Tools: hv: Reopen the devices if read() or write() returns errors
The state machine in the hv_utils driver can run out of order in some
corner cases, e.g. if the kvp daemon doesn't call write() fast enough
due to some reason, kvp_timeout_func() can run first and move the state
to HVUTIL_READY; next, when kvp_on_msg() is called it returns -EINVAL
since kvp_transaction.state is smaller than HVUTIL_USERSPACE_REQ; later,
the daemon's write() gets an error -EINVAL, and the daemon will exit().
We can reproduce the issue by sending a SIGSTOP signal to the daemon, wait
for 1 minute, and send a SIGCONT signal to the daemon: the daemon will
exit() quickly.
We can fix the issue by forcing a reset of the device (which means the
daemon can close() and open() the device again) and doing extra necessary
clean-up.
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
diff --git a/tools/hv/hv_vss_daemon.c b/tools/hv/hv_vss_daemon.c
index 92902a8..dd11187 100644
--- a/tools/hv/hv_vss_daemon.c
+++ b/tools/hv/hv_vss_daemon.c
@@ -28,6 +28,8 @@
#include <stdbool.h>
#include <dirent.h>
+static bool fs_frozen;
+
/* Don't use syslog() in the function since that can cause write to disk */
static int vss_do_freeze(char *dir, unsigned int cmd)
{
@@ -155,18 +157,27 @@ static int vss_operate(int operation)
continue;
}
error |= vss_do_freeze(ent->mnt_dir, cmd);
- if (error && operation == VSS_OP_FREEZE)
- goto err;
+ if (operation == VSS_OP_FREEZE) {
+ if (error)
+ goto err;
+ fs_frozen = true;
+ }
}
endmntent(mounts);
if (root_seen) {
error |= vss_do_freeze("/", cmd);
- if (error && operation == VSS_OP_FREEZE)
- goto err;
+ if (operation == VSS_OP_FREEZE) {
+ if (error)
+ goto err;
+ fs_frozen = true;
+ }
}
+ if (operation == VSS_OP_THAW && !error)
+ fs_frozen = false;
+
goto out;
err:
save_errno = errno;
@@ -175,6 +186,7 @@ static int vss_operate(int operation)
endmntent(mounts);
}
vss_operate(VSS_OP_THAW);
+ fs_frozen = false;
/* Call syslog after we thaw all filesystems */
if (ent)
syslog(LOG_ERR, "FREEZE of %s failed; error:%d %s",
@@ -196,13 +208,13 @@ void print_usage(char *argv[])
int main(int argc, char *argv[])
{
- int vss_fd, len;
+ int vss_fd = -1, len;
int error;
struct pollfd pfd;
int op;
struct hv_vss_msg vss_msg[1];
int daemonize = 1, long_index = 0, opt;
- int in_handshake = 1;
+ int in_handshake;
__u32 kernel_modver;
static struct option long_options[] = {
@@ -232,6 +244,18 @@ int main(int argc, char *argv[])
openlog("Hyper-V VSS", 0, LOG_USER);
syslog(LOG_INFO, "VSS starting; pid is:%d", getpid());
+reopen_vss_fd:
+ if (vss_fd != -1)
+ close(vss_fd);
+ if (fs_frozen) {
+ if (vss_operate(VSS_OP_THAW) || fs_frozen) {
+ syslog(LOG_ERR, "failed to thaw file system: err=%d",
+ errno);
+ exit(EXIT_FAILURE);
+ }
+ }
+
+ in_handshake = 1;
vss_fd = open("/dev/vmbus/hv_vss", O_RDWR);
if (vss_fd < 0) {
syslog(LOG_ERR, "open /dev/vmbus/hv_vss failed; error: %d %s",
@@ -284,8 +308,7 @@ int main(int argc, char *argv[])
if (len != sizeof(struct hv_vss_msg)) {
syslog(LOG_ERR, "read failed; error:%d %s",
errno, strerror(errno));
- close(vss_fd);
- return EXIT_FAILURE;
+ goto reopen_vss_fd;
}
op = vss_msg->vss_hdr.operation;
@@ -312,14 +335,18 @@ int main(int argc, char *argv[])
default:
syslog(LOG_ERR, "Illegal op:%d\n", op);
}
+
+ /*
+ * The write() may return an error due to the faked VSS_OP_THAW
+ * message upon hibernation. Ignore the error by resetting the
+ * dev file, i.e. closing and re-opening it.
+ */
vss_msg->error = error;
len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
if (len != sizeof(struct hv_vss_msg)) {
syslog(LOG_ERR, "write failed; error: %d %s", errno,
strerror(errno));
-
- if (op == VSS_OP_FREEZE)
- vss_operate(VSS_OP_THAW);
+ goto reopen_vss_fd;
}
}