Re: [Qemu-devel] [RFC PATCH 2/8] qemu-nbd: Switch to qemu_set_fd_handler

[Paolo Bonzini <pbonzini@redhat.com>]

On 29/04/2015 12:37, Fam Zheng wrote:
> Achieved by:
> 
> - Remembering the server fd with a global variable, in order to access
>   it from nbd_client_closed.
> 
> - Checking nbd_can_accept() and updating server_fd handler whenever
>   client connects or disconnects.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  qemu-nbd.c | 21 +++++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index 7e690ff..5af6d11 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -53,6 +53,7 @@ static int persistent = 0;
>  static enum { RUNNING, TERMINATE, TERMINATING, TERMINATED } state;
>  static int shared = 1;
>  static int nb_fds;
> +static int server_fd;
>  
>  static void usage(const char *name)
>  {
> @@ -340,7 +341,7 @@ out:
>      return (void *) EXIT_FAILURE;
>  }
>  
> -static int nbd_can_accept(void *opaque)
> +static int nbd_can_accept(void)
>  {
>      return nb_fds < shared;
>  }
> @@ -351,19 +352,21 @@ static void nbd_export_closed(NBDExport *exp)
>      state = TERMINATED;
>  }
>  
> +static void nbd_update_server_fd_handler(int fd);
> +
>  static void nbd_client_closed(NBDClient *client)
>  {
>      nb_fds--;
>      if (nb_fds == 0 && !persistent && state == RUNNING) {
>          state = TERMINATE;
>      }
> +    nbd_update_server_fd_handler(server_fd);
>      qemu_notify_event();
>      nbd_client_put(client);
>  }
>  
>  static void nbd_accept(void *opaque)
>  {
> -    int server_fd = (uintptr_t) opaque;
>      struct sockaddr_in addr;
>      socklen_t addr_len = sizeof(addr);
>  
> @@ -380,12 +383,22 @@ static void nbd_accept(void *opaque)
>  
>      if (nbd_client_new(exp, fd, nbd_client_closed)) {
>          nb_fds++;
> +        nbd_update_server_fd_handler(server_fd);
>      } else {
>          shutdown(fd, 2);
>          close(fd);
>      }
>  }
>  
> +static void nbd_update_server_fd_handler(int fd)
> +{
> +    if (nbd_can_accept()) {
> +        qemu_set_fd_handler(fd, nbd_accept, NULL, (void *)(uintptr_t)fd);
> +    } else {
> +        qemu_set_fd_handler(fd, NULL, NULL, NULL);
> +    }
> +}
> +
>  int main(int argc, char **argv)
>  {
>      BlockBackend *blk;
> @@ -761,8 +774,8 @@ int main(int argc, char **argv)
>          memset(&client_thread, 0, sizeof(client_thread));
>      }
>  
> -    qemu_set_fd_handler2(fd, nbd_can_accept, nbd_accept, NULL,
> -                         (void *)(uintptr_t)fd);
> +    server_fd = fd;
> +    nbd_update_server_fd_handler(fd);
>  
>      /* now when the initialization is (almost) complete, chdir("/")
>       * to free any busy filesystems */
> 

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>