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![Alex Ng](/assets/img/avatar_default.png)
Since a loop device is backed by a file, a backup will already result in its parent filesystem being frozen. It's sufficient to just freeze the parent filesystem, so we can skip the loop device. This avoids a situation where a loop device and its parent filesystem are both frozen and then thawed out of order. For example, if the loop device is enumerated first, we would thaw it while its parent filesystem is still frozen. The thaw operation fails and the loop device remains frozen. Signed-off-by: Alex Ng <alexng@messages.microsoft.com> Signed-off-by: Vyronas Tsingaras <vyronas@vtsingaras.me> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
279 lines
6.3 KiB
C
279 lines
6.3 KiB
C
/*
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* An implementation of the host initiated guest snapshot for Hyper-V.
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*
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*
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* Copyright (C) 2013, Microsoft, Inc.
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* Author : K. Y. Srinivasan <kys@microsoft.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published
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* by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
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* NON INFRINGEMENT. See the GNU General Public License for more
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* details.
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*
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*/
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#include <sys/types.h>
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#include <sys/poll.h>
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#include <sys/ioctl.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <mntent.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 <ctype.h>
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#include <errno.h>
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#include <linux/fs.h>
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#include <linux/major.h>
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#include <linux/hyperv.h>
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#include <syslog.h>
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#include <getopt.h>
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/* Don't use syslog() in the function since that can cause write to disk */
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static int vss_do_freeze(char *dir, unsigned int cmd)
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{
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int ret, fd = open(dir, O_RDONLY);
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if (fd < 0)
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return 1;
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ret = ioctl(fd, cmd, 0);
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/*
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* If a partition is mounted more than once, only the first
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* FREEZE/THAW can succeed and the later ones will get
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* EBUSY/EINVAL respectively: there could be 2 cases:
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* 1) a user may mount the same partition to differnt directories
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* by mistake or on purpose;
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* 2) The subvolume of btrfs appears to have the same partition
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* mounted more than once.
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*/
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if (ret) {
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if ((cmd == FIFREEZE && errno == EBUSY) ||
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(cmd == FITHAW && errno == EINVAL)) {
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close(fd);
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return 0;
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}
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}
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close(fd);
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return !!ret;
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}
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static int vss_operate(int operation)
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{
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char match[] = "/dev/";
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FILE *mounts;
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struct mntent *ent;
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struct stat sb;
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char errdir[1024] = {0};
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unsigned int cmd;
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int error = 0, root_seen = 0, save_errno = 0;
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switch (operation) {
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case VSS_OP_FREEZE:
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cmd = FIFREEZE;
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break;
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case VSS_OP_THAW:
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cmd = FITHAW;
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break;
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default:
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return -1;
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}
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mounts = setmntent("/proc/mounts", "r");
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if (mounts == NULL)
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return -1;
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while ((ent = getmntent(mounts))) {
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if (strncmp(ent->mnt_fsname, match, strlen(match)))
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continue;
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if (stat(ent->mnt_fsname, &sb) == -1)
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continue;
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if (S_ISBLK(sb.st_mode) && major(sb.st_rdev) == LOOP_MAJOR)
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continue;
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if (hasmntopt(ent, MNTOPT_RO) != NULL)
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continue;
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if (strcmp(ent->mnt_type, "vfat") == 0)
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continue;
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if (strcmp(ent->mnt_dir, "/") == 0) {
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root_seen = 1;
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continue;
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}
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error |= vss_do_freeze(ent->mnt_dir, cmd);
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if (error && operation == VSS_OP_FREEZE)
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goto err;
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}
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endmntent(mounts);
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if (root_seen) {
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error |= vss_do_freeze("/", cmd);
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if (error && operation == VSS_OP_FREEZE)
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goto err;
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}
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goto out;
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err:
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save_errno = errno;
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if (ent) {
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strncpy(errdir, ent->mnt_dir, sizeof(errdir)-1);
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endmntent(mounts);
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}
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vss_operate(VSS_OP_THAW);
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/* Call syslog after we thaw all filesystems */
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if (ent)
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syslog(LOG_ERR, "FREEZE of %s failed; error:%d %s",
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errdir, save_errno, strerror(save_errno));
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else
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syslog(LOG_ERR, "FREEZE of / failed; error:%d %s", save_errno,
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strerror(save_errno));
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out:
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return error;
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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 vss_fd, len;
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int error;
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struct pollfd pfd;
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int op;
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struct hv_vss_msg vss_msg[1];
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int daemonize = 1, long_index = 0, opt;
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int in_handshake = 1;
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__u32 kernel_modver;
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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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return 1;
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openlog("Hyper-V VSS", 0, LOG_USER);
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syslog(LOG_INFO, "VSS starting; pid is:%d", getpid());
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vss_fd = open("/dev/vmbus/hv_vss", O_RDWR);
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if (vss_fd < 0) {
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syslog(LOG_ERR, "open /dev/vmbus/hv_vss 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 ourselves with the kernel.
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*/
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vss_msg->vss_hdr.operation = VSS_OP_REGISTER1;
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len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
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if (len < 0) {
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syslog(LOG_ERR, "registration to kernel failed; error: %d %s",
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errno, strerror(errno));
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close(vss_fd);
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exit(EXIT_FAILURE);
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}
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pfd.fd = vss_fd;
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while (1) {
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pfd.events = POLLIN;
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pfd.revents = 0;
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if (poll(&pfd, 1, -1) < 0) {
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syslog(LOG_ERR, "poll failed; error:%d %s", errno, strerror(errno));
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if (errno == EINVAL) {
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close(vss_fd);
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exit(EXIT_FAILURE);
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}
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else
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continue;
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}
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len = read(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
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if (in_handshake) {
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if (len != sizeof(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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kernel_modver = *(__u32 *)vss_msg;
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in_handshake = 0;
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syslog(LOG_INFO, "VSS: kernel module version: %d",
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kernel_modver);
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continue;
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}
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if (len != sizeof(struct hv_vss_msg)) {
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syslog(LOG_ERR, "read failed; error:%d %s",
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errno, strerror(errno));
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close(vss_fd);
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return EXIT_FAILURE;
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}
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op = vss_msg->vss_hdr.operation;
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error = HV_S_OK;
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switch (op) {
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case VSS_OP_FREEZE:
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case VSS_OP_THAW:
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error = vss_operate(op);
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syslog(LOG_INFO, "VSS: op=%s: %s\n",
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op == VSS_OP_FREEZE ? "FREEZE" : "THAW",
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error ? "failed" : "succeeded");
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if (error) {
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error = HV_E_FAIL;
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syslog(LOG_ERR, "op=%d failed!", op);
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syslog(LOG_ERR, "report it with these files:");
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syslog(LOG_ERR, "/etc/fstab and /proc/mounts");
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}
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break;
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case VSS_OP_HOT_BACKUP:
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syslog(LOG_INFO, "VSS: op=CHECK HOT BACKUP\n");
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break;
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default:
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syslog(LOG_ERR, "Illegal op:%d\n", op);
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}
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vss_msg->error = error;
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len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
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if (len != sizeof(struct hv_vss_msg)) {
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syslog(LOG_ERR, "write failed; error: %d %s", errno,
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strerror(errno));
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if (op == VSS_OP_FREEZE)
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vss_operate(VSS_OP_THAW);
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}
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}
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close(vss_fd);
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exit(0);
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}
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