops-total=4000
+
+Now we can define the drives, and for each one of them we use two
+chained throttle filters: the drive's own filter and the combined
+filter.
+
+   -drive driver=throttle,throttle-group=limits012,
+          file.driver=throttle,file.throttle-group=limits0
+          file.file.driver=qcow2,file.file.file.filename=/path/to/disk0.qcow2
+   -drive driver=throttle,throttle-group=limits012,
+          file.driver=throttle,file.throttle-group=limits1
+          file.file.driver=qcow2,file.file.file.filename=/path/to/disk1.qcow2
+   -drive driver=throttle,throttle-group=limits012,
+          file.driver=throttle,file.throttle-group=limits2
+          file.file.driver=qcow2,file.file.file.filename=/path/to/disk2.qcow2
+
+In this example the individual drives have IOPS limits of 2000, 2500
+and 3000 respectively but the total combined I/O can never exceed 4000
+IOPS.

include/block/export.h

@@ -0,0 +1,89 @@
+/*
+ * Declarations for block exports
+ *
+ * Copyright (c) 2012, 2020 Red Hat, Inc.
+ *
+ * Authors:
+ * Paolo Bonzini <pbonzini@redhat.com>
+ * Kevin Wolf <kwolf@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * later.  See the COPYING file in the top-level directory.
+ */
+
+#ifndef BLOCK_EXPORT_H
+#define BLOCK_EXPORT_H
+
+#include "qapi/qapi-types-block-export.h"
+#include "qemu/queue.h"
+
+typedef struct BlockExport BlockExport;
+
+typedef struct BlockExportDriver {
+    /* The export type that this driver services */
+    BlockExportType type;
+
+    /*
+     * The size of the driver-specific state that contains BlockExport as its
+     * first field.
+     */
+    size_t instance_size;
+
+    /* Creates and starts a new block export */
+    int (*create)(BlockExport *, BlockExportOptions *, Error **);
+
+    /*
+     * Frees a removed block export. This function is only called after all
+     * references have been dropped.
+     */
+    void (*delete)(BlockExport *);
+
+    /*
+     * Start to disconnect all clients and drop other references held
+     * internally by the export driver. When the function returns, there may
+     * still be active references while the export is in the process of
+     * shutting down.
+     */
+    void (*request_shutdown)(BlockExport *);
+} BlockExportDriver;
+
+struct BlockExport {
+    const BlockExportDriver *drv;
+
+    /* Unique identifier for the export */
+    char *id;
+
+    /*
+     * Reference count for this block export. This includes strong references
+     * both from the owner (qemu-nbd or the monitor) and clients connected to
+     * the export.
+     */
+    int refcount;
+
+    /*
+     * True if one of the references in refcount belongs to the user. After the
+     * user has dropped their reference, they may not e.g. remove the same
+     * export a second time (which would decrease the refcount without having
+     * it incremented first).
+     */
+    bool user_owned;
+
+    /* The AioContext whose lock protects this BlockExport object. */
+    AioContext *ctx;
+
+    /* The block device to export */
+    BlockBackend *blk;
+
+    /* List entry for block_exports */
+    QLIST_ENTRY(BlockExport) next;
+};
+
+BlockExport *blk_exp_add(BlockExportOptions *export, Error **errp);
+BlockExport *blk_exp_find(const char *id);
+void blk_exp_ref(BlockExport *exp);
+void blk_exp_unref(BlockExport *exp);
+void blk_exp_request_shutdown(BlockExport *exp);
+void blk_exp_close_all(void);
+void blk_exp_close_all_type(BlockExportType type);
+
+#endif

include/block/nbd.h

@@ -20,11 +20,13 @@
 #ifndef NBD_H
 #define NBD_H
 
-#include "qapi/qapi-types-block.h"
+#include "block/export.h"
 #include "io/channel-socket.h"
 #include "crypto/tlscreds.h"
 #include "qapi/error.h"
 
+extern const BlockExportDriver blk_exp_nbd;
+
 /* Handshake phase structs - this struct is passed on the wire */
 
 struct NBDOption {
@@ -328,21 +330,10 @@ int nbd_errno_to_system_errno(int err);
 typedef struct NBDExport NBDExport;
 typedef struct NBDClient NBDClient;
 
-NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset,
-                          uint64_t size, const char *name, const char *desc,
-                          const char *bitmap, bool readonly, bool shared,
-                          void (*close)(NBDExport *), bool writethrough,
-                          BlockBackend *on_eject_blk, Error **errp);
-void nbd_export_close(NBDExport *exp);
-void nbd_export_remove(NBDExport *exp, NbdServerRemoveMode mode, Error **errp);
-void nbd_export_get(NBDExport *exp);
-void nbd_export_put(NBDExport *exp);
-
-BlockBackend *nbd_export_get_blockdev(NBDExport *exp);
+void nbd_export_set_on_eject_blk(BlockExport *exp, BlockBackend *blk);
 
 AioContext *nbd_export_aio_context(NBDExport *exp);
 NBDExport *nbd_export_find(const char *name);
-void nbd_export_close_all(void);
 
 void nbd_client_new(QIOChannelSocket *sioc,
                     QCryptoTLSCreds *tlscreds,
@@ -351,8 +342,11 @@ void nbd_client_new(QIOChannelSocket *sioc,
 void nbd_client_get(NBDClient *client);
 void nbd_client_put(NBDClient *client);
 
+void nbd_server_is_qemu_nbd(bool value);
+bool nbd_server_is_running(void);
 void nbd_server_start(SocketAddress *addr, const char *tls_creds,
-                      const char *tls_authz, Error **errp);
+                      const char *tls_authz, uint32_t max_connections,
+                      Error **errp);
 void nbd_server_start_options(NbdServerOptions *arg, Error **errp);
 
 /* nbd_read

meson.build

@@ -970,6 +970,7 @@ subdir('dump')
 
 block_ss.add(files(
   'block.c',
+  'blockdev-nbd.c',
   'blockjob.c',
   'job.c',
   'qemu-io-cmds.c',
@@ -982,7 +983,6 @@ subdir('block')
 
 blockdev_ss.add(files(
   'blockdev.c',
-  'blockdev-nbd.c',
   'iothread.c',
   'job-qmp.c',
 ))

qapi/block-core.json

@@ -5194,172 +5194,6 @@
              'iothread': 'StrOrNull',
              '*force': 'bool' } }
 
