tools/hv/hv_vss_daemon.c

   1 /*
   2  * An implementation of the host initiated guest snapshot for Hyper-V.
   3  *
   4  *
   5  * Copyright (C) 2013, Microsoft, Inc.
   6  * Author : K. Y. Srinivasan <kys@microsoft.com>
   7  *
   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.
  11  *
  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
  16  * details.
  17  *
  18  */
  19
  20
  21 #include <sys/types.h>
  22 #include <sys/poll.h>
  23 #include <sys/ioctl.h>
  24 #include <fcntl.h>
  25 #include <stdio.h>
  26 #include <mntent.h>
  27 #include <stdlib.h>
  28 #include <unistd.h>
  29 #include <string.h>
  30 #include <ctype.h>
  31 #include <errno.h>
  32 #include <linux/fs.h>
  33 #include <linux/hyperv.h>
  34 #include <syslog.h>
  35 #include <getopt.h>
  36
  37 /* Don't use syslog() in the function since that can cause write to disk */
  38 static int vss_do_freeze(char *dir, unsigned int cmd)
  39 {
  40         int ret, fd = open(dir, O_RDONLY);
  41
  42         if (fd < 0)
  43                 return 1;
  44
  45         ret = ioctl(fd, cmd, 0);
  46
  47         /*
  48          * If a partition is mounted more than once, only the first
  49          * FREEZE/THAW can succeed and the later ones will get
  50          * EBUSY/EINVAL respectively: there could be 2 cases:
  51          * 1) a user may mount the same partition to differnt directories
  52          *  by mistake or on purpose;
  53          * 2) The subvolume of btrfs appears to have the same partition
  54          * mounted more than once.
  55          */
  56         if (ret) {
  57                 if ((cmd == FIFREEZE && errno == EBUSY) ||
  58                     (cmd == FITHAW && errno == EINVAL)) {
  59                         close(fd);
  60                         return 0;
  61                 }
  62         }
  63
  64         close(fd);
  65         return !!ret;
  66 }
  67
  68 static int vss_operate(int operation)
  69 {
  70         char match[] = "/dev/";
  71         FILE *mounts;
  72         struct mntent *ent;
  73         char errdir[1024] = {0};
  74         unsigned int cmd;
  75         int error = 0, root_seen = 0, save_errno = 0;
  76
  77         switch (operation) {
  78         case VSS_OP_FREEZE:
  79                 cmd = FIFREEZE;
  80                 break;
  81         case VSS_OP_THAW:
  82                 cmd = FITHAW;
  83                 break;
  84         default:
  85                 return -1;
  86         }
  87
  88         mounts = setmntent("/proc/mounts", "r");
  89         if (mounts == NULL)
  90                 return -1;
  91
  92         while ((ent = getmntent(mounts))) {
  93                 if (strncmp(ent->mnt_fsname, match, strlen(match)))
  94                         continue;
  95                 if (hasmntopt(ent, MNTOPT_RO) != NULL)
  96                         continue;
  97                 if (strcmp(ent->mnt_type, "vfat") == 0)
  98                         continue;
  99                 if (strcmp(ent->mnt_dir, "/") == 0) {
 100                         root_seen = 1;
 101                         continue;
 102                 }
 103                 error |= vss_do_freeze(ent->mnt_dir, cmd);
 104                 if (error && operation == VSS_OP_FREEZE)
 105                         goto err;
 106         }
 107
 108         endmntent(mounts);
 109
 110         if (root_seen) {
 111                 error |= vss_do_freeze("/", cmd);
 112                 if (error && operation == VSS_OP_FREEZE)
 113                         goto err;
 114         }
 115
 116         goto out;
 117 err:
 118         save_errno = errno;
 119         if (ent) {
 120                 strncpy(errdir, ent->mnt_dir, sizeof(errdir)-1);
 121                 endmntent(mounts);
 122         }
 123         vss_operate(VSS_OP_THAW);
 124         /* Call syslog after we thaw all filesystems */
 125         if (ent)
 126                 syslog(LOG_ERR, "FREEZE of %s failed; error:%d %s",
 127                        errdir, save_errno, strerror(save_errno));
 128         else
 129                 syslog(LOG_ERR, "FREEZE of / failed; error:%d %s", save_errno,
 130                        strerror(save_errno));
 131 out:
 132         return error;
 133 }
 134
 135 void print_usage(char *argv[])
 136 {
 137         fprintf(stderr, "Usage: %s [options]\n"
 138                 "Options are:\n"
 139                 "  -n, --no-daemon        stay in foreground, don't daemonize\n"
 140                 "  -h, --help             print this help\n", argv[0]);
 141 }
 142
 143 int main(int argc, char *argv[])
 144 {
 145         int vss_fd, len;
 146         int error;
 147         struct pollfd pfd;
 148         int     op;
 149         struct hv_vss_msg vss_msg[1];
 150         int daemonize = 1, long_index = 0, opt;
 151         int in_handshake = 1;
