[libvirt] [PATCH sandbox 2/4] Sync and unmount filesystems during shutdown
Daniel P. Berrange
berrange at redhat.com
Fri Sep 4 11:40:35 UTC 2015
To ensure that all pending I/O for filesytems backed by block
devices is flushed to disk, it is important to sync and unmount
the filesystems during shutdown. To avoid relying on the kernel
reboot-on-panic behaviour, we also explicitly call reboot to
power off the guest.
Signed-off-by: Daniel P. Berrange <berrange at redhat.com>
---
libvirt-sandbox/libvirt-sandbox-init-common.c | 166 ++++++++++++++++++++++++++
libvirt-sandbox/libvirt-sandbox-init-qemu.c | 1 +
2 files changed, 167 insertions(+)
diff --git a/libvirt-sandbox/libvirt-sandbox-init-common.c b/libvirt-sandbox/libvirt-sandbox-init-common.c
index 760509f..a3b4687 100644
--- a/libvirt-sandbox/libvirt-sandbox-init-common.c
+++ b/libvirt-sandbox/libvirt-sandbox-init-common.c
@@ -44,6 +44,8 @@
#include <unistd.h>
#include <limits.h>
#include <grp.h>
+#include <mntent.h>
+#include <sys/reboot.h>
#include "libvirt-sandbox-rpcpacket.h"
@@ -52,6 +54,8 @@ static gboolean verbose = FALSE;
static int sigwrite;
#define ATTR_UNUSED __attribute__((__unused__))
+static void sync_data(void);
+static void umount_fs(void);
static void sig_child(int sig ATTR_UNUSED)
{
@@ -598,6 +602,14 @@ static GVirSandboxRPCPacket *gvir_sandbox_encode_exit(int status,
pkt->header.type = GVIR_SANDBOX_PROTOCOL_TYPE_MESSAGE;
pkt->header.serial = serial;
+ /* The host may destroy the guest any time after receiving
+ * the exit code messages. So although the main() has code
+ * to sync + unmount we can't rely on that running. So we
+ * opportunistically sync + unmount here too.
+ */
+ sync_data();
+ umount_fs();
+
if (!gvir_sandbox_rpcpacket_encode_header(pkt, error))
goto error;
if (!gvir_sandbox_rpcpacket_encode_payload_msg(pkt,
@@ -613,7 +625,151 @@ static GVirSandboxRPCPacket *gvir_sandbox_encode_exit(int status,
return NULL;
}
+/* Copied & adapted from libguestfs daemon/sync.c under LGPLv2+ */
+static void sync_data(void)
+{
+ DIR *dir;
+ struct dirent *d;
+ char *dev_path;
+ int fd;
+
+ if (debug)
+ fprintf(stderr, "Syncing data\n");
+ sync();
+
+ /* On Linux, sync(2) doesn't perform a barrier, so qemu (which may
+ * have a writeback cache, even with cache=none) will still have
+ * some unwritten data. Force the data out of any qemu caches, by
+ * calling fsync on all block devices. Note we still need the
+ * call to sync above in order to schedule the writes.
+ * Thanks to: Avi Kivity, Kevin Wolf.
+ */
+
+ if (!(dir = opendir("/dev"))) {
+ fprintf(stderr, "opendir: /dev failed %s\n", strerror(errno));
+ return;
+ }
+
+ for (;;) {
+ errno = 0;
+ d = readdir(dir);
+ if (!d)
+ break;
+
+ if (!(g_str_has_prefix(d->d_name, "sd") ||
+ g_str_has_prefix(d->d_name, "hd") ||
+ g_str_has_prefix(d->d_name, "ubd") ||
+ g_str_has_prefix(d->d_name, "vd") ||
+ g_str_has_prefix(d->d_name, "sr"))) {
+ continue;
+ }
+
+ dev_path = g_strdup_printf("/dev/%s", d->d_name);
+
+ if (debug)
+ fprintf(stderr, "Syncing fd %s\n", dev_path);
+ if ((fd = open(dev_path, O_RDONLY)) < 0) {
+ fprintf(stderr, "cannot open %s: %s\n", dev_path,
+ strerror(errno));
+ g_free(dev_path);
+ continue;
+ }
+
+ /* fsync the device. */
+ if (debug) {
+ fprintf(stderr, "fsync %s\n", dev_path);
+ }
+
+ if (fsync(fd) < 0) {
+ fprintf(stderr, "failed to fsync %s: %s\n",
+ dev_path, strerror(errno));
