mdmon.c

   1
   2 /*
   3  * md array manager.
   4  * When md arrays have user-space managed metadata, this is the program
   5  * that does the managing.
   6  *
   7  * Given one argument: the name of the array (e.g. /dev/md0) that is
   8  * the container.
   9  * We fork off a helper that runs high priority and mlocked.  It responds to
  10  * device failures and other events that might stop writeout, or that are
  11  * trivial to deal with.
  12  * The main thread then watches for new arrays being created in the container
  13  * and starts monitoring them too ... along with a few other tasks.
  14  *
  15  * The main thread communicates with the priority thread by writing over
  16  * a pipe.
  17  * Separate programs can communicate with the main thread via Unix-domain
  18  * socket.
  19  * The two threads share address space and open file table.
  20  *
  21  */
  22
  23 #ifndef _GNU_SOURCE
  24 #define _GNU_SOURCE
  25 #endif
  26
  27 #include        <unistd.h>
  28 #include        <stdlib.h>
  29 #include        <sys/types.h>
  30 #include        <sys/stat.h>
  31 #include        <sys/socket.h>
  32 #include        <sys/un.h>
  33 #include        <sys/mman.h>
  34 #include        <sys/syscall.h>
  35 #include        <sys/wait.h>
  36 #include        <stdio.h>
  37 #include        <errno.h>
  38 #include        <string.h>
  39 #include        <fcntl.h>
  40 #include        <signal.h>
  41
  42 #include        <sched.h>
  43
  44 #include        "mdadm.h"
  45 #include        "mdmon.h"
  46
  47 struct active_array *discard_this;
  48 struct active_array *pending_discard;
  49
  50 int mon_tid, mgr_tid;
  51
  52 int run_child(void *v)
  53 {
  54         struct supertype *c = v;
  55
  56         do_monitor(c);
  57         return 0;
  58 }
  59
  60 int clone_monitor(struct supertype *container)
  61 {
  62         static char stack[4096];
  63
  64         mon_tid = clone(run_child, stack+4096-64,
  65                    CLONE_FS|CLONE_FILES|CLONE_VM|CLONE_SIGHAND|CLONE_THREAD,
  66                    container);
  67
  68         mgr_tid = syscall(SYS_gettid);
  69
  70         return mon_tid;
  71 }
  72
  73 static struct superswitch *find_metadata_methods(char *vers)
  74 {
  75         if (strcmp(vers, "ddf") == 0)
  76                 return &super_ddf;
  77         if (strcmp(vers, "imsm") == 0)
  78                 return &super_imsm;
  79         return NULL;
  80 }
  81
  82
  83 int make_pidfile(char *devname, int o_excl)
  84 {
  85         char path[100];
  86         char pid[10];
  87         int fd;
  88         sprintf(path, "/var/run/mdadm/%s.pid", devname);
  89
  90         fd = open(path, O_RDWR|O_CREAT|o_excl, 0600);
  91         if (fd < 0)
  92                 return -errno;
  93         sprintf(pid, "%d\n", getpid());
  94         write(fd, pid, strlen(pid));
  95         close(fd);
  96         return 0;
  97 }
  98
  99 static void try_kill_monitor(char *devname)
 100 {
 101         char buf[100];
 102         int fd;
 103         pid_t pid;
 104
 105         sprintf(buf, "/var/run/mdadm/%s.pid", devname);
 106         fd = open(buf, O_RDONLY);
 107         if (fd < 0)
 108                 return;
 109
 110         if (read(fd, buf, sizeof(buf)) < 0) {
 111                 close(fd);
 112                 return;
 113         }
 114
 115         close(fd);
 116         pid = strtoul(buf, NULL, 10);
 117
 118         /* kill this process if it is mdmon */
 119         sprintf(buf, "/proc/%lu/cmdline", (unsigned long) pid);
 120         fd = open(buf, O_RDONLY);
 121         if (fd < 0)
 122                 return;
 123
 124         if (read(fd, buf, sizeof(buf)) < 0) {
 125                 close(fd);
 126                 return;
 127         }
 128
 129         if (strstr(buf, "mdmon") != NULL)
 130                 kill(pid, SIGTERM);
 131 }
 132
 133 void remove_pidfile(char *devname)
 134 {
 135         char buf[100];
 136
 137         sprintf(buf, "/var/run/mdadm/%s.pid", devname);
 138         unlink(buf);
 139 }
 140
 141 int make_control_sock(char *devname)
