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Linux/tools/hv/hv_vss_daemon.c

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  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 #include <stdbool.h>
 40 #include <dirent.h>
 41 
 42 /* Don't use syslog() in the function since that can cause write to disk */
 43 static int vss_do_freeze(char *dir, unsigned int cmd)
 44 {
 45         int ret, fd = open(dir, O_RDONLY);
 46 
 47         if (fd < 0)
 48                 return 1;
 49 
 50         ret = ioctl(fd, cmd, 0);
 51 
 52         /*
 53          * If a partition is mounted more than once, only the first
 54          * FREEZE/THAW can succeed and the later ones will get
 55          * EBUSY/EINVAL respectively: there could be 2 cases:
 56          * 1) a user may mount the same partition to differnt directories
 57          *  by mistake or on purpose;
 58          * 2) The subvolume of btrfs appears to have the same partition
 59          * mounted more than once.
 60          */
 61         if (ret) {
 62                 if ((cmd == FIFREEZE && errno == EBUSY) ||
 63                     (cmd == FITHAW && errno == EINVAL)) {
 64                         close(fd);
 65                         return 0;
 66                 }
 67         }
 68 
 69         close(fd);
 70         return !!ret;
 71 }
 72 
 73 static bool is_dev_loop(const char *blkname)
 74 {
 75         char *buffer;
 76         DIR *dir;
 77         struct dirent *entry;
 78         bool ret = false;
 79 
 80         buffer = malloc(PATH_MAX);
 81         if (!buffer) {
 82                 syslog(LOG_ERR, "Can't allocate memory!");
 83                 exit(1);
 84         }
 85 
 86         snprintf(buffer, PATH_MAX, "%s/loop", blkname);
 87         if (!access(buffer, R_OK | X_OK)) {
 88                 ret = true;
 89                 goto free_buffer;
 90         } else if (errno != ENOENT) {
 91                 syslog(LOG_ERR, "Can't access: %s; error:%d %s!",
 92                        buffer, errno, strerror(errno));
 93         }
 94 
 95         snprintf(buffer, PATH_MAX, "%s/slaves", blkname);
 96         dir = opendir(buffer);
 97         if (!dir) {
 98                 if (errno != ENOENT)
 99                         syslog(LOG_ERR, "Can't opendir: %s; error:%d %s!",
100                                buffer, errno, strerror(errno));
101                 goto free_buffer;
102         }
103 
104         while ((entry = readdir(dir)) != NULL) {
105                 if (strcmp(entry->d_name, ".") == 0 ||
106                     strcmp(entry->d_name, "..") == 0)
107                         continue;
108 
109                 snprintf(buffer, PATH_MAX, "%s/slaves/%s", blkname,
110                          entry->d_name);
111                 if (is_dev_loop(buffer)) {
112                         ret = true;
113                         break;
114                 }
115         }
116         closedir(dir);
117 free_buffer:
118         free(buffer);
119         return ret;
120 }
121 
122 static int vss_operate(int operation)
123 {
124         char match[] = "/dev/";
125         FILE *mounts;
126         struct mntent *ent;
127         struct stat sb;
128         char errdir[1024] = {0};
129         char blkdir[23]; /* /sys/dev/block/XXX:XXX */
130         unsigned int cmd;
131         int error = 0, root_seen = 0, save_errno = 0;
132 
133         switch (operation) {
134         case VSS_OP_FREEZE:
135                 cmd = FIFREEZE;
136                 break;
137         case VSS_OP_THAW:
138                 cmd = FITHAW;
139                 break;
140         default:
141                 return -1;
142         }
143 
144         mounts = setmntent("/proc/mounts", "r");
145         if (mounts == NULL)
146                 return -1;
147 
148         while ((ent = getmntent(mounts))) {
149                 if (strncmp(ent->mnt_fsname, match, strlen(match)))
150                         continue;
151                 if (stat(ent->mnt_fsname, &sb)) {
152                         syslog(LOG_ERR, "Can't stat: %s; error:%d %s!",
153                                ent->mnt_fsname, errno, strerror(errno));
154                 } else {
155                         sprintf(blkdir, "/sys/dev/block/%d:%d",
156                                 major(sb.st_rdev), minor(sb.st_rdev));
157                         if (is_dev_loop(blkdir))
158                                 continue;
159                 }
160                 if (hasmntopt(ent, MNTOPT_RO) != NULL)
161                         continue;
162                 if (strcmp(ent->mnt_type, "vfat") == 0)
163                         continue;
164                 if (strcmp(ent->mnt_dir, "/") == 0) {
165                         root_seen = 1;
166                         continue;
167                 }
168                 error |= vss_do_freeze(ent->mnt_dir, cmd);
169                 if (error && operation == VSS_OP_FREEZE)
170                         goto err;
171         }
172 
173         endmntent(mounts);
174 
175         if (root_seen) {
176                 error |= vss_do_freeze("/", cmd);
177                 if (error && operation == VSS_OP_FREEZE)
178                         goto err;
179         }
180 
181         goto out;
182 err:
183         save_errno = errno;
184         if (ent) {
185                 strncpy(errdir, ent->mnt_dir, sizeof(errdir)-1);
186                 endmntent(mounts);
187         }
188         vss_operate(VSS_OP_THAW);
189         /* Call syslog after we thaw all filesystems */
190         if (ent)
191                 syslog(LOG_ERR, "FREEZE of %s failed; error:%d %s",
192                        errdir, save_errno, strerror(save_errno));
193         else