-##
-# @NbdServerOptions:
-#
-# @addr: Address on which to listen.
-# @tls-creds: ID of the TLS credentials object (since 2.6).
-# @tls-authz: ID of the QAuthZ authorization object used to validate
-#             the client's x509 distinguished name. This object is
-#             is only resolved at time of use, so can be deleted and
-#             recreated on the fly while the NBD server is active.
-#             If missing, it will default to denying access (since 4.0).
-#
-# Keep this type consistent with the nbd-server-start arguments. The only
-# intended difference is using SocketAddress instead of SocketAddressLegacy.
-#
-# Since: 4.2
-##
-{ 'struct': 'NbdServerOptions',
-  'data': { 'addr': 'SocketAddress',
-            '*tls-creds': 'str',
-            '*tls-authz': 'str'} }
-
-##
-# @nbd-server-start:
-#
-# Start an NBD server listening on the given host and port.  Block
-# devices can then be exported using @nbd-server-add.  The NBD
-# server will present them as named exports; for example, another
-# QEMU instance could refer to them as "nbd:HOST:PORT:exportname=NAME".
-#
-# Keep this type consistent with the NbdServerOptions type. The only intended
-# difference is using SocketAddressLegacy instead of SocketAddress.
-#
-# @addr: Address on which to listen.
-# @tls-creds: ID of the TLS credentials object (since 2.6).
-# @tls-authz: ID of the QAuthZ authorization object used to validate
-#             the client's x509 distinguished name. This object is
-#             is only resolved at time of use, so can be deleted and
-#             recreated on the fly while the NBD server is active.
-#             If missing, it will default to denying access (since 4.0).
-#
-# Returns: error if the server is already running.
-#
-# Since: 1.3.0
-##
-{ 'command': 'nbd-server-start',
-  'data': { 'addr': 'SocketAddressLegacy',
-            '*tls-creds': 'str',
-            '*tls-authz': 'str'} }
-
-##
-# @BlockExportNbd:
-#
-# An NBD block export.
-#
-# @device: The device name or node name of the node to be exported
-#
-# @name: Export name. If unspecified, the @device parameter is used as the
-#        export name. (Since 2.12)
-#
-# @description: Free-form description of the export, up to 4096 bytes.
-#               (Since 5.0)
-#
-# @writable: Whether clients should be able to write to the device via the
-#            NBD connection (default false).
-#
-# @bitmap: Also export the dirty bitmap reachable from @device, so the
-#          NBD client can use NBD_OPT_SET_META_CONTEXT with
-#          "qemu:dirty-bitmap:NAME" to inspect the bitmap. (since 4.0)
-#
-# Since: 5.0
-##
-{ 'struct': 'BlockExportNbd',
-  'data': {'device': 'str', '*name': 'str', '*description': 'str',
-           '*writable': 'bool', '*bitmap': 'str' } }
-
-##
-# @nbd-server-add:
-#
-# Export a block node to QEMU's embedded NBD server.
-#
-# Returns: error if the server is not running, or export with the same name
-#          already exists.
-#
-# Since: 1.3.0
-##
-{ 'command': 'nbd-server-add',
-  'data': 'BlockExportNbd', 'boxed': true }
-
-##
-# @NbdServerRemoveMode:
-#
-# Mode for removing an NBD export.
-#
-# @safe: Remove export if there are no existing connections, fail otherwise.
-#
-# @hard: Drop all connections immediately and remove export.
-#
-# Potential additional modes to be added in the future:
-#
-# hide: Just hide export from new clients, leave existing connections as is.
-# Remove export after all clients are disconnected.
-#
-# soft: Hide export from new clients, answer with ESHUTDOWN for all further
-# requests from existing clients.
-#
-# Since: 2.12
-##
-{'enum': 'NbdServerRemoveMode', 'data': ['safe', 'hard']}
-
-##
-# @nbd-server-remove:
-#
-# Remove NBD export by name.
-#
-# @name: Export name.
-#
-# @mode: Mode of command operation. See @NbdServerRemoveMode description.
-#        Default is 'safe'.
-#
-# Returns: error if
-#            - the server is not running
-#            - export is not found
-#            - mode is 'safe' and there are existing connections
-#
-# Since: 2.12
-##
-{ 'command': 'nbd-server-remove',
-  'data': {'name': 'str', '*mode': 'NbdServerRemoveMode'} }
-
-##
-# @nbd-server-stop:
-#
-# Stop QEMU's embedded NBD server, and unregister all devices previously
-# added via @nbd-server-add.
-#
-# Since: 1.3.0
-##
-{ 'command': 'nbd-server-stop' }
-
-##
-# @BlockExportType:
-#
-# An enumeration of block export types
-#
-# @nbd: NBD export
-#
-# Since: 4.2
-##
-{ 'enum': 'BlockExportType',
-  'data': [ 'nbd' ] }
-
-##
-# @BlockExport:
-#
-# Describes a block export, i.e. how single node should be exported on an
-# external interface.
-#
-# Since: 4.2
-##
-{ 'union': 'BlockExport',
-  'base': { 'type': 'BlockExportType' },
-  'discriminator': 'type',
-  'data': {
-      'nbd': 'BlockExportNbd'
-   } }
-
 ##
 # @QuorumOpType:
 #