 142 {
 143         char path[100];
 144         int sfd;
 145         long fl;
 146         struct sockaddr_un addr;
 147
 148         sprintf(path, "/var/run/mdadm/%s.sock", devname);
 149         unlink(path);
 150         sfd = socket(PF_LOCAL, SOCK_STREAM, 0);
 151         if (sfd < 0)
 152                 return -1;
 153
 154         addr.sun_family = PF_LOCAL;
 155         strcpy(addr.sun_path, path);
 156         if (bind(sfd, &addr, sizeof(addr)) < 0) {
 157                 close(sfd);
 158                 return -1;
 159         }
 160         listen(sfd, 10);
 161         fl = fcntl(sfd, F_GETFL, 0);
 162         fl |= O_NONBLOCK;
 163         fcntl(sfd, F_SETFL, fl);
 164         return sfd;
 165 }
 166
 167 int socket_hup_requested;
 168 static void hup(int sig)
 169 {
 170         socket_hup_requested = 1;
 171 }
 172
 173 static void wake_me(int sig)
 174 {
 175
 176 }
 177
 178 /* if we are debugging and starting mdmon by hand then don't fork */
 179 static int do_fork(void)
 180 {
 181         #ifdef DEBUG
 182         if (env_no_mdmon())
 183                 return 0;
 184         #endif
 185
 186         return 1;
 187 }
 188
 189
 190
 191 int main(int argc, char *argv[])
 192 {
 193         int mdfd;
 194         struct mdinfo *mdi, *di;
 195         struct supertype *container;
 196         sigset_t set;
 197         struct sigaction act;
 198         int pfd[2];
 199         int status;
 200
 201         if (argc != 2) {
 202                 fprintf(stderr, "Usage: md-manage /device/name/for/container\n");
 203                 exit(2);
 204         }
 205         mdfd = open(argv[1], O_RDWR);
 206         if (mdfd < 0) {
 207                 fprintf(stderr, "md-manage: %s: %s\n", argv[1],
 208                         strerror(errno));
 209                 exit(1);
 210         }
 211         if (md_get_version(mdfd) < 0) {
 212                 fprintf(stderr, "md-manage: %s: Not an md device\n",
 213                         argv[1]);
 214                 exit(1);
 215         }
 216
 217         /* Fork, and have the child tell us when they are ready */
 218         if (do_fork()) {
 219                 pipe(pfd);
 220                 switch(fork()) {
 221                 case -1:
 222                         fprintf(stderr, "mdmon: failed to fork: %s\n",
 223                                 strerror(errno));
 224                         exit(1);
 225                 case 0: /* child */
 226                         close(pfd[0]);
 227                         break;
 228                 default: /* parent */
 229                         close(pfd[1]);
 230                         if (read(pfd[0], &status, sizeof(status)) != sizeof(status)) {
 231                                 wait(&status);
 232                                 status = WEXITSTATUS(status);
 233                         }
 234                         exit(status);
 235                 }
 236         } else
 237                 pfd[0] = pfd[1] = -1;
 238         /* hopefully it is a container - we'll check later */
 239
 240         container = malloc(sizeof(*container));
 241         container->devnum = fd2devnum(mdfd);
 242         container->devname = devnum2devname(container->devnum);
 243         container->device_name = argv[1];
 244
 245         /* If this fails, we hope it already exists */
 246         mkdir("/var/run/mdadm", 0600);
 247         /* pid file lives in /var/run/mdadm/mdXX.pid */
 248         if (make_pidfile(container->devname, O_EXCL) < 0) {
 249                 if (ping_monitor(container->devname) == 0) {
 250                         fprintf(stderr, "mdmon: %s already managed\n",
 251                                 container->devname);
 252                         exit(3);
 253                 } else {
 254                         int err;
 255
 256                         /* cleanup the old monitor, this one is taking over */
 257                         try_kill_monitor(container->devname);
 258                         err = make_pidfile(container->devname, 0);
 259                         if (err < 0) {
