From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:44309) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RML7f-0000li-39 for qemu-devel@nongnu.org; Fri, 04 Nov 2011 10:52:01 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RML7d-0003EW-SG for qemu-devel@nongnu.org; Fri, 04 Nov 2011 10:51:58 -0400 Received: from mail-gx0-f173.google.com ([209.85.161.173]:48301) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RML7d-0003CV-9b for qemu-devel@nongnu.org; Fri, 04 Nov 2011 10:51:57 -0400 Received: by mail-gx0-f173.google.com with SMTP id r5so2981762ggn.4 for ; Fri, 04 Nov 2011 07:51:56 -0700 (PDT) Sender: Paolo Bonzini From: Paolo Bonzini Date: Fri, 4 Nov 2011 15:51:22 +0100 Message-Id: <1320418284-11081-6-git-send-email-pbonzini@redhat.com> In-Reply-To: <1320418284-11081-1-git-send-email-pbonzini@redhat.com> References: <1320418284-11081-1-git-send-email-pbonzini@redhat.com> Subject: [Qemu-devel] [PATCH 5/7] qemu-nbd: print error messages from the daemon through a pipe List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: kwolf@redhat.com In order to get nice error messages, keep the qemu-nbd process running until before issuing NBD_DO_IT and connected to the daemon with a pipe. This lets the qemu-nbd process relay error messages from the daemon and exit with a nonzero status if appropriate. Suggested-by: Kevin Wolf Signed-off-by: Paolo Bonzini --- qemu-nbd.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++------- 1 files changed, 59 insertions(+), 9 deletions(-) diff --git a/qemu-nbd.c b/qemu-nbd.c index 515a657..7490008 100644 --- a/qemu-nbd.c +++ b/qemu-nbd.c @@ -225,8 +225,13 @@ static void *nbd_client_thread(void *arg) /* update partition table */ pthread_create(&show_parts_thread, NULL, show_parts, NULL); - fprintf(stderr, "NBD device %s is now connected to %s\n", - device, srcpath); + if (verbose) { + fprintf(stderr, "NBD device %s is now connected to %s\n", + device, srcpath); + } else { + /* Close stderr so that the qemu-nbd process exits. */ + dup2(STDOUT_FILENO, STDERR_FILENO); + } ret = nbd_client(fd); if (ret) { @@ -405,6 +410,58 @@ int main(int argc, char **argv) return 0; } + if (device && !verbose) { + int stderr_fd[2]; + pid_t pid; + int ret; + + if (qemu_pipe(stderr_fd) == -1) { + err(EXIT_FAILURE, "Error setting up communication pipe"); + } + + /* Now daemonize, but keep a communication channel open to + * print errors and exit with the proper status code. + */ + pid = fork(); + if (pid == 0) { + close(stderr_fd[0]); + ret = qemu_daemon(0, 0); + + /* Temporarily redirect stderr to the parent's pipe... */ + dup2(stderr_fd[1], STDERR_FILENO); + if (ret == -1) { + err(EXIT_FAILURE, "Failed to daemonize"); + } + + /* ... close the descriptor we inherited and go on. */ + close(stderr_fd[1]); + } else { + bool errors = false; + char *buf; + + /* In the parent. Print error messages from the child until + * it closes the pipe. + */ + close(stderr_fd[1]); + buf = g_malloc(1024); + while ((ret = read(stderr_fd[0], buf, 1024)) > 0) { + errors = true; + ret = qemu_write_full(STDERR_FILENO, buf, ret); + if (ret == -1) { + exit(EXIT_FAILURE); + } + } + if (ret == -1) { + err(EXIT_FAILURE, "Cannot read from daemon"); + } + + /* Usually the daemon should not print any message. + * Exit with zero status in that case. + */ + exit(errors); + } + } + bdrv_init(); bs = bdrv_new("hda"); @@ -432,13 +494,6 @@ int main(int argc, char **argv) err(EXIT_FAILURE, "Failed to open %s", device); } - if (!verbose) { - /* detach client and server */ - if (qemu_daemon(0, 0) == -1) { - err(EXIT_FAILURE, "Failed to daemonize"); - } - } - if (sockpath == NULL) { sockpath = g_malloc(128); snprintf(sockpath, 128, SOCKET_PATH, basename(device)); -- 1.7.6.4