nbd: implement .bdrv_detach/attach_aio_context()

Drop the assumption that we're using the main AioContext.  Convert
qemu_aio_set_fd_handler() calls to aio_set_fd_handler().

The .bdrv_detach/attach_aio_context() interfaces also need to be
implemented to move the socket fd handler from the old to the new
AioContext.
Acked-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

block/nbd-client.c

@@ -49,7 +49,7 @@ static void nbd_teardown_connection(NbdClientSession *client)
     shutdown(client->sock, 2);
     nbd_recv_coroutines_enter_all(client);
 
-    qemu_aio_set_fd_handler(client->sock, NULL, NULL, NULL);
+    nbd_client_session_detach_aio_context(client);
     closesocket(client->sock);
     client->sock = -1;
 }
@@ -103,11 +103,14 @@ static int nbd_co_send_request(NbdClientSession *s,
     struct nbd_request *request,
     QEMUIOVector *qiov, int offset)
 {
+    AioContext *aio_context;
     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);
+    aio_context = bdrv_get_aio_context(s->bs);
+    aio_set_fd_handler(aio_context, s->sock,
+                       nbd_reply_ready, nbd_restart_write, s);
     if (qiov) {
         if (!s->is_unix) {
             socket_set_cork(s->sock, 1);
@@ -126,7 +129,7 @@ static int nbd_co_send_request(NbdClientSession *s,
     } else {
         rc = nbd_send_request(s->sock, request);
     }
-    qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, NULL, s);
+    aio_set_fd_handler(aio_context, s->sock, nbd_reply_ready, NULL, s);
     s->send_coroutine = NULL;
     qemu_co_mutex_unlock(&s->send_mutex);
     return rc;
@@ -335,6 +338,19 @@ int nbd_client_session_co_discard(NbdClientSession *client, int64_t sector_num,
 
 }
 
+void nbd_client_session_detach_aio_context(NbdClientSession *client)
+{
+    aio_set_fd_handler(bdrv_get_aio_context(client->bs), client->sock,
+                       NULL, NULL, NULL);
+}
+
+void nbd_client_session_attach_aio_context(NbdClientSession *client,
+                                           AioContext *new_context)
+{
+    aio_set_fd_handler(new_context, client->sock,
+                       nbd_reply_ready, NULL, client);
+}
+
 void nbd_client_session_close(NbdClientSession *client)
 {
     struct nbd_request request = {
@@ -381,7 +397,7 @@ int nbd_client_session_init(NbdClientSession *client, BlockDriverState *bs,
     /* 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);
+    nbd_client_session_attach_aio_context(client, bdrv_get_aio_context(bs));
 
     logout("Established connection with NBD server\n");
     return 0;

block/nbd-client.h

@@ -47,4 +47,8 @@ int nbd_client_session_co_writev(NbdClientSession *client, int64_t sector_num,
 int nbd_client_session_co_readv(NbdClientSession *client, int64_t sector_num,
                                 int nb_sectors, QEMUIOVector *qiov);
 
+void nbd_client_session_detach_aio_context(NbdClientSession *client);
+void nbd_client_session_attach_aio_context(NbdClientSession *client,
+                                           AioContext *new_context);
+
 #endif /* NBD_CLIENT_H */

block/nbd.c

@@ -323,46 +323,67 @@ static int64_t nbd_getlength(BlockDriverState *bs)
     return s->client.size;
 }
 