 260                                 fprintf(stderr, "mdmon: %s Cannot create pidfile\n",
 261                                         container->devname);
 262                                 if (err == -EROFS) {
 263                                         /* FIXME implement a mechanism to
 264                                          * prevent duplicate monitor instances
 265                                          */
 266                                         fprintf(stderr,
 267                                                 "mdmon: continuing on read-only file system\n");
 268                                 } else
 269                                         exit(3);
 270                         }
 271                 }
 272         }
 273
 274         container->sock = make_control_sock(container->devname);
 275         if (container->sock < 0)
 276                 fprintf(stderr, "mdmon: Cannot create socket in /var/run/mdadm\n");
 277         container->arrays = NULL;
 278
 279         mdi = sysfs_read(mdfd, container->devnum,
 280                          GET_VERSION|GET_LEVEL|GET_DEVS);
 281
 282         if (!mdi) {
 283                 fprintf(stderr, "mdmon: failed to load sysfs info for %s\n",
 284                         container->devname);
 285                 exit(3);
 286         }
 287         if (mdi->array.level != UnSet) {
 288                 fprintf(stderr, "mdmon: %s is not a container - cannot monitor\n",
 289                         argv[1]);
 290                 exit(3);
 291         }
 292         if (mdi->array.major_version != -1 ||
 293             mdi->array.minor_version != -2) {
 294                 fprintf(stderr, "mdmon: %s does not use external metadata - cannot monitor\n",
 295                         argv[1]);
 296                 exit(3);
 297         }
 298
 299         container->ss = find_metadata_methods(mdi->text_version);
 300         if (container->ss == NULL) {
 301                 fprintf(stderr, "mdmon: %s uses unknown metadata: %s\n",
 302                         argv[1], mdi->text_version);
 303                 exit(3);
 304         }
 305
 306         container->devs = NULL;
 307         for (di = mdi->devs; di; di = di->next) {
 308                 struct mdinfo *cd = malloc(sizeof(*cd));
 309                 *cd = *di;
 310                 cd->next = container->devs;
 311                 container->devs = cd;
 312         }
 313         sysfs_free(mdi);
 314
 315
 316         if (container->ss->load_super(container, mdfd, argv[1])) {
 317                 fprintf(stderr, "mdmon: Cannot load metadata for %s\n",
 318                         argv[1]);
 319                 exit(3);
 320         }
 321
 322         /* Ok, this is close enough.  We can say goodbye to our parent now.
 323          */
 324         status = 0;
 325         write(pfd[1], &status, sizeof(status));
 326         close(pfd[1]);
 327
 328         chdir("/");
 329         setsid();
 330         close(0);
 331         open("/dev/null", O_RDWR);
 332         close(1);
 333         dup(0);
 334 #ifndef DEBUG
 335         close(2);
 336         dup(0);
 337 #endif
 338
 339         mlockall(MCL_FUTURE);
 340
 341         /* SIGUSR is sent between parent and child.  So both block it
 342          * and enable it only with pselect.
 343          */
 344         sigemptyset(&set);
 345         sigaddset(&set, SIGUSR1);
 346         sigaddset(&set, SIGHUP);
 347         sigprocmask(SIG_BLOCK, &set, NULL);
 348         act.sa_handler = wake_me;
 349         act.sa_flags = 0;
 350         sigaction(SIGUSR1, &act, NULL);
 351         act.sa_handler = hup;
 352         sigaction(SIGHUP, &act, NULL);
 353         act.sa_handler = SIG_IGN;
 354         sigaction(SIGPIPE, &act, NULL);
 355
 356         if (clone_monitor(container) < 0) {
 357                 fprintf(stderr, "mdmon: failed to start monitor process: %s\n",
 358                         strerror(errno));
 359                 exit(2);
 360         }
 361
 362         do_manager(container);
 363
 364         exit(0);
 365 }