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[Qemu-devel] [PATCH 5/7] qemu-nbd: print error messages from the daemon
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH 5/7] qemu-nbd: print error messages from the daemon through a pipe |
Date: |
Fri, 4 Nov 2011 15:51:22 +0100 |
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 <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
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
- [Qemu-devel] [PATCH 0/7] reorganize operation of "qemu-nbd -c" and fix it, Paolo Bonzini, 2011/11/04
- [Qemu-devel] [PATCH 1/7] nbd: treat EPIPE from NBD_DO_IT as success, Paolo Bonzini, 2011/11/04
- [Qemu-devel] [PATCH 3/7] qemu-nbd: rename socket variable, Paolo Bonzini, 2011/11/04
- [Qemu-devel] [PATCH 2/7] qemu-nbd: trap SIGTERM, Paolo Bonzini, 2011/11/04
- [Qemu-devel] [PATCH 5/7] qemu-nbd: print error messages from the daemon through a pipe,
Paolo Bonzini <=
- [Qemu-devel] [PATCH 4/7] qemu-nbd: move client to a thread, Paolo Bonzini, 2011/11/04
- [Qemu-devel] [PATCH 7/7] qemu-nbd: open the block device after starting the client thread, Paolo Bonzini, 2011/11/04
- [Qemu-devel] [PATCH 6/7] qemu-nbd: fix socket creation race, Paolo Bonzini, 2011/11/04
- Re: [Qemu-devel] [PATCH 0/7] reorganize operation of "qemu-nbd -c" and fix it, Kevin Wolf, 2011/11/08