2 * An implementation of the host initiated guest snapshot for Hyper-V.
5 * Copyright (C) 2013, Microsoft, Inc.
6 * Author : K. Y. Srinivasan <kys@microsoft.com>
8 * This program is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License version 2 as published
10 * by the Free Software Foundation.
12 * This program is distributed in the hope that it will be useful, but
13 * WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
15 * NON INFRINGEMENT. See the GNU General Public License for more
21 #include <sys/types.h>
23 #include <sys/ioctl.h>
25 #include <sys/sysmacros.h>
35 #include <linux/major.h>
36 #include <linux/hyperv.h>
40 /* Don't use syslog() in the function since that can cause write to disk */
41 static int vss_do_freeze(char *dir, unsigned int cmd)
43 int ret, fd = open(dir, O_RDONLY);
48 ret = ioctl(fd, cmd, 0);
51 * If a partition is mounted more than once, only the first
52 * FREEZE/THAW can succeed and the later ones will get
53 * EBUSY/EINVAL respectively: there could be 2 cases:
54 * 1) a user may mount the same partition to differnt directories
55 * by mistake or on purpose;
56 * 2) The subvolume of btrfs appears to have the same partition
57 * mounted more than once.
60 if ((cmd == FIFREEZE && errno == EBUSY) ||
61 (cmd == FITHAW && errno == EINVAL)) {
71 static int vss_operate(int operation)
73 char match[] = "/dev/";
77 char errdir[1024] = {0};
79 int error = 0, root_seen = 0, save_errno = 0;
92 mounts = setmntent("/proc/mounts", "r");
96 while ((ent = getmntent(mounts))) {
97 if (strncmp(ent->mnt_fsname, match, strlen(match)))
99 if (stat(ent->mnt_fsname, &sb) == -1)
101 if (S_ISBLK(sb.st_mode) && major(sb.st_rdev) == LOOP_MAJOR)
103 if (hasmntopt(ent, MNTOPT_RO) != NULL)
105 if (strcmp(ent->mnt_type, "vfat") == 0)
107 if (strcmp(ent->mnt_dir, "/") == 0) {
111 error |= vss_do_freeze(ent->mnt_dir, cmd);
112 if (error && operation == VSS_OP_FREEZE)
119 error |= vss_do_freeze("/", cmd);
120 if (error && operation == VSS_OP_FREEZE)
128 strncpy(errdir, ent->mnt_dir, sizeof(errdir)-1);
131 vss_operate(VSS_OP_THAW);
132 /* Call syslog after we thaw all filesystems */
134 syslog(LOG_ERR, "FREEZE of %s failed; error:%d %s",
135 errdir, save_errno, strerror(save_errno));
137 syslog(LOG_ERR, "FREEZE of / failed; error:%d %s", save_errno,
138 strerror(save_errno));
143 void print_usage(char *argv[])
145 fprintf(stderr, "Usage: %s [options]\n"
147 " -n, --no-daemon stay in foreground, don't daemonize\n"
148 " -h, --help print this help\n", argv[0]);
151 int main(int argc, char *argv[])
157 struct hv_vss_msg vss_msg[1];
158 int daemonize = 1, long_index = 0, opt;
159 int in_handshake = 1;
162 static struct option long_options[] = {
163 {"help", no_argument, 0, 'h' },
164 {"no-daemon", no_argument, 0, 'n' },
168 while ((opt = getopt_long(argc, argv, "hn", long_options,
169 &long_index)) != -1) {
183 if (daemonize && daemon(1, 0))
186 openlog("Hyper-V VSS", 0, LOG_USER);
187 syslog(LOG_INFO, "VSS starting; pid is:%d", getpid());
189 vss_fd = open("/dev/vmbus/hv_vss", O_RDWR);
191 syslog(LOG_ERR, "open /dev/vmbus/hv_vss failed; error: %d %s",
192 errno, strerror(errno));
196 * Register ourselves with the kernel.
198 vss_msg->vss_hdr.operation = VSS_OP_REGISTER1;
200 len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
202 syslog(LOG_ERR, "registration to kernel failed; error: %d %s",
203 errno, strerror(errno));
214 if (poll(&pfd, 1, -1) < 0) {
215 syslog(LOG_ERR, "poll failed; error:%d %s", errno, strerror(errno));
216 if (errno == EINVAL) {
224 len = read(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
227 if (len != sizeof(kernel_modver)) {
228 syslog(LOG_ERR, "invalid version negotiation");
231 kernel_modver = *(__u32 *)vss_msg;
233 syslog(LOG_INFO, "VSS: kernel module version: %d",
238 if (len != sizeof(struct hv_vss_msg)) {
239 syslog(LOG_ERR, "read failed; error:%d %s",
240 errno, strerror(errno));
245 op = vss_msg->vss_hdr.operation;
251 error = vss_operate(op);
252 syslog(LOG_INFO, "VSS: op=%s: %s\n",
253 op == VSS_OP_FREEZE ? "FREEZE" : "THAW",
254 error ? "failed" : "succeeded");
258 syslog(LOG_ERR, "op=%d failed!", op);
259 syslog(LOG_ERR, "report it with these files:");
260 syslog(LOG_ERR, "/etc/fstab and /proc/mounts");
263 case VSS_OP_HOT_BACKUP:
264 syslog(LOG_INFO, "VSS: op=CHECK HOT BACKUP\n");
267 syslog(LOG_ERR, "Illegal op:%d\n", op);
269 vss_msg->error = error;
270 len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
271 if (len != sizeof(struct hv_vss_msg)) {
272 syslog(LOG_ERR, "write failed; error: %d %s", errno,
275 if (op == VSS_OP_FREEZE)
276 vss_operate(VSS_OP_THAW);