From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:42360) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ROv1p-00068R-CV for qemu-devel@nongnu.org; Fri, 11 Nov 2011 12:36:38 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ROv1o-0000Jk-7l for qemu-devel@nongnu.org; Fri, 11 Nov 2011 12:36:37 -0500 Received: from mx1.redhat.com ([209.132.183.28]:36148) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ROv1o-0000Je-0e for qemu-devel@nongnu.org; Fri, 11 Nov 2011 12:36:36 -0500 From: Kevin Wolf Date: Fri, 11 Nov 2011 18:39:21 +0100 Message-Id: <1321033168-8739-10-git-send-email-kwolf@redhat.com> In-Reply-To: <1321033168-8739-1-git-send-email-kwolf@redhat.com> References: <1321033168-8739-1-git-send-email-kwolf@redhat.com> Subject: [Qemu-devel] [PATCH 09/16] qemu-nbd: print error messages from the daemon through a pipe List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: anthony@codemonkey.ws Cc: kwolf@redhat.com, qemu-devel@nongnu.org From: Paolo Bonzini 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 Signed-off-by: Kevin Wolf --- qemu-nbd.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++-------- 1 files changed, 59 insertions(+), 9 deletions(-) diff --git a/qemu-nbd.c b/qemu-nbd.c index ffc2a8a..b330d8d 100644 --- a/qemu-nbd.c +++ b/qemu-nbd.c @@ -226,8 +226,13 @@ 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) { @@ -406,6 +411,58 @@ 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"); @@ -433,13 +490,6 @@ 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