qapi/block-export.json

@@ -0,0 +1,291 @@
+# -*- Mode: Python -*-
+# vim: filetype=python
+
+##
+# == Block device exports
+##
+
+{ 'include': 'sockets.json' }
+
+##
+# @NbdServerOptions:
+#
+# Keep this type consistent with the nbd-server-start arguments. The only
+# intended difference is using SocketAddress instead of SocketAddressLegacy.
+#
+# @addr: Address on which to listen.
+# @tls-creds: ID of the TLS credentials object (since 2.6).
+# @tls-authz: ID of the QAuthZ authorization object used to validate
+#             the client's x509 distinguished name. This object is
+#             is only resolved at time of use, so can be deleted and
+#             recreated on the fly while the NBD server is active.
+#             If missing, it will default to denying access (since 4.0).
+# @max-connections: The maximum number of connections to allow at the same
+#                   time, 0 for unlimited. (since 5.2; default: 0)
+#
+# Since: 4.2
+##
+{ 'struct': 'NbdServerOptions',
+  'data': { 'addr': 'SocketAddress',
+            '*tls-creds': 'str',
+            '*tls-authz': 'str',
+            '*max-connections': 'uint32' } }
+
+##
+# @nbd-server-start:
+#
+# Start an NBD server listening on the given host and port.  Block
+# devices can then be exported using @nbd-server-add.  The NBD
+# server will present them as named exports; for example, another
+# QEMU instance could refer to them as "nbd:HOST:PORT:exportname=NAME".
+#
+# Keep this type consistent with the NbdServerOptions type. The only intended
+# difference is using SocketAddressLegacy instead of SocketAddress.
+#
+# @addr: Address on which to listen.
+# @tls-creds: ID of the TLS credentials object (since 2.6).
+# @tls-authz: ID of the QAuthZ authorization object used to validate
+#             the client's x509 distinguished name. This object is
+#             is only resolved at time of use, so can be deleted and
+#             recreated on the fly while the NBD server is active.
+#             If missing, it will default to denying access (since 4.0).
+# @max-connections: The maximum number of connections to allow at the same
+#                   time, 0 for unlimited. (since 5.2; default: 0)
+#
+# Returns: error if the server is already running.
+#
+# Since: 1.3.0
+##
+{ 'command': 'nbd-server-start',
+  'data': { 'addr': 'SocketAddressLegacy',
+            '*tls-creds': 'str',
+            '*tls-authz': 'str',
+            '*max-connections': 'uint32' } }
+
+##
+# @BlockExportOptionsNbd:
+#
+# An NBD block export (options shared between nbd-server-add and the NBD branch
+# of block-export-add).
+#
+# @name: Export name. If unspecified, the @device parameter is used as the
+#        export name. (Since 2.12)
+#
+# @description: Free-form description of the export, up to 4096 bytes.
+#               (Since 5.0)
+#
+# @bitmap: Also export the dirty bitmap reachable from @device, so the
+#          NBD client can use NBD_OPT_SET_META_CONTEXT with
+#          "qemu:dirty-bitmap:NAME" to inspect the bitmap. (since 4.0)
+#
+# Since: 5.0
+##
+{ 'struct': 'BlockExportOptionsNbd',
+  'data': { '*name': 'str', '*description': 'str',
+            '*bitmap': 'str' } }
+
+##
+# @NbdServerAddOptions:
+#
+# An NBD block export.
+#
+# @device: The device name or node name of the node to be exported
+#
+# @writable: Whether clients should be able to write to the device via the
+#            NBD connection (default false).
+#
+# Since: 5.0
+##
+{ 'struct': 'NbdServerAddOptions',
+  'base': 'BlockExportOptionsNbd',
+  'data': { 'device': 'str',
+            '*writable': 'bool' } }
+
+##
+# @nbd-server-add:
+#
+# Export a block node to QEMU's embedded NBD server.
+#
+# The export name will be used as the id for the resulting block export.
+#
+# Features:
+# @deprecated: This command is deprecated. Use @block-export-add instead.
+#
+# Returns: error if the server is not running, or export with the same name
+#          already exists.
+#
+# Since: 1.3.0
+##
+{ 'command': 'nbd-server-add',
+  'data': 'NbdServerAddOptions', 'boxed': true, 'features': ['deprecated'] }
+
+##
+# @BlockExportRemoveMode:
+#
+# Mode for removing a block export.
+#
+# @safe: Remove export if there are no existing connections, fail otherwise.
+#
+# @hard: Drop all connections immediately and remove export.
+#
+# Potential additional modes to be added in the future:
+#
+# hide: Just hide export from new clients, leave existing connections as is.
+# Remove export after all clients are disconnected.
+#
+# soft: Hide export from new clients, answer with ESHUTDOWN for all further
+# requests from existing clients.
+#
+# Since: 2.12
+##
+{'enum': 'BlockExportRemoveMode', 'data': ['safe', 'hard']}
+
+##
+# @nbd-server-remove:
+#
+# Remove NBD export by name.
+#
+# @name: Block export id.
+#
+# @mode: Mode of command operation. See @BlockExportRemoveMode description.
+#        Default is 'safe'.
+#
+# Features:
+# @deprecated: This command is deprecated. Use @block-export-del instead.
+#
+# Returns: error if
+#            - the server is not running
+#            - export is not found
+#            - mode is 'safe' and there are existing connections
+#
+# Since: 2.12
+##
+{ 'command': 'nbd-server-remove',
+  'data': {'name': 'str', '*mode': 'BlockExportRemoveMode'},
+  'features': ['deprecated'] }
+
+##
+# @nbd-server-stop:
+#
+# Stop QEMU's embedded NBD server, and unregister all devices previously
+# added via @nbd-server-add.
+#
+# Since: 1.3.0
+##
+{ 'command': 'nbd-server-stop' }
+
+##
+# @BlockExportType:
+#
+# An enumeration of block export types
+#
+# @nbd: NBD export
+#
+# Since: 4.2
+##
+{ 'enum': 'BlockExportType',
+  'data': [ 'nbd' ] }
+
+##
+# @BlockExportOptions:
+#
+# Describes a block export, i.e. how single node should be exported on an
+# external interface.
+#
+# @id: A unique identifier for the block export (across all export types)
+#
+# @node-name: The node name of the block node to be exported (since: 5.2)
+#
+# @writable: True if clients should be able to write to the export
+#            (default false)
+#
+# @writethrough: If true, caches are flushed after every write request to the
+#                export before completion is signalled. (since: 5.2;
+#                default: false)
+#
+# Since: 4.2
+##
+{ 'union': 'BlockExportOptions',
+  'base': { 'type': 'BlockExportType',
+            'id': 'str',
+            'node-name': 'str',
+            '*writable': 'bool',
+            '*writethrough': 'bool' },
+  'discriminator': 'type',
+  'data': {
+      'nbd': 'BlockExportOptionsNbd'
+   } }
+
+##
+# @block-export-add:
+#
+# Creates a new block export.
+#
+# Since: 5.2
+##
+{ 'command': 'block-export-add',
+  'data': 'BlockExportOptions', 'boxed': true }
+
+##
+# @block-export-del:
+#
+# Request to remove a block export. This drops the user's reference to the
+# export, but the export may still stay around after this command returns until
+# the shutdown of the export has completed.
+#
+# @id: Block export id.
+#
+# @mode: Mode of command operation. See @BlockExportRemoveMode description.
+#        Default is 'safe'.
+#
+# Returns: Error if the export is not found or @mode is 'safe' and the export
+#          is still in use (e.g. by existing client connections)
+#
+# Since: 5.2
+##
+{ 'command': 'block-export-del',
+  'data': { 'id': 'str', '*mode': 'BlockExportRemoveMode' } }
+
+##
+# @BLOCK_EXPORT_DELETED:
+#
+# Emitted when a block export is removed and its id can be reused.
+#
+# @id: Block export id.
+#
+# Since: 5.2
+##
+{ 'event': 'BLOCK_EXPORT_DELETED',
+  'data': { 'id': 'str' } }
+
+##
+# @BlockExportInfo:
+#
+# Information about a single block export.
+#
+# @id: The unique identifier for the block export
+#
+# @type: The block export type
+#
+# @node-name: The node name of the block node that is exported
+#
+# @shutting-down: True if the export is shutting down (e.g. after a
+#                 block-export-del command, but before the shutdown has
+#                 completed)
+#
+# Since:  5.2
+##
+{ 'struct': 'BlockExportInfo',
+  'data': { 'id': 'str',
+            'type': 'BlockExportType',
+            'node-name': 'str',
+            'shutting-down': 'bool' } }
+
+##
+# @query-block-exports:
+#
+# Returns: A list of BlockExportInfo describing all block exports
+#
+# Since: 5.2
+##
+{ 'command': 'query-block-exports', 'returns': ['BlockExportInfo'] }

