linux/tools/hv/hv_fcopy_daemon.c
Dexuan Cui 9fc3c01a1f 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>
2020-01-26 22:10:10 -05:00

267 lines
6.0 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* An implementation of host to guest copy functionality for Linux.
*
* Copyright (C) 2014, Microsoft, Inc.
*
* Author : K. Y. Srinivasan <kys@microsoft.com>
*/
#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <linux/hyperv.h>
#include <linux/limits.h>
#include <syslog.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <getopt.h>
static int target_fd;
static char target_fname[PATH_MAX];
static unsigned long long filesize;
static int hv_start_fcopy(struct hv_start_fcopy *smsg)
{
int error = HV_E_FAIL;
char *q, *p;
filesize = 0;
p = (char *)smsg->path_name;
snprintf(target_fname, sizeof(target_fname), "%s/%s",
(char *)smsg->path_name, (char *)smsg->file_name);
syslog(LOG_INFO, "Target file name: %s", target_fname);
/*
* Check to see if the path is already in place; if not,
* create if required.
*/
while ((q = strchr(p, '/')) != NULL) {
if (q == p) {
p++;
continue;
}
*q = '\0';
if (access((char *)smsg->path_name, F_OK)) {
if (smsg->copy_flags & CREATE_PATH) {
if (mkdir((char *)smsg->path_name, 0755)) {
syslog(LOG_ERR, "Failed to create %s",
(char *)smsg->path_name);
goto done;
}
} else {
syslog(LOG_ERR, "Invalid path: %s",
(char *)smsg->path_name);
goto done;
}
}
p = q + 1;
*q = '/';
}
if (!access(target_fname, F_OK)) {
syslog(LOG_INFO, "File: %s exists", target_fname);
if (!(smsg->copy_flags & OVER_WRITE)) {
error = HV_ERROR_ALREADY_EXISTS;
goto done;
}
}
target_fd = open(target_fname,
O_RDWR | O_CREAT | O_TRUNC | O_CLOEXEC, 0744);
if (target_fd == -1) {
syslog(LOG_INFO, "Open Failed: %s", strerror(errno));
goto done;
}
error = 0;
done:
if (error)
target_fname[0] = '\0';
return error;
}
static int hv_copy_data(struct hv_do_fcopy *cpmsg)
{
ssize_t bytes_written;
int ret = 0;
bytes_written = pwrite(target_fd, cpmsg->data, cpmsg->size,
cpmsg->offset);
filesize += cpmsg->size;
if (bytes_written != cpmsg->size) {
switch (errno) {
case ENOSPC:
ret = HV_ERROR_DISK_FULL;
break;
default:
ret = HV_E_FAIL;
break;
}
syslog(LOG_ERR, "pwrite failed to write %llu bytes: %ld (%s)",
filesize, (long)bytes_written, strerror(errno));
}
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;
}
void print_usage(char *argv[])
{
fprintf(stderr, "Usage: %s [options]\n"
"Options are:\n"
" -n, --no-daemon stay in foreground, don't daemonize\n"
" -h, --help print this help\n", argv[0]);
}
int main(int argc, char *argv[])
{
int fcopy_fd = -1;
int error;
int daemonize = 1, long_index = 0, opt;
int version = FCOPY_CURRENT_VERSION;
union {
struct hv_fcopy_hdr hdr;
struct hv_start_fcopy start;
struct hv_do_fcopy copy;
__u32 kernel_modver;
} buffer = { };
int in_handshake;
static struct option long_options[] = {
{"help", no_argument, 0, 'h' },
{"no-daemon", no_argument, 0, 'n' },
{0, 0, 0, 0 }
};
while ((opt = getopt_long(argc, argv, "hn", long_options,
&long_index)) != -1) {
switch (opt) {
case 'n':
daemonize = 0;
break;
case 'h':
default:
print_usage(argv);
exit(EXIT_FAILURE);
}
}
if (daemonize && daemon(1, 0)) {
syslog(LOG_ERR, "daemon() failed; error: %s", strerror(errno));
exit(EXIT_FAILURE);
}
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) {
syslog(LOG_ERR, "open /dev/vmbus/hv_fcopy failed; error: %d %s",
errno, strerror(errno));
exit(EXIT_FAILURE);
}
/*
* Register with the kernel.
*/
if ((write(fcopy_fd, &version, sizeof(int))) != sizeof(int)) {
syslog(LOG_ERR, "Registration failed: %s", strerror(errno));
exit(EXIT_FAILURE);
}
while (1) {
/*
* In this loop we process fcopy messages after the
* handshake is complete.
*/
ssize_t len;
len = pread(fcopy_fd, &buffer, sizeof(buffer), 0);
if (len < 0) {
syslog(LOG_ERR, "pread failed: %s", strerror(errno));
goto reopen_fcopy_fd;
}
if (in_handshake) {
if (len != sizeof(buffer.kernel_modver)) {
syslog(LOG_ERR, "invalid version negotiation");
exit(EXIT_FAILURE);
}
in_handshake = 0;
syslog(LOG_INFO, "kernel module version: %u",
buffer.kernel_modver);
continue;
}
switch (buffer.hdr.operation) {
case START_FILE_COPY:
error = hv_start_fcopy(&buffer.start);
break;
case WRITE_TO_FILE:
error = hv_copy_data(&buffer.copy);
break;
case COMPLETE_FCOPY:
error = hv_copy_finished();
break;
case CANCEL_FCOPY:
error = hv_copy_cancel();
break;
default:
error = HV_E_FAIL;
syslog(LOG_ERR, "Unknown operation: %d",
buffer.hdr.operation);
}
/*
* 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));
goto reopen_fcopy_fd;
}
}
}