[v5,10/11] nbd-server: Use a separate BlockBackend

diff --git a/block.c b/block.c
index 30d64e6..101f8c6 100644
--- a/block.c
+++ b/block.c
@@ -25,6 +25,7 @@ 
 #include "trace.h"
 #include "block/block_int.h"
 #include "block/blockjob.h"
+#include "block/nbd.h"
 #include "qemu/error-report.h"
 #include "qemu/module.h"
 #include "qapi/qmp/qerror.h"
@@ -2206,6 +2207,7 @@  static void bdrv_close(BlockDriverState *bs)
 void bdrv_close_all(void)
 {
     block_job_cancel_sync_all();
+    nbd_export_close_all();
 
     /* Drop references from requests still in flight, such as canceled block
      * jobs whose AIO context has not been polled yet */
diff --git a/blockdev-nbd.c b/blockdev-nbd.c
index 12cae0e..c437d32 100644
--- a/blockdev-nbd.c
+++ b/blockdev-nbd.c
@@ -176,8 +176,8 @@  void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
         writable = false;
     }
 
-    exp = nbd_export_new(blk, 0, -1, writable ? 0 : NBD_FLAG_READ_ONLY, NULL,
-                         errp);
+    exp = nbd_export_new(blk_bs(blk), 0, -1, writable ? 0 : NBD_FLAG_READ_ONLY,
+                         NULL, false, blk, errp);
     if (!exp) {
         return;
     }
diff --git a/include/block/nbd.h b/include/block/nbd.h
index cb91820..ebdba0d 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -103,8 +103,9 @@  int nbd_disconnect(int fd);
 typedef struct NBDExport NBDExport;
 typedef struct NBDClient NBDClient;
 
-NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
+NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset, off_t size,
                           uint32_t nbdflags, void (*close)(NBDExport *),
+                          bool writethrough, BlockBackend *on_eject_blk,
                           Error **errp);
 void nbd_export_close(NBDExport *exp);
 void nbd_export_get(NBDExport *exp);
diff --git a/nbd/server.c b/nbd/server.c
index 29e2099..207625e 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -69,6 +69,7 @@  struct NBDExport {
 
     AioContext *ctx;
 
+    BlockBackend *eject_notifier_blk;
     Notifier eject_notifier;
 };
 
@@ -809,11 +810,18 @@  static void nbd_eject_notifier(Notifier *n, void *data)
     nbd_export_close(exp);
 }
 
-NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
+NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset, off_t size,
                           uint32_t nbdflags, void (*close)(NBDExport *),
+                          bool writethrough, BlockBackend *on_eject_blk,
                           Error **errp)
 {
+    BlockBackend *blk;
     NBDExport *exp = g_malloc0(sizeof(NBDExport));
+
+    blk = blk_new();
+    blk_insert_bs(blk, bs);
+    blk_set_enable_write_cache(blk, !writethrough);
+
     exp->refcount = 1;
     QTAILQ_INIT(&exp->clients);
     exp->blk = blk;
@@ -829,11 +837,14 @@  NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
 
     exp->close = close;
     exp->ctx = blk_get_aio_context(blk);
-    blk_ref(blk);
     blk_add_aio_context_notifier(blk, blk_aio_attached, blk_aio_detach, exp);
 
-    exp->eject_notifier.notify = nbd_eject_notifier;
-    blk_add_remove_bs_notifier(blk, &exp->eject_notifier);
+    if (on_eject_blk) {
+        blk_ref(on_eject_blk);
+        exp->eject_notifier_blk = on_eject_blk;
+        exp->eject_notifier.notify = nbd_eject_notifier;
+        blk_add_remove_bs_notifier(on_eject_blk, &exp->eject_notifier);
+    }
 
     /*
      * NBD exports are used for non-shared storage migration.  Make sure
@@ -846,6 +857,7 @@  NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
     return exp;
 
 fail:
+    blk_unref(blk);
     g_free(exp);
     return NULL;
 }
@@ -916,7 +928,10 @@  void nbd_export_put(NBDExport *exp)
         }
 
         if (exp->blk) {
-            notifier_remove(&exp->eject_notifier);
+            if (exp->eject_notifier_blk) {
+                notifier_remove(&exp->eject_notifier);
+                blk_unref(exp->eject_notifier_blk);
+            }
             blk_remove_aio_context_notifier(exp->blk, blk_aio_attached,
                                             blk_aio_detach, exp);
             blk_unref(exp->blk);
diff --git a/qemu-nbd.c b/qemu-nbd.c
index 321f02b..9e6aaa9 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -910,8 +910,8 @@  int main(int argc, char **argv)
         }
     }
 
-    exp = nbd_export_new(blk, dev_offset, fd_size, nbdflags, nbd_export_closed,
-                         &local_err);
+    exp = nbd_export_new(bs, dev_offset, fd_size, nbdflags, nbd_export_closed,
+                         writethrough, NULL, &local_err);
     if (!exp) {
         error_report_err(local_err);
         exit(EXIT_FAILURE);