qapi/meson.build

@@ -17,8 +17,9 @@ qapi_all_modules = [
   'acpi',
   'audio',
   'authz',
-  'block-core',
   'block',
+  'block-core',
+  'block-export',
   'char',
   'common',
   'control',
@@ -49,6 +50,7 @@ qapi_all_modules = [
 
 qapi_storage_daemon_modules = [
   'block-core',
+  'block-export',
   'char',
   'common',
   'control',

qapi/qapi-schema.json

@@ -66,6 +66,7 @@
 { 'include': 'run-state.json' }
 { 'include': 'crypto.json' }
 { 'include': 'block.json' }
+{ 'include': 'block-export.json' }
 { 'include': 'char.json' }
 { 'include': 'dump.json' }
 { 'include': 'job.json' }

qemu-io-cmds.c

@@ -2383,14 +2383,7 @@ static const cmdinfo_t sleep_cmd = {
 
 static void help_oneline(const char *cmd, const cmdinfo_t *ct)
 {
-    if (cmd) {
-        printf("%s ", cmd);
-    } else {
-        printf("%s ", ct->name);
-        if (ct->altname) {
-            printf("(or %s) ", ct->altname);
-        }
-    }
+    printf("%s ", cmd);
 
     if (ct->args) {
         printf("%s ", ct->args);
@@ -2420,7 +2413,7 @@ static int help_f(BlockBackend *blk, int argc, char **argv)
 {
     const cmdinfo_t *ct;
 