+ }
+ if (close(fd) < 0) {
+ fprintf(stderr, "failed to close %s: %s\n",
+ dev_path, strerror(errno));
+ }
+ g_free(dev_path);
+ }
+
+ /* Check readdir didn't fail */
+ if (errno != 0) {
+ fprintf(stderr, "Failed to read /dev: %s\n",
+ strerror(errno));
+ }
+
+ /* Close the directory handle */
+ if (closedir(dir) < 0) {
+ fprintf(stderr, "Failed to block /dev: %s\n",
+ strerror(errno));
+ }
+
+ if (debug)
+ fprintf(stderr, "Syncing complete\n");
+}
+
+
+static int
+compare_longest_first (gconstpointer vp1, gconstpointer vp2)
+{
+ int n1 = strlen(vp1);
+ int n2 = strlen(vp2);
+ return n2 - n1;
+}
+
+
+/* Copied & adapted from libguestfs daemon/sync.c under LGPLv2+ */
+static void umount_fs(void)
+{
+ FILE *fp;
+ struct mntent *m;
+ GList *mounts = NULL, *tmp;
+
+ if (debug)
+ fprintf(stderr, "Unmounting all filesystems\n");
+ if (!(fp = setmntent ("/proc/mounts", "r"))) {
+ fprintf(stderr, "Failed to open /proc/mounts: %s\n",
+ strerror(errno));
+ return;
+ }
+
+ while ((m = getmntent (fp)) != NULL) {
+ if (debug)
+ fprintf(stderr, "Got fsname=%s dir=%s type=%s opts=%s freq=%d passno=%d\n",
+ m->mnt_fsname, m->mnt_dir, m->mnt_type, m->mnt_opts,
+ m->mnt_freq, m->mnt_passno);
+
+ mounts = g_list_append(mounts, g_strdup(m->mnt_dir));
+ }
+ endmntent(fp);
+
+ mounts = g_list_sort(mounts, compare_longest_first);
+
+ /* Unmount them. */
+ tmp = mounts;
+ while (tmp) {
+ char *dir = tmp->data;
+
+ if (debug)
+ fprintf(stderr, "Unmounting %s\n", dir);
+ if (umount(dir) < 0) {
+ /* We expect some failures, so don't pollute
+ * logs with them uneccessarily
+ */
+ if (debug || errno != EBUSY)
+ fprintf(stderr, "cannot unmount %s: %s\n",
+ dir, strerror(errno));
+ /* ignore failure */
+ }
+ g_free(dir);
+
+ tmp = tmp->next;
+ }
+
+ g_list_free(mounts);
+ if (debug)
+ fprintf(stderr, "Unmounting complete\n");
+}
static gssize read_data(int fd, char *buf, size_t len)
@@ -1204,6 +1360,7 @@ static void libvirt_sandbox_version(void)
int main(int argc, char **argv) {
gchar *configfile = NULL;
+ gboolean poweroff = FALSE;
GError *error = NULL;
GOptionContext *context;
GOptionEntry options[] = {
@@ -1215,6 +1372,8 @@ int main(int argc, char **argv) {
N_("display debugging information"), NULL },
{ "config", 'c', 0, G_OPTION_ARG_STRING, &configfile,
N_("config file path"), "URI"},
+ { "poweroff", 'p', 0, G_OPTION_ARG_NONE, &poweroff,
+ N_("clean power off when exiting"), NULL},
{ NULL, 0, 0, G_OPTION_ARG_NONE, NULL, NULL, NULL }
};
const char *help_msg = N_("Run '" PACKAGE " --help' to see a full list of available command line options");
@@ -1290,6 +1449,13 @@ int main(int argc, char **argv) {
if (error)
g_error_free(error);
+ sync_data();
+
+ if (poweroff) {
+ umount_fs();
+ reboot(RB_POWER_OFF);
+ /* Should not be reached, but if it is, kernel will panic anyway */
+ }
return ret;
error:
diff --git a/libvirt-sandbox/libvirt-sandbox-init-qemu.c b/libvirt-sandbox/libvirt-sandbox-init-qemu.c
index cd6055a..8bde224 100644
--- a/libvirt-sandbox/libvirt-sandbox-init-qemu.c
+++ b/libvirt-sandbox/libvirt-sandbox-init-qemu.c
@@ -424,6 +424,7 @@ main(int argc ATTR_UNUSED, char **argv ATTR_UNUSED)
args[narg++] = SANDBOXCONFIGDIR "/.libs/ld.so";
args[narg++] = SANDBOXCONFIGDIR "/.libs/libvirt-sandbox-init-common";
+ args[narg++] = "--poweroff";
if (debug)
args[narg++] = "-d";
--
2.4.3
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