From 9fc3c01a1fae669a2ef9f13ee1e1a26e057d79f8 Mon Sep 17 00:00:00 2001 From: Dexuan Cui Date: Sat, 25 Jan 2020 21:49:41 -0800 Subject: 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 Reviewed-by: Michael Kelley Signed-off-by: Sasha Levin --- tools/hv/hv_vss_daemon.c | 49 +++++++++++++++++++++++++++++++++++++----------- 1 file changed, 38 insertions(+), 11 deletions(-) (limited to 'tools/hv/hv_vss_daemon.c') diff --git a/tools/hv/hv_vss_daemon.c b/tools/hv/hv_vss_daemon.c index 92902a88f671..dd111870beee 100644 --- a/tools/hv/hv_vss_daemon.c +++ b/tools/hv/hv_vss_daemon.c @@ -28,6 +28,8 @@ #include #include +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 @@ err: 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; } } -- cgit v1.2.3-59-g8ed1b