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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 <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 }
268 

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