194                 syslog(LOG_ERR, "FREEZE of / failed; error:%d %s", save_errno,
195                        strerror(save_errno));
196 out:
197         return error;
198 }
199 
200 void print_usage(char *argv[])
201 {
202         fprintf(stderr, "Usage: %s [options]\n"
203                 "Options are:\n"
204                 "  -n, --no-daemon        stay in foreground, don't daemonize\n"
205                 "  -h, --help             print this help\n", argv[0]);
206 }
207 
208 int main(int argc, char *argv[])
209 {
210         int vss_fd, len;
211         int error;
212         struct pollfd pfd;
213         int     op;
214         struct hv_vss_msg vss_msg[1];
215         int daemonize = 1, long_index = 0, opt;
216         int in_handshake = 1;
217         __u32 kernel_modver;
218 
219         static struct option long_options[] = {
220                 {"help",        no_argument,       0,  'h' },
221                 {"no-daemon",   no_argument,       0,  'n' },
222                 {0,             0,                 0,  0   }
223         };
224 
225         while ((opt = getopt_long(argc, argv, "hn", long_options,
226                                   &long_index)) != -1) {
227                 switch (opt) {
228                 case 'n':
229                         daemonize = 0;
230                         break;
231                 case 'h':
232                 default:
233                         print_usage(argv);
234                         exit(EXIT_FAILURE);
235                 }
236         }
237 
238         if (daemonize && daemon(1, 0))
239                 return 1;
240 
241         openlog("Hyper-V VSS", 0, LOG_USER);
242         syslog(LOG_INFO, "VSS starting; pid is:%d", getpid());
243 
244         vss_fd = open("/dev/vmbus/hv_vss", O_RDWR);
245         if (vss_fd < 0) {
246                 syslog(LOG_ERR, "open /dev/vmbus/hv_vss failed; error: %d %s",
247                        errno, strerror(errno));
248                 exit(EXIT_FAILURE);
249         }
250         /*
251          * Register ourselves with the kernel.
252          */
253         vss_msg->vss_hdr.operation = VSS_OP_REGISTER1;
254 
255         len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
256         if (len < 0) {
257                 syslog(LOG_ERR, "registration to kernel failed; error: %d %s",
258                        errno, strerror(errno));
259                 close(vss_fd);
260                 exit(EXIT_FAILURE);
261         }
262 
263         pfd.fd = vss_fd;
264 
265         while (1) {
266                 pfd.events = POLLIN;
267                 pfd.revents = 0;
268 
269                 if (poll(&pfd, 1, -1) < 0) {
270                         syslog(LOG_ERR, "poll failed; error:%d %s", errno, strerror(errno));
271                         if (errno == EINVAL) {
272                                 close(vss_fd);
273                                 exit(EXIT_FAILURE);
274                         }
275                         else
276                                 continue;
277                 }
278 
279                 len = read(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
280 
281                 if (in_handshake) {
282                         if (len != sizeof(kernel_modver)) {
283                                 syslog(LOG_ERR, "invalid version negotiation");
284                                 exit(EXIT_FAILURE);
285                         }
286                         kernel_modver = *(__u32 *)vss_msg;
287                         in_handshake = 0;
288                         syslog(LOG_INFO, "VSS: kernel module version: %d",
289                                kernel_modver);
290                         continue;
291                 }
292 
293                 if (len != sizeof(struct hv_vss_msg)) {
294                         syslog(LOG_ERR, "read failed; error:%d %s",
295                                errno, strerror(errno));
296                         close(vss_fd);
297                         return EXIT_FAILURE;
298                 }
299 
300                 op = vss_msg->vss_hdr.operation;
301                 error =  HV_S_OK;
302 
303                 switch (op) {
304                 case VSS_OP_FREEZE:
305                 case VSS_OP_THAW:
306                         error = vss_operate(op);
307                         syslog(LOG_INFO, "VSS: op=%s: %s\n",
308                                 op == VSS_OP_FREEZE ? "FREEZE" : "THAW",
309                                 error ? "failed" : "succeeded");
310 
311                         if (error) {
312                                 error = HV_E_FAIL;
313                                 syslog(LOG_ERR, "op=%d failed!", op);
314                                 syslog(LOG_ERR, "report it with these files:");
315                                 syslog(LOG_ERR, "/etc/fstab and /proc/mounts");
316                         }
317                         break;
318                 case VSS_OP_HOT_BACKUP:
319                         syslog(LOG_INFO, "VSS: op=CHECK HOT BACKUP\n");
320                         break;
321                 default:
322                         syslog(LOG_ERR, "Illegal op:%d\n", op);
323                 }
324                 vss_msg->error = error;
325                 len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
326                 if (len != sizeof(struct hv_vss_msg)) {
327                         syslog(LOG_ERR, "write failed; error: %d %s", errno,
328                                strerror(errno));
329 
330                         if (op == VSS_OP_FREEZE)
331                                 vss_operate(VSS_OP_THAW);
332                 }
333         }
334 
335         close(vss_fd);
336         exit(0);
337 }
338 

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