 152         __u32 kernel_modver;
 153
 154         static struct option long_options[] = {
 155                 {"help",        no_argument,       0,  'h' },
 156                 {"no-daemon",   no_argument,       0,  'n' },
 157                 {0,             0,                 0,  0   }
 158         };
 159
 160         while ((opt = getopt_long(argc, argv, "hn", long_options,
 161                                   &long_index)) != -1) {
 162                 switch (opt) {
 163                 case 'n':
 164                         daemonize = 0;
 165                         break;
 166                 case 'h':
 167                 default:
 168                         print_usage(argv);
 169                         exit(EXIT_FAILURE);
 170                 }
 171         }
 172
 173         if (daemonize && daemon(1, 0))
 174                 return 1;
 175
 176         openlog("Hyper-V VSS", 0, LOG_USER);
 177         syslog(LOG_INFO, "VSS starting; pid is:%d", getpid());
 178
 179         vss_fd = open("/dev/vmbus/hv_vss", O_RDWR);
 180         if (vss_fd < 0) {
 181                 syslog(LOG_ERR, "open /dev/vmbus/hv_vss failed; error: %d %s",
 182                        errno, strerror(errno));
 183                 exit(EXIT_FAILURE);
 184         }
 185         /*
 186          * Register ourselves with the kernel.
 187          */
 188         vss_msg->vss_hdr.operation = VSS_OP_REGISTER1;
 189
 190         len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
 191         if (len < 0) {
 192                 syslog(LOG_ERR, "registration to kernel failed; error: %d %s",
 193                        errno, strerror(errno));
 194                 close(vss_fd);
 195                 exit(EXIT_FAILURE);
 196         }
 197
 198         pfd.fd = vss_fd;
 199
 200         while (1) {
 201                 pfd.events = POLLIN;
 202                 pfd.revents = 0;
 203
 204                 if (poll(&pfd, 1, -1) < 0) {
 205                         syslog(LOG_ERR, "poll failed; error:%d %s", errno, strerror(errno));
 206                         if (errno == EINVAL) {
 207                                 close(vss_fd);
 208                                 exit(EXIT_FAILURE);
 209                         }
 210                         else
 211                                 continue;
 212                 }
 213
 214                 len = read(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
 215
 216                 if (in_handshake) {
 217                         if (len != sizeof(kernel_modver)) {
 218                                 syslog(LOG_ERR, "invalid version negotiation");
 219                                 exit(EXIT_FAILURE);
 220                         }
 221                         kernel_modver = *(__u32 *)vss_msg;
 222                         in_handshake = 0;
 223                         syslog(LOG_INFO, "VSS: kernel module version: %d",
 224                                kernel_modver);
 225                         continue;
 226                 }
 227
 228                 if (len != sizeof(struct hv_vss_msg)) {
 229                         syslog(LOG_ERR, "read failed; error:%d %s",
 230                                errno, strerror(errno));
 231                         close(vss_fd);
 232                         return EXIT_FAILURE;
 233                 }
 234
 235                 op = vss_msg->vss_hdr.operation;
 236                 error =  HV_S_OK;
 237
 238                 switch (op) {
 239                 case VSS_OP_FREEZE:
 240                 case VSS_OP_THAW:
 241                         error = vss_operate(op);
 242                         syslog(LOG_INFO, "VSS: op=%s: %s\n",
 243                                 op == VSS_OP_FREEZE ? "FREEZE" : "THAW",
 244                                 error ? "failed" : "succeeded");
 245
 246                         if (error) {
 247                                 error = HV_E_FAIL;
 248                                 syslog(LOG_ERR, "op=%d failed!", op);
 249                                 syslog(LOG_ERR, "report it with these files:");
 250                                 syslog(LOG_ERR, "/etc/fstab and /proc/mounts");
 251                         }
 252                         break;
 253                 default:
 254                         syslog(LOG_ERR, "Illegal op:%d\n", op);
 255                 }
 256                 vss_msg->error = error;
 257                 len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
 258                 if (len != sizeof(struct hv_vss_msg)) {
 259                         syslog(LOG_ERR, "write failed; error: %d %s", errno,
 260                                strerror(errno));
 261                         exit(EXIT_FAILURE);
 262                 }
 263         }
 264
 265         close(vss_fd);
 266         exit(0);
 267 }