Commit 9fc3c01a authored by Dexuan Cui's avatar Dexuan Cui Committed by Sasha Levin
Browse files

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: default avatarDexuan Cui <decui@microsoft.com>
Reviewed-by: default avatarMichael Kelley <mikelley@microsoft.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 3a6fb6c4

tools/hv/hv_fcopy_daemon.c

+32 −5
Original line number Diff line number Diff line
@@ -80,6 +80,8 @@ static int hv_start_fcopy(struct hv_start_fcopy *smsg) 


	error = 0;

done:

	if (error)

		target_fname[0] = '\0';

	return error;

}
@@ -108,15 +110,29 @@ static int hv_copy_data(struct hv_do_fcopy *cpmsg) 
	return ret;

}



/*

 * Reset target_fname to "" in the two below functions for hibernation: if

 * the fcopy operation is aborted by hibernation, the daemon should remove the

 * partially-copied file; to achieve this, the hv_utils driver always fakes a

 * CANCEL_FCOPY message upon suspend, and later when the VM resumes back,

 * the daemon calls hv_copy_cancel() to remove the file; if a file is copied

 * successfully before suspend, hv_copy_finished() must reset target_fname to

 * avoid that the file can be incorrectly removed upon resume, since the faked

 * CANCEL_FCOPY message is spurious in this case.

 */

static int hv_copy_finished(void)

{

	close(target_fd);

	target_fname[0] = '\0';

	return 0;

}

static int hv_copy_cancel(void)

{

	close(target_fd);

	if (strlen(target_fname) > 0) {

		unlink(target_fname);

		target_fname[0] = '\0';

	}

	return 0;



}
@@ -131,7 +147,7 @@ void print_usage(char *argv[]) 


int main(int argc, char *argv[])

{

	int fcopy_fd;

	int fcopy_fd = -1;

	int error;

	int daemonize = 1, long_index = 0, opt;

	int version = FCOPY_CURRENT_VERSION;
@@ -141,7 +157,7 @@ int main(int argc, char *argv[]) 
		struct hv_do_fcopy copy;

		__u32 kernel_modver;

	} buffer = { };

	int in_handshake = 1;

	int in_handshake;



	static struct option long_options[] = {

		{"help",	no_argument,	   0,  'h' },
@@ -170,6 +186,12 @@ int main(int argc, char *argv[]) 
	openlog("HV_FCOPY", 0, LOG_USER);

	syslog(LOG_INFO, "starting; pid is:%d", getpid());



reopen_fcopy_fd:

	if (fcopy_fd != -1)

		close(fcopy_fd);

	/* Remove any possible partially-copied file on error */

	hv_copy_cancel();

	in_handshake = 1;

	fcopy_fd = open("/dev/vmbus/hv_fcopy", O_RDWR);



	if (fcopy_fd < 0) {
@@ -196,7 +218,7 @@ int main(int argc, char *argv[]) 
		len = pread(fcopy_fd, &buffer, sizeof(buffer), 0);

		if (len < 0) {

			syslog(LOG_ERR, "pread failed: %s", strerror(errno));

			exit(EXIT_FAILURE);

			goto reopen_fcopy_fd;

		}



		if (in_handshake) {
@@ -231,9 +253,14 @@ int main(int argc, char *argv[]) 


		}



		/*

		 * pwrite() may return an error due to the faked CANCEL_FCOPY

		 * message upon hibernation. Ignore the error by resetting the

		 * dev file, i.e. closing and re-opening it.

		 */

		if (pwrite(fcopy_fd, &error, sizeof(int), 0) != sizeof(int)) {

			syslog(LOG_ERR, "pwrite failed: %s", strerror(errno));

			exit(EXIT_FAILURE);

			goto reopen_fcopy_fd;

		}

	}

}

tools/hv/hv_kvp_daemon.c

+21 −15
Original line number Diff line number Diff line
@@ -76,7 +76,7 @@ enum { 
	DNS

};



static int in_hand_shake = 1;

static int in_hand_shake;



static char *os_name = "";

static char *os_major = "";
@@ -1360,7 +1360,7 @@ void print_usage(char *argv[]) 


int main(int argc, char *argv[])

{

	int kvp_fd, len;

	int kvp_fd = -1, len;

	int error;

	struct pollfd pfd;

	char    *p;
@@ -1400,14 +1400,6 @@ int main(int argc, char *argv[]) 
	openlog("KVP", 0, LOG_USER);

	syslog(LOG_INFO, "KVP starting; pid is:%d", getpid());



	kvp_fd = open("/dev/vmbus/hv_kvp", O_RDWR | O_CLOEXEC);



	if (kvp_fd < 0) {

		syslog(LOG_ERR, "open /dev/vmbus/hv_kvp failed; error: %d %s",

			errno, strerror(errno));

		exit(EXIT_FAILURE);

	}



	/*

	 * Retrieve OS release information.

	 */
@@ -1423,6 +1415,18 @@ int main(int argc, char *argv[]) 
		exit(EXIT_FAILURE);

	}



reopen_kvp_fd:

	if (kvp_fd != -1)

		close(kvp_fd);

	in_hand_shake = 1;

	kvp_fd = open("/dev/vmbus/hv_kvp", O_RDWR | O_CLOEXEC);



	if (kvp_fd < 0) {

		syslog(LOG_ERR, "open /dev/vmbus/hv_kvp failed; error: %d %s",

		       errno, strerror(errno));

		exit(EXIT_FAILURE);

	}



	/*

	 * Register ourselves with the kernel.

	 */
@@ -1456,9 +1460,7 @@ int main(int argc, char *argv[]) 
		if (len != sizeof(struct hv_kvp_msg)) {

			syslog(LOG_ERR, "read failed; error:%d %s",

			       errno, strerror(errno));



			close(kvp_fd);

			return EXIT_FAILURE;

			goto reopen_kvp_fd;

		}



		/*
@@ -1617,13 +1619,17 @@ int main(int argc, char *argv[]) 
			break;

		}



		/* Send the value back to the kernel. */

		/*

		 * Send the value back to the kernel. Note: the write() may

		 * return an error due to hibernation; we can ignore the error

		 * by resetting the dev file, i.e. closing and re-opening it.

		 */

kvp_done:

		len = write(kvp_fd, hv_msg, sizeof(struct hv_kvp_msg));

		if (len != sizeof(struct hv_kvp_msg)) {

			syslog(LOG_ERR, "write failed; error: %d %s", errno,

			       strerror(errno));

			exit(EXIT_FAILURE);

			goto reopen_kvp_fd;

		}

	}

tools/hv/hv_vss_daemon.c

+38 −11
Original line number Diff line number Diff line
@@ -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)

{
@@ -155,17 +157,26 @@ static int vss_operate(int operation) 
			continue;

		}

		error |= vss_do_freeze(ent->mnt_dir, cmd);

		if (error && operation == VSS_OP_FREEZE)

		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)

		if (operation == VSS_OP_FREEZE) {

			if (error)

				goto err;

			fs_frozen = true;

		}

	}



	if (operation == VSS_OP_THAW && !error)

		fs_frozen = false;



	goto out;

err:
@@ -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;

		}

	}

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