-    if (argc == 1) {
+    if (argc < 2) {
         help_all();
         return 0;
     }

qemu-nbd.c

@@ -65,12 +65,11 @@
 
 #define MBR_SIZE 512
 
-static NBDExport *export;
 static int verbose;
 static char *srcpath;
 static SocketAddress *saddr;
 static int persistent = 0;
-static enum { RUNNING, TERMINATE, TERMINATING, TERMINATED } state;
+static enum { RUNNING, TERMINATE, TERMINATED } state;
 static int shared = 1;
 static int nb_fds;
 static QIONetListener *server;
@@ -332,12 +331,6 @@ static int nbd_can_accept(void)
     return state == RUNNING && nb_fds < shared;
 }
 
-static void nbd_export_closed(NBDExport *export)
-{
-    assert(state == TERMINATING);
-    state = TERMINATED;
-}
-
 static void nbd_update_server_watch(void);
 
 static void nbd_client_closed(NBDClient *client, bool negotiated)
@@ -524,7 +517,6 @@ int main(int argc, char **argv)
     const char *port = NULL;
     char *sockpath = NULL;
     char *device = NULL;
-    int64_t fd_size;
     QemuOpts *sn_opts = NULL;
     const char *sn_id_or_name = NULL;
     const char *sopt = "hVb:o:p:rsnc:dvk:e:f:tl:x:T:D:B:L";
@@ -587,6 +579,7 @@ int main(int argc, char **argv)
     int old_stderr = -1;
     unsigned socket_activation;
     const char *pid_file_name = NULL;
+    BlockExportOptions *export_opts;
 
 #if HAVE_NBD_DEVICE
     /* The client thread uses SIGTERM to interrupt the server.  A signal
@@ -1037,6 +1030,17 @@ int main(int argc, char **argv)
     }
     bs = blk_bs(blk);
 
+    if (dev_offset) {
+        QDict *raw_opts = qdict_new();
+        qdict_put_str(raw_opts, "driver", "raw");
+        qdict_put_str(raw_opts, "file", bs->node_name);
+        qdict_put_int(raw_opts, "offset", dev_offset);
+        bs = bdrv_open(NULL, NULL, raw_opts, flags, &error_fatal);
+        blk_remove_bs(blk);
+        blk_insert_bs(blk, bs, &error_fatal);
+        bdrv_unref(bs);
+    }
+
     blk_set_enable_write_cache(blk, !writethrough);
 
     if (sn_opts) {
@@ -1054,24 +1058,29 @@ int main(int argc, char **argv)
     }
 
     bs->detect_zeroes = detect_zeroes;
-    fd_size = blk_getlength(blk);
-    if (fd_size < 0) {
-        error_report("Failed to determine the image length: %s",
-                     strerror(-fd_size));
-        exit(EXIT_FAILURE);
-    }
 
-    if (dev_offset >= fd_size) {
-        error_report("Offset (%" PRIu64 ") has to be smaller than the image "
-                     "size (%" PRId64 ")", dev_offset, fd_size);
-        exit(EXIT_FAILURE);
-    }
-    fd_size -= dev_offset;
+    nbd_server_is_qemu_nbd(true);
 
-    export = nbd_export_new(bs, dev_offset, fd_size, export_name,
-                            export_description, bitmap, readonly, shared > 1,
-                            nbd_export_closed, writethrough, NULL,
-                            &error_fatal);
+    export_opts = g_new(BlockExportOptions, 1);
+    *export_opts = (BlockExportOptions) {
+        .type               = BLOCK_EXPORT_TYPE_NBD,
+        .id                 = g_strdup("qemu-nbd-export"),
+        .node_name          = g_strdup(bdrv_get_node_name(bs)),
+        .has_writethrough   = true,
+        .writethrough       = writethrough,
+        .has_writable       = true,
+        .writable           = !readonly,
+        .u.nbd = {
+            .has_name           = true,
+            .name               = g_strdup(export_name),
+            .has_description    = !!export_description,
+            .description        = g_strdup(export_description),
+            .has_bitmap         = !!bitmap,
+            .bitmap             = g_strdup(bitmap),
+        },
+    };
+    blk_exp_add(export_opts, &error_fatal);
+    qapi_free_BlockExportOptions(export_opts);
 
     if (device) {
 #if HAVE_NBD_DEVICE
@@ -1111,10 +1120,8 @@ int main(int argc, char **argv)
     do {
         main_loop_wait(false);
         if (state == TERMINATE) {
-            state = TERMINATING;
-            nbd_export_close(export);
-            nbd_export_put(export);
-            export = NULL;
+            blk_exp_close_all();
+            state = TERMINATED;
         }
     } while (state != TERMINATED);