+static void nbd_detach_aio_context(BlockDriverState *bs)
+{
+    BDRVNBDState *s = bs->opaque;
+
+    nbd_client_session_detach_aio_context(&s->client);
+}
+
+static void nbd_attach_aio_context(BlockDriverState *bs,
+                                   AioContext *new_context)
+{
+    BDRVNBDState *s = bs->opaque;
+
+    nbd_client_session_attach_aio_context(&s->client, new_context);
+}
+
 static BlockDriver bdrv_nbd = {
-    .format_name         = "nbd",
-    .protocol_name       = "nbd",
-    .instance_size       = sizeof(BDRVNBDState),
-    .bdrv_parse_filename = nbd_parse_filename,
-    .bdrv_file_open      = nbd_open,
-    .bdrv_co_readv       = nbd_co_readv,
-    .bdrv_co_writev      = nbd_co_writev,
-    .bdrv_close          = nbd_close,
-    .bdrv_co_flush_to_os = nbd_co_flush,
-    .bdrv_co_discard     = nbd_co_discard,
-    .bdrv_getlength      = nbd_getlength,
+    .format_name                = "nbd",
+    .protocol_name              = "nbd",
+    .instance_size              = sizeof(BDRVNBDState),
+    .bdrv_parse_filename        = nbd_parse_filename,
+    .bdrv_file_open             = nbd_open,
+    .bdrv_co_readv              = nbd_co_readv,
+    .bdrv_co_writev             = nbd_co_writev,
+    .bdrv_close                 = nbd_close,
+    .bdrv_co_flush_to_os        = nbd_co_flush,
+    .bdrv_co_discard            = nbd_co_discard,
+    .bdrv_getlength             = nbd_getlength,
+    .bdrv_detach_aio_context    = nbd_detach_aio_context,
+    .bdrv_attach_aio_context    = nbd_attach_aio_context,
 };
 
 static BlockDriver bdrv_nbd_tcp = {
-    .format_name         = "nbd",
-    .protocol_name       = "nbd+tcp",
-    .instance_size       = sizeof(BDRVNBDState),
-    .bdrv_parse_filename = nbd_parse_filename,
-    .bdrv_file_open      = nbd_open,
-    .bdrv_co_readv       = nbd_co_readv,
-    .bdrv_co_writev      = nbd_co_writev,
-    .bdrv_close          = nbd_close,
-    .bdrv_co_flush_to_os = nbd_co_flush,
-    .bdrv_co_discard     = nbd_co_discard,
-    .bdrv_getlength      = nbd_getlength,
+    .format_name                = "nbd",
+    .protocol_name              = "nbd+tcp",
+    .instance_size              = sizeof(BDRVNBDState),
+    .bdrv_parse_filename        = nbd_parse_filename,
+    .bdrv_file_open             = nbd_open,
+    .bdrv_co_readv              = nbd_co_readv,
+    .bdrv_co_writev             = nbd_co_writev,
+    .bdrv_close                 = nbd_close,
+    .bdrv_co_flush_to_os        = nbd_co_flush,
+    .bdrv_co_discard            = nbd_co_discard,
+    .bdrv_getlength             = nbd_getlength,
+    .bdrv_detach_aio_context    = nbd_detach_aio_context,
+    .bdrv_attach_aio_context    = nbd_attach_aio_context,
 };
 
 static BlockDriver bdrv_nbd_unix = {
-    .format_name         = "nbd",
-    .protocol_name       = "nbd+unix",
-    .instance_size       = sizeof(BDRVNBDState),
-    .bdrv_parse_filename = nbd_parse_filename,
-    .bdrv_file_open      = nbd_open,
-    .bdrv_co_readv       = nbd_co_readv,
-    .bdrv_co_writev      = nbd_co_writev,
-    .bdrv_close          = nbd_close,
-    .bdrv_co_flush_to_os = nbd_co_flush,
-    .bdrv_co_discard     = nbd_co_discard,
-    .bdrv_getlength      = nbd_getlength,
+    .format_name                = "nbd",
+    .protocol_name              = "nbd+unix",
+    .instance_size              = sizeof(BDRVNBDState),
+    .bdrv_parse_filename        = nbd_parse_filename,
+    .bdrv_file_open             = nbd_open,
+    .bdrv_co_readv              = nbd_co_readv,
+    .bdrv_co_writev             = nbd_co_writev,
+    .bdrv_close                 = nbd_close,
+    .bdrv_co_flush_to_os        = nbd_co_flush,
+    .bdrv_co_discard            = nbd_co_discard,
+    .bdrv_getlength             = nbd_getlength,
+    .bdrv_detach_aio_context    = nbd_detach_aio_context,
+    .bdrv_attach_aio_context    = nbd_attach_aio_context,
 };
 
 static void bdrv_nbd_init(void)