Make QEMU driver compatible with older vitastor_client and with systems without io_uring

src/qemu_driver.c

@@ -259,7 +259,7 @@ static void vitastor_bh_uring_handler(void *opaque)
 static void vitastor_schedule_uring_handler(VitastorClient *client)
 {
     void *opaque = client;
-    if (!client->bh_uring_scheduled)
+    if (client->uring_eventfd >= 0 && !client->bh_uring_scheduled)
     {
         client->bh_uring_scheduled = 1;
 #if QEMU_VERSION_MAJOR > 4 || QEMU_VERSION_MAJOR == 4 && QEMU_VERSION_MINOR >= 2
@@ -401,19 +401,38 @@ static int vitastor_file_open(BlockDriverState *bs, QDict *options, int flags, E
     client->rdma_gid_index = qdict_get_try_int(options, "rdma-gid-index", 0);
     client->rdma_mtu = qdict_get_try_int(options, "rdma-mtu", 0);
     client->ctx = bdrv_get_aio_context(bs);
-    client->proxy = vitastor_c_create_qemu(
+#if defined VITASTOR_C_API_VERSION && VITASTOR_C_API_VERSION >= 2
+    client->proxy = vitastor_c_create_qemu_uring(
         vitastor_aio_set_fd_handler, client, client->config_path, client->etcd_host, client->etcd_prefix,
         client->use_rdma, client->rdma_device, client->rdma_port_num, client->rdma_gid_index, client->rdma_mtu, 0
     );
-    client->uring_eventfd = vitastor_c_uring_register_eventfd(client->proxy);
-    if (client->uring_eventfd < 0)
+#else
+    client->proxy = vitastor_c_create_uring(
+        client->config_path, client->etcd_host, client->etcd_prefix,
+        client->use_rdma, client->rdma_device, client->rdma_port_num, client->rdma_gid_index, client->rdma_mtu, 0
+    );
+#endif
+    if (!client->proxy)
     {
-        fprintf(stderr, "failed to create eventfd: %s\n", strerror(errno));
-        error_setg(errp, "failed to create eventfd");
-        vitastor_close(bs);
-        return -1;
+        fprintf(stderr, "vitastor: failed to create io_uring: %s - I/O will be slower\n", strerror(errno));
+        client->uring_eventfd = -1;
+        client->proxy = vitastor_c_create_qemu(
+            vitastor_aio_set_fd_handler, client, client->config_path, client->etcd_host, client->etcd_prefix,
+            client->use_rdma, client->rdma_device, client->rdma_port_num, client->rdma_gid_index, client->rdma_mtu, 0
+        );
+    }
+    else
+    {
+        client->uring_eventfd = vitastor_c_uring_register_eventfd(client->proxy);
+        if (client->uring_eventfd < 0)
+        {
+            fprintf(stderr, "vitastor: failed to create io_uring eventfd: %s\n", strerror(errno));
+            error_setg(errp, "failed to create io_uring eventfd");
+            vitastor_close(bs);
+            return -1;
+        }
+        universal_aio_set_fd_handler(client->ctx, client->uring_eventfd, vitastor_uring_handler, NULL, client);
     }
-    universal_aio_set_fd_handler(client->ctx, client->uring_eventfd, vitastor_uring_handler, NULL, client);
     image = client->image = g_strdup(qdict_get_try_str(options, "image"));
     client->readonly = (flags & BDRV_O_RDWR) ? 1 : 0;
     // Get image metadata (size and readonly flag) or just wait until the client is ready

src/ringloop.cpp

@@ -2,6 +2,7 @@
 // License: VNPL-1.1 or GNU GPL-2.0+ (see README.md for details)
 
 #include <stdlib.h>
+#include <unistd.h>
 
 #include <stdexcept>
 

src/vitastor_c.cpp

@@ -72,14 +72,8 @@ static void vitastor_c_write_handler(void *opaque)
     data->callback(data->fd, EPOLLOUT);
 }
 
