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[Qemu-devel] [PATCH 08/16] qemu-nbd: move client to a thread
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PATCH 08/16] qemu-nbd: move client to a thread |
Date: |
Fri, 11 Nov 2011 18:39:20 +0100 |
From: Paolo Bonzini <address@hidden>
This avoids that qemu-nbd uses both forking and threads, which do
not behave well together.
qemu-nbd is already Unix only, and there is no qemu_thread_join,
so for now use pthreads.
Since the parent and child no longer have separate file descriptors,
we can open the NBD device before daemonizing, instead of checking
with access(2) and restricting the open to the client only.
Reported-by: Pierre Riteau <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
---
qemu-nbd.c | 173 ++++++++++++++++++++++++++++++++----------------------------
1 files changed, 93 insertions(+), 80 deletions(-)
diff --git a/qemu-nbd.c b/qemu-nbd.c
index 20b69c1..ffc2a8a 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -31,6 +31,7 @@
#include <arpa/inet.h>
#include <signal.h>
#include <libgen.h>
+#include <pthread.h>
#define SOCKET_PATH "/var/lock/qemu-nbd-%s"
@@ -38,6 +39,9 @@
static int sigterm_wfd;
static int verbose;
+static char *device;
+static char *srcpath;
+static char *sockpath;
static void usage(const char *name)
{
@@ -172,21 +176,70 @@ static void termsig_handler(int signum)
}
}
-static void show_parts(const char *device)
+static void *show_parts(void *arg)
{
- if (fork() == 0) {
- int nbd;
+ int nbd;
+
+ /* linux just needs an open() to trigger
+ * the partition table update
+ * but remember to load the module with max_part != 0 :
+ * modprobe nbd max_part=63
+ */
+ nbd = open(device, O_RDWR);
+ if (nbd != -1) {
+ close(nbd);
+ }
+ return NULL;
+}
- /* linux just needs an open() to trigger
- * the partition table update
- * but remember to load the module with max_part != 0 :
- * modprobe nbd max_part=63
- */
- nbd = open(device, O_RDWR);
- if (nbd != -1)
- close(nbd);
- exit(0);
+static void *nbd_client_thread(void *arg)
+{
+ int fd = *(int *)arg;
+ off_t size;
+ size_t blocksize;
+ uint32_t nbdflags;
+ int sock;
+ int ret;
+ pthread_t show_parts_thread;
+
+ do {
+ sock = unix_socket_outgoing(sockpath);
+ if (sock == -1) {
+ if (errno != ENOENT && errno != ECONNREFUSED) {
+ goto out;
+ }
+ sleep(1); /* wait parent */
+ }
+ } while (sock == -1);
+
+ ret = nbd_receive_negotiate(sock, NULL, &nbdflags,
+ &size, &blocksize);
+ if (ret == -1) {
+ goto out;
+ }
+
+ ret = nbd_init(fd, sock, nbdflags, size, blocksize);
+ if (ret == -1) {
+ goto out;
+ }
+
+ /* 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);
+
+ ret = nbd_client(fd);
+ if (ret) {
+ goto out;
}
+ close(fd);
+ kill(getpid(), SIGTERM);
+ return (void *) EXIT_SUCCESS;
+
+out:
+ kill(getpid(), SIGTERM);
+ return (void *) EXIT_FAILURE;
}
int main(int argc, char **argv)
@@ -201,8 +254,6 @@ int main(int argc, char **argv)
struct sockaddr_in addr;
socklen_t addr_len = sizeof(addr);
off_t fd_size;
- char *device = NULL;
- char *sockpath = NULL;
const char *sopt = "hVb:o:p:rsnP:c:dvk:e:t";
struct option lopt[] = {
{ "help", 0, NULL, 'h' },
@@ -238,8 +289,11 @@ int main(int argc, char **argv)
int nb_fds = 0;
int max_fd;
int persistent = 0;
+ pthread_t client_thread;
- /* Set up a SIGTERM handler so that we exit with a nice status code. */
+ /* The client thread uses SIGTERM to interrupt the server. A signal
+ * 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) {
@@ -356,9 +410,10 @@ int main(int argc, char **argv)
bs = bdrv_new("hda");
- if ((ret = bdrv_open(bs, argv[optind], flags, NULL)) < 0) {
+ srcpath = argv[optind];
+ if ((ret = bdrv_open(bs, srcpath, flags, NULL)) < 0) {
errno = -ret;
- err(EXIT_FAILURE, "Failed to bdrv_open '%s'", argv[optind]);
+ err(EXIT_FAILURE, "Failed to bdrv_open '%s'", srcpath);
}
fd_size = bs->total_sectors * 512;
@@ -368,12 +423,14 @@ int main(int argc, char **argv)
err(EXIT_FAILURE, "Could not find partition %d", partition);
if (device) {
- pid_t pid;
- int sock;
+ int ret;
- /* want to fail before daemonizing */
- if (access(device, R_OK|W_OK) == -1) {
- err(EXIT_FAILURE, "Could not access '%s'", device);
+ /* Open before spawning new threads. In the future, we may
+ * drop privileges after opening.
