[Qemu-devel] [PATCH 21/25] qemu-nbd: use common main loop

[Paolo Bonzini <pbonzini@redhat.com>]

Using a single main loop for sockets will help yielding from the socket
coroutine back to the main loop, and later reentering it.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 qemu-nbd.c |  112 ++++++++++++++++++++++++------------------------------------
 1 files changed, 45 insertions(+), 67 deletions(-)

diff --git a/qemu-nbd.c b/qemu-nbd.c
index d5ac75e..347c776 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -35,12 +35,15 @@
 
 #define SOCKET_PATH    "/var/lock/qemu-nbd-%s"
 
-static int sigterm_wfd;
 static NBDExport *exp;
 static int verbose;
 static char *device;
 static char *srcpath;
 static char *sockpath;
+static bool sigterm_reported;
+static bool nbd_started;
+static int shared = 1;
+static int nb_fds;
 
 static void usage(const char *name)
 {
@@ -169,10 +172,8 @@ static int find_partition(BlockDriverState *bs, int partition,
 
 static void termsig_handler(int signum)
 {
-    static int sigterm_reported;
-    if (!sigterm_reported) {
-        sigterm_reported = (write(sigterm_wfd, "", 1) == 1);
-    }
+    sigterm_reported = true;
+    qemu_notify_event();
 }
 
 static void *show_parts(void *arg)
@@ -243,6 +244,36 @@ out:
     return (void *) EXIT_FAILURE;
 }
 
+static int nbd_can_accept(void *opaque)
+{
+    return nb_fds < shared;
+}
+
+static void nbd_read(void *opaque)
+{
+    int fd = (uintptr_t) opaque;
+
+    if (nbd_trip(exp, fd) != 0) {
+        qemu_set_fd_handler2(fd, NULL, NULL, NULL, NULL);
+        close(fd);
+        nb_fds--;
+    }
+}
+
+static void nbd_accept(void *opaque)
+{
+    int server_fd = (uintptr_t) opaque;
+    struct sockaddr_in addr;
+    socklen_t addr_len = sizeof(addr);
+
+    int fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len);
+    nbd_started = true;
+    if (fd != -1 && nbd_negotiate(exp, fd) != -1) {
+        qemu_set_fd_handler2(fd, NULL, nbd_read, NULL, (void *) (intptr_t) fd);
+        nb_fds++;
+    }
+}
+
 int main(int argc, char **argv)
 {
     BlockDriverState *bs;
@@ -251,8 +282,6 @@ int main(int argc, char **argv)
     bool disconnect = false;
     const char *bindto = "0.0.0.0";
     int port = NBD_DEFAULT_PORT;
-    struct sockaddr_in addr;
-    socklen_t addr_len = sizeof(addr);
     off_t fd_size;
     const char *sopt = "hVb:o:p:rsnP:c:dvk:e:t";
     struct option lopt[] = {
@@ -280,13 +309,7 @@ int main(int argc, char **argv)
     int flags = BDRV_O_RDWR;
     int partition = -1;
     int ret;
-    int shared = 1;
-    fd_set fds;
-    int *sharing_fds;
     int fd;
-    int i;
-    int nb_fds = 0;
-    int max_fd;
     int persistent = 0;
     pthread_t client_thread;
 
@@ -294,12 +317,6 @@ int main(int argc, char **argv)
      * handler ensures that "qemu-nbd -v -c" exits with a nice status code.
      */
     struct sigaction sa_sigterm;
-    int sigterm_fd[2];
-    if (qemu_pipe(sigterm_fd) == -1) {
-        err(EXIT_FAILURE, "Error setting up communication pipe");
-    }
-
-    sigterm_wfd = sigterm_fd[1];
     memset(&sa_sigterm, 0, sizeof(sa_sigterm));
     sa_sigterm.sa_handler = termsig_handler;
     sigaction(SIGTERM, &sa_sigterm, NULL);
@@ -490,16 +507,16 @@ int main(int argc, char **argv)
     }
 
     exp = nbd_export_new(bs, dev_offset, fd_size, nbdflags);
-    sharing_fds = g_malloc((shared + 1) * sizeof(int));
 
     if (sockpath) {
-        sharing_fds[0] = unix_socket_incoming(sockpath);
+        fd = unix_socket_incoming(sockpath);
     } else {
-        sharing_fds[0] = tcp_socket_incoming(bindto, port);
+        fd = tcp_socket_incoming(bindto, port);
     }
 
-    if (sharing_fds[0] == -1)
+    if (fd == -1) {
         return 1;
+    }
 
     if (device) {
         int ret;
@@ -514,54 +531,15 @@ int main(int argc, char **argv)
         memset(&client_thread, 0, sizeof(client_thread));
     }
 
-    max_fd = sharing_fds[0];
-    nb_fds++;
+    qemu_init_main_loop();
+    qemu_set_fd_handler2(fd, nbd_can_accept, nbd_accept, NULL,
+                         (void *)(uintptr_t)fd);
 
     do {
-        FD_ZERO(&fds);
-        FD_SET(sigterm_fd[0], &fds);
-        for (i = 0; i < nb_fds; i++)
-            FD_SET(sharing_fds[i], &fds);
-
-        do {
-            ret = select(max_fd + 1, &fds, NULL, NULL, NULL);
-        } while (ret == -1 && errno == EINTR);
-        if (ret == -1 || FD_ISSET(sigterm_fd[0], &fds)) {
-            break;
-        }
-
-        if (FD_ISSET(sharing_fds[0], &fds))
-            ret--;
-        for (i = 1; i < nb_fds && ret; i++) {
-            if (FD_ISSET(sharing_fds[i], &fds)) {
-                if (nbd_trip(exp, sharing_fds[i]) != 0) {
-                    close(sharing_fds[i]);
-                    nb_fds--;
-                    sharing_fds[i] = sharing_fds[nb_fds];
-                    i--;
-                }
-                ret--;
-            }
-        }
-        /* new connection ? */
-        if (FD_ISSET(sharing_fds[0], &fds)) {
-            if (nb_fds < shared + 1) {
-                sharing_fds[nb_fds] = accept(sharing_fds[0],
-                                             (struct sockaddr *)&addr,
-                                             &addr_len);
-                if (sharing_fds[nb_fds] != -1 &&
-                    nbd_negotiate(exp, sharing_fds[nb_fds]) != -1) {
-                        if (sharing_fds[nb_fds] > max_fd)
-                            max_fd = sharing_fds[nb_fds];
-                        nb_fds++;
-                }
-            }
-        }
-    } while (persistent || nb_fds > 1);
+        main_loop_wait(false);
+    } while (!sigterm_reported && (persistent || !nbd_started || nb_fds > 0));
 
-    close(sharing_fds[0]);
     nbd_export_close(exp);
-    g_free(sharing_fds);
     if (sockpath) {
         unlink(sockpath);
     }
-- 
1.7.7.1