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 <sys/stat.h>
  25 #include <sys/sysmacros.h>
  26 #include <fcntl.h>
  27 #include <stdio.h>
  28 #include <mntent.h>
  29 #include <stdlib.h>
  30 #include <unistd.h>
  31 #include <string.h>
  32 #include <ctype.h>
  33 #include <errno.h>
  34 #include <linux/fs.h>
  35 #include <linux/major.h>
  36 #include <linux/hyperv.h>
  37 #include <syslog.h>
  38 #include <getopt.h>
  39
  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)
  42 {
  43         int ret, fd = open(dir, O_RDONLY);
  44
  45         if (fd < 0)
  46                 return 1;
  47
  48         ret = ioctl(fd, cmd, 0);
  49
  50         /*
  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.
  58          */
  59         if (ret) {
  60                 if ((cmd == FIFREEZE && errno == EBUSY) ||
  61                     (cmd == FITHAW && errno == EINVAL)) {
  62                         close(fd);
  63                         return 0;
  64                 }
  65         }
  66
  67         close(fd);
  68         return !!ret;
  69 }
  70
  71 static int vss_operate(int operation)
  72 {
  73         char match[] = "/dev/";
  74         FILE *mounts;
  75         struct mntent *ent;
  76         struct stat sb;
  77         char errdir[1024] = {0};
  78         unsigned int cmd;
  79         int error = 0, root_seen = 0, save_errno = 0;
  80
  81         switch (operation) {
  82         case VSS_OP_FREEZE:
  83                 cmd = FIFREEZE;
  84                 break;
  85         case VSS_OP_THAW:
  86                 cmd = FITHAW;
  87                 break;
  88         default:
  89                 return -1;
  90         }
  91
  92         mounts = setmntent("/proc/mounts", "r");
  93         if (mounts == NULL)
  94                 return -1;
  95
  96         while ((ent = getmntent(mounts))) {
  97                 if (strncmp(ent->mnt_fsname, match, strlen(match)))
  98                         continue;
  99                 if (stat(ent->mnt_fsname, &sb) == -1)
 100                         continue;
 101                 if (S_ISBLK(sb.st_mode) && major(sb.st_rdev) == LOOP_MAJOR)
 102                         continue;
 103                 if (hasmntopt(ent, MNTOPT_RO) != NULL)
 104                         continue;
 105                 if (strcmp(ent->mnt_type, "vfat") == 0)
 106                         continue;
 107                 if (strcmp(ent->mnt_dir, "/") == 0) {
 108                         root_seen = 1;
 109                         continue;
 110                 }
 111                 error |= vss_do_freeze(ent->mnt_dir, cmd);
 112                 if (error && operation == VSS_OP_FREEZE)
 113                         goto err;
 114         }
 115
 116         endmntent(mounts);
 117
 118         if (root_seen) {
 119                 error |= vss_do_freeze("/", cmd);
 120                 if (error && operation == VSS_OP_FREEZE)
 121                         goto err;
 122         }
 123
 124         goto out;
 125 err:
 126         save_errno = errno;
 127         if (ent) {
 128                 strncpy(errdir, ent->mnt_dir, sizeof(errdir)-1);
 129                 endmntent(mounts);
 130         }
 131         vss_operate(VSS_OP_THAW);
 132         /* Call syslog after we thaw all filesystems */
 133         if (ent)
 134                 syslog(LOG_ERR, "FREEZE of %s failed; error:%d %s",
 135                        errdir, save_errno, strerror(save_errno));
 136         else
 137                 syslog(LOG_ERR, "FREEZE of / failed; error:%d %s", save_errno,
 138                        strerror(save_errno));
 139 out:
 140         return error;
 141 }
 142
 143 void print_usage(char *argv[])
 144 {
 145         fprintf(stderr, "Usage: %s [options]\n"
 146                 "Options are:\n"
 147                 "  -n, --no-daemon        stay in foreground, don't daemonize\n"
 148                 "  -h, --help             print this help\n", argv[0]);
 149 }
 150
 151 int main(int argc, char *argv[])
 152 {
 153         int vss_fd, len;
 154         int error;
 155         struct pollfd pfd;
 156         int     op;
 157         struct hv_vss_msg vss_msg[1];
 158         int daemonize = 1, long_index = 0, opt;
 159         int in_handshake = 1;
 160         __u32 kernel_modver;
 161
 162         static struct option long_options[] = {
 163                 {"help",        no_argument,       0,  'h' },
 164                 {"no-daemon",   no_argument,       0,  'n' },
 165                 {0,             0,                 0,  0   }
 166         };
 167
 168         while ((opt = getopt_long(argc, argv, "hn", long_options,
 169                                   &long_index)) != -1) {
 170                 switch (opt) {
 171                 case 'n':
 172                         daemonize = 0;
 173                         break;
 174                 case 'h':
 175                 default:
 176                         print_usage(argv);
 177                         exit(EXIT_FAILURE);
 178                 }
 179         }
 180
 181         if (daemonize && daemon(1, 0))
 182                 return 1;
 183
 184         openlog("Hyper-V VSS", 0, LOG_USER);
 185         syslog(LOG_INFO, "VSS starting; pid is:%d", getpid());
 186
 187         vss_fd = open("/dev/vmbus/hv_vss", O_RDWR);
 188         if (vss_fd < 0) {
 189                 syslog(LOG_ERR, "open /dev/vmbus/hv_vss failed; error: %d %s",
 190                        errno, strerror(errno));
 191                 exit(EXIT_FAILURE);
 192         }
 193         /*
 194          * Register ourselves with the kernel.
