Fix deletion deadlock

src/bdev_lsvd.cc

@@ -228,19 +228,23 @@ int bdev_lsvd_create(str pool_name, str image_name, str user_cfg)
     return bdev_lsvd_create(image_name, be, cfg.value());
 }
 
-int bdev_lsvd_delete(str img_name)
+void bdev_lsvd_delete(str img_name, std::function<void(int)> cb)
 {
-    // TODO this currently deadlocks because of spdk's threading model, need to
-    // make it async
     log_info("Deleting image '{}'", img_name);
-    auto p = std::promise<int>();
-    spdk_bdev_unregister_by_name(
+    auto rc = spdk_bdev_unregister_by_name(
         img_name.c_str(), &lsvd_if,
+        // some of the ugliest lifetime management code you'll ever see, but
+        // it should work
         [](void *arg, int rc) {
-            log_info("Image deletion complete, rc = {}", rc);
-            auto p = (std::promise<int> *)arg;
-            p->set_value(rc);
+            log_info("Image deletion done, rc = {}", rc);
+            auto cb = (std::function<void(int)> *)arg;
+            (*cb)(rc);
+            delete cb;
         },
-        &p);
-    return p.get_future().get();
+        new std::function<void(int)>(cb));
+
+    if (rc != 0) {
+        log_error("Failed to delete image '{}': {}", img_name, rc);
+        cb(rc);
+    }
 }

src/bdev_lsvd.h

@@ -1,9 +1,10 @@
 #pragma once
 
 #include <rados/librados.h>
+#include <functional>
 
 #include "config.h"
 
 int bdev_lsvd_create(str img_name, rados_ioctx_t io_ctx, lsvd_config cfg);
 int bdev_lsvd_create(str pool_name, str image_name, str cfg_path);
-int bdev_lsvd_delete(str img_name);
+void bdev_lsvd_delete(str img_name, std::function<void(int)> cb);

src/bdev_lsvd_rpc.cc

@@ -22,9 +22,12 @@ struct rpc_create_lsvd {
 };
 
 static const struct spdk_json_object_decoder rpc_create_lsvd_decoders[] = {
-    {"image_name", offsetof(rpc_create_lsvd, image_name), spdk_json_decode_string, false},
-    {"pool_name", offsetof(rpc_create_lsvd, pool_name), spdk_json_decode_string, false},
-    {"config", offsetof(rpc_create_lsvd, config), spdk_json_decode_string, true},
+    {"image_name", offsetof(rpc_create_lsvd, image_name),
+     spdk_json_decode_string, false},
+    {"pool_name", offsetof(rpc_create_lsvd, pool_name), spdk_json_decode_string,
+     false},
+    {"config", offsetof(rpc_create_lsvd, config), spdk_json_decode_string,
+     true},
 };
 
 static void rpc_bdev_lsvd_create(spdk_jsonrpc_request *req_json,
@@ -64,33 +67,37 @@ struct rpc_delete_lsvd {
 };
 
 static const struct spdk_json_object_decoder rpc_delete_lsvd_decoders[] = {
-    {"image_name", offsetof(struct rpc_delete_lsvd, image_name), spdk_json_decode_string, false},
+    {"image_name", offsetof(struct rpc_delete_lsvd, image_name),
+     spdk_json_decode_string, false},
 };
 
 static void rpc_bdev_lsvd_delete(struct spdk_jsonrpc_request *req_json,
                                  const struct spdk_json_val *params)
 {
-    spdk_json_write_ctx *w;
     std::unique_ptr<rpc_delete_lsvd,
                     decltype([](auto p) { free(p->image_name); })>
         req(new rpc_delete_lsvd());
 
     int rc = spdk_json_decode_object(params, rpc_delete_lsvd_decoders,
                                      SPDK_COUNTOF(rpc_delete_lsvd_decoders),
                                      req.get());
-    PR_GOTO_IF(rc != 0, fail, "failed to decode json object");
-
-    rc = bdev_lsvd_delete(req->image_name);
-    PR_GOTO_IF(rc != 0, fail, "failed to destroy lsvd bdev");
-
-    w = spdk_jsonrpc_begin_result(req_json);
-    PR_GOTO_IF(w == nullptr, fail, "failed to create json result");
-    spdk_json_write_bool(w, true);
-    spdk_jsonrpc_end_result(req_json, w);
-
-fail:
-    spdk_jsonrpc_send_error_response(req_json, rc,
-                                     "failed to create lsvd bdev");
+    if (rc != 0) {
+        spdk_jsonrpc_send_error_response(req_json, rc,
+                                         "Failed to parse rpc json");
+        return;
+    }
+
+    bdev_lsvd_delete(req->image_name, [=](int rc) {
+        if (rc == 0) {
+            auto w = spdk_jsonrpc_begin_result(req_json);
+            spdk_json_write_bool(w, true);
+            spdk_jsonrpc_end_result(req_json, w);
+        } else {
+            log_error("Failed to destroy lsvd bdev, rc = {}", rc);
+            spdk_jsonrpc_send_error_response(req_json, rc,
+                                             "Failed to destroy lsvd bdev");
+        }
+    });
 }
 
 SPDK_RPC_REGISTER("bdev_lsvd_delete", rpc_bdev_lsvd_delete, SPDK_RPC_RUNTIME)