-vitastor_c *vitastor_c_create_qemu(QEMUSetFDHandler *aio_set_fd_handler, void *aio_context,
-    const char *config_path, const char *etcd_host, const char *etcd_prefix,
-    int use_rdma, const char *rdma_device, int rdma_port_num, int rdma_gid_index, int rdma_mtu, int log_level)
+static vitastor_c *vitastor_c_create_qemu_common(QEMUSetFDHandler *aio_set_fd_handler, void *aio_context)
 {
-    json11::Json cfg_json = vitastor_c_common_config(
-        config_path, etcd_host, etcd_prefix, use_rdma,
-        rdma_device, rdma_port_num, rdma_gid_index, rdma_mtu, log_level
-    );
     vitastor_c *self = new vitastor_c;
     self->aio_set_fd_handler = aio_set_fd_handler;
     self->aio_ctx = aio_context;
@@ -97,7 +91,41 @@ vitastor_c *vitastor_c_create_qemu(QEMUSetFDHandler *aio_set_fd_handler, void *a
             self->aio_set_fd_handler(self->aio_ctx, fd, false, NULL, NULL, NULL, NULL);
         }
     });
-    self->ringloop = new ring_loop_t(512);
+    return self;
+}
+
+vitastor_c *vitastor_c_create_qemu(QEMUSetFDHandler *aio_set_fd_handler, void *aio_context,
+    const char *config_path, const char *etcd_host, const char *etcd_prefix,
+    int use_rdma, const char *rdma_device, int rdma_port_num, int rdma_gid_index, int rdma_mtu, int log_level)
+{
+    json11::Json cfg_json = vitastor_c_common_config(
+        config_path, etcd_host, etcd_prefix, use_rdma,
+        rdma_device, rdma_port_num, rdma_gid_index, rdma_mtu, log_level
+    );
+    auto self = vitastor_c_create_qemu_common(aio_set_fd_handler, aio_context);
+    self->cli = new cluster_client_t(NULL, self->tfd, cfg_json);
+    return self;
+}
+
+vitastor_c *vitastor_c_create_qemu_uring(QEMUSetFDHandler *aio_set_fd_handler, void *aio_context,
+    const char *config_path, const char *etcd_host, const char *etcd_prefix,
+    int use_rdma, const char *rdma_device, int rdma_port_num, int rdma_gid_index, int rdma_mtu, int log_level)
+{
+    ring_loop_t *ringloop = NULL;
+    try
+    {
+        ringloop = new ring_loop_t(512);
+    }
+    catch (std::exception & e)
+    {
+        return NULL;
+    }
+    json11::Json cfg_json = vitastor_c_common_config(
+        config_path, etcd_host, etcd_prefix, use_rdma,
+        rdma_device, rdma_port_num, rdma_gid_index, rdma_mtu, log_level
+    );
+    auto self = vitastor_c_create_qemu_common(aio_set_fd_handler, aio_context);
+    self->ringloop = ringloop;
     self->cli = new cluster_client_t(self->ringloop, self->tfd, cfg_json);
     return self;
 }
@@ -105,12 +133,21 @@ vitastor_c *vitastor_c_create_qemu(QEMUSetFDHandler *aio_set_fd_handler, void *a
 vitastor_c *vitastor_c_create_uring(const char *config_path, const char *etcd_host, const char *etcd_prefix,
     int use_rdma, const char *rdma_device, int rdma_port_num, int rdma_gid_index, int rdma_mtu, int log_level)
 {
+    ring_loop_t *ringloop = NULL;
+    try
+    {
+        ringloop = new ring_loop_t(512);
+    }
+    catch (std::exception & e)
+    {
+        return NULL;
+    }
     json11::Json cfg_json = vitastor_c_common_config(
         config_path, etcd_host, etcd_prefix, use_rdma,
         rdma_device, rdma_port_num, rdma_gid_index, rdma_mtu, log_level
     );
     vitastor_c *self = new vitastor_c;
-    self->ringloop = new ring_loop_t(512);
+    self->ringloop = ringloop;
     self->epmgr = new epoll_manager_t(self->ringloop);
     self->cli = new cluster_client_t(self->ringloop, self->epmgr->tfd, cfg_json);
     return self;

src/vitastor_c.h

@@ -7,7 +7,7 @@
 #define VITASTOR_QEMU_PROXY_H
 
 // C API wrapper version
-#define VITASTOR_C_API_VERSION 1
+#define VITASTOR_C_API_VERSION 2
 
 #ifndef POOL_ID_BITS
 #define POOL_ID_BITS 16
@@ -34,6 +34,9 @@ typedef void QEMUSetFDHandler(void *ctx, int fd, int is_external, IOHandler *fd_
 vitastor_c *vitastor_c_create_qemu(QEMUSetFDHandler *aio_set_fd_handler, void *aio_context,
     const char *config_path, const char *etcd_host, const char *etcd_prefix,
     int use_rdma, const char *rdma_device, int rdma_port_num, int rdma_gid_index, int rdma_mtu, int log_level);
+vitastor_c *vitastor_c_create_qemu_uring(QEMUSetFDHandler *aio_set_fd_handler, void *aio_context,
+    const char *config_path, const char *etcd_host, const char *etcd_prefix,
+    int use_rdma, const char *rdma_device, int rdma_port_num, int rdma_gid_index, int rdma_mtu, int log_level);
 vitastor_c *vitastor_c_create_uring(const char *config_path, const char *etcd_host, const char *etcd_prefix,
     int use_rdma, const char *rdma_device, int rdma_port_num, int rdma_gid_index, int rdma_mtu, int log_level);
 vitastor_c *vitastor_c_create_uring_json(const char **options, int options_len);