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![Dexuan Cui](/assets/img/avatar_default.png)
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>
266 lines
6 KiB
C
266 lines
6 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* An implementation of host to guest copy functionality for Linux.
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*
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* Copyright (C) 2014, Microsoft, Inc.
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*
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* Author : K. Y. Srinivasan <kys@microsoft.com>
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*/
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#include <sys/types.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <errno.h>
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#include <linux/hyperv.h>
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#include <linux/limits.h>
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#include <syslog.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <getopt.h>
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static int target_fd;
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static char target_fname[PATH_MAX];
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static unsigned long long filesize;
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static int hv_start_fcopy(struct hv_start_fcopy *smsg)
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{
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int error = HV_E_FAIL;
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char *q, *p;
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filesize = 0;
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p = (char *)smsg->path_name;
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snprintf(target_fname, sizeof(target_fname), "%s/%s",
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(char *)smsg->path_name, (char *)smsg->file_name);
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syslog(LOG_INFO, "Target file name: %s", target_fname);
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/*
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* Check to see if the path is already in place; if not,
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* create if required.
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*/
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while ((q = strchr(p, '/')) != NULL) {
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if (q == p) {
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p++;
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continue;
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}
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*q = '\0';
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if (access((char *)smsg->path_name, F_OK)) {
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if (smsg->copy_flags & CREATE_PATH) {
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if (mkdir((char *)smsg->path_name, 0755)) {
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syslog(LOG_ERR, "Failed to create %s",
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(char *)smsg->path_name);
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goto done;
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}
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} else {
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syslog(LOG_ERR, "Invalid path: %s",
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(char *)smsg->path_name);
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goto done;
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}
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}
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p = q + 1;
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*q = '/';
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}
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if (!access(target_fname, F_OK)) {
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syslog(LOG_INFO, "File: %s exists", target_fname);
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if (!(smsg->copy_flags & OVER_WRITE)) {
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error = HV_ERROR_ALREADY_EXISTS;
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goto done;
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}
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}
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target_fd = open(target_fname,
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O_RDWR | O_CREAT | O_TRUNC | O_CLOEXEC, 0744);
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if (target_fd == -1) {
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syslog(LOG_INFO, "Open Failed: %s", strerror(errno));
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goto done;
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}
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error = 0;
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done:
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if (error)
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target_fname[0] = '\0';
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return error;
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}
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static int hv_copy_data(struct hv_do_fcopy *cpmsg)
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{
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ssize_t bytes_written;
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int ret = 0;
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bytes_written = pwrite(target_fd, cpmsg->data, cpmsg->size,
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cpmsg->offset);
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filesize += cpmsg->size;
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if (bytes_written != cpmsg->size) {
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switch (errno) {
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case ENOSPC:
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ret = HV_ERROR_DISK_FULL;
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break;
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default:
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ret = HV_E_FAIL;
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break;
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}
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syslog(LOG_ERR, "pwrite failed to write %llu bytes: %ld (%s)",
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filesize, (long)bytes_written, strerror(errno));
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}
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return ret;
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}
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/*
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* Reset target_fname to "" in the two below functions for hibernation: if
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* the fcopy operation is aborted by hibernation, the daemon should remove the
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* partially-copied file; to achieve this, the hv_utils driver always fakes a
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* CANCEL_FCOPY message upon suspend, and later when the VM resumes back,
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* the daemon calls hv_copy_cancel() to remove the file; if a file is copied
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* successfully before suspend, hv_copy_finished() must reset target_fname to
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* avoid that the file can be incorrectly removed upon resume, since the faked
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* CANCEL_FCOPY message is spurious in this case.