 195          */
 196         vss_msg->vss_hdr.operation = VSS_OP_REGISTER1;
 197
 198         len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
 199         if (len < 0) {
 200                 syslog(LOG_ERR, "registration to kernel failed; error: %d %s",
 201                        errno, strerror(errno));
 202                 close(vss_fd);
 203                 exit(EXIT_FAILURE);
 204         }
 205
 206         pfd.fd = vss_fd;
 207
 208         while (1) {
 209                 pfd.events = POLLIN;
 210                 pfd.revents = 0;
 211
 212                 if (poll(&pfd, 1, -1) < 0) {
 213                         syslog(LOG_ERR, "poll failed; error:%d %s", errno, strerror(errno));
 214                         if (errno == EINVAL) {
 215                                 close(vss_fd);
 216                                 exit(EXIT_FAILURE);
 217                         }
 218                         else
 219                                 continue;
 220                 }
 221
 222                 len = read(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
 223
 224                 if (in_handshake) {
 225                         if (len != sizeof(kernel_modver)) {
 226                                 syslog(LOG_ERR, "invalid version negotiation");
 227                                 exit(EXIT_FAILURE);
 228                         }
 229                         kernel_modver = *(__u32 *)vss_msg;
 230                         in_handshake = 0;
 231                         syslog(LOG_INFO, "VSS: kernel module version: %d",
 232                                kernel_modver);
 233                         continue;
 234                 }
 235
 236                 if (len != sizeof(struct hv_vss_msg)) {
 237                         syslog(LOG_ERR, "read failed; error:%d %s",
 238                                errno, strerror(errno));
 239                         close(vss_fd);
 240                         return EXIT_FAILURE;
 241                 }
 242
 243                 op = vss_msg->vss_hdr.operation;
 244                 error =  HV_S_OK;
 245
 246                 switch (op) {
 247                 case VSS_OP_FREEZE:
 248                 case VSS_OP_THAW:
 249                         error = vss_operate(op);
 250                         syslog(LOG_INFO, "VSS: op=%s: %s\n",
 251                                 op == VSS_OP_FREEZE ? "FREEZE" : "THAW",
 252                                 error ? "failed" : "succeeded");
 253
 254                         if (error) {
 255                                 error = HV_E_FAIL;
 256                                 syslog(LOG_ERR, "op=%d failed!", op);
 257                                 syslog(LOG_ERR, "report it with these files:");
 258                                 syslog(LOG_ERR, "/etc/fstab and /proc/mounts");
 259                         }
 260                         break;
 261                 case VSS_OP_HOT_BACKUP:
 262                         syslog(LOG_INFO, "VSS: op=CHECK HOT BACKUP\n");
 263                         break;
 264                 default:
 265                         syslog(LOG_ERR, "Illegal op:%d\n", op);
 266                 }
 267                 vss_msg->error = error;
 268                 len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
 269                 if (len != sizeof(struct hv_vss_msg)) {
 270                         syslog(LOG_ERR, "write failed; error: %d %s", errno,
 271                                strerror(errno));
 272
 273                         if (op == VSS_OP_FREEZE)
 274                                 vss_operate(VSS_OP_THAW);
 275                 }
 276         }
 277
 278         close(vss_fd);
 279         exit(0);
 280 }