+ */
+ fd = open(device, O_RDWR);
+ if (fd == -1) {
+ err(EXIT_FAILURE, "Failed to open %s", device);
}
if (!verbose) {
@@ -388,64 +445,14 @@ int main(int argc, char **argv)
snprintf(sockpath, 128, SOCKET_PATH, basename(device));
}
- pid = fork();
- if (pid < 0)
- return 1;
- if (pid != 0) {
- off_t size;
- size_t blocksize;
-
- ret = 0;
- bdrv_close(bs);
-
- do {
- sock = unix_socket_outgoing(sockpath);
- if (sock == -1) {
- if (errno != ENOENT && errno != ECONNREFUSED) {
- ret = 1;
- goto out;
- }
- sleep(1); /* wait children */
- }
- } while (sock == -1);
-
- fd = open(device, O_RDWR);
- if (fd == -1) {
- ret = 1;
- goto out;
- }
-
- ret = nbd_receive_negotiate(sock, NULL, &nbdflags,
- &size, &blocksize);
- if (ret == -1) {
- ret = 1;
- goto out;
- }
-
- ret = nbd_init(fd, sock, nbdflags, size, blocksize);
- if (ret == -1) {
- ret = 1;
- goto out;
- }
-
- printf("NBD device %s is now connected to file %s\n",
- device, argv[optind]);
-
- /* update partition table */
-
- show_parts(device);
-
- ret = nbd_client(fd);
- if (ret) {
- ret = 1;
- }
- close(fd);
- out:
- kill(pid, SIGTERM);
-
- return ret;
+ ret = pthread_create(&client_thread, NULL, nbd_client_thread, &fd);
+ if (ret != 0) {
+ errx(EXIT_FAILURE, "Failed to create client thread: %s",
+ strerror(ret));
}
- /* children */
+ } else {
+ /* Shut up GCC warnings. */
+ memset(&client_thread, 0, sizeof(client_thread));
}
sharing_fds = g_malloc((shared + 1) * sizeof(int));
@@ -517,5 +524,11 @@ int main(int argc, char **argv)
unlink(sockpath);
}
- return 0;
+ if (device) {
+ void *ret;
+ pthread_join(client_thread, &ret);
+ exit(ret != NULL);
+ } else {
+ exit(EXIT_SUCCESS);
+ }
}
--
1.7.6.4
- [Qemu-devel] [PULL 00/16] Block patches for 1.0, Kevin Wolf, 2011/11/11
- [Qemu-devel] [PATCH 01/16] vvfat: Fix read-write mode, Kevin Wolf, 2011/11/11
- [Qemu-devel] [PATCH 02/16] block: add eject request callback, Kevin Wolf, 2011/11/11
- [Qemu-devel] [PATCH 03/16] atapi: implement eject requests, Kevin Wolf, 2011/11/11
- [Qemu-devel] [PATCH 04/16] scsi-disk: implement eject requests, Kevin Wolf, 2011/11/11
- [Qemu-devel] [PATCH 05/16] nbd: treat EPIPE from NBD_DO_IT as success, Kevin Wolf, 2011/11/11
- [Qemu-devel] [PATCH 07/16] qemu-nbd: rename socket variable, Kevin Wolf, 2011/11/11
- [Qemu-devel] [PATCH 09/16] qemu-nbd: print error messages from the daemon through a pipe, Kevin Wolf, 2011/11/11
- [Qemu-devel] [PATCH 08/16] qemu-nbd: move client to a thread,
Kevin Wolf <=
- [Qemu-devel] [PATCH 11/16] qemu-nbd: open the block device after starting the client thread, Kevin Wolf, 2011/11/11
- [Qemu-devel] [PATCH 15/16] block: Introduce bdrv_co_flush_to_os, Kevin Wolf, 2011/11/11
- [Qemu-devel] [PATCH 14/16] block: Rename bdrv_co_flush to bdrv_co_flush_to_disk, Kevin Wolf, 2011/11/11
- [Qemu-devel] [PATCH 16/16] block: Make cache=unsafe flush to the OS, Kevin Wolf, 2011/11/11
- [Qemu-devel] [PATCH 10/16] qemu-nbd: fix socket creation race, Kevin Wolf, 2011/11/11
- [Qemu-devel] [PATCH 12/16] block: Fix vpc initialization of the Dynamic Disk Header, Kevin Wolf, 2011/11/11
- [Qemu-devel] [PATCH 06/16] qemu-nbd: trap SIGTERM, Kevin Wolf, 2011/11/11
- [Qemu-devel] [PATCH 13/16] hw/pc.c: Fix use-while-uninitialized of fd_type[], Kevin Wolf, 2011/11/11
- Re: [Qemu-devel] [PULL 00/16] Block patches for 1.0, Anthony Liguori, 2011/11/13