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*/
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static int hv_copy_finished(void)
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{
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close(target_fd);
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target_fname[0] = '\0';
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return 0;
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}
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static int hv_copy_cancel(void)
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{
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close(target_fd);
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if (strlen(target_fname) > 0) {
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unlink(target_fname);
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target_fname[0] = '\0';
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}
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return 0;
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}
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void print_usage(char *argv[])
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{
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fprintf(stderr, "Usage: %s [options]\n"
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"Options are:\n"
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" -n, --no-daemon stay in foreground, don't daemonize\n"
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" -h, --help print this help\n", argv[0]);
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}
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int main(int argc, char *argv[])
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{
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int fcopy_fd = -1;
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int error;
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int daemonize = 1, long_index = 0, opt;
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int version = FCOPY_CURRENT_VERSION;
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union {
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struct hv_fcopy_hdr hdr;
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struct hv_start_fcopy start;
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struct hv_do_fcopy copy;
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__u32 kernel_modver;
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} buffer = { };
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int in_handshake;
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static struct option long_options[] = {
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{"help", no_argument, 0, 'h' },
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{"no-daemon", no_argument, 0, 'n' },
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{0, 0, 0, 0 }
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};
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while ((opt = getopt_long(argc, argv, "hn", long_options,
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&long_index)) != -1) {
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switch (opt) {
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case 'n':
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daemonize = 0;
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break;
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case 'h':
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default:
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print_usage(argv);
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exit(EXIT_FAILURE);
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}
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}
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if (daemonize && daemon(1, 0)) {
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syslog(LOG_ERR, "daemon() failed; error: %s", strerror(errno));
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exit(EXIT_FAILURE);
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}
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openlog("HV_FCOPY", 0, LOG_USER);
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syslog(LOG_INFO, "starting; pid is:%d", getpid());
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reopen_fcopy_fd:
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if (fcopy_fd != -1)
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close(fcopy_fd);
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/* Remove any possible partially-copied file on error */
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hv_copy_cancel();
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in_handshake = 1;
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fcopy_fd = open("/dev/vmbus/hv_fcopy", O_RDWR);
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if (fcopy_fd < 0) {
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syslog(LOG_ERR, "open /dev/vmbus/hv_fcopy failed; error: %d %s",
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errno, strerror(errno));
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exit(EXIT_FAILURE);
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}
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/*
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* Register with the kernel.
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*/
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if ((write(fcopy_fd, &version, sizeof(int))) != sizeof(int)) {
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syslog(LOG_ERR, "Registration failed: %s", strerror(errno));
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exit(EXIT_FAILURE);
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}
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while (1) {
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/*
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* In this loop we process fcopy messages after the
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* handshake is complete.
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*/
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ssize_t len;
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len = pread(fcopy_fd, &buffer, sizeof(buffer), 0);
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if (len < 0) {
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syslog(LOG_ERR, "pread failed: %s", strerror(errno));
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goto reopen_fcopy_fd;
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}
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if (in_handshake) {
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if (len != sizeof(buffer.kernel_modver)) {
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syslog(LOG_ERR, "invalid version negotiation");
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exit(EXIT_FAILURE);
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}
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in_handshake = 0;
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syslog(LOG_INFO, "kernel module version: %u",
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buffer.kernel_modver);
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continue;
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}
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switch (buffer.hdr.operation) {
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case START_FILE_COPY:
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error = hv_start_fcopy(&buffer.start);
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break;
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case WRITE_TO_FILE:
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error = hv_copy_data(&buffer.copy);
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break;
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case COMPLETE_FCOPY:
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error = hv_copy_finished();
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break;
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case CANCEL_FCOPY:
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error = hv_copy_cancel();
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break;
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default:
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error = HV_E_FAIL;
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syslog(LOG_ERR, "Unknown operation: %d",
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buffer.hdr.operation);
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}
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/*
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* pwrite() may return an error due to the faked CANCEL_FCOPY
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* message upon hibernation. Ignore the error by resetting the
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* dev file, i.e. closing and re-opening it.
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*/
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if (pwrite(fcopy_fd, &error, sizeof(int), 0) != sizeof(int)) {
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syslog(LOG_ERR, "pwrite failed: %s", strerror(errno));
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goto reopen_fcopy_fd;
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